Discussion:
Can I ask a question of how gravity acts like a force on this newsgroup?
2021-05-07 00:43:46 UTC
I've been trying to understand how gravity acts like a force.
I'm sure the math works out but I don't understand the logic.

On the net are many rubber trampoline examples which imply that you have to
bend (toward the south pole in those 2D examples).

I don't see what is moving.

I realize EVERYTHING is moving (at half a millions miles per second or so,
given rotation, orbit around the sun, the sun spinning up and around the
galaxy, the galaxy moving, etc.).

But if I think about gravity in the frame of reference from the earth I'm
not moving with respect to the earth. Am I?

I'm standing still with respect to the earth, aren't I?

So what's moving?

When I dig further I find out that it's more the curvature in time than in
space that causes this effect we call gravity. Most explain this feeling of
feet (slower time).

But what's moving?

I don't yet understand logically how the time gradient (plus the curviture
in space) feels like a force.

That's why I'm here.
Is this the kind of question we can fruitfully ask on this newsgroup?
--
Doveryay, no proveryay.
Dono.
2021-05-07 01:24:42 UTC
On the net are many rubber trampoline examples which imply that you have to
bend (toward the south pole in those 2D examples).
This is a misconception. What the model shows is how a gravitating body (like the Sun) attracts other , smaller gravitating bodies (like the planets) in order to make them start revolving around it.
Obviously, this model does not explain how the Earth attracts the bodies resting on it. We do not have an explanation of the gravitation, we only have limited models. These models, like the Schwarzschild solution to the Einstein Field Equations explain the motion of gravitating bodies to a very good match with Newtonian equations. For example, the Schwrazschild solution explains much better than the Newtonian equations the precession of the planets in their revolution around the Sun. They also explain that light "gravitates", being bent by the presence of large gravitating bodies. If you want to understand in depth these issues, you will need to study general relativity.
Dono.
2021-05-07 01:45:10 UTC
Post by Dono.
On the net are many rubber trampoline examples which imply that you have to
bend (toward the south pole in those 2D examples).
This is a misconception. What the model shows is how a gravitating body (like the Sun) attracts other , smaller gravitating bodies (like the planets) in order to make them start revolving around it.
Obviously, this model does not explain how the Earth attracts the bodies resting on it. We do not have an explanation of the gravitation, we only have limited models. These models, like the Schwarzschild solution to the Einstein Field Equations explain the motion of gravitating bodies to a very good match with Newtonian equations. For example, the Schwrazschild solution explains much better than the Newtonian equations the precession of the planets in their revolution around the Sun. They also explain that light "gravitates", being bent by the presence of large gravitating bodies. If you want to understand in depth these issues, you will need to study general relativity.
One more thing, if we lifted you in the air and we let you go, you would fall to the Earth , the equations of motion would be exactly like the ones based on Newton attraction. Your fall is being stopped by the electromagnetic force that precludes you from penetrating the crust of the Earth.
2021-05-07 05:18:02 UTC
Bertram Schuller
2021-05-07 13:15:24 UTC
Post by Dono.
Your fall is being stopped by the electromagnetic force that precludes
you from penetrating the crust of the Earth.
Agreed. Understood. I'd fall to the center of mass of the earth if the
effect of the Pauli exclusion principle didn't stop me from doing so.
Not true, you are mislead. The freefall (no force involved) will decay
toward the center. Many people don't understand this thing, without
flowchart diagrams drown.
Bertram Schuller
2021-05-07 13:16:46 UTC
Post by Bertram Schuller
Post by Dono.
Your fall is being stopped by the electromagnetic force that precludes
you from penetrating the crust of the Earth.
Agreed. Understood. I'd fall to the center of mass of the earth if the
effect of the Pauli exclusion principle didn't stop me from doing so.
Not true, you are mislead. The freefall (no force involved) will decay
toward the center. Many people don't understand this thing, without
flowchart diagrams drown.
me too. Not the freefall will decay, but the acceleration, hence also the
1st order speed.
2021-05-07 14:19:02 UTC
Post by Bertram Schuller
Post by Dono.
Your fall is being stopped by the electromagnetic force that precludes
you from penetrating the crust of the Earth.
Agreed. Understood. I'd fall to the center of mass of the earth if the
effect of the Pauli exclusion principle didn't stop me from doing so.
Not true, you are mislead. The freefall (no force involved) will decay
toward the center. Many people don't understand this thing, without
flowchart diagrams drown.
I won't dispute what you say as my goal right now is to attain a visual
picture in my mind of how gravity works WITHOUT MOVEMENT.

You can't travel in a straight line (however distorted) if you're not
traveling in the first place.

I'm not disputing the math - I believe the math shows that most of what we
feel as gravity is due to time dilation (more so than to space warpage).

But what I'm trying to arrive at is a model that is intuitive in explaining
how we move in time and how that movement is the movement that is necessary
for us to follow the time gradient in falling to the surface of the earth.
--
Doveryay, no proveryay.
Bertram Schuller
2021-05-07 14:26:46 UTC
Post by Bertram Schuller
Not true, you are mislead. The freefall (no force involved) will decay
toward the center. Many people don't understand this thing, without
flowchart diagrams drown.
I won't dispute what you say as my goal right now is to attain a visual
picture in my mind of how gravity works WITHOUT MOVEMENT.
You can't travel in a straight line (however distorted) if you're not
traveling in the first place.
You can, since the "gravity" is a phenomenon, best described by the
I'm not disputing the math - I believe the math shows that most of what
we feel as gravity is due to time dilation (more so than to space
warpage). But what I'm trying to arrive at is a model that is intuitive
in explaining how we move in time and how that movement is the movement
that is necessary for us to follow the time gradient in falling to the
surface of the earth.
You are confused. See above. Also, what movement stands for.

Also, empirical data, from experts in the field.

Immunization with SARS Coronavirus Vaccines Leads toPulmonary
Immunopathology on Challenge with theSARS Virus
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3335060/pdf/pone.0035421.pdf

and also

New Jersey doctor dies of Covid on trip to India — After getting both
Pfizer shots in USA…
https://citizenfreepress.com/breaking/new-jersey-doctor-dies-of-covid-on-
trip-to-india-after-getting-both-pfizer-shots-in-u-s/

We are deeply saddened by the loss of Dr. Rajendra Kapila, a true
legend in the NYC ID community. He had such a wonderful presence at our
ID intercity rounds with his incredible knowledge and sense of humor. He
will be missed. https://t.co/xi9Hv89uIp

— Weill Cornell Infectious Diseases Division (@WCM_ID) May 4, 2021
2021-05-07 14:34:25 UTC
Post by Bertram Schuller
Immunization with SARS Coronavirus Vaccines
plonk
--
Doveryay, no proveryay.
Bertram Schuller
2021-05-07 14:49:03 UTC
Post by Bertram Schuller
Immunization with SARS Coronavirus Vaccines Leads toPulmonary
Immunopathology on Challenge with theSARS Virus
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3335060/pdf/pone.0035421.pdf
plonk
idiot, you can't read science papers, references. I gave too much time,
you are stupid like a rock, from the very beginning. Piss off, cretin.
J***@.
1970-01-01 00:00:00 UTC
A freefalling object can be assigned a ( static, 4d ) SpaceTime path,
in a ( static, 4d ) TimeScape, where it's (notionally)
"Moving at The Speed of Causality" ( c, the speed of light in a vacuum ).

Photons are confined to the (bent) space axis.
We humans are mostly confined to the (bent) time axis.

Because our time axis is bent, here on Earth,
a freefalling human ( Moving at The speed of Causality, c )
moves a tiny bit along space axis.

At low speeds, when precision doesn't matter much,
the Newtonian gravity model is close enough.
Thomas 'PointedEars' Lahn
2021-05-07 23:52:33 UTC
Post by Dono.
One more thing, if we lifted you in the air and we let you go,
you would fall to the Earth...
I'm aware of Einstein's happiest thought which is essentially that!

"What Was Albert Einstein�s Happiest Thought?"
Post by Dono.
the equations of motion would be exactly like the ones based on
Newton attraction.
I was trained in classical physics so I have an intuitive understanding of
Newtonian gravity
Today the term “classical physics” *includes* general relativity, and is
used instead to make the distinction to quantum physics.
but we all know that it's "wrong"
Unfortunately, not all of us know this.
so that's why I'm trying to integrate time dilation into my mental model
of where gravity comes from.
This is not what general relativity says, and not what can be observed, so
this attempt is hopeless.

"Gravitational" time dilation has the same reason as gravity, namely
spacetime curvature; it is NOT a *consequence* of gravity.
Post by Dono.
Your fall is being stopped by the electromagnetic force that
precludes you from penetrating the crust of the Earth.
Agreed. Understood. I'd fall to the center of mass of the earth if the
effect of the Pauli exclusion principle didn't stop me from doing so.
Quantum mechanics and the Pauli exclusion principle may be, but do not have
to be, invoked here. The fact that even in classical physics the repulsive
Coulomb force approaches infinity as the distance between like-charged
particles approaches zero suffices to understand this:

F = k Q q/r²

PointedEars
--
Q: Why is electricity so dangerous?
A: It doesn't conduct itself.

(from: WolframAlpha)
2021-05-07 05:18:26 UTC
Post by Dono.
This is a misconception.
Thanks for trying to help me understand how time dilation (mostly I think?)
causes what we call the "gravitational force" (even when we're not moving
with respect to our position on earth).

I agree with you that the trampoline model is a misconception.

What I seek is a non-mathematical model that has fewer misconceptions
involved and which takes into account the effect of time dilation on our
perception of "gravity."

I trust that the math works - but I'm seeking an intuitive answer if that's
even possible.
Post by Dono.
What the model shows is how a gravitating body (like the Sun) attracts
other , smaller gravitating bodies (like the planets) in order to make
them start revolving around it.
Yes. It shows that a marble, when pushed, will tend to circle around the
bowling ball which is distorting the "fabric of trampoline" so to speak.

That distortion causes what the marble (planet) thinks is a straight line
motion into a curved motion around the bowling ball (sun) in the distorted
fabric (spacetime but in this model it's only space & not time distortion).
Post by Dono.
Obviously, this model does not explain how the Earth attracts the bodies
resting on it.
Oh! I get it! I didn't realize that statement is true until you said it!
Yes. You are right.

Thank you for that sentence which opened my eyes to the fact I'm looking at
the wrong model to explain how gravity makes me slide down a steep sandy
hillside even when I'm standing still at the top (I happen to do that a lot
as I live near many sandy beach dunes).
Post by Dono.
We do not have an explanation of the gravitation, we only have limited models.
The best explanation for gravity I can think of is that there is a time
move faster than our feet, which (somehow) causes us to arc toward the earth
(somehow) due to that gradient (since gradients are what makes things move).

But I am standing still - not moving (with respect to the earth)!

When I looked up how we can feel gravity when we're not moving (relative to
the earth) I found that there are some explanations which claim everything
moves through time in a spacetime diagram at the speed of c.

Massless particles moves through space at the speed of c with zero movement
through time while the rest of us with mass move through space and time (the
faster through space, the slower through time, and vice versa) but still at
the speed of c in all cases.

To summarize, when I looked to see HOW we were moving, it turns out that
some people said we're all moving through time at a tremendous speed (given
we're only moving at about half a million miles per second through space so
MOST of our motion is through time).

The closest I can get to a "model" of why we "fall" to earth is that we're
actually MOVING through space & time at the speed of c, where most of that
movement is in time, so even an infinitesimal difference between a clock at
my head and a clock at my foot causes a gradient that we feel as gravity.

That's the BEST I can do so far - but it could be completely wrong.
Is it?
Post by Dono.
These models, like the Schwarzschild solution to the Einstein Field Equations
explain the motion of gravitating bodies to a very good match with Newtonian
equations. For example, the Schwrazschild solution explains much better than
the Newtonian equations the precession of the planets in their revolution
around the Sun. They also explain that light "gravitates", being bent by
the presence of large gravitating bodies. If you want to understand in depth
these issues, you will need to study general relativity.
I think I have a good handle on general relativity as I've taken classical
college level physics and astronomy but I don't have a mathematical mind.

I'm quite positive the math works out fantastically but if I were to derive
all my intuition from an understanding of equations such as Schroedinger's
Equation, then I'd be Paul Dirac and not who I really am inside.

People like Stephen Hawking think mathematically but I think visually.

My current visual representation of the time dilation of gravity is here:

"The REAL source of Gravity might SURPRISE you"

My main issue understanding that description is understanding the 4velocity.

"We are all moving at the speed of light"

One question I have is it true that we move at the speed of c through time?

"Do we travel through time at the speed of light?"

Is THAT the motion that causes us to follow the geodesic of time dilation?
--
Doveryay, no proveryay.
J***@.
1970-01-01 00:00:00 UTC
Thermodynamics is the easiest way to understand gravity
and/or electromagnetism.

From our perspective, clocks tick ever-slower the closer
they are to the start of the Big Bang.

Locally, those clocks tick normally, as they do here.

I -assume- that there was no entropy at
the ( infinitely precise ) start of the Big Bang;
i.e. infinite "eXergy" ( energy that can do "work", force * distance );
e.g. infinite gravitational and/or electromagnetic energy.

"God" (nature) programmed us to consume residual eXergy as
the cosmos goes from infinitely hot/dense to infinitely cold/sparse.
Paparios
2021-05-07 15:10:54 UTC
I've been trying to understand how gravity acts like a force.
I'm sure the math works out but I don't understand the logic.
On the net are many rubber trampoline examples which imply that you have to
bend (toward the south pole in those 2D examples).
I don't see what is moving.
I realize EVERYTHING is moving (at half a millions miles per second or so,
given rotation, orbit around the sun, the sun spinning up and around the
galaxy, the galaxy moving, etc.).
But if I think about gravity in the frame of reference from the earth I'm
not moving with respect to the earth. Am I?
I'm standing still with respect to the earth, aren't I?
So what's moving?
When I dig further I find out that it's more the curvature in time than in
space that causes this effect we call gravity. Most explain this feeling of
feet (slower time).
But what's moving?
I don't yet understand logically how the time gradient (plus the curviture
in space) feels like a force.
That's why I'm here.
Is this the kind of question we can fruitfully ask on this newsgroup?
--
Doveryay, no proveryay.
All bodies in the Universe follow geodesic trajectories. A geodesic is commonly a curve representing in some sense the shortest path between two points in a surface, or more generally in a Riemannian manifold.
You can also say that objects are in "free fall". You and me are in free fall but the Earth ground stop us from continue our free fall towards the center of Earth.
How does this work? Well, it can be summed up as “Space-time tells matter how to move; matter tells space-time how to curve”. The whole thing is just the result of the geometry of the Universe.
Maciej Wozniak
2021-05-07 15:52:47 UTC
All bodies in the Universe follow geodesic trajectories. A geodesic is commonly a curve representing in some sense the shortest path between two points in a surface, or more generally in a Riemannian manifold.
You can also say that objects are in "free fall". You and me are in free fall but the Earth ground stop us from continue our free fall towards the center of Earth.
How does this work? Well, it can be summed up as “Space-time tells matter how to move; matter tells space-time how to curve”. The whole thing is just the result of the geometry of the Universe.
Sorry, poor halfbrain, it's only geometry of your moronic cult.
Go educate yourself - a geometry is an axiomatic construction.
The universe has no.
2021-05-07 16:31:17 UTC
Post by Paparios
All bodies in the Universe follow geodesic trajectories.
Yes. Slices of conic sections is how I understand celestial motion.
Hyperbolas. Elipses. Rarely circles.

The celestial bodies move in what they think are straight lines, but their
celestial trajectories are dictated by the curvature of spacetime.

But they are ALREADY moving (a body in motion stays in motion).
Post by Paparios
A geodesic is commonly a curve representing in some sense the shortest
path between two points in a surface, or more generally in a Riemannian manifold.
Yes. Spacetime is not flat.

I had forgot about Riemannian manifolds so I looked it up to refresh myself.
<https://www.sciencedirect.com/topics/mathematics/riemannian-manifolds>

I admit metric tensors aren't anything I enjoy though, which is why I seek a
visual graphical explanation of geodesics, such as this useful description.

Post by Paparios
You can also say that objects are in "free fall".
That "free fall" is the "motion" that I do not yet understand!
Post by Paparios
You and me are in free fall but the Earth ground stop us from
continue our free fall towards the center of Earth.
What I accept as truth is that statement but I don't understand
WHY we are in free fall. Where is the motion coming from?

I understand that the ground stops us.
I accept that we are in free fall.

I just don't understand WHY we are in free fall when we're not moving
(with respect to the earth).
Post by Paparios
How does this work? Well, it can be summed up as "Space-time tells
matter how to move; matter tells space-time how to curve".
Yes. I know. I've heard that J.A. Wheeler quote a thousand times.
It's actually wrong in a way in that ENERGY is also involved.

But just accepting it as a true statement doesn't mean I understand it.
Nor does it mean I can explain it to someone else who doesn't know physics.

If I can't explain it to someone who doesn't know physics, then I don't
really understand it at the level that I want to understand it (without
math!).

I do think I understand, visually, how mass energy warps spacetime toward it
and once you have curvature in space & in time then any object ALREADY
MOVING will follow what it thinks is a straight line in that curved
spacetime manifold.

But if I'm standing at the surface of the earth I am not moving through
space (with respect to earth) so there should be no space gradient (other

Even the time gradient is infinitesimally tiny between my feet and my head
(and yes, I know the time gradient works even on point particles).

If I "assume" I'm moving at the speed of c through spacetime (mostly through
time) then and only then do I have MOTION.

To be clear, my confusion is all about figuring out where the MOTION is.

(I'm standing still with respect to the earth but I am moving at an
extremely fast speed through time but even the earth is moving through time
at almost the same speed although probably at a different speed than I am
due to its energy mass content being huge versus mine being small.)

My confusion is mostly on figuring out WHERE IS THE MOTION?
Post by Paparios
The whole thing is just the result of the geometry of the Universe.
Yes. I agree. I accept that fact that the curvature of spacetime (mostly
time) due to the energy mass content of earth warping spacetime toward it by
displacing spacetime is the "geometry" that is important in my free fall to
earth.

And I agree there is a space gradient and a time gradient between my feet
and my head which is very small but which is a factor in my feeling of
gravity.

But that very small gradient needs something MUCH MUCH MUCH LARGER to have
the 9.8 meters per second forces I feel when sliding down a sandy dune.

I "think" that larger thing is the fact we're moving through time at the
speed of c, which is a huge amount of motion.

If I multiply that huge amount of motion (mostly through time) times the
meters per second "force" that I feel.

But the frame of reference is static!

The earth is moving through time at the same velocity I am moving through
time.
The earth is moving through space at the same velocity I am moving through
space.

Neither of us is accelerating (as far as I can understand).
I can't find the acceleration in my model.

That's why I'm confused.
Where is the differential motion (through space or time)?
--
Doveryay, no proveryay.
Paparios
2021-05-07 16:48:42 UTC
Post by Paparios
All bodies in the Universe follow geodesic trajectories.
Yes. Slices of conic sections is how I understand celestial motion.
Hyperbolas. Elipses. Rarely circles.
The celestial bodies move in what they think are straight lines, but their
celestial trajectories are dictated by the curvature of spacetime.
But they are ALREADY moving (a body in motion stays in motion).
Post by Paparios
A geodesic is commonly a curve representing in some sense the shortest
path between two points in a surface, or more generally in a Riemannian manifold.
Yes. Spacetime is not flat.
I had forgot about Riemannian manifolds so I looked it up to refresh myself.
<https://www.sciencedirect.com/topics/mathematics/riemannian-manifolds>
I admit metric tensors aren't anything I enjoy though, which is why I seek a
visual graphical explanation of geodesics, such as this useful description.
http://youtu.be/UfThVvBWZxM
Post by Paparios
You can also say that objects are in "free fall".
That "free fall" is the "motion" that I do not yet understand!
Post by Paparios
You and me are in free fall but the Earth ground stop us from
continue our free fall towards the center of Earth.
What I accept as truth is that statement but I don't understand
WHY we are in free fall. Where is the motion coming from?
I understand that the ground stops us.
I accept that we are in free fall.
I just don't understand WHY we are in free fall when we're not moving
(with respect to the earth).
Post by Paparios
How does this work? Well, it can be summed up as "Space-time tells
matter how to move; matter tells space-time how to curve".
Yes. I know. I've heard that J.A. Wheeler quote a thousand times.
It's actually wrong in a way in that ENERGY is also involved.
But just accepting it as a true statement doesn't mean I understand it.
Nor does it mean I can explain it to someone else who doesn't know physics.
If I can't explain it to someone who doesn't know physics, then I don't
really understand it at the level that I want to understand it (without
math!).
I do think I understand, visually, how mass energy warps spacetime toward it
and once you have curvature in space & in time then any object ALREADY
MOVING will follow what it thinks is a straight line in that curved
spacetime manifold.
But if I'm standing at the surface of the earth I am not moving through
space (with respect to earth) so there should be no space gradient (other
Even the time gradient is infinitesimally tiny between my feet and my head
(and yes, I know the time gradient works even on point particles).
If I "assume" I'm moving at the speed of c through spacetime (mostly through
time) then and only then do I have MOTION.
To be clear, my confusion is all about figuring out where the MOTION is.
(I'm standing still with respect to the earth but I am moving at an
extremely fast speed through time but even the earth is moving through time
at almost the same speed although probably at a different speed than I am
due to its energy mass content being huge versus mine being small.)
My confusion is mostly on figuring out WHERE IS THE MOTION?
Post by Paparios
The whole thing is just the result of the geometry of the Universe.
Yes. I agree. I accept that fact that the curvature of spacetime (mostly
time) due to the energy mass content of earth warping spacetime toward it by
displacing spacetime is the "geometry" that is important in my free fall to
earth.
And I agree there is a space gradient and a time gradient between my feet
and my head which is very small but which is a factor in my feeling of
gravity.
But that very small gradient needs something MUCH MUCH MUCH LARGER to have
the 9.8 meters per second forces I feel when sliding down a sandy dune.
I "think" that larger thing is the fact we're moving through time at the
speed of c, which is a huge amount of motion.
If I multiply that huge amount of motion (mostly through time) times the
meters per second "force" that I feel.
But the frame of reference is static!
The earth is moving through time at the same velocity I am moving through
time.
The earth is moving through space at the same velocity I am moving through
space.
Neither of us is accelerating (as far as I can understand).
I can't find the acceleration in my model.
Well, actually we ARE accelerating at 9.8 m/s/s up the ground. See, if you jump from the Eiffel tower you gain speed by free falling towards the center of Earth (at 9.8 m/s/s). That acceleration is due to the mass of Earth which changes the geometry of the geodesics. When you hit the ground, whatever speed you got turns out to 0 m/s. If you are standing on the ground you still feel the 9.8 m/s/s acceleration towards the ground but that acceleration is balanced by an opposite acceleration created by your body components which results in a net vertical speed of 0 m/s.
That
Doveryay, no proveryay.'s why I'm confused.
Where is the differential motion (through space or time)?
--
Maciej Wozniak
2021-05-07 17:12:05 UTC
Post by Paparios
Well, actually we ARE accelerating at 9.8 m/s/s up the ground. See, if you jump from the Eiffel tower you gain speed by free falling towards the center of Earth (at 9.8 m/s/s). That acceleration is due to the mass of Earth which changes the geometry of the geodesics. When you hit the ground, whatever speed you got turns out to 0 m/s. If you are standing on the ground you still feel the 9.8 m/s/s acceleration towards the ground but that acceleration is balanced by an opposite acceleration created by your body components which results in a net vertical speed of 0 m/s.
Paparios, poor halfbrain, do you know what the
word "acceleration" means? I can't say I'm surprised
you don't.
2021-05-07 20:37:49 UTC
Post by Paparios
Well, actually we ARE accelerating at 9.8 m/s/s up the ground.
I agree. The question is NOT that we are; it's WHY we are.
Post by Paparios
See, if you jump from the Eiffel tower you gain speed by free
falling towards the center of Earth (at 9.8 m/s/s).
I agree. I don't doubt the math one bit.
I'm trying to find a model that EXPLAINS why this is the case.
Post by Paparios
That acceleration is due to the mass of Earth which changes the
geometry of the geodesics.
The geometric change is in both space & time - which I agree with.
As far as I know, it's far more curvature in time than in space.

The question is WHY.
And what MODEL can we use to visualize it.
Post by Paparios
When you hit the ground, whatever speed you got turns out to 0 m/s.
I agree.
I should probably give up asking because nobody understands me.

I'm asking WHY - not what.
Post by Paparios
If you are standing on the ground you still feel the 9.8 m/s/s
acceleration towards the ground but that acceleration is balanced
by an opposite acceleration created by your body components which
results in a net vertical speed of 0 m/s.
I agree.
Those statements are NOT where my confusion lies.

The confusion lies in the WHY of that first statement of yours.
"Well, actually we ARE accelerating at 9.8/m/s/s up the ground"

Why?
Put in other words, WHY are we accelerating in the first place?

I know it's due to time more so than to space.
And I'm well aware it's along a geodesic.
And I'm also well aware that we're moving through time at the speed of c.

What I can't figure out yet is a MODEL that explains WHY we "feel"
an acceleration (mostly due to time curvature) when both the earth
and our bodies are moving through time at the same speed of c.

The _closest_ I can get to an answer is that we're moving so fast
through time that even the tiny gradient between our clocks at our
head and our feet is enough to force us into the ground at 9.8m/s/s

Otherwise we'd stay in the air when we stepped off the Eifel Tower
as there is no force of gravity, per se (it doesn't exist).

What exists is curvature in space and more so in time.
And what exists is MOVEMENT through time at the the speed of c.
And what exists is NO MOVEMENT through space.

Somehow the curvature in time coupled with the movement in time
causes us to move along the geodesic in time such that it causes
this thing we feel as a force of 9.8m/s/s acceleration along that
geodesic in time curvature (but not so much in space curvature).
which
--
Doveryay, no proveryay.
Paparios
2021-05-07 22:33:46 UTC
Post by Paparios
Well, actually we ARE accelerating at 9.8 m/s/s up the ground.
I agree. The question is NOT that we are; it's WHY we are.
The why is due to the Earth mass and its density. If Earth were to be a gaseous body, its surface would not stop our acceleration. Also Earth density, while high is not that high enough to stop neutrinos to cross the Earth mass without even noticing it is there.
Post by Paparios
See, if you jump from the Eiffel tower you gain speed by free
falling towards the center of Earth (at 9.8 m/s/s).
I agree. I don't doubt the math one bit.
I'm trying to find a model that EXPLAINS why this is the case.
Post by Paparios
That acceleration is due to the mass of Earth which changes the
geometry of the geodesics.
The geometric change is in both space & time - which I agree with.
As far as I know, it's far more curvature in time than in space.
The question is WHY.
And what MODEL can we use to visualize it.
The best model to all this mass-energy-geometry play is General Relativity. In any case, physical models, such as GR can not answer the WHY you are looking for. All physical models try to explain observations and results from experiments. Why Nature follows the invariance of some physical quantities is unknown to us. We as humans can only process thoughts (through our brain) and we are severely limited and don't have enough power to look into the WHY of Nature. We do not really know what time is and why it moves in only one direction. We do not know if there are more dimensions besides x,y,z,t.

The only thing we can do is to formulate models and if some observations falsify those models, then we try to find better models of how Nature appears to work.

As of now, GR, QED and the Standard Models are the best models which allow to predict what it will be observed in an experiment. However, those three models are not fully compatible and physicists are looking for new models which allow to merge both the domain of GR (great masses and large speeds) with QED (very small particles), probably to be called Quantum Gravity. We are not near to reach a working model of Quantum Gravity, but if we reach that level, the WHY will for sure continue to be unknown.
Maciej Wozniak
2021-05-08 04:13:12 UTC
Post by Paparios
Post by Paparios
Well, actually we ARE accelerating at 9.8 m/s/s up the ground.
I agree. The question is NOT that we are; it's WHY we are.
The why is due to the Earth mass and its density. If Earth were to be a gaseous body, its surface would not stop our acceleration.
Paparios, poor mumbling idiot, Earth is not a gaseous body, the
surface is stopping our acceleration and thus we AREN'T
accelerating. Surprise?
Post by Paparios
The best model to all this mass-energy-geometry play is General Relativity.
Your Shit doesn't even provide a consistent system of coordinates,
but you like it anyway.
Walker Huckabee
2021-05-08 10:18:18 UTC
Post by Paparios
Post by Paparios
Well, actually we ARE accelerating at 9.8 m/s/s up the ground.
I agree. The question is NOT that we are; it's WHY we are.
The why is due to the Earth mass and its density. If Earth were to be a
gaseous body, its surface would not stop our acceleration. Also Earth
density, while high is not that high enough to stop neutrinos to cross
the Earth mass without even noticing it is there.
you are wasting your time on an obvious cretin, but it's all right.
2021-05-07 23:08:19 UTC
A geodesic is commonly a curve representing in some sense the shortest
path between two points in a surface, or more generally in a Riemannian manifold.
Not true. A geodesic makes the variational integral *stationary*, and in general relativity (with its pseudo-metric manifold) the time-like geodesic paths are the longest (not the shortest) paths. That's why the inertial twin ages more than the non-inertial twin.
The _closest_ I can get to an answer is that we're moving so fast
through time that even the tiny gradient between our clocks at our
head and our feet is enough to force us into the ground at 9.8m/s/s
Right, it is analogous to a military tank, rolling on two tracks. If the two tracks are going at the same speed, the tank goes straight, but if one track is going slower than the other, the tank veers in the direction of the slower track. Your feet are advancing in time more slowly than your head, so you tend to veer (as you go forward in time) in the direction of your feet, i.e., downward in the direction of slower time. You are like a tank going forward in time. (Actually this would more technically be described in terms of the world lines of your constituent particles, but you get the overall idea.)
2021-05-07 23:40:46 UTC
Right, it is analogous to a military tank, rolling on two tracks.
If the two tracks are going at the same speed, the tank goes straight,
but if one track is going slower than the other, the tank veers
in the direction of the slower track.
Right. This requires MOTION. That's why I was looking for the motion.
I think the main contributor to motion is time and it seems that you concur.

(1) We move through spacetime at the speed of c
(2) Since our speed through space is very slow we mostly move through time
(3) That movement through time happens even when we stand still on the earth

(a) There is a time gradient between our head and our feet
(b) The "track" of time at our heat moves faster than at our feet
(c) This causes us to arc toward the slowest track of time (ie to earth)

It's the "geodesic equation."
I think.
so you tend to veer (as you go forward in time) in the direction
of your feet, i.e., downward in the direction of slower time.
You are like a tank going forward in time.
That's the best explanation of where the MOTION is that I can think of also.

ScienceClic English "A new way to visualize General Relativity"
(Actually this would more technically be described in terms
of the world lines of your constituent particles,
but you get the overall idea.)
Yes. The world lines describe it as shown in that video.
The only difference is they transposed time & space on the x & y axis.
(World lines usually have time on the Y axis but not in that video.

This video explains a few more components of the illusion of gravity:

But Why: "What is Gravity? The Illusion of Force by a Curved Dimension"

This video says the same thing but not as eloquently:

The Science Asylum: "Why Do Things REALLY Fall? (with General Relativity)"
--
Doveryay, no proveryay.
2021-05-08 00:30:52 UTC
Right, it is analogous to a military tank, rolling on two tracks.
If the two tracks are going at the same speed, the tank goes straight,
but if one track is going slower than the other, the tank veers
in the direction of the slower track. Your feet are advancing in
time more slowly than your head, so you tend to veer (as you go
forward in time) in the direction of your feet, i.e., downward in the
direction of slower time. You are like a tank going forward in time.
Right. This requires MOTION.
Be careful not to confuse different meanings of the word "motion". If you define motion as a change in space coordinate for a change in time coordinate, then no, the explanation does not require any initial motion. However, when discussing relativity we talk about a generalized sense of "motion", usually in terms of the proper time tau of an object. The spatial velocity of an object in terms of coordinates x,y,z,t has the components dx/dtau, dy/dtau, and dz/dtau, and what you could call the temporal component of the 4-velocity is dt/dtau. In general, for every object, we have (dt/dtau)^2 - (dx/dtau)^2 - (dy/dtau)^2 - (dz/dtau)^2 = 1. So, in this sense, every object is "moving", but this does not mean that every object has spatial components of "motion".

The tank analogy is an analogy. In that case, the object (tank) originally is moving purely in the x direction (say), and it veers into the y direction. In the case of gravity, the object originally is "moving" purely in the t direction, and it veers into the z direction.
(3) movement through time happens even when we stand still...
Yes, in terms of any coordinate system we always have some non-zero value of dt/dtau, so we are "moving" in that sense, even if dx/dtau, etc., are zero.
(a) There is a time gradient between our head and our feet
More accurate to say there is a time *rate* gradient.
It's the "geodesic equation."
The geodesic equation gives, for any given initial trajectory, the extrapolation that extremizes (usually maximizes) the elapsed proper time.
ScienceClic English "A new way to visualize General Relativity"
This isn't a *new* way to visualize general relativity. It is very old and standard. You can read about it in any good book on relativity.
2021-05-08 14:29:46 UTC
Right. This requires MOTION.
Be careful not to confuse different meanings of the word "motion".
Thank you for your admonishments and cautions as I may well be wrong in how
I'm trying to understand where the "force" of gravity comes from, without
using math in that explanation.

As I see it (and I may very well be wrong of course as I am not a Physics
Major), motion is required for Newton's laws to be upheld (body at rest,
body in motion) on an apple dropped from the tree.

While force can be independent of motion the reason I'm searching for the
motion of that apple dropped from the tree is that a body at rest will stay
at rest (regardless of curved space & rate-of-time dilation).

As Feynman said in that lecture someone recommended I listen to, we must
trust Newton's laws in order to understand more about how nature works.

I'm trusting in the laws which means I have to find the apple's motion.
The ONLY motion I can find in its 4D coordinates is motion through time.

There is no other motion (with respect to the surface of the earth).
Is there?
If you define motion as a change in space coordinate for a change
in time coordinate, then no, the explanation does not require any
initial motion.
That sentence may be true but I do not understand how it can work yet.

Where is the "force" if there isn't any "motion?"

My questions will always revolve around motion. The key question to ask of
you if that sentence is correct is simply "How is a warped space or dilated
time going to make the apple move if there is no motion (and hence no force
on that apple)?"
However, when discussing relativity we talk about a generalized sense
of "motion", usually in terms of the proper time tau of an object.
The spatial velocity of an object in terms of coordinates x,y,z,t
has the components dx/dtau, dy/dtau, and dz/dtau, and what you could
call the temporal component of the 4-velocity is dt/dtau.
That last one is where the motion is, I think (but I'm not sure).
In general, for every object, we have (dt/dtau)^2 - (dx/dtau)^2 -
(dy/dtau)^2 - (dz/dtau)^2 = 1. So, in this sense, every object is
"moving", but this does not mean that every object has spatial
components of "motion".
I agree if I understand "spatial" as being xyz but not t.
The tank analogy is an analogy.
I'm well aware all analogies fail and even that Richard Feynman video said
that it's impossible to find a single analogy that doesn't fail in some way.

I prefer an "explanation" to an analogy but the analogy is an intuitive
model (just like the trampoline & bowling ball is an intuitive model).
In that case, the object (tank) originally is moving purely in the x
direction (say), and it veers into the y direction. In the case of
gravity, the object originally is "moving" purely in the t direction,
and it veers into the z direction.
Yes. That's how I'm beginning to understand the "motion" that allows
the apple to move along the curved space & dilated rate of time gradient.

BELOW MAY BE WRONG BUT IT IS HOW I UNDERSTAND THE "FORCE" OF GRAVITY:

Sans motion (with respect to the earth's surface, in 3D space only)
(1) The apple is at rest at 1 meter above the earth's surface
(2) We snip the stem and _still_ the apple should "stay at rest"
(3) There is no reason for the apple to fall to the ground

With motion (with respect to the earth's surface, in 4D spacetime)
(1) The apple is NOT at rest at 1 meter above the earth's surface
(The apple is moving through time almost at the speed of c)
(2) We snip the stem and the apple _remains_ in motion through time
(And there is a rate gradient in time which is slower toward the ground)
(3) Somehow (as you mentioned) that motion in time curves into space
What was moving purely in the t direction veers into the z direction

Somehow that is the explanation, I think (but I'm not quite sure yet).
(a) There is a gradient in space but no motion in space.
(b) There is a gradient in time and also a high velocity motion in time.
(c) Even though the rate of time gradient is tiny, the velocity is immense

That immense velocity through time times the infinitesimal rate gradient in
time causes the apple to continue in motion through time along the rate
gradient in time which causes the apple to arc downward at 9.8m/s/s in
space.

That last sentence is, I think, how I understand the "force" of gravity.

(Notice I haven't accounted for the curvature of space in that explanation
so it's missing the component of gravity NOT due to motion through time!)
(3) movement through time happens even when we stand still...
Yes, in terms of any coordinate system we always have some non-zero
value of dt/dtau, so we are "moving" in that sense, even if dx/dtau, etc.,
are zero.
I think that's the only motion we have (with respect to the ground).
(a) There is a time gradient between our head and our feet
More accurate to say there is a time *rate* gradient.
OK. I've inserted "rate" into the explanation above where one question I
have is whether the rate gradient of time, in and of itself, is enough to
cause motion of the apple?

I don't think so because I believe in Newton's laws of motion which would
imply even with the rate gradient of time existing, there can be no motion
in space if there is no motion in the apple.

If there was no motion through time, the apple would just sit there in space
even in the presence of the rate gradient of time - wouldn't it?
It's the "geodesic equation."
The geodesic equation gives, for any given initial trajectory,
the extrapolation that extremizes (usually maximizes) the elapsed proper time.
Yes. But there must be motion which is why I focus on the motion.
It's not obvious where the motion is when an apple falls from a tree.
There is no relative motion in terms of space so the motion is elsewhere.
The motion is in time.
I think.
ScienceClic English "A new way to visualize General Relativity"
This isn't a *new* way to visualize general relativity.
It is very old and standard.
What I'm seeking is a "good way" to explain where the required motion is.
With that motion, there is no "force".
A body at rest tends to stay at rest.

So there _must_ be motion (unless Newton's laws are wrong).
I think the motion is in time.

And I think the velocity through time is astronomically tremendous.
Everything I see says we're all moving at the speed of c.
http://youtu.be/k73psdcmzEY
Will Powell "We are all moving at the speed of light"
http://youtu.be/iBTez-nTKes
Sabine Hossenfelder "Do we travel through time at the speed of light?"

ScienceClic "We all move at the Speed of Light"

*In summary, is this a good one sentence explanation or is it still wrong?*

The apple is not moving so much in space (relative to Earth) but it's moving
at a tremendous velocity in time (although so is Earth) and there is a rate
of time gradient the apple is passing through such that the movement through
that rate gradient bends the apple's movement toward the slower time
gradient (which is closer to the center of mass energy of Earth).
--
Doveryay, no proveryay.
Odd Bodkin
2021-05-08 15:15:38 UTC
Right. This requires MOTION.
Be careful not to confuse different meanings of the word "motion".
Thank you for your admonishments and cautions as I may well be wrong in how
I'm trying to understand where the "force" of gravity comes from, without
using math in that explanation.
As I see it (and I may very well be wrong of course as I am not a Physics
Major), motion is required for Newton's laws to be upheld (body at rest,
body in motion) on an apple dropped from the tree.
While force can be independent of motion the reason I'm searching for the
motion of that apple dropped from the tree is that a body at rest will stay
at rest (regardless of curved space & rate-of-time dilation).
This is a statement that is true in an inertial frame only. It is NOT true,
even classically, in an accelerating frame. Examples of rotating frames
serve to illustrate.
As Feynman said in that lecture someone recommended I listen to, we must
trust Newton's laws in order to understand more about how nature works.
I'm trusting in the laws which means I have to find the apple's motion.
The ONLY motion I can find in its 4D coordinates is motion through time.
There is no other motion (with respect to the surface of the earth).
Is there?
If you define motion as a change in space coordinate for a change
in time coordinate, then no, the explanation does not require any
initial motion.
That sentence may be true but I do not understand how it can work yet.
Where is the "force" if there isn't any "motion?"
My questions will always revolve around motion. The key question to ask of
you if that sentence is correct is simply "How is a warped space or dilated
time going to make the apple move if there is no motion (and hence no force
on that apple)?"
Interestingly enough, the apple DOES stay at rest IN AN INERTIAL FRAME. It
does not speed up. It only speeds up in a “non free fall frame” held aloft
over the earth’s surface. Part of the problem is that you’re looking at the
“motion” in this non inertial frame.

To help learn this, look at videos of Coriolis motion of a ball tossed
between two people on a rotating carousel. Ask yourself where the force is.
If you can’t find one, then ask whether Newton’s laws hold here. Then ask
how that applies in GR.
However, when discussing relativity we talk about a generalized sense
of "motion", usually in terms of the proper time tau of an object.
The spatial velocity of an object in terms of coordinates x,y,z,t
has the components dx/dtau, dy/dtau, and dz/dtau, and what you could
call the temporal component of the 4-velocity is dt/dtau.
That last one is where the motion is, I think (but I'm not sure).
In general, for every object, we have (dt/dtau)^2 - (dx/dtau)^2 -
(dy/dtau)^2 - (dz/dtau)^2 = 1. So, in this sense, every object is
"moving", but this does not mean that every object has spatial
components of "motion".
I agree if I understand "spatial" as being xyz but not t.
The tank analogy is an analogy.
I'm well aware all analogies fail and even that Richard Feynman video said
that it's impossible to find a single analogy that doesn't fail in some way.
I prefer an "explanation" to an analogy but the analogy is an intuitive
model (just like the trampoline & bowling ball is an intuitive model).
In that case, the object (tank) originally is moving purely in the x
direction (say), and it veers into the y direction. In the case of
gravity, the object originally is "moving" purely in the t direction,
and it veers into the z direction.
Yes. That's how I'm beginning to understand the "motion" that allows
the apple to move along the curved space & dilated rate of time gradient.
Sans motion (with respect to the earth's surface, in 3D space only)
(1) The apple is at rest at 1 meter above the earth's surface
(2) We snip the stem and _still_ the apple should "stay at rest"
(3) There is no reason for the apple to fall to the ground
With motion (with respect to the earth's surface, in 4D spacetime)
(1) The apple is NOT at rest at 1 meter above the earth's surface
(The apple is moving through time almost at the speed of c)
(2) We snip the stem and the apple _remains_ in motion through time
(And there is a rate gradient in time which is slower toward the ground)
(3) Somehow (as you mentioned) that motion in time curves into space
What was moving purely in the t direction veers into the z direction
Somehow that is the explanation, I think (but I'm not quite sure yet).
(a) There is a gradient in space but no motion in space.
(b) There is a gradient in time and also a high velocity motion in time.
(c) Even though the rate of time gradient is tiny, the velocity is immense
That immense velocity through time times the infinitesimal rate gradient in
time causes the apple to continue in motion through time along the rate
gradient in time which causes the apple to arc downward at 9.8m/s/s in
space.
That last sentence is, I think, how I understand the "force" of gravity.
(Notice I haven't accounted for the curvature of space in that explanation
so it's missing the component of gravity NOT due to motion through time!)
(3) movement through time happens even when we stand still...
Yes, in terms of any coordinate system we always have some non-zero
value of dt/dtau, so we are "moving" in that sense, even if dx/dtau, etc.,
are zero.
I think that's the only motion we have (with respect to the ground).
(a) There is a time gradient between our head and our feet
More accurate to say there is a time *rate* gradient.
OK. I've inserted "rate" into the explanation above where one question I
have is whether the rate gradient of time, in and of itself, is enough to
cause motion of the apple?
I don't think so because I believe in Newton's laws of motion which would
imply even with the rate gradient of time existing, there can be no motion
in space if there is no motion in the apple.
If there was no motion through time, the apple would just sit there in space
even in the presence of the rate gradient of time - wouldn't it?
It's the "geodesic equation."
The geodesic equation gives, for any given initial trajectory,
the extrapolation that extremizes (usually maximizes) the elapsed proper time.
Yes. But there must be motion which is why I focus on the motion.
It's not obvious where the motion is when an apple falls from a tree.
There is no relative motion in terms of space so the motion is elsewhere.
The motion is in time.
I think.
ScienceClic English "A new way to visualize General Relativity"
This isn't a *new* way to visualize general relativity.
It is very old and standard.
What I'm seeking is a "good way" to explain where the required motion is.
With that motion, there is no "force".
A body at rest tends to stay at rest.
So there _must_ be motion (unless Newton's laws are wrong).
I think the motion is in time.
And I think the velocity through time is astronomically tremendous.
Everything I see says we're all moving at the speed of c.
http://youtu.be/k73psdcmzEY
Will Powell "We are all moving at the speed of light"
http://youtu.be/iBTez-nTKes
Sabine Hossenfelder "Do we travel through time at the speed of light?"
http://youtu.be/au0QJYISe4c
ScienceClic "We all move at the Speed of Light"
*In summary, is this a good one sentence explanation or is it still wrong?*
The apple is not moving so much in space (relative to Earth) but it's moving
at a tremendous velocity in time (although so is Earth) and there is a rate
of time gradient the apple is passing through such that the movement through
that rate gradient bends the apple's movement toward the slower time
gradient (which is closer to the center of mass energy of Earth).
--
Odd Bodkin — Maker of fine toys, tools, tables
Paparios
2021-05-08 16:02:50 UTC
Right. This requires MOTION.
Be careful not to confuse different meanings of the word "motion".
Thank you for your admonishments and cautions as I may well be wrong in how
I'm trying to understand where the "force" of gravity comes from, without
using math in that explanation.
Current models do not require the use of a "force". Objects move following geodesic paths through spacetime, where those paths follow the curvature generated by mass. The larger the mass the stronger the path curvature is. It is known that, within the horizon of a black hole, light rays are so curved that they can never leave the volume within the horizon of the black hole. In that case, the geodesic paths are extremely curved.
As I see it (and I may very well be wrong of course as I am not a Physics
Major), motion is required for Newton's laws to be upheld (body at rest,
body in motion) on an apple dropped from the tree.
While force can be independent of motion the reason I'm searching for the
motion of that apple dropped from the tree is that a body at rest will stay
at rest (regardless of curved space & rate-of-time dilation).
Well, when you write a body at rest, you have to consider a system of coordinates (x,y,z,t) relative to which the body is at rest. For instance, I'm seated writing this. I'm at rest relative to my surroundings, meaning my x,y,z coordinates do not change. Why those coordinates do not change? Well my seat sustain my body mass avoiding me to fall into the ground.

The same thinking applies to the apple. The apple is at rest on a branch of the tree, which is the body which sustain the apple and avoids the apple to fall to the ground. Once the apple breaks with the tree, it will follow a geodesic path (free fall) into the ground, where the ground stops the apple movement to continue to the center of Earth. No force is then necessary to apply to the apple to initiate or sustain its fall.
As Feynman said in that lecture someone recommended I listen to, we must
trust Newton's laws in order to understand more about how nature works.
I'm trusting in the laws which means I have to find the apple's motion.
The ONLY motion I can find in its 4D coordinates is motion through time.
There is no other motion (with respect to the surface of the earth).
Is there?
If you define motion as a change in space coordinate for a change
in time coordinate, then no, the explanation does not require any
initial motion.
That sentence may be true but I do not understand how it can work yet.
Where is the "force" if there isn't any "motion?"
My questions will always revolve around motion. The key question to ask of
you if that sentence is correct is simply "How is a warped space or dilated
time going to make the apple move if there is no motion (and hence no force
on that apple)?"
The answer to those questions is quite simple. All bodies are in free fall following geodesic paths. The Sun follows a geodesic path around the center of the Milky Way (at 26000 light years away) taking 240 million years to complete its orbit. The black hole at the center of the galaxy (4.3 million sun mass) provides the curvature defining the Sun path.
However, when discussing relativity we talk about a generalized sense
of "motion", usually in terms of the proper time tau of an object.
The spatial velocity of an object in terms of coordinates x,y,z,t
has the components dx/dtau, dy/dtau, and dz/dtau, and what you could
call the temporal component of the 4-velocity is dt/dtau.
That last one is where the motion is, I think (but I'm not sure).
In general, for every object, we have (dt/dtau)^2 - (dx/dtau)^2 -
(dy/dtau)^2 - (dz/dtau)^2 = 1. So, in this sense, every object is
"moving", but this does not mean that every object has spatial
components of "motion".
I agree if I understand "spatial" as being xyz but not t.
The tank analogy is an analogy.
I'm well aware all analogies fail and even that Richard Feynman video said
that it's impossible to find a single analogy that doesn't fail in some way.
I prefer an "explanation" to an analogy but the analogy is an intuitive
model (just like the trampoline & bowling ball is an intuitive model).
In that case, the object (tank) originally is moving purely in the x
direction (say), and it veers into the y direction. In the case of
gravity, the object originally is "moving" purely in the t direction,
and it veers into the z direction.
Yes. That's how I'm beginning to understand the "motion" that allows
the apple to move along the curved space & dilated rate of time gradient.
Sans motion (with respect to the earth's surface, in 3D space only)
(1) The apple is at rest at 1 meter above the earth's surface
(2) We snip the stem and _still_ the apple should "stay at rest"
(3) There is no reason for the apple to fall to the ground
The apple is inside a gravity well, generated by the great mass of Earth (5.97237×10^24 kg). As the apple is free from the stem (which avoids the apple to follow its geodesic path) the apple will resume its free fall. There is no force generating that motion. If Earth would not be there near the apple tree, the apple would still follow a geodesic path around the bigger mass in its surroundings.
With motion (with respect to the earth's surface, in 4D spacetime)
(1) The apple is NOT at rest at 1 meter above the earth's surface
(The apple is moving through time almost at the speed of c)
No body "moves through time almost at the speed of c". I don't know from where you got this so wrong.
(2) We snip the stem and the apple _remains_ in motion through time
(And there is a rate gradient in time which is slower toward the ground)
(3) Somehow (as you mentioned) that motion in time curves into space
What was moving purely in the t direction veers into the z direction
Motion is always through spacetime: the apple coordinates x,y,z,t are all changing. If the apple is at 1 meter, its movement will produce changes in the z and t coordinates.
Somehow that is the explanation, I think (but I'm not quite sure yet).
(a) There is a gradient in space but no motion in space.
(b) There is a gradient in time and also a high velocity motion in time.
(c) Even though the rate of time gradient is tiny, the velocity is immense
None of (a), (b) and (c) makes any sense. Earth mass produce a spacetime gravity well (which in 2D, is sometimes represented by the ruber surface with a big iron ball). If the iron ball is not present the ruber sheet will be flat and a small ball will just follow a straight path. If the big iron ball is curving the ruber surface, the small ball will follow a curved path arounf the gravity well generated by the big iron ball.
Secondly, there is no such a "high velocity motion in time". All bodies speed within our galaxy follow geodesic paths around the black hole at speed way below the speed of light (the Sun moves at 220 km/s in its orbit). Earth moves at 30 km/s around the Sun.
That immense velocity through time times the infinitesimal rate gradient in
time causes the apple to continue in motion through time along the rate
gradient in time which causes the apple to arc downward at 9.8m/s/s in
space.
That last sentence is, I think, how I understand the "force" of gravity.
You have some misunderstanding of what speed is (v=dx/dt). Your "immense velocity through time" does not make any sense.
(Notice I haven't accounted for the curvature of space in that explanation
so it's missing the component of gravity NOT due to motion through time!)
(3) movement through time happens even when we stand still...
Yes, in terms of any coordinate system we always have some non-zero
value of dt/dtau, so we are "moving" in that sense, even if dx/dtau, etc.,
are zero.
I think that's the only motion we have (with respect to the ground).
(a) There is a time gradient between our head and our feet
More accurate to say there is a time *rate* gradient.
OK. I've inserted "rate" into the explanation above where one question I
have is whether the rate gradient of time, in and of itself, is enough to
cause motion of the apple?
I don't think so because I believe in Newton's laws of motion which would
imply even with the rate gradient of time existing, there can be no motion
in space if there is no motion in the apple.
If there was no motion through time, the apple would just sit there in space
even in the presence of the rate gradient of time - wouldn't it?
It's the "geodesic equation."
The geodesic equation gives, for any given initial trajectory,
the extrapolation that extremizes (usually maximizes) the elapsed proper time.
Yes. But there must be motion which is why I focus on the motion.
It's not obvious where the motion is when an apple falls from a tree.
There is no relative motion in terms of space so the motion is elsewhere.
The motion is in time.
I think.
ScienceClic English "A new way to visualize General Relativity"
This isn't a *new* way to visualize general relativity.
It is very old and standard.
What I'm seeking is a "good way" to explain where the required motion is.
With that motion, there is no "force".
A body at rest tends to stay at rest.
So there _must_ be motion (unless Newton's laws are wrong).
I think the motion is in time.
And I think the velocity through time is astronomically tremendous.
Everything I see says we're all moving at the speed of c.
http://youtu.be/k73psdcmzEY
Well, that video is completely misleading. It deals with SR and the Lorentz Tranformations. The movement through time at speed c is completely useless as bodies move through space at speeds given by v=dx/dt <<c
Will Powell "We are all moving at the speed of light"
http://youtu.be/iBTez-nTKes
Sabine Hossenfelder "Do we travel through time at the speed of light?"
Same misleading stuff. SR deals with inertial movements (those are movements at a constant speed v=dx/dt). There is a quantity which is called the INTERVAL, defined by the equation ds^2=dx^2+dy^2+dz^2-c^2dt^2. The interval is invariant with respect to a change of coordinates (from (x,y,z,t) to (x',y',z',t').
http://youtu.be/au0QJYISe4c
ScienceClic "We all move at the Speed of Light"
More nonsensical. You should follow some good courses, which are available in the internet. I recommend you to follow Professor Susskind courses, particularly in this subject, the Special Relativity course available at

*In summary, is this a good one sentence explanation or is it still wrong?*
The apple is not moving so much in space (relative to Earth) but it's moving
at a tremendous velocity in time (although so is Earth) and there is a rate
of time gradient the apple is passing through such that the movement through
that rate gradient bends the apple's movement toward the slower time
gradient (which is closer to the center of mass energy of Earth).
--
Doveryay, no proveryay.
Maciej Wozniak
2021-05-08 16:21:29 UTC
Post by Paparios
on that apple)?"
The answer to those questions is quite simple. All bodies are in free fall following geodesic paths. The Sun follows a geodesic path around the center of the Milky Way
And the Moon follows a geodesic path around Earth; it's not any
ellipse at all!
See, Ilya, Paparios is really, really stupid, even considering the standards
of physics.
Python
2021-05-08 16:49:20 UTC
Post by Maciej Wozniak
Post by Paparios
on that apple)?"
The answer to those questions is quite simple. All bodies are in free fall following geodesic paths. The Sun follows a geodesic path around the center of the Milky Way
And the Moon follows a geodesic path around Earth; it's not any
ellipse at all!
The trajectory expressed a foor-coordinates (x,y,z,t) manifold is a
geodesic. The ellipse is the projection of this manifold in 3D space.

If you were computer literate you may start from:
https://en.wikipedia.org/wiki/Two-body_problem_in_general_relativity

to write a program displaying this:

Unfortunately you can't, so you will pretend that such calculations have
been made by members of a plot of some kind...
Maciej Wozniak
2021-05-08 18:08:59 UTC
Post by Python
Post by Paparios
on that apple)?"
The answer to those questions is quite simple. All bodies are in free fall following geodesic paths. The Sun follows a geodesic path around the center of the Milky Way
And the Moon follows a geodesic path around Earth; it's not any
ellipse at all!
The trajectory expressed a foor-coordinates (x,y,z,t) manifold is a
geodesic.
1)your moronic Shit doesn't provide any x,y,z,t
2)spacetime trajectory of Sun isn't "around the center
of Milky Way". Poor Paparios is talking about spatial
trajectory. Not surprising from a geocentric idiot
like him or you.

And, BTW, how are these geostationary satellites,
moving wrt each other or not?
2021-05-08 16:21:48 UTC
While force can be independent of motion the reason I'm searching for the
motion of that apple dropped from the tree is that a body at rest will stay
at rest (regardless of curved space & rate-of-time dilation).
But this has already been explained to you. Again, you are mixing up different meanings of the word "motion". Newton used the word "motion" to refer only to spatial motion, but the word "motion" can also be used (loosely) to refer to the advance in the time direction. Remember?
I'm trusting in Newton's laws which means I have to find the apple's motion.
According to Newton's laws, the apple hanging on the tree is subject to two forces, one downward exerted by gravity and one upward exerted by the branch, and the net force is zero, so the apple does not accelerate. According to general relativity, the gradient in the rate of time causes the apple to tend to veer on its trajectory through time into the space (downward) direction, but it is prevented from veering downward by the electromagnetic force applied by the branch.
The ONLY motion I can find in its 4D coordinates is motion through time.
Again, you are mixing up the meanings of the word "motion", and yes, one can say that every object's world line has a trajectory through space-time, and this trajectory can veer off due to curvature resulting from the presence of a nearby gravitating body. Of course, this is a reciprocal interaction, since the apple also causes the earth to (very slightly) veer upward.
There is no other motion (with respect to the surface of the earth). Is there?
Nope. The only "motions" are the ones explained above.
If you define motion as a change in space coordinate for a change
in time coordinate, then no, the explanation does not require any
initial motion.
That sentence may be true but I do not understand how it can work yet.
You don't? What part of it don't you understand?
Where is the "force" if there isn't any "motion?" "How is a warped space or dilated
time going to make the apple move if there is no motion (and hence no force on
that apple)?"
Again, the world line of every object has a trajectory in spacetime, even if the object's space coordinates are initially not changing, and this world line will be a geodesic (if no electromagnetic forces are applied to the object), meaning it follows the path that maximizes the invariant proper time. The curvature of spacetime (corresponding to the gradient in the rate of proper time with elevation) implies that the geodesic path veers into the downard spatial direction.
One question I have is whether the rate gradient of time, in and of itself, is enough to
cause motion of the apple? I don't think so because I believe in Newton's laws of
motion which would imply even with the rate gradient of time existing, there can be
no motion in space if there is no motion in the apple.
That sentence doesn't make sense. In both Newtonian physics and general relativity the apple is not moving spatially relative to the earth until the stem breaks and the apple begins to fall. After the stem breaks and the apple begins to fall, it begins to have spatial motion relative to the earth. This is all true, both in Newtonian physics and in general relativity, so your statements make no sense. You still seem to be confusing spatial motion with advancing in time.
If there was no motion through time, the apple would just sit there in space
even in the presence of the rate gradient of time - wouldn't it?
Again, you are just confusing yourself by using the word "motion" in two different ways. The world line of every object has a trajectory through spacetime, always. The world line of an object tends to follow a geodesic through spacetime (if not subjected to non-gravitational forces).
Yes. But there must be motion which is why I focus on the motion.
I think you are succumbing to an unhealthy mania, refusing to understand that the word "motion" has different meanings. The way to understand this is to recognize that the world line of every object has a trajectory through spacetime, always. For any increment of its proper time dtau, it has coordinate increments dt, dx, dy, dz, and the magnitude of the 4-velocity is always 1.
So there _must_ be motion (unless Newton's laws are wrong).
I think the motion is in time.
Well, Newton's laws *are* wrong, but that's not related to the different meanings of the word "motion".
*In summary, is this a good one sentence explanation or is it still wrong?*
The apple is not moving so much in space (relative to Earth) but it's moving
at a tremendous velocity in time (although so is Earth) and there is a rate
of time gradient the apple is passing through such that the movement through
that rate gradient bends the apple's movement toward the slower time
gradient (which is closer to the center of mass energy of Earth).
That's an approximately correct informal way of describing things, omitting the spatial curvature of course. It's also true that the Earth is pulled (very slightly) toward the apple, because the law of equal action and reaction still applies.
2021-05-08 23:38:26 UTC
According to Newton's laws, the apple hanging on the tree
is subject to two forces, one downward exerted by gravity
and one upward exerted by the branch, and the net force
is zero, so the apple does not accelerate.
Yes. We agree 100% I think. On everything you said above.
Newton did not require a pre-existing motion (aka a "trajectory").

Can you provide insight into those further clarifications below perhaps?
According to general relativity, the gradient in the rate of
time causes the apple to tend to veer on its trajectory through
time into the space (downward) direction, but it is prevented
from veering downward by the electromagnetic force applied by the branch.
We agree.

The first few sentences of this video say the same thing, essentially:

PBS Space Time "Does Time Cause Gravity?"
When he says:
"You are currently hurtling through time at the speed of light.
But be careful. If even a tiny bit of your breakneck temporal velocity
leaks into one of the dimensions of space... you will rapidly accelerate
to your doom. You think I'm kidding? I just described the true source of
gravity. Don't look down."

Thank you for confirming that the pre-existing motion (aka trajectory)
through time is indeed extant. If we accept that main premise then we have
most of the puzzle solved - with a couple (hopefully?) minor clarifications.

Here's the first of the (hopefully?) minor clarifications:
(1) Isn't Earth also following that same "trajectory through time"
such that there is no relative motion between the apple & Earth?

I suspect the answer is there is still a time gradient between the apple and
Earth even if it's true the Earth & the Apple are moving through time at the
same speed of nearly c. This time gradient was shown prior by tank tracks;
but it is shown in that video above with two boats moving in a stream.
http://youtu.be/UKxQTvqcpSg

However perhaps more importantly, I suspect the energy mass of Earth is so
much greater than that of the Apple that Earth may be moving through time
slower than the apple such that there _is_ a difference in velocity between
the apple and Earth through time.

Physics Videos by Eugene Khutoryansky
"Gravitational Time Dilation causes gravitational attraction"
"Even if the Earth is not moving through space, it would still be moving
through time. The path that the Earth takes through space and time is
what we would call its world line."

And then later in that same video they add the apple to the equation.
http://youtu.be/gcvq1DAM-DE
"Different parts of the object will want to move through time at
different rates. As the object continues traveling through space-time
in a straight line, the object starts moving towards the Earth. Hence
we have the appearance of a gravitational attraction."

But notice the earth isn't moving through time at the same velocity
as the apple (in that case a yellow barbell) is moving through time.

Question: Is the Earth moving through time slower than is the apple?
Question: Is there no (relative) movement in space (is it just time)?
--
Doveryay, no proveryay.
2021-05-09 00:29:11 UTC
(1) Isn't Earth also following that same "trajectory through time"
such that there is no relative motion between the apple & Earth?
Initially, while the branch is holding the apple at a constant distance from the earth, the spatial distance between apple and earth is not changing, and their world lines are parallel in terms of (say) the global stationary coordinates.
I suspect the energy mass of Earth is so much greater than that of the Apple
that Earth may be moving through time slower than the apple...
The rate of proper time (tau) for a given coordinate time (t) for a particle of the apple or the earth at any given event depends on the trajectory and the gravitational potential at that event. The gravitational potential is different at the earth's surface than it is in the interior of the earth, so a clock at the center of the earth would run slower than a clock on the surface in terms of a global stationary system of coordinates (meaning the metric components are essentially independent of the time coordinate).

In general, since the earth is so much more massive than an apple, we can treat the gravitational field of the earth as essentially spherically symmetrical, and regard the earth as spatially at rest in terms of these coordinates, and the apple is initially at rest (spatially) in terms of these coordinates too, when held aloft by the branch.
Question: Is the Earth moving through time slower than is the apple?
You need to quantify what you mean by "speed through time". You probably are thinking of a global stationary system of coordinates t,x,y,z as described above, in terms of which the metric coefficients are independent of t, and each particle's rate of proper time is dtau/dt, and this is different for each particle of the apple and for each particle of the earth, depending on the gravitational potential at each location. For example, the particles of the earth near the surface would tend to veer downward toward the center, but they are being held in place by electromagnetic forces, just as the apple is by the branch.
Question: Is there no (relative) movement in space (is it just time)?
While the branch is holding the apple at a constant elevation, the apple is at a constant elevation. In terms of the global stationary coordinates, there is no relative movement in space between apple and earth in this condition... by definition.
2021-05-10 11:21:22 UTC
You need to quantify what you mean by "speed through time".
You probably are thinking of a global stationary system of
coordinates t,x,y,z as described above, in terms of which the
metric coefficients are independent of t, and each particle's
rate of proper time is dtau/dt, and this is different for each
particle of the apple and for each particle of the earth,
depending on the gravitational potential at each location.
Thank you for your patient and accurate corrections!

I think _that_ explanation goes a long way toward solving the dilemma,
coupled with what Derek Muller said in this video with this equation.
http://youtu.be/XRr1kaXKBsU
"The second derivative of your position with respect to time
is equal to your acceleration (if you were in flat spacetime);
but you're not in flat spacetime. [So you have to subtract from
that spatial position a term which is related to the curvature
of spacetime times your velocity through time, squared.]"

While I really didn't want to delve into equations in order to explain the
true source of gravity - what I think may be the case is this equation may
be the key in explaining why our velocity through time matters far more than
the curvature of space does to the feeling we call gravity.

While I'm not sure of the absolute magnitude of the term that Derek says is
"related to the curvature of space" for the apple - the velocity through
time of that apple is immense - and - it's squared!
--
Doveryay, no proveryay.
Maciej Wozniak
2021-05-10 11:51:51 UTC
You need to quantify what you mean by "speed through time".
You probably are thinking of a global stationary system of
coordinates t,x,y,z as described above, in terms of which the
metric coefficients are independent of t, and each particle's
rate of proper time is dtau/dt, and this is different for each
particle of the apple and for each particle of the earth,
depending on the gravitational potential at each location.
Thank you for your patient and accurate corrections!
I think _that_ explanation goes a long way toward solving the dilemma,
coupled with what Derek Muller said in this video with this equation.
http://youtu.be/XRr1kaXKBsU
"The second derivative of your position with respect to time
is equal to your acceleration (if you were in flat spacetime);
but you're not in flat spacetime. [So you have to subtract from
that spatial position a term which is related to the curvature
of spacetime times your velocity through time, squared.]"
While I really didn't want to delve into equations in order to explain the
true source of gravity - what I think may be the case is this equation may
be the key in explaining why our velocity through time matters far more than
the curvature of space does to the feeling we call gravity.
While I'm not sure of the absolute magnitude of the term that Derek says is
"related to the curvature of space" for the apple - the velocity through
time of that apple is immense - and - it's squared!
Well, your Derek is a mumbling idiot, and with treating him
seriously you'll become another, for sure.
Tom Roberts
2021-05-10 16:10:43 UTC
You need to quantify what you mean by "speed through time".
Yes. Indeed that is a PUN on "speed".

Let me caution you both that "speed through time" makes no sense, as
speed is a ratio of (distance moved)/(time it took to move), with
both measured in a specified coordinate system (usually a locally-
inertial frame).

There are lots of crackpot webpages and newsgroup posts attempting to
discuss this, without recognizing the pun -- all are nonsense.

That said, remember that in SR and GR a timelike object's worldline has
a tangent 4-vector with norm c. This fact may be where people with
insufficient understanding of physics got that notion. But the tangent
4-vector and its norm are both invariant under any change of
coordinates, and do not behave like "speed" at all.
While I really didn't want to delve into equations in order to
explain the true source of gravity - what I think may be the case is
this equation may be the key in explaining why our velocity through
time matters far more than the curvature of space does to the feeling
we call gravity.
This is garbled and based on an oxymoron, but there is a small,
coordinate-dependent, approximate kernel of truth buried inside.

In GR, gravity is merely an aspect of the spacetime geometry, and is not
a force. In the Newtonian approximation to GR, using coordinates fixed
to the earth surface to describe the behavior of test particles nearby,
the metric components are those of Minkowski spacetime with the time
component getting an additional term proportional to the Newtonian
gravitational potential -- the effects of spatial curvature have been
approximated away, and in these coordinates the (approximate) spacetime
curvature is due only to the time coordinate.

But that is not at all "velocity through time", which remains an
oxymoron. And remember it is AN APPROXIMATION and does not hold for GR
in general, only in the Newtonian limit and appropriate "Newtonian-like"
coordinates.

In GR, the analog to Newton's gravitational force is a certain set of
the components of the geometrical connection. The connection is
explicitly coordinate dependent -- that makes "gravitational force"
directly related to the fictitious "centrifugal and Coriolis forces"
(which are merely different components of the connection).

*** Remember, please, that no physical phenomena can possibly
*** depend on coordinates, because coordinates are ARBITRARY
*** human constructs used only for description (modeling).

Tom Roberts
Maciej Wozniak
2021-05-10 19:31:05 UTC
Post by Tom Roberts
In GR, gravity is merely an aspect of the spacetime geometry
And in the marxism-leninism, communism is the best.
2021-05-10 20:45:16 UTC
Post by Tom Roberts
You need to quantify what you mean by "speed through time".
Yes. Indeed that is a PUN on "speed".
Let me caution you both that "speed through time" makes no sense
Thank you for that cautionary warning about "speed through time" sense.

Your advice is well taken because our immense "speed through time" is
something that "blows your mind" when I first learned it, as spoken in the
video below by Sabine Hossenfelder (who teaches the public about physics).

She says "*It's right we do travel through time at the speed of light*"
http://youtu.be/iBTez-nTKes

She then goes on to clarify what she calls the "fine print" of the
incongruous units between speed & time by saying "At first it does not seem
to make much sense to talk about the speed in time. A speed is distance per
time so if you travel in time a speed would be time per time and you would
end up with the arguably correct but rather lame insight that we travel
through time at one second per second."

Sabine then expounds further by clarifying "This however is not where the
statement that we travel through time at the speed of light comes from. It
comes from good old Albert Einstein."

She then covers a few basics such as "Einstein based his theory of special
relativity on an idea from Hermann Minkowski which is that space & time
belong together to a common entity called spacetime..."

And then she normalizes the units by saying "But you cannot add space &
time... space and time have different units... so if you want to add them
you have to put a constant in front of one of them... it does not matter
where you put that constant but by convention we put it in front of the time
coordinate."

Here is where she brings up the speed of light when she reveals "The
constant you have to put here so that we can add these directions must have
units of space over time so that's the speed... let's call it c... you all
know that c is the speed of light but (and this is really important - you do
not need to know this if you formulate special relativity). You can put a
dummy parameter there that could be any speed and you will later find that
it is the speed of massless particles."

Futher Sabine analyzes the situation by saying "Now of course there is a
difference between time and space so that can't be all there is to
spacetime. You can move around in space either which way but you cannot move
around in time as you please."

Then Sabine spells it out by differentiating time & distance by interpreting
"So what makes time different from space in Einsteins spacetime is the way
you add them. If you want to calculate a distance in space you use Euclid's
formula. But in spacetime this works differently. A distance between two
points in spacetime is usually called delta s. A distance in spacetime is
now the square root of minus the squares of the distances in each of the
dimensions of space plus [c squared times the delta difference in time
squared]."

She then points out the math of what it means to have a delta s in spacetime
of zero which she works through to explain that we all travel at the speed
of light through time when she finally concludes at time point 355 seconds
http://youtu.be/iBTez-nTKes

"And there you have it. Relative to yourself you do not move through space
so the three space velocities are zero. You then only move through the time
like direction and in this direction you move with the speed of light."

Just before her final conclusion of...
"*So we indeed all travel through time with the speed of light*".
--
Doveryay, no proveryay.
Paparios
2021-05-11 00:49:18 UTC
Post by Tom Roberts
You need to quantify what you mean by "speed through time".
Yes. Indeed that is a PUN on "speed".
Let me caution you both that "speed through time" makes no sense
Thank you for that cautionary warning about "speed through time" sense.
Your advice is well taken because our immense "speed through time" is
something that "blows your mind" when I first learned it, as spoken in the
video below by Sabine Hossenfelder (who teaches the public about physics).
She says "*It's right we do travel through time at the speed of light*"
http://youtu.be/iBTez-nTKes
She then goes on to clarify what she calls the "fine print" of the
incongruous units between speed & time by saying "At first it does not seem
to make much sense to talk about the speed in time. A speed is distance per
time so if you travel in time a speed would be time per time and you would
end up with the arguably correct but rather lame insight that we travel
through time at one second per second."
Sabine then expounds further by clarifying "This however is not where the
statement that we travel through time at the speed of light comes from. It
comes from good old Albert Einstein."
She then covers a few basics such as "Einstein based his theory of special
relativity on an idea from Hermann Minkowski which is that space & time
belong together to a common entity called spacetime..."
And then she normalizes the units by saying "But you cannot add space &
time... space and time have different units... so if you want to add them
you have to put a constant in front of one of them... it does not matter
where you put that constant but by convention we put it in front of the time
coordinate."
Here is where she brings up the speed of light when she reveals "The
constant you have to put here so that we can add these directions must have
units of space over time so that's the speed... let's call it c... you all
know that c is the speed of light but (and this is really important - you do
not need to know this if you formulate special relativity). You can put a
dummy parameter there that could be any speed and you will later find that
it is the speed of massless particles."
Futher Sabine analyzes the situation by saying "Now of course there is a
difference between time and space so that can't be all there is to
spacetime. You can move around in space either which way but you cannot move
around in time as you please."
Then Sabine spells it out by differentiating time & distance by interpreting
"So what makes time different from space in Einsteins spacetime is the way
you add them. If you want to calculate a distance in space you use Euclid's
formula. But in spacetime this works differently. A distance between two
points in spacetime is usually called delta s. A distance in spacetime is
now the square root of minus the squares of the distances in each of the
dimensions of space plus [c squared times the delta difference in time
squared]."
She then points out the math of what it means to have a delta s in spacetime
of zero which she works through to explain that we all travel at the speed
of light through time when she finally concludes at time point 355 seconds
http://youtu.be/iBTez-nTKes
"And there you have it. Relative to yourself you do not move through space
so the three space velocities are zero. You then only move through the time
like direction and in this direction you move with the speed of light."
That movement is not from a body (less a falling apple) but it is a movement of a light ray.
You are not realizing that when you write "Relative to yourself you do not move through space", you are saying that dx=dy=dz=0.
In four-dimensional spacetime, the analog to "distance" is the interval. The spacetime interval is the quantity s^2 and not s itself.
The general equation for the interval is ds^2=c^2dt^2-dx^2-dy^2-dz^2. Note we are mixing space and time coordinates

You can not simply set dx=dy=dz=0 and then divide by dt^2 and then postulate that ds^2/dt^2 = c^2 is a body speed. It is simply the speed of a light ray

If K is a system of coordinates (x,y,z,t), where two events are identified by the coordinates (x1,y1,z1,t1) and (x2,y2,z2,t2), then the interval between those two events is given by:

Δs^2 = c^2(t2-t1) - (x2-x1)^2 - (y2-y1)^2 - (z2-z1)^2

Those two same events can be observed from another system k of coordinates (x',y',z',t'). and the interval will be given by:

Δs^2 = c^2(t'2-t'1) - (x'2-x'1)^2 - (y'2-y'1)^2 - (z'2-z'1)^2

Does there exist a system K' where those two events occur at the same point in space? The answer is yes. For that to occur we must have:

(x'2-x'1)^2 + (y'2-y'1)^2 + (z'2-z'1)^2 = 0 and therefore, through the interval we must have:

Δs^2 = c^2(t2-t1) - (x2-x1)^2 - (y2-y1)^2 - (z2-z1)^2 = c^2(t'2-t'1) > 0

The interval is a real and positive number and it is called a "timelike" interval.

Does there exist a system k where the two events occur at the same time?. The answer is yes. For that to occur we must have (t2' -t1') = 0:

Δs^2 = c^2(t2-t1) - (x2-x1)^2 - (y2-y1)^2 - (z2-z1)^2 = - (x'2-x'1)^2 - (y'2-y'1)^2 - (z'2-z'1)^2 < 0

For this case the interval is an imaginary number and the interval is "spacelike".

If Δs^2 = 0, then the interval is "lightlike".
Just before her final conclusion of...
"*So we indeed all travel through time with the speed of light*".
--
Doveryay, no proveryay.
2021-05-12 05:56:53 UTC
Post by Paparios
That movement is not from a body (less a falling apple)
but it is a movement of a light ray.
Nobody who knows deeply about physics would have said what you just said.

While the term "the speed of light" (or the constant, "c") happens to be the
velocity through the vaccum of space a massless particle travels at, that
speed has nothing whatsoever, per se, to do with "light" (or with what you
called "a light ray").

PBS Space Time "The Speed of Light is NOT About Light"
"There must be a cosmic speed limit (of causality)... Why?
This absolute speed limit... let's call it c... is the one parameter
defining the Lorentz Transformation. Through this parameter the Lorenz
Transformation predicts the cosmic speed limit c."

Light is merely a narrow portion of the electromagnetic spectrum which our
primate eyeballs have evolved to recognize, and as such is not what "c" is.

The speed "c" is a fundamental invariant physical constant in our universe.
https://cxp.cengage.com/contentservice/assets/owms01h/references/chemtables/gen_chem/ConstantsTable.html

Hence I must respectfully discount what you claim about motion through time.

As far as I can tell (and I may very well be wrong), we move at that same
fundamental speed of causality "c" that
http://youtu.be/k73psdcmzEY
Will Powell "We are all moving at the speed of light"
"Nothing moves faster than light and nothing moves slower than light.
We are all moving at light speed [through spacetime]"

More precisely... "Einstein's special relativity forces us to think of
time as a dimension we travel through - just like we travel through the
three dimensions of space. The unit of measurement of this space-time is
called the 'proper distance' and it supersedes both meters and seconds.

Because meters and seconds are unified by the proper distance, speed loses
its meaning. We are only in control of the direction we travel through
space-time. Fast moving objects appear to be ageing slowly - they are
moving almost entirely through space and very little through time.

Slow moving objects age quickly - they are moving almost entirely
through time and very little through space. Transforming between frames of
reference moving at different speeds is very much like a rotation.
In fact it IS a rotation - a hyperbolic rotation. In the context of
special relativity however, it is called a Lorentz transformation."

The end result is that we're moving through spacetime at breakneck speeds
which is, I think, where the feeling of gravity comes from because while the
difference in rate of time is puny between our head and our feet, our speed
is immense such that a tiny difference can still result in an acceleration
of 9.8m/s/s toward the center of mass energy of Earth.
--
Doveryay, no proveryay.
Maciej Wozniak
2021-05-12 07:15:52 UTC
Post by Paparios
That movement is not from a body (less a falling apple)
but it is a movement of a light ray.
Nobody who knows deeply about physics would have said what you just said.
While the term "the speed of light" (or the constant, "c") happens to be the
velocity through the vaccum of space a massless particle travels at, that
speed has nothing whatsoever, per se, to do with "light" (or with what you
called "a light ray").
http://youtu.be/msVuCEs8Ydo
PBS Space Time "The Speed of Light is NOT About Light"
"There must be a cosmic speed limit (of causality)... Why?
This absolute speed limit... let's call it c... is the one parameter
defining the Lorentz Transformation. Through this parameter the Lorenz
Transformation predicts the cosmic speed limit c."
Light is merely a narrow portion of the electromagnetic spectrum which our
primate eyeballs have evolved to recognize, and as such is not what "c" is.
:) Soon you'l become one of us here, no matter how firmly you'll
deny it.
Paparios
2021-05-12 13:56:17 UTC
Post by Paparios
That movement is not from a body (less a falling apple)
but it is a movement of a light ray.
Nobody who knows deeply about physics would have said what you just said.
In optics a ray is an idealized model of light, obtained by choosing a line that is perpendicular to the wavefronts of the actual light, and that points in the direction of energy flow.
While the term "the speed of light" (or the constant, "c") happens to be the
velocity through the vaccum of space a massless particle travels at, that
speed has nothing whatsoever, per se, to do with "light" (or with what you
called "a light ray").
It sure does. The speed of light (in vacuum) is the maximun speed of propagation of interactions in Nature. Though this speed is most commonly associated with light, it is also the speed at which all massless particles and field perturbations travel in vacuum, including electromagnetic radiation (of which light is a small range in the frequency spectrum) and gravitational waves.
Currently that speed limit is 299792458 metres per second.

No object with mass (like a falling apple) can reach that speed.
http://youtu.be/msVuCEs8Ydo
PBS Space Time "The Speed of Light is NOT About Light"
"There must be a cosmic speed limit (of causality)... Why?
This absolute speed limit... let's call it c... is the one parameter
defining the Lorentz Transformation. Through this parameter the Lorenz
Transformation predicts the cosmic speed limit c."
Light is merely a narrow portion of the electromagnetic spectrum which our
primate eyeballs have evolved to recognize, and as such is not what "c" is.
If you think that light refers to only what our eyes see you are completely confused about what c is.
The speed "c" is a fundamental invariant physical constant in our universe.
https://cxp.cengage.com/contentservice/assets/owms01h/references/chemtables/gen_chem/ConstantsTable.html
Hence I must respectfully discount what you claim about motion through time.
As far as I can tell (and I may very well be wrong), we move at that same
fundamental speed of causality "c" that
http://youtu.be/k73psdcmzEY
Will Powell "We are all moving at the speed of light"
"Nothing moves faster than light and nothing moves slower than light.
We are all moving at light speed [through spacetime]"
Which is a complete bogus claim. Movement requires a change in time t of the space coordinates (x,y,z) of a given object. If I'm seated typing in my computer, my x,y,z coordinates do not change so I'm not moving (less at speed c). Your videos misrepresent what ds^2 really is:
In four-dimensional spacetime, the analog to distance is the interval. Although time comes in as a fourth dimension, it is treated differently than the spatial dimensions. Minkowski space hence differs in important respects from four-dimensional Euclidean space. The fundamental reason for merging space and time into spacetime is that space and time are separately not invariant, which is to say that, under the proper conditions, different observers will disagree on the length of time between two events (because of time dilation) or the distance between the two events (because of length contraction). But special relativity provides a new invariant, called the spacetime interval, which combines distances in space and in time. All observers who measure the time and distance between any two events will end up computing the same spacetime interval.

Suppose an observer measures two events as being separated in time by Δt and a spatial distance Δx. Then the spacetime interval Δs^2 between the two events that are separated by a distance Δx in space and by Δct=cΔt in the ct-coordinate is:
Δs^2 = Δ(ct)^2 - Δx^2
The constant c, the speed of light, converts time units (like seconds) into space units (like meters). Seconds times meters/second = meters.

<SNIP> more confusion about invariant and coordinates
Maciej Wozniak
2021-05-12 14:53:58 UTC
Post by Paparios
Post by Paparios
That movement is not from a body (less a falling apple)
but it is a movement of a light ray.
Nobody who knows deeply about physics would have said what you just said.
In optics a ray is an idealized model of light, obtained by choosing a line that is perpendicular to the wavefronts of the actual light, and that points in the direction of energy flow.
While the term "the speed of light" (or the constant, "c") happens to be the
velocity through the vaccum of space a massless particle travels at, that
speed has nothing whatsoever, per se, to do with "light" (or with what you
called "a light ray").
It sure does. The speed of light (in vacuum) is the maximun speed of propagation of interactions in Nature. Though this speed is most commonly associated with light, it is also the speed at which all massless particles and field perturbations travel in vacuum, including electromagnetic radiation (of which light is a small range in the frequency spectrum) and gravitational waves.
Currently that speed limit is 299792458 metres per second.
No object with mass (like a falling apple) can reach that speed.
http://youtu.be/msVuCEs8Ydo
PBS Space Time "The Speed of Light is NOT About Light"
"There must be a cosmic speed limit (of causality)... Why?
This absolute speed limit... let's call it c... is the one parameter
defining the Lorentz Transformation. Through this parameter the Lorenz
Transformation predicts the cosmic speed limit c."
Light is merely a narrow portion of the electromagnetic spectrum which our
primate eyeballs have evolved to recognize, and as such is not what "c" is.
If you think that light refers to only what our eyes see you are completely confused about what c is.
The speed "c" is a fundamental invariant physical constant in our universe.
https://cxp.cengage.com/contentservice/assets/owms01h/references/chemtables/gen_chem/ConstantsTable.html
Hence I must respectfully discount what you claim about motion through time.
As far as I can tell (and I may very well be wrong), we move at that same
fundamental speed of causality "c" that
http://youtu.be/k73psdcmzEY
Will Powell "We are all moving at the speed of light"
"Nothing moves faster than light and nothing moves slower than light.
We are all moving at light speed [through spacetime]"
In four-dimensional spacetime, the analog to distance is the interval. Although time comes in as a fourth dimension, it is treated differently than the spatial dimensions. Minkowski space hence differs in important respects from four-dimensional Euclidean space. The fundamental reason for merging space and time into spacetime is that space and time are separately not invariant, which is to say that, under the proper conditions, different observers will disagree on the length of time between two events
Paparios, poor idiot, if you had some contact with any reality
you would know that different observers will usually disagree
on just anything.
Post by Paparios
(because of time dilation) or the distance between the two events (because of length contraction). But special relativity provides a new invariant, called the spacetime interval, which combines distances in space and in time. All observers who measure the time and distance between any two events will end up computing the same spacetime interval.
:)
Sure, every observer will compute it geocentrically, just like you.
2021-05-12 16:29:26 UTC
Post by Paparios
http://youtu.be/k73psdcmzEY
Will Powell "We are all moving at the speed of light"
"Nothing moves faster than light and nothing moves slower than light.
We are all moving at light speed [through spacetime]"
Which is a complete bogus claim. Movement requires a change in time t
of the space coordinates (x,y,z) of a given object.
Thanks for clarifying as a "movement" through the 4D spacetime is the most
critical basic piece of the puzzle (as I've said from the very beginning).

To put it as simply as I can, for two objects to converge along what starts
off as parallel paths in a curved spacetime geodesic _requires_ movement.
"*We all travel at exactly the speed of light through spacetime*."
https://medium.com/predict/we-all-travel-through-spacetime-at-the-speed-of-light-d60cb389dfc

There cannot be any understanding of what we call the force of gravity
without understanding _where_ that movement in spacetime is occurring.

We All Travel Through Spacetime at the Speed of Light
https://medium.com/predict/we-all-travel-through-spacetime-at-the-speed-of-light-d60cb389dfc2
"*Everything travels through spacetime at the speed of light*.
Me, you, the cat (even Schrodinger's cat), the Earth, the sun, bits
and bytes, and any particles including photons (light particles)."

Without movement there is no feeling that we call the force of gravity.
--
Doveryay, no proveryay.
mitchr...@gmail.com
2021-05-12 16:56:12 UTC
Post by Paparios
http://youtu.be/k73psdcmzEY
Will Powell "We are all moving at the speed of light"
"Nothing moves faster than light and nothing moves slower than light.
We are all moving at light speed [through spacetime]"
Which is a complete bogus claim. Movement requires a change in time t
of the space coordinates (x,y,z) of a given object.
Thanks for clarifying as a "movement" through the 4D spacetime is the most
critical basic piece of the puzzle (as I've said from the very beginning).
To put it as simply as I can, for two objects to converge along what starts
off as parallel paths in a curved spacetime geodesic _requires_ movement.
"*We all travel at exactly the speed of light through spacetime*."
https://medium.com/predict/we-all-travel-through-spacetime-at-the-speed-of-light-d60cb389dfc
There cannot be any understanding of what we call the force of gravity
without understanding _where_ that movement in spacetime is occurring.
We All Travel Through Spacetime at the Speed of Light
https://medium.com/predict/we-all-travel-through-spacetime-at-the-speed-of-light-d60cb389dfc2
"*Everything travels through spacetime at the speed of light*.
Me, you, the cat (even Schrodinger's cat), the Earth, the sun, bits
and bytes, and any particles including photons (light particles)."
Without movement there is no feeling that we call the force of gravity.
Wrong... we feel weight...
2021-05-12 17:33:11 UTC
Post by ***@gmail.com
Without movement there is no feeling that we call the force of gravity.
Wrong... we feel weight...
The goal is not to be so precise in our wording that we could pass scrutiny
for accuracy in a doctoral thesis - the goal is to explain the source of
gravity (which requires an immense movement given the gradients are slight)
in a way that is essentially correct & yet both believable & understandable.

For example, without (immense) movement - there is no gravity.
Hence we need to figure out the source of that (immense) movement.

Likewise without intuitive models there is no understanding.
Hence we need to come up with intuitive models to be believed & understood.

That's my goal.

Speaking of intuitive models, in my response to someone else moments ago
where I listed the masters at teaching I forgot to mention Destin who is
yet another master at explaining complicated physics to the public at large.
Derek (Getting Smarter Every Day)
"A Baffling Balloon Behavior - Smarter Every Day 113"

There are others like Brady Haran of Numberphile & sixty symbols and the
John/Hank Green Vlog brothers of Crash Course Physics and CGP Gray and a
whole bunch of other Youtubers who try to educate the general populate that
I also forgot to mention.
--
Doveryay, no proveryay.
2021-05-13 06:45:34 UTC
Almost every person I've cited has earned a doctorate in physics.
Each one is reliable & credible & none of them are quacks (to my knowledge).

This is the transcript of Dr. Sabine Hossenfelder's description of the true
source of gravity, for example, where she covers in detail our motion.
*Do we really travel through time with the speed of light?*
http://backreaction.blogspot.com/2020/08/do-we-really-travel-through-time-with.html

Here is her video:
*Do we travel through time at the speed of light?*
http://youtu.be/iBTez-nTKes

And this is her channel:
Sabine Hossenfelder: *Science without the gobblegook*

You are welcome to claim that everyone is wrong but they're all saying the
same thing so if they're wrong we need to find someone credible who says so.

All these Physics PhD's could be wrong but they are saying the same thing.
You are welcome to refute everything they are saying but under what premise?

Do you have a reliable cite which _directly_ debunks their movement claims?
--
Doveryay, no proveryay.
Maciej Wozniak
2021-05-13 06:50:06 UTC
Almost every person I've cited has earned a doctorate in physics.
Each one is reliable & credible & none of them are quacks (to my knowledge).
Your knowledge sucks, Ilya. There can't be no reliable/credible
persons with a doctorate in physics.
Paparios
2021-05-13 14:29:13 UTC
Almost every person I've cited has earned a doctorate in physics.
Each one is reliable & credible & none of them are quacks (to my knowledge).
There are many physicists with PhD which, while they know every aspect of this subject (spacetime physics), use such a colloquial and informal language which confuses people like you and others (which have not taken formal course in the subject). One of those common "language errors" is the famous paragraph many PhDs and even physics web pages use: "moving clocks run slow".

To explain Special Relativity you have to use a very precise language to avoid these types of confusion.
This is the transcript of Dr. Sabine Hossenfelder's description of the true
source of gravity, for example, where she covers in detail our motion.
*Do we really travel through time with the speed of light?*
http://backreaction.blogspot.com/2020/08/do-we-really-travel-through-time-with.html
*Do we travel through time at the speed of light?*
http://youtu.be/iBTez-nTKes
Sabine Hossenfelder: *Science without the gobblegook*
Well, in his transcript of the video (the first link), she uses exactly this colloquial and informal language, which has confused you. She writes:

"At first, it does not seem to make much sense to even talk about a speed in time. A speed is distance per time. So, if you travel in time, a speed would be time per time, and you would end up with the arguably correct but rather lame insight that we travel through time at one second per second".

That paragraph is correct even if she, somehow, makes the reader to doubt what she writes when she uses "At first".

Then she writes:

"The constant you have to put here so that you can add these directions must have units of space over time, so that’s a speed. Let’s call it “c”".

Here she goes in a way that will completely confuse their readers. She then follows with:

"So what makes time different from space in Einstein’s space-time? What makes time different from space is the way you add them".

Later she writes:

"A distance between two points in in space-time is usually called Δs, so that’s what we will call it too. A distance in space-time is now the square-root of minus the squares of the distances in each of the dimensions of space, plus c square times the squared distance in time".

In her colloquial and informal language she is calling the spacetime INTERVAL a distance. The spacetime interval has a very precise definition:

If one event (E1) occurs at location x1 at time t1 and another event (E2) occurs at location x2 at time t2, then the INTERVAL between these two events is given by the following expression:

s12 = √(c²(t2 - t1)² - (x2 - x1)²)

Furthermore, from the principle of invariance of the speed of light, it follows that if the interval between two events is a given quantity A in a system of coordinates (x,t) it will be the same quantity A in a system of coordinates (x',t') or (x'',t''), etc.

This means the spacetime interval is an INVARIANT number
You are welcome to claim that everyone is wrong but they're all saying the
same thing so if they're wrong we need to find someone credible who says so.
All these Physics PhD's could be wrong but they are saying the same thing.
You are welcome to refute everything they are saying but under what premise?
Do you have a reliable cite which _directly_ debunks their movement claims?
--
Sure, see section 2 Intervals (on page 3 ) of the Landau Lifshitz book "The Classical Theory of Fields", available in https://archive.org/details/LandauTheClassicalTheoryOfFields
2021-05-13 19:40:07 UTC
Post by Paparios
To explain Special Relativity you have to use a very
precise language to avoid these types of confusion.
Yes.

While _many_ physisicsts say that we all move at the 4velocity of c
(as there is no other velocity) and that we merely trade off time against
space depending on our mass (or lack thereof) there's a healthy two-way
discussion of the precise language of that Sabine Hossenfelder video here.
http://backreaction.blogspot.com/2020/08/do-we-really-travel-through-time-with.html

For example:
"One of my personal a-ha moments when trying to get my head round SR
as an amateur (reading Susskind's SR book) was when it was shown that
the magnitude of the 4-velocity is always c.

So basically... everything is always moving at the speed of light in a
4 dimensional space...

ergo in a frame in which you are not moving in space, all your velocity
is in time and you are moving in time at c.

While if you move with nonzero velocity in space, your time component
changes accordingly to keep the overall magnitude of your 4-velocity
as c, hence time dilation."

Of course there's also precise language of what we mean by the word "time"
http://backreaction.blogspot.com/2014/04/the-problem-of-now.html
--
Doveryay, no proveryay.
Maciej Wozniak
2021-05-13 19:57:59 UTC
Post by Paparios
To explain Special Relativity you have to use a very
precise language to avoid these types of confusion.
Yes.
While _many_ physisicsts say that we all move at the 4velocity of c
(as there is no other velocity) and that we merely trade off time against
space depending on our mass (or lack thereof) there's a healthy two-way
discussion of the precise language of that Sabine Hossenfelder video here.
http://backreaction.blogspot.com/2020/08/do-we-really-travel-through-time-with.html
"One of my personal a-ha moments when trying to get my head round SR
as an amateur (reading Susskind's SR book) was when it was shown that
the magnitude of the 4-velocity is always c.
So basically... everything is always moving at the speed of light in a
4 dimensional space...
Ilya, poor idiot, nothing is moving in 4-dimensional space.
It's static.
Paparios
2021-05-12 15:28:57 UTC
http://youtu.be/msVuCEs8Ydo
http://youtu.be/k73psdcmzEY
I would also recommend you to watch a proper lecture on Special Relativity. The one lecture which excels on this is the one of Professor Susskind, available at http://youtu.be/toGH5BdgRZ4

Also worth watching is the lecture from Professor Greene (again the first hour is enough) available at

2021-05-12 17:07:05 UTC
Post by Paparios
I would also recommend you to watch a proper lecture on Special Relativity.
There are (as I see it) three kinds of physics lectures
(1) Intended to be strictly mathematical
(e.g., anything from MIT or Stanford or Princeton or CalTech on YouTube)
(2) Intended to be interesting
(e.g., anything from Sean Carroll or Brian Greene on YouTube)
(3) Intended to be understood
(e.g., anything from Sabine Hossenfelder or Derek Muller on YouTube)

Clearly I prefer the latter more so than the former (as I am not a student
of physics nor of mathematics nor do I ever deem to ever want to be one).
Post by Paparios
The one lecture which excels on this is the one of Professor Susskind,
available at http://youtu.be/toGH5BdgRZ4
As I've already said elsewhere in this thread I've watched _all_ the
lectures (all that I could find anyway) by the masters whom I listed as
Leonard Susskind
Walter Lewin
Richard Feynman

And I've watched most of the gravity discussions by the more modern teachers
Sean Carroll
Brian Cox
Brian Greene
David Tong
Don Lincoln

And to a lesser extend (due to their astronomical focus)
Michio Kaku
Neil deGrasse Tyson
Keith Cooper

But I prefer to watch people who explain it to the general public
Derek Muller (Veritasium)
"Why Gravity is NOT a Force"
http://youtu.be/XRr1kaXKBsU

Henry Reich (minutephysics)

Sabine Hossenfelder
"Is Gravity a Force?"

Nick Lucid (The Science Asylum)
"Why Do Things REALLY Fall? (with General Relativity)"
http://youtu.be/5HKH1ZjGutA

Michael David Stevens (Vsauce)
"Which Way Is Down?"

But Why?
"What is Gravity? The Illusion of Force by a Curved Dimension"
http://youtu.be/jhpKUapI3cY

Jim Al-Khalili (Spark)
"Does Gravity Really Affect The Passage Of Time?"

PBS Space Time
"Is Gravity An Illusion?"

Erik Verlinde (Big Think)
"Gravity Doesn't Exist"

Post by Paparios
Just the first hour of the first lecture there will clarify
Unfortunately that's not how it works.
I said from the very beginning I trust that the math pans out.

I just wanted to understand the origin of this thing we call gravity.
Without the math.
Post by Paparios
Also worth watching is the lecture from Professor Greene
(again the first hour is enough) available at
http://youtu.be/XFV2feKDK9E
I put Brian Greene in the "conversational physics" category as he
delves too deeply into string theory for my tastes, just as Sean
Carroll dives too deeply into parallel universes for my tastes.

Suffice to say I've listened to every respectable YouTuber that
discussed the topic of where gravity really comes from, and I don't
learn as much from Feynman (because he requires infinite intelligence
to understand) as I do from Michio Kaku (who breaks it down into
understandable chunks) nor do I learn as much from him as I do
from the masters at teaching such as Sabine Hossenfelder (who makes it
understood by the general public).

I admit my huge educational flaws in that I am merely a college educated
member of the general public who just wants to better understand gravity.

*I'm not a physicist nor am I a mathematician (nor do I understand them).*

People like Leonard Susskind are certainly respected by me.
But I don't learn as much from them as I do from people like Derek Muller.

My goal is to understand the source of gravity at the level that I believe
in it and at the level that I can explain it to someone else who will then
also believe in it.

That's not going to be done with pure math.
It's just not.

It requires us to invoke models and intuitive logical reasoning.
(Which I admit is the challenge when discussing the source of gravity.)

But I think I have a grasp of the source of gravity given knowledge of
what we call gravity requires movement which must be immense in magnitude.

*Do we really travel through time with the speed of light?*
http://backreaction.blogspot.com/2020/08/do-we-really-travel-through-time-with.html
--
Doveryay, no proveryay.
Paparios
2021-05-08 01:04:04 UTC
Right, it is analogous to a military tank, rolling on two tracks.
If the two tracks are going at the same speed, the tank goes straight,
but if one track is going slower than the other, the tank veers
in the direction of the slower track.
Right. This requires MOTION. That's why I was looking for the motion.
I think the main contributor to motion is time and it seems that you concur.
(1) We move through spacetime at the speed of c
This is wrong. Only light moves at speed c!!! We move through spacetime at much lower speeds, dependent on the frame of reference used to measure that speed. On Earth surface we move on the Equator at 1600 km/hr. Earth moves around the Sun at 30 km/sec, etc.
(2) Since our speed through space is very slow we mostly move through time
This does not make any sense. Our movement is through spacetime!!
(3) That movement through time happens even when we stand still on the earth
This is strongly dependent in the system of coordinates used to define speeds. Remebre that speed is defined as distance / time.
(a) There is a time gradient between our head and our feet
Wrong. What it is present is a very small gradient in gravity, which generates a measurable gravitarional time dilation. In stronger masses, tidal forces have to be considered.
(b) The "track" of time at our heat moves faster than at our feet
While true the gravitational time dilation at a human body is extremely low. Time passes faster for the head compared the feet, adding up to approximately 90 billionth of a second over a 79-year lifetime.
(c) This causes us to arc toward the slowest track of time (ie to earth)
This does not make any sense.
Odd Bodkin
2021-05-08 11:30:29 UTC
Post by Paparios
Right, it is analogous to a military tank, rolling on two tracks.
If the two tracks are going at the same speed, the tank goes straight,
but if one track is going slower than the other, the tank veers
in the direction of the slower track.
Right. This requires MOTION. That's why I was looking for the motion.
I think the main contributor to motion is time and it seems that you concur.
(1) We move through spacetime at the speed of c
This is wrong. Only light moves at speed c!!! We move through spacetime
at much lower speeds,
Careful. The speed through spacetime is not the same as the speed through
space.

dependent on the frame of reference used to measure that speed. On Earth
surface we move on the Equator at 1600 km/hr. Earth moves around the Sun at
30 km/sec, etc.
Post by Paparios
(2) Since our speed through space is very slow we mostly move through time
This does not make any sense. Our movement is through spacetime!!
(3) That movement through time happens even when we stand still on the earth
This is strongly dependent in the system of coordinates used to define
speeds. Remebre that speed is defined as distance / time.
(a) There is a time gradient between our head and our feet
Wrong. What it is present is a very small gradient in gravity, which
generates a measurable gravitarional time dilation. In stronger masses,
tidal forces have to be considered.
(b) The "track" of time at our heat moves faster than at our feet
While true the gravitational time dilation at a human body is extremely
low. Time passes faster for the head compared the feet, adding up to
approximately 90 billionth of a second over a 79-year lifetime.
(c) This causes us to arc toward the slowest track of time (ie to earth)
This does not make any sense.
--
Odd Bodkin -- maker of fine toys, tools, tables
Maciej Wozniak
2021-05-08 13:01:58 UTC
Post by Odd Bodkin
Post by Paparios
Right, it is analogous to a military tank, rolling on two tracks.
If the two tracks are going at the same speed, the tank goes straight,
but if one track is going slower than the other, the tank veers
in the direction of the slower track.
Right. This requires MOTION. That's why I was looking for the motion.
I think the main contributor to motion is time and it seems that you concur.
(1) We move through spacetime at the speed of c
This is wrong. Only light moves at speed c!!! We move through spacetime
at much lower speeds,
Careful. The speed through spacetime is not the same as the speed through
space.
Buhahahahahaha. Poor idiot Paparios.
Post by Odd Bodkin
dependent on the frame of reference used to measure that speed. On Earth
surface we move on the Equator at 1600 km/hr. Earth moves around the Sun at
30 km/sec, etc.
On the equator it is 1600 km/h; on the pole it is 0, but still,
of course, an observer on the pole and an observer
on the equator are completely immpobile wrt each other.
Aren't they, poor halfbrain?
Post by Odd Bodkin
Post by Paparios
This does not make any sense. Our movement is through spacetime!!
Paparios, poor geocentric halfbrain, there is NO movement
through your moronic spacetime. It's 4-dimensional, you know.
Thomas 'PointedEars' Lahn
2021-05-07 23:56:52 UTC
Post by Paparios
Well, actually we ARE accelerating at 9.8 m/s/s up the ground.
I agree. The question is NOT that we are; it's WHY we are.
Actually, the ground is accelerating upwards in our rest frame.

PointedEars
--
Q: Who's on the case when the electricity goes out?
A: Sherlock Ohms.

(from: WolframAlpha)
Walker Huckabee
2021-05-08 10:16:45 UTC
Post by Thomas 'PointedEars' Lahn
Post by Paparios
Well, actually we ARE accelerating at 9.8 m/s/s up the ground.
I agree. The question is NOT that we are; it's WHY we are.
Actually, the ground is accelerating upwards in our rest frame.
finally a valid statement from pointedhead. Those classes you take are
not for nothing I can see.
2021-05-09 00:38:20 UTC
Post by Thomas 'PointedEars' Lahn
Actually, the ground is accelerating upwards in our rest frame.
I've probably seen every video by Derek Muller the creator of Veritasium who
asks basic questions of people to make them think about things they never
thought about before. I've seen that video but I looked closer just now.

Derek says "Man falling from roof is not in a gravitational field.
There are no gravitational fields. And he is not accelerating."
http://youtu.be/XRr1kaXKBsU

But there is motion involved.

Derek also explains the real reason objects fall to earth is they are
_moving_ on straight paths on a curved surface (aka geodesics).
http://youtu.be/XRr1kaXKBsU

Unfortunately acceleration is also involved somehow.
"the floor of the rocket accelerates into them... and you will feel
a force pushing up on your feet. The same force you feel...
being at rest at the surface of Earth.... you are accelerating
and there is no gravitational field."
http://youtu.be/XRr1kaXKBsU

It gets confusing when Derek explains "the only force on you are these
normal forces (from the floor) pushing you up. So you are accelerating"
http://youtu.be/XRr1kaXKBsU

The guy in the inertial frame of reference is the guy falling off the roof.
"And he would see you accelerating up at 9.8m/s/s"
http://youtu.be/XRr1kaXKBsU

Derek explains "What an acceleration really is, is it's a deviation from a
geodesic. You can't follow a straight line path through space-time...
because the floor prevents you from doing that. It applies a force upward
on you so you're accelerating up."
http://youtu.be/XRr1kaXKBsU

When Derek tried to explain how that could be the case he threw up an
equation which opened my eyes to WHY (perhaps?) the rate of time gradient is
more important than the curvature of space (I think?).

His equation shows a multiplier of the curvature of space times the SQUARE
of the time gradient! (Maybe this is why time matters more than space?)
http://youtu.be/XRr1kaXKBsU

He says "It is possible for you to be accelerating even though your spatial
coordinates are not changing."

This is hard to understand so Derek pulled out an equation and explained
"If you were in flat space time... if you're accelerating... your spatial
coordinates have to change" but "you're not in FLAT space-time."

Derek goes on and says "your position can be not changing which means your
acceleration must be exactly equal to the curvature in spacetime term times

He concludes "In curved spacetime you need to accelerate just to stand
still."
http://youtu.be/XRr1kaXKBsU

"In an accelerating frame of reference, light deflects down."
http://youtu.be/XRr1kaXKBsU

The conclusion is that the Earth accelerates into us.

Notice this explanation sounds COMPLETELY DIFFERENT from my previous logical
non mathematical explanation using the rate gradient of time. Sigh.

Now I have to unify this "accelerating of the earth into my feet" concept
into the "moving at the speed of time in a time gradient" concept.

Sigh.

This stuff boggles my mind as it's hard to bring intuition into this.
--
Doveryay, no proveryay.
Walker Huckabee
2021-05-09 08:58:55 UTC
Derek says "Man falling from roof is not in a gravitational field.
There are no gravitational fields. And he is not accelerating."
then he's an idiot. You, a much bigger idiot than him. Get yourself a
basic education, fucking moron.
Maciej Wozniak
2021-05-09 18:13:58 UTC
Post by Thomas 'PointedEars' Lahn
Actually, the ground is accelerating upwards in our rest frame.
I've probably seen every video by Derek Muller the creator of Veritasium who
asks basic questions of people to make them think about things they never
thought about before. I've seen that video but I looked closer just now.
Derek says "Man falling from roof is not in a gravitational field.
There are no gravitational fields. And he is not accelerating."
http://youtu.be/XRr1kaXKBsU
But there is motion involved.
Derek also explains the real reason objects fall to earth is they are
_moving_ on straight paths on a curved surface (aka geodesics).
http://youtu.be/XRr1kaXKBsU
Unfortunately acceleration is also involved somehow.
"the floor of the rocket accelerates into them... and you will feel
a force pushing up on your feet. The same force you feel...
being at rest at the surface of Earth.... you are accelerating
and there is no gravitational field."
http://youtu.be/XRr1kaXKBsU
It gets confusing when Derek explains "the only force on you are these
normal forces (from the floor) pushing you up. So you are accelerating"
http://youtu.be/XRr1kaXKBsU
The guy in the inertial frame of reference is the guy falling off the roof.
"And he would see you accelerating up at 9.8m/s/s"
http://youtu.be/XRr1kaXKBsU
Derek explains "What an acceleration really is, is it's a deviation from a
geodesic. You can't follow a straight line path through space-time...
because the floor prevents you from doing that. It applies a force upward
on you so you're accelerating up."
http://youtu.be/XRr1kaXKBsU
When Derek tried to explain how that could be the case he threw up an
equation which opened my eyes to WHY (perhaps?) the rate of time gradient is
more important than the curvature of space (I think?).
His equation shows a multiplier of the curvature of space times the SQUARE
of the time gradient! (Maybe this is why time matters more than space?)
http://youtu.be/XRr1kaXKBsU
He says "It is possible for you to be accelerating even though your spatial
coordinates are not changing."
This is hard to understand so Derek pulled out an equation and explained
"If you were in flat space time... if you're accelerating... your spatial
coordinates have to change" but "you're not in FLAT space-time."
Derek goes on and says "your position can be not changing which means your
acceleration must be exactly equal to the curvature in spacetime term times
He concludes "In curved spacetime you need to accelerate just to stand
still."
http://youtu.be/XRr1kaXKBsU
"In an accelerating frame of reference, light deflects down."
http://youtu.be/XRr1kaXKBsU
The conclusion is that the Earth accelerates into us.
Notice this explanation sounds COMPLETELY DIFFERENT from my previous logical
non mathematical explanation using the rate gradient of time. Sigh.
Now I have to unify this "accelerating of the earth into my feet" concept
into the "moving at the speed of time in a time gradient" concept.
Keep listening to mumbling religious cranks and
This stuff boggles my mind as it's hard to bring intuition into this.
If physics was intuitive and comprehendable for just
anyone - why would anyone worship the gurus and
Python
2021-05-09 21:04:14 UTC
Maciej Wozniak wrote:
...
Post by Maciej Wozniak
If physics was intuitive and comprehendable for just
anyone - why would anyone worship the gurus and
Sure Maciej, also these "gurus" forbid the publishing of
hundreds of book explaining all of this and prevent hundred of
thousands students, from high school to Universities and
engineering schools to learn about it, every year.
Maciej Wozniak
2021-05-10 04:01:30 UTC
Post by Python
...
Post by Maciej Wozniak
If physics was intuitive and comprehendable for just
anyone - why would anyone worship the gurus and
Sure Maciej, also these "gurus" forbid the publishing of
hundreds of book explaining all of this and prevent hundred of
thousands students, from high school to Universities and
engineering schools to learn about it, every year.
More, they train hundreds of fanatic doggies doing
NOTHING but hurling insults and slanders on any
opposition.
BTW, how are these geostationary satellites, in
motion wrt each other or not?
Maciej Wozniak
2021-05-10 07:50:36 UTC
Post by Python
...
Post by Maciej Wozniak
If physics was intuitive and comprehendable for just
anyone - why would anyone worship the gurus and
Sure Maciej, also these "gurus" forbid the publishing of
hundreds of book explaining all of this and prevent hundred of
thousands students, from high school to Universities and
engineering schools to learn about it, every year.
See, poor halfbrain: just some days ago you insulted
Augsburg Hochschule for teaching something you
don't like.

What if they dared to teach against your beloved Shit?
You would scream about Bavarian nazis and their bottles
of vodka, wouldn't you? And your idiot gurus alltogether.
They simply couldn't, even if they didn't belong to your
moronic cult themself.
Odd Bodkin
2021-05-10 10:04:37 UTC
Post by Python
...
Post by Maciej Wozniak
If physics was intuitive and comprehendable for just
anyone - why would anyone worship the gurus and
Sure Maciej, also these "gurus" forbid the publishing of
hundreds of book explaining all of this and prevent hundred of
thousands students, from high school to Universities and
engineering schools to learn about it, every year.
Why indeed should surgery be anything other than comprehensible for just
anyone? Why indeed should the practice of law be anything other than
comprehensible for just anyone? Why indeed should orchestral comprehension
be anything other than comprehensible for just anyone?

Why indeed should there be anything at all that requires specialized
training and certification after years of practice, if all it does is make
--
Odd Bodkin — Maker of fine toys, tools, tables
Maciej Wozniak
2021-05-10 11:14:04 UTC
Post by Odd Bodkin
Post by Python
...
Post by Maciej Wozniak
If physics was intuitive and comprehendable for just
anyone - why would anyone worship the gurus and
Sure Maciej, also these "gurus" forbid the publishing of
hundreds of book explaining all of this and prevent hundred of
thousands students, from high school to Universities and
engineering schools to learn about it, every year.
Why indeed should surgery be anything other than comprehensible for just
anyone?
In general it is, Bod. The surgeons were never trying to announce
that when common sense is against them - it's too bad
for common sense. Oppositely, they esteem common sense much,
like other sane people (and even some insane, right, Python?)
Post by Odd Bodkin
Why indeed should there be anything at all that requires specialized
training and certification after years of practice
Sorry, trash, it's not the case of you and your Shit
at all. As for building models of the reality you're not
even amateurs; you're just a bunch of fanatics screaming
of THE BEST WAY we're allegedly FORCED to, and casting
insults and slanders on the opposition. You're using your
moronc newspeak to cover this simple fact - without it
anybody would see who you are.
Ross A. Finlayson
2021-05-10 08:40:52 UTC
Post by Paparios
Well, actually we ARE accelerating at 9.8 m/s/s up the ground.
I agree. The question is NOT that we are; it's WHY we are.
Post by Paparios
See, if you jump from the Eiffel tower you gain speed by free
falling towards the center of Earth (at 9.8 m/s/s).
I agree. I don't doubt the math one bit.
I'm trying to find a model that EXPLAINS why this is the case.
Post by Paparios
That acceleration is due to the mass of Earth which changes the
geometry of the geodesics.
The geometric change is in both space & time - which I agree with.
As far as I know, it's far more curvature in time than in space.
The question is WHY.
And what MODEL can we use to visualize it.
Post by Paparios
When you hit the ground, whatever speed you got turns out to 0 m/s.
I agree.
I should probably give up asking because nobody understands me.
I'm asking WHY - not what.
Post by Paparios
If you are standing on the ground you still feel the 9.8 m/s/s
acceleration towards the ground but that acceleration is balanced
by an opposite acceleration created by your body components which
results in a net vertical speed of 0 m/s.
I agree.
Those statements are NOT where my confusion lies.
The confusion lies in the WHY of that first statement of yours.
"Well, actually we ARE accelerating at 9.8/m/s/s up the ground"
Why?
Put in other words, WHY are we accelerating in the first place?
I know it's due to time more so than to space.
And I'm well aware it's along a geodesic.
And I'm also well aware that we're moving through time at the speed of c.
What I can't figure out yet is a MODEL that explains WHY we "feel"
an acceleration (mostly due to time curvature) when both the earth
and our bodies are moving through time at the same speed of c.
The _closest_ I can get to an answer is that we're moving so fast
through time that even the tiny gradient between our clocks at our
head and our feet is enough to force us into the ground at 9.8m/s/s
Otherwise we'd stay in the air when we stepped off the Eifel Tower
as there is no force of gravity, per se (it doesn't exist).
What exists is curvature in space and more so in time.
And what exists is MOVEMENT through time at the the speed of c.
And what exists is NO MOVEMENT through space.
Somehow the curvature in time coupled with the movement in time
causes us to move along the geodesic in time such that it causes
this thing we feel as a force of 9.8m/s/s acceleration along that
geodesic in time curvature (but not so much in space curvature).
which
--
Doveryay, no proveryay.
In quark dynamics there's asymptotic freedom of
what would be the strong nuclear force,
it was discovered in the 1970's and most surprises people.

One way to explain this up is to essentially unify
the strong nuclear force and gravity, where gravity's
effect as a force in a field is a fall gravity instead of a
pull gravity, while all falling out inverse square classically.

Making for a unified field theory is a unified force theory.

Then, that might not be a model of GR per se, but,
there's simply putting the derivation atop what the
frame it builds, that for Lorentz transformation as
about essential invariance, that a space contraction
of a unified field theory a fall gravity explains and
models the same things as length contraction and
"time" dilation in GR.

So, gravity acts like a force and it's well known, that,
for example, the force vector is measured as according
to the distance source-source, not source-image, i.e.,
the geodesy is always current, as if gravity's "speed"
weren't less than infinite.

The geodesy is always current so all the world-lines
in the geodesy are always having been computed
as if instantaneously all the distances were constant.

It's the ground that is accelerating as under potential,
to us - as if we were floating in our heads.

Basically we're all on the same dot
going from zero to t in t.

Working it up this way from first principles in theory
I find it easier this way to organize everything.

or "why does light have a speed and what is it", that
it's effectively as about a singularity theory after the
great important of mass-energy equivalence,
that the entire universe somehow fits in the
simplest possible framework of singularity and continuum,
is for the quantum and relativistic and absolute and continuous,
what must all be a one theory.
Thomas 'PointedEars' Lahn
2021-05-14 17:47:51 UTC
Post by Ross A. Finlayson
In quark dynamics there's asymptotic freedom of
what would be the strong nuclear force,
it was discovered in the 1970's and most surprises people.
Somewhat true:

<https://en.wikipedia.org/wiki/Quantum_chromodynamics>
Post by Ross A. Finlayson
One way to explain this up is to essentially unify
the strong nuclear force and gravity,
The strong interaction is 10³⁸ times as strong as the gravitational one.
Its range is on the order of 10⁻¹⁵ m (charge radius of a proton).

The range of the gravitational interaction infinite.

Good luck unifying those two. Generations of *real* physicists have tried
and failed.
Post by Ross A. Finlayson
Ouch.

PointedEars
--
Q: How many theoretical physicists specializing in general relativity
does it take to change a light bulb?
A: Two: one to hold the bulb and one to rotate the universe.
(from: WolframAlpha)
mitchr...@gmail.com
2021-05-14 17:54:12 UTC
Forces have a strength that changes motion and can give weight...

Mitchell Raemsch
mitchr...@gmail.com
2021-05-15 18:26:12 UTC
Post by ***@gmail.com
Forces have a strength that changes motion and can give weight...
Mitchell Raemsch
The force of gravity has a strength that can create weight... or not in free fall...
Ross A. Finlayson
2021-05-16 23:42:08 UTC
Post by Thomas 'PointedEars' Lahn
Post by Ross A. Finlayson
In quark dynamics there's asymptotic freedom of
what would be the strong nuclear force,
it was discovered in the 1970's and most surprises people.
<https://en.wikipedia.org/wiki/Quantum_chromodynamics>
Post by Ross A. Finlayson
One way to explain this up is to essentially unify
the strong nuclear force and gravity,
The strong interaction is 10³⁸ times as strong as the gravitational one.
Its range is on the order of 10⁻¹⁵ m (charge radius of a proton).
The range of the gravitational interaction infinite.
Good luck unifying those two. Generations of *real* physicists have tried
and failed.
Post by Ross A. Finlayson
Ouch.
PointedEars
--
Q: How many theoretical physicists specializing in general relativity
does it take to change a light bulb?
A: Two: one to hold the bulb and one to rotate the universe.
(from: WolframAlpha)
Good luck, unifying physics.

The idea is to make it a fall gravity as the mechanism for all the
kinetics, that there is the field with the gradient and gravity everywhere
where the graviton as also the atom and force carrier for gravity,
both real and virtual where classical particles are their own partner.

This mediated by charge, of course is usually where the strong
nuclear gravitational (or, "gravificational") and gravity would
share the same direction of their vector more or less and resolve
to the same thing this way. Now, in the theory, it might seems as
direct to have the energy content in the charge mediated by kinetics,
it's relevant to understand that "unifying" the kinetic about the "four
or five forces, now including gravity, of particle mechanics and the
fields of electromagnetism", is also as about unifying under charge,
for conservation about charge and momentum.

So, giving gravitic (or "gravific" some fall gravity with the true centrifgual)
assignment as a force in the theory: puts back into place the usual
classical concern and all the Newtonian, in theory, besides what holding
up for the modern standard model of particle physics is for example
the real virtual graviton as the atom, also pulls in usual ideas of supersymmetry,
and why string theory is a model of a continuum theory for atoms.

The point to sort out is that with a fall gravity this way, and for example
again to the point noticing asymptotic freedom instead of confinement,
or "singularities as the centers of mass of massy objects", it might help
to sort of understand how instead of massy bodies always constantly
gravitating, instead they are more than less at rest with respect to each
other, which besides of course the usual classical and kinetic with respect
to light speed the usual inverse square force (or, force vector) of gravity,
that also the total effects of large frames fall out, and also the nuclear
organization of protons and neutrons as it were and their quarks:
it's simple this way to so organize things this way, here as how charge
confinement works, all quite naturally with respect to particle physics,
the quantum, and results in general relativity.

"How does gravity act like a force?" Most always as a vector in a field
of a space as it were, or for example a point on a manifold, as among the
most usual "field occupation numbers", as it were, here though the point
is that it acts like a force because it is the force (in the unified field theory
which is a unified force theory).

Ken Seto
2021-05-07 21:14:00 UTC
I've been trying to understand how gravity acts like a force.
I'm sure the math works out but I don't understand the logic.
On the net are many rubber trampoline examples which imply that you have to
bend (toward the south pole in those 2D examples).
I don't see what is moving.
I realize EVERYTHING is moving (at half a millions miles per second or so,
given rotation, orbit around the sun, the sun spinning up and around the
galaxy, the galaxy moving, etc.).
But if I think about gravity in the frame of reference from the earth I'm
not moving with respect to the earth. Am I?
I'm standing still with respect to the earth, aren't I?
So what's moving?
When I dig further I find out that it's more the curvature in time than in
space that causes this effect we call gravity. Most explain this feeling of
feet (slower time).
But what's moving?
I don't yet understand logically how the time gradient (plus the curviture
in space) feels like a force.
That's why I'm here.
Is this the kind of question we can fruitfully ask on this newsgroup?
Gravity between the earth and the moon is a composite force as follows:
1. It is an attractive EM force derived from that the earth and the moon are expanding in the same direction as the universe expands.em

2. The earth and the moon are confined to follow the divergent structure of the aether called the E-Matrix. This gives rise to a repulsive effect between the earth and the moon as the universe expands.

3. Gravity between the earth and the moon is the combined result of the above opposing forces. That’s why gravity is so weak compared to the electromagnetic force.

4. The paper in the following link describes the above concept of gravity:
http://www.modelmechanics.org/2015gravity.pdf
Michael Moroney
2021-05-07 22:45:23 UTC
I've been trying to understand how gravity acts like a force.
I'm sure the math works out but I don't understand the logic.
On the net are many rubber trampoline examples which imply that you have to
bend (toward the south pole in those 2D examples).
I don't see what is moving.
I realize EVERYTHING is moving (at half a millions miles per second or so,
given rotation, orbit around the sun, the sun spinning up and around the
galaxy, the galaxy moving, etc.).
But if I think about gravity in the frame of reference from the earth I'm
not moving with respect to the earth. Am I?
I'm standing still with respect to the earth, aren't I?
So what's moving?
When I dig further I find out that it's more the curvature in time than in
space that causes this effect we call gravity. Most explain this feeling of
feet (slower time).
But what's moving?
I don't yet understand logically how the time gradient (plus the curviture
in space) feels like a force.
That's why I'm here.
Is this the kind of question we can fruitfully ask on this newsgroup?
legitimate question and deserves a legitimate answer, not false assertions.
Ken Seto
2021-05-08 19:18:31 UTC
Post by Michael Moroney
I've been trying to understand how gravity acts like a force.
I'm sure the math works out but I don't understand the logic.
On the net are many rubber trampoline examples which imply that you have to
bend (toward the south pole in those 2D examples).
I don't see what is moving.
I realize EVERYTHING is moving (at half a millions miles per second or so,
given rotation, orbit around the sun, the sun spinning up and around the
galaxy, the galaxy moving, etc.).
But if I think about gravity in the frame of reference from the earth I'm
not moving with respect to the earth. Am I?
I'm standing still with respect to the earth, aren't I?
So what's moving?
When I dig further I find out that it's more the curvature in time than in
space that causes this effect we call gravity. Most explain this feeling of
feet (slower time).
But what's moving?
I don't yet understand logically how the time gradient (plus the curviture
in space) feels like a force.
That's why I'm here.
Is this the kind of question we can fruitfully ask on this newsgroup?
legitimate question and deserves a legitimate answer, not false assertions.
I did give him a legitimate answer. you are too stupid to understand it is not my problem. I suggest that you and your moronic daughter solve (-6/-2) before commenting what I wrote. Gee, you are so fucking stupid.
Michael Moroney
2021-05-08 23:13:47 UTC
Post by Ken Seto
Post by Michael Moroney
I've been trying to understand how gravity acts like a force.
I'm sure the math works out but I don't understand the logic.
On the net are many rubber trampoline examples which imply that you have to
bend (toward the south pole in those 2D examples).
I don't see what is moving.
I realize EVERYTHING is moving (at half a millions miles per second or so,
given rotation, orbit around the sun, the sun spinning up and around the
galaxy, the galaxy moving, etc.).
But if I think about gravity in the frame of reference from the earth I'm
not moving with respect to the earth. Am I?
I'm standing still with respect to the earth, aren't I?
So what's moving?
When I dig further I find out that it's more the curvature in time than in
space that causes this effect we call gravity. Most explain this feeling of
feet (slower time).
But what's moving?
I don't yet understand logically how the time gradient (plus the curviture
in space) feels like a force.
That's why I'm here.
Is this the kind of question we can fruitfully ask on this newsgroup?
Ilya, you'll find that this group has been overrun by cranks and
crackpots, many of whom have their own versions of made-up physics. Ken
is just one example of this.
Post by Ken Seto
Post by Michael Moroney
legitimate question and deserves a legitimate answer, not false assertions.
I did give him a legitimate answer.
No, you replied with your untested and unsupported false assertions, of
your own make-believe S particles and G strings.
Post by Ken Seto
I suggest that you and your moronic daughter solve (-6/-2) before commenting what I wrote. Gee, you are so fucking stupid.
And once again you project your own failure to be able to do any math
onto us. (Ilya take note: Ken's math is limited to around the third
2021-05-08 23:49:52 UTC
Post by Michael Moroney
Ilya, you'll find that this group has been overrun by cranks and
crackpots, many of whom have their own versions of made-up physics. Ken
is just one example of this.
Thanks. I'm making full use of my newsreader killfile functionality.
[sci.physics.relativity]
!delete anything from "Ken Seto"
!delete anything from "Walker Huckabee"
!delete anything from "Maciej Wozniak"
!delete anything from "Bertram Schuller"

Some of the others I'm leaving as the benefit of the doubt.
But I'm only responding to those who are working on the problem set.

In the end I think it's a worthwhile effort as it's good to have friends
with whom I can ask detailed questions without diving into the equations.

I just want to have a model that works logically & intuitively in my mind
at the level that I believe in it and I can explain it to other people.
--
Doveryay, no proveryay.
mitchr...@gmail.com
2021-05-09 00:24:54 UTC
Post by Michael Moroney
Ilya, you'll find that this group has been overrun by cranks and
crackpots, many of whom have their own versions of made-up physics. Ken
is just one example of this.
Thanks. I'm making full use of my newsreader killfile functionality.
[sci.physics.relativity]
!delete anything from "Ken Seto"
!delete anything from "Walker Huckabee"
!delete anything from "Maciej Wozniak"
!delete anything from "Bertram Schuller"
Some of the others I'm leaving as the benefit of the doubt.
But I'm only responding to those who are working on the problem set.
In the end I think it's a worthwhile effort as it's good to have friends
with whom I can ask detailed questions without diving into the equations.
I just want to have a model that works logically & intuitively in my mind
at the level that I believe in it and I can explain it to other people.
--
Doveryay, no proveryay.
There are four forces. Gravity is one because it can change
motion and give weight... or not... it has strength for giving both...
because it is geometry does not rule out that it is
force... and it is primary.

Mitchell Raemsch
Maciej Wozniak
2021-05-09 05:48:10 UTC
I just want to have a model that works logically & intuitively in my mind
at the level that I believe in it and I can explain it to other people.
You can also want to be a jedi knight, you know.
Ken Seto
2021-05-09 11:31:21 UTC
Post by Michael Moroney
Ilya, you'll find that this group has been overrun by cranks and
crackpots, many of whom have their own versions of made-up physics. Ken
is just one example of this.
Thanks. I'm making full use of my newsreader killfile functionality.
[sci.physics.relativity]
!delete anything from "Ken Seto"
!delete anything from "Walker Huckabee"
!delete anything from "Maciej Wozniak"
!delete anything from "Bertram Schuller"
Big mistake is listening to Morony.
My theory is the only valid theory of gravity.
http://www.modelmechanics,org/2015gravity.pdf
Some of the others I'm leaving as the benefit of the doubt.
But I'm only responding to those who are working on the problem set.
In the end I think it's a worthwhile effort as it's good to have friends
with whom I can ask detailed questions without diving into the equations.
I just want to have a model that works logically & intuitively in my mind
at the level that I believe in it and I can explain it to other people.
--
Doveryay, no proveryay.
Odd Bodkin
2021-05-09 11:33:39 UTC
Post by Ken Seto
Post by Michael Moroney
Ilya, you'll find that this group has been overrun by cranks and
crackpots, many of whom have their own versions of made-up physics. Ken
is just one example of this.
Thanks. I'm making full use of my newsreader killfile functionality.
[sci.physics.relativity]
!delete anything from "Ken Seto"
!delete anything from "Walker Huckabee"
!delete anything from "Maciej Wozniak"
!delete anything from "Bertram Schuller"
Big mistake is listening to Morony.
Empty gesture, Ken. He already killfiled you.
Post by Ken Seto
My theory is the only valid theory of gravity.
http://www.modelmechanics,org/2015gravity.pdf
Some of the others I'm leaving as the benefit of the doubt.
But I'm only responding to those who are working on the problem set.
In the end I think it's a worthwhile effort as it's good to have friends
with whom I can ask detailed questions without diving into the equations.
I just want to have a model that works logically & intuitively in my mind
at the level that I believe in it and I can explain it to other people.
--
Doveryay, no proveryay.
--
Odd Bodkin — Maker of fine toys, tools, tables
Ken Seto
2021-05-09 13:10:09 UTC
Post by Ken Seto
Post by Michael Moroney
Ilya, you'll find that this group has been overrun by cranks and
crackpots, many of whom have their own versions of made-up physics. Ken
is just one example of this.
Thanks. I'm making full use of my newsreader killfile functionality.
[sci.physics.relativity]
!delete anything from "Ken Seto"
!delete anything from "Walker Huckabee"
!delete anything from "Maciej Wozniak"
!delete anything from "Bertram Schuller"
Big mistake is listening to Morony.
Empty gesture, Ken. He already kill filed you.
I know. I just want point out to everybody to know that Morony is a moron and that
kill filing me is a Big Mistake.
I have the only valid physical explanation of gravity.
http://www.modelmechanics.org/2015gravity.pdf
My theory is the only valid theory of gravity.
Post by Ken Seto
http://www.modelmechanics,org/2015gravity.pdf
Some of the others I'm leaving as the benefit of the doubt.
But I'm only responding to those who are working on the problem set.
In the end I think it's a worthwhile effort as it's good to have friends
with whom I can ask detailed questions without diving into the equations.
I just want to have a model that works logically & intuitively in my mind
at the level that I believe in it and I can explain it to other people.
--
Doveryay, no proveryay.
--
Odd Bodkin — Maker of fine toys, tools, tables
Odd Bodkin
2021-05-09 13:49:25 UTC
Post by Ken Seto
Post by Ken Seto
Post by Michael Moroney
Ilya, you'll find that this group has been overrun by cranks and
crackpots, many of whom have their own versions of made-up physics. Ken
is just one example of this.
Thanks. I'm making full use of my newsreader killfile functionality.
[sci.physics.relativity]
!delete anything from "Ken Seto"
!delete anything from "Walker Huckabee"
!delete anything from "Maciej Wozniak"
!delete anything from "Bertram Schuller"
Big mistake is listening to Morony.
Empty gesture, Ken. He already kill filed you.
I know. I just want point out to everybody to know that Morony is a moron and that
kill filing me is a Big Mistake.
So YOU think you are worth attention. Does anyone else think you are worth
attention?

And what does that tell you?
Post by Ken Seto
I have the only valid physical explanation of gravity.
http://www.modelmechanics.org/2015gravity.pdf
My theory is the only valid theory of gravity.
Post by Ken Seto
http://www.modelmechanics,org/2015gravity.pdf
Some of the others I'm leaving as the benefit of the doubt.
But I'm only responding to those who are working on the problem set.
In the end I think it's a worthwhile effort as it's good to have friends
with whom I can ask detailed questions without diving into the equations.
I just want to have a model that works logically & intuitively in my mind
at the level that I believe in it and I can explain it to other people.
--
Doveryay, no proveryay.
--
Odd Bodkin — Maker of fine toys, tools, tables
--
Odd Bodkin -- maker of fine toys, tools, tables
Michael Moroney
2021-05-09 17:00:33 UTC
Post by Ken Seto
Post by Ken Seto
Post by Michael Moroney
Ilya, you'll find that this group has been overrun by cranks and
crackpots, many of whom have their own versions of made-up physics. Ken
is just one example of this.
Thanks. I'm making full use of my newsreader killfile functionality.
[sci.physics.relativity]
!delete anything from "Ken Seto"
!delete anything from "Walker Huckabee"
!delete anything from "Maciej Wozniak"
!delete anything from "Bertram Schuller"
Big mistake is listening to Morony.
Empty gesture, Ken. He already kill filed you.
I know. I just want point out to everybody to know that Morony is a moron and that
kill filing me is a Big Mistake.
I think everybody reading your posts will have no problem figuring out
who is the moron here.

Post by Ken Seto
I have the only valid physical explanation of gravity.
http://www.modelmechanics.org/2015gravity.pdf
And once again, you need to provide scientific observation, experimental
results, mathematical relationships, ways to predict outcomes, etc. etc.
etc. Otherwise, your failed Muddle Mechanics remains a total disaster.
Michael Moroney
2021-05-09 17:04:03 UTC
Post by Michael Moroney
Ilya, you'll find that this group has been overrun by cranks and
crackpots, many of whom have their own versions of made-up physics. Ken
is just one example of this.
Thanks. I'm making full use of my newsreader killfile functionality.
[sci.physics.relativity]
!delete anything from "Walker Huckabee"
!delete anything from "Bertram Schuller"
Unfortunately, these are two nyms of the nymshifting troll, a Kremlin
operative sent to disrupt everything. It will keep shifting nyms to
stay out of killfiles.
Walker Huckabee
2021-05-09 19:40:32 UTC
Post by Michael Moroney
Post by Michael Moroney
Ilya, you'll find that this group has been overrun by cranks and
crackpots, many of whom have their own versions of made-up physics.
Ken is just one example of this.
Thanks. I'm making full use of my newsreader killfile functionality.
[sci.physics.relativity]
!delete anything from "Walker Huckabee" !delete anything from
"Bertram Schuller"
Unfortunately, these are two nyms of the nymshifting troll, a Kremlin
operative sent to disrupt everything. It will keep shifting nyms to
stay out of killfiles.
I don't know those people, I am a different person, a nice person. So
your advice makes no any sense. I don't know who you are. Which country
are you?
Michael Moroney
2021-05-10 03:03:40 UTC
On 5/9/2021 3:40 PM, the nymshifting troll, trolling as Walker Huckabee
Post by Walker Huckabee
Post by Michael Moroney
Post by Michael Moroney
Ilya, you'll find that this group has been overrun by cranks and
crackpots, many of whom have their own versions of made-up physics.
Ken is just one example of this.
Thanks. I'm making full use of my newsreader killfile functionality.
[sci.physics.relativity]
!delete anything from "Walker Huckabee"
!delete anything from "Bertram Schuller"
Unfortunately, these are two nyms of the nymshifting troll, a Kremlin
operative sent to disrupt everything. It will keep shifting nyms to
stay out of killfiles.
I don't know those people, I am a different person, a nice person. So
your advice makes no any sense. I don't know who you are. Which country
are you?
What happened, nymshifter? You don't know "Walker Huckabee" but post as
"Walker Huckabee"? You forgot to nymshift this time? Back to the Kremlin
for your punishment, for being so sloppy!
Lamar Scheibe
2021-05-10 14:27:43 UTC
Post by Michael Moroney
Post by Walker Huckabee
I don't know those people, I am a different person, a nice person. So
your advice makes no any sense. I don't know who you are. Which country
are you?
What happened, nymshifter? You don't know "Walker Huckabee" but post as
"Walker Huckabee"? You forgot to nymshift this time? Back to the Kremlin
for your punishment, for being so sloppy!
read somewhere, that without a substantial incentive, the kremlin will
not hitchhike gringos to the International Space Station (ISS) anymore,
unless they give a head to the driver.
Maciej Wozniak
2021-05-09 05:50:16 UTC
Post by Michael Moroney
I've been trying to understand how gravity acts like a force.
I'm sure the math works out but I don't understand the logic.
On the net are many rubber trampoline examples which imply that you have to
bend (toward the south pole in those 2D examples).
I don't see what is moving.
I realize EVERYTHING is moving (at half a millions miles per second or so,
given rotation, orbit around the sun, the sun spinning up and around the
galaxy, the galaxy moving, etc.).
But if I think about gravity in the frame of reference from the earth I'm
not moving with respect to the earth. Am I?
I'm standing still with respect to the earth, aren't I?
So what's moving?
When I dig further I find out that it's more the curvature in time than in
space that causes this effect we call gravity. Most explain this feeling of
feet (slower time).
But what's moving?
I don't yet understand logically how the time gradient (plus the curviture
in space) feels like a force.
That's why I'm here.
Is this the kind of question we can fruitfully ask on this newsgroup?
Ilya, you'll find that this group has been overrun by cranks and
crackpots
Yeah, they wave their arms and scream "We're FORCED!!!
To THE BEST WAY!!! There is no choice!!! We're gurus!!!"
Thomas 'PointedEars' Lahn
2021-05-07 23:42:46 UTC
I've been trying to understand how gravity acts like a force.
It does not. But that is a good approximation.
I'm sure the math works out but I don't understand the logic.
Watch this:

<https://www.microsoft.com/en-us/research/project/tuva-richard-feynman/#!1-physical-law>
On the net are many rubber trampoline examples which imply that you have
to be bend (toward the south pole in those 2D examples).
They do NOT imply that; you misunderstood. But, of course, where there is
no motion (in some sense) there cannot be a path. A path is defined as a
set of positions, which means that for an object to describe that path,
there has to be a change of position of that object, i. e. motion.

Rubber sheet experiments are *analogies* for how gravity works according to
general relativity, where it is NOT a force. They intend to depict
spacetime as a curved surface for lack of ability of depicting it as a
curved hypervolume, so to speak.

For a better visualization, read e.g.

I don't see what is moving.
I realize EVERYTHING is moving (at half a millions miles per second or so,
given rotation, orbit around the sun, the sun spinning up and around the
galaxy, the galaxy moving, etc.).
As our universe is dominated by gravity (among other interactions),
everything is moving *relative to something else*.
But if I think about gravity in the frame of reference from the earth I'm
not moving with respect to the earth. Am I?
That depends on whether you choose an Earth-Centered Inertial (ECI) frame or
an Earth-Centered Earth-Fixed (ECEF) frame of reference. In an ECI frame
you are certainly moving then, in an ECEF you are not.
I'm standing still with respect to the earth, aren't I?
You are. (The proper way to say it is “Earth”, not “the earth”.)
So what's moving?
A matter of definition following the free *choice* of a frame of reference.
When I dig further I find out that it's more the curvature in time than in
space that causes this effect we call gravity
This is wrong. Instead: According to general relativity, gravity is an
observable effect of the curvature of a spacetime, which corresponds to the
after special relativity was first postulated, space and time cannot be
considered separately or even to be separate.
Most explain this feeling of gravity based the time *gradient* between
No, you misunderstood. The "time gradient", i. e. difference in elapsed
proper time is *another* consequence of the curvature of spaceTIME, called
“gravitational time dilation” (a convenient misnomer).
But what's moving?
Nothing *has* to be moving.
I don't yet understand logically how the time gradient (plus the curviture
in space) feels like a force.
This is unsurprising, because that is pure fantasy.
Is this the kind of question we can fruitfully ask on this newsgroup?
Yes. However, it is best to read previous discussions on the subject first.
We have been over this ad nauseam.

PointedEars
--
Q: Why is electricity so dangerous?
A: It doesn't conduct itself.

(from: WolframAlpha)
2021-05-08 00:59:08 UTC
Post by Thomas 'PointedEars' Lahn
I'm sure the math works out but I don't understand the logic.
<https://www.microsoft.com/en-us/research/project/tuva-richard-feynman/#!1-physical-law>
I've watched almost all the physics lectures from all the great masters.
Leonard Susskind
Walter Lewin

And some of the more modern teachers
Sean Carroll
Brian Cox
Brian Greene
David Tong

As with Walter Lewin, Richard Feynman is wonderfully interesting where in
that video he explained the history of how each set of laws, if you trust
them, lead to new sets of laws.
Tycho
Gallileo
Newton
Cavendish
et. al

He showed gravitational "forces" rule the universe.
Elipses
Balls
Tides

But he didn't explain HOW gravitation is "generated."

But he said a few things which were intriguing.

For example at 46:00 minutes he discussed the inverse square law with
respect to electromagnitism (which gives us hints of quantum physics).

His example was two electrons have inverse square laws of both gravitation
and charge repulsion (where one is vastly greater than the other).

What I love about Feynman is he tries to avoid as much mathematics as he can
(which he can't of course) in explaining HOW things work, particularly how
gravity works.
--
Doveryay, no proveryay.
J***@.
1970-01-01 00:00:00 UTC
HOW is gravitation "generated" ?
Gravitational Energy is residual exergy.

From our perspective, clocks tick ever-slower the closer
they are to the start of the Big Bang.

Locally, those clocks tick normally, as they do here.

The more distant the black hole ( in Space & Time ),
the more massive it is.

The 12.5 billion year-old J2157-3602
is 34 billion solar masses,
13 thousand Sagittarius A* masses.

Sagittarius A* was probably much more massive
13.8 billion years ago, before entropy did its thing.

I assume that there was no entropy at
the ( infinitely precise ) start of the Big Bang;
i.e. infinite "eXergy" ( energy that can do "work", force * distance );
e.g. infinite gravitational and/or electromagnetic energy.

"God" (nature) programmed us to consume residual eXergy as
the cosmos goes from infinitely hot/dense to infinitely cold/sparse.
Thomas 'PointedEars' Lahn
2021-05-08 02:37:52 UTC
As with Walter Lewin, Richard Feynman is wonderfully interesting where in
that video he explained the history of how each set of laws, if you trust
them,
It has nothing to do with “trust” (or “belief”). That is not how science
works. Watch his last Messenger lecture, too.
lead to new sets of laws.
[…]
But he didn't explain HOW gravitation is "generated."
That is unsurprising because he discusses *Newton’s* theory of gravity
there, and Newton himself didn’t have a clue how gravity works; he famously
wrote that even at the end of the «Principia»: «Hypotheses non fingo» (“I
frame no hypotheses”), and that it should be enough that he had found the
law by which gravitation can be described (Feynman jokes about briefly in
his second Messenger lecture). He literally left it to the reader and to
posterity to find it out.

Einstein was one of those “various people who have looked further” (Feynman)
and found – by pure application of logic, which is remarkable in itself –
that gravity cannot be a (real) force. But this, like everything in
science, is not set in stone. The current scientific consensus is that
general relativity is the best theory of gravity that we have, but that it
is still insufficient as it breaks down when things become really small. It
predicts *mathematical* singularities then that (so far) cannot be avoided
by choosing other coordinates, and the uncertainty principle from quantum
mechanics forbids *physical* singularities to occur. The apparent
requirement for a theory of quantum gravity (or something equivalent) might
lead to the realization that gravity is a force/interaction after all
(transferred by gravitons, then), only that it manifests itself in the
curvature of spacetime at larger than quantum-mechanical scales.

PointedEars
--
Q: What did the female magnet say to the male magnet?
A: From the back, I found you repulsive, but from the front
I find myself very attracted to you.
(from: WolframAlpha)
mitchr...@gmail.com
2021-05-08 01:56:45 UTC
I've been trying to understand how gravity acts like a force.
I'm sure the math works out but I don't understand the logic.
On the net are many rubber trampoline examples which imply that you have to
bend (toward the south pole in those 2D examples).
I don't see what is moving.
I realize EVERYTHING is moving (at half a millions miles per second or so,
given rotation, orbit around the sun, the sun spinning up and around the
galaxy, the galaxy moving, etc.).
But if I think about gravity in the frame of reference from the earth I'm
not moving with respect to the earth. Am I?
If you share same movement there is a still comparison.
I'm standing still with respect to the earth, aren't I?
So what's moving?
The Earth with its gravity orbit.
When I dig further I find out that it's more the curvature in time than in
space that causes this effect we call gravity. Most explain this feeling of
feet (slower time).
The mathematical time curve is Gamma.
Gravity and motion come with it.
But what's moving?
How many levels of motion are there?
I don't yet understand logically how the time gradient (plus the curviture
in space) feels like a force.
That's why I'm here.
Is this the kind of question we can fruitfully ask on this newsgroup?
--
Doveryay, no proveryay.
Maciej Wozniak
2021-05-08 04:19:40 UTC
I've been trying to understand how gravity acts like a force.
I'm sure the math works out but I don't understand the logic.
In math, samely like in other domains, some theories work,
other don't. Euclidean math works, Riemann's farting don't;
GR shit is not even able to provide a consistent system of
coordinates.

If you understod the logic you would know. But you don't,
so the mumble "we are accelerating with acceleration
stopped by Earth surface" can impress you.
Walker Huckabee
2021-05-08 10:13:56 UTC
I've been trying to understand how gravity acts like a force.
I'm sure the math works out but I don't understand the logic.
In math, samely like in other domains, some theories work, other don't.
Euclidean math works, Riemann's farting don't; GR shit is not even able
to provide a consistent system of coordinates.
If you understod the logic you would know. But you don't, so the mumble
"we are accelerating with acceleration stopped by Earth surface" can
impress you.
you two guys are understanding each other I can see. Which is very good.
Tom Roberts
2021-05-08 17:36:15 UTC
[There has been much confusion and misinformation in this thread, as
well as a few sensible responses. I will answer the original question,
but cannot follow the many side issues raised.]
I've been trying to understand how gravity acts like a force.
Our best model of gravity is General Relativity. In GR, gravity is not a
force, and does not "act like a force". What we call "gravity" is an
aspect of the geometry of spacetime, as I'll discuss below.
On the net are many rubber trampoline examples [...]
These are very poor examples, as they attempt to "explain" gravity with
an analogy that requires gravity -- how else does a ball remain on the
rubber sheet, and fall down into a depression?
I realize EVERYTHING is moving [...]
For concepts like "moving", one must ALWAYS specify the coordinates one
is using. After all, every object can be described as at rest in some
set of coordinates (e.g. its instantaneously co-moving inertial frame).

confusions. You MUST learn how to be more precise in thought and word,
or you will never be able to understand subtle concepts like those in
modern physics.
But if I think about gravity in the frame of reference from the
earth I'm not moving with respect to the earth. Am I? I'm standing
still with respect to the earth, aren't I?
Hmmm. Note that in physics, "frame" invariably means "inertial frame",
or "locally inertial frame"; the earth is rotating, and thus not at rest
in any such frame. You are not describing "motion" and "at rest" with
sufficient precision to understand the underlying concepts -- that is
the root of your lack of understanding.

[You are not alone in that around here.]

Let us start from the basics. Throughout this discussion I am speaking a
bit loosely, and using approximations that I don't always mention.

In GR, massive objects affect the geometry of spacetime, and that
geometry affects the motions of all objects. So let's start with the
simplest situation: the motion of a test particle. A test particle is a
pointlike object with nonzero mass, but a mass that is so small that its
effects on the geometry can be neglected [#]. For purposes of
discussion, consider a universe containing just a single massive object
that is spherical, with mass M and radius R, made of solid material
(i.e. our test particle cannot penetrate it); label it "M" for
discussion. Outside M, the entire universe is vacuum [@] (except for the
test particle).

[#] If the object in question has a mass large enough to
significantly affect the geometry, the analysis is far
too complicated for a discussion here. In practice this
means the mass of the test particle is much smaller than
the masses of other objects in the physical situation;
for instance a satellite or human compared to the earth.

[@] I have to make such approximations and assumptions
to keep this discussion reasonable in length.

In GR, given the above assumptions, the test particle follows a geodesic
path through spacetime. The geometry of spacetime for this case is
known, and outside M it is called "Schwarzschild spacetime" after the
man who first derived and described it. Applying GR, one can calculate
the geodesic paths of this geometry; they are all affected by M. Of
course which path our test particle follows depends upon the initial
conditions we assume for it. Let us consider three such paths, relative
to approximately-inertial coordinates in which M is at rest:

A) The particle is initially at rest in these coordinates, at a distance
r from M's center, with r > R. This geodesic remains on a radius of the
geometry, accelerating towards M; if M is the earth and r is less than a
few hundred km above the surface, the acceleration is 9.8 m/s^2. Note
this is the same path that Newtonian mechanics predicts, using its
gravitational force, but here the path is purely a consequence of the
geometry induced by M; no actual force is involved. (The particle will
eventually hit M, but we stop our analysis before then.)

B) The particle is initially located at radius r from M's center, with r
R, but has a sideways velocity such that the particle's path is a
circular orbit around M. This is obviously a different geodesic than in
(A). Again this is the same path that Newtonian mechanics predicts,
using its gravitational force, but here the path is purely a consequence
of the geometry induced by M; no actual force is involved. (Here the
particle orbits M forever.)

C) The particle is initially at rest on the surface of M. Since the
particle cannot penetrate M, the surface pushes upward on the particle
with precisely the right force to keep the particle at rest on the
surface. This is not a geodesic path, and the upward force is
proportional to the mass of the test particle -- it is precisely the
force required to divert the particle from its geodesic path of (A) and
remain at rest on the surface of M. The force on the particle is
determined by the geodesic path it would follow if it were not being
pushed upward by the surface, so the force depends on M, R, and the mass
of the test particle (just as in the gravitational force of Newtonian
mechanics).

In (A),(B),(C) I described the paths using approximately-inertial
coordinates in which M is at rest. I could have used locally-inertial
coordinates in which the test particle is at rest -- in these
coordinates "gravity disappears" because any other test particles nearby
move in uniform straight lines relative to these coordinates. In essence
such coordinates move with the test particle as it falls. So in GR
gravity is not a force, but it is similar to the "fictitious forces" of
"centrifugal and Coriolis forces" -- they all induce accelerations
relative to non-inertial coordinates, and they all disappear in
locally-inertial frames.

[Important note: coordinates at rest on the surface of
the earth are not inertial frames. Locally-inertial
frames at the surface are all accelerating downward at
9.8 m/s^2.]

So near earth, GR predicts that the behavior of objects much smaller
than the earth ("test particles") is essentially the same as predicted
by Newtonian mechanics. But GR's explanation is quite different:
spacetime geometry rather than Newton's gravitational force. As
Newtonian mechanics has been experimentally validated so thoroughly near
earth, if GR did not predict the same behavior it would have been
rejected long ago.

[Another note: I used "approximately-inertial" coordinates
above; how is that possible? Consider (B) above, with
M the earth and the ISS as the test particle. The ISS
path through spacetime is a helix with axis parallel
to the time coordinate, period 90 minutes, and radius
350km+6371km; this is a very long and thin helix with
period along its axis > 240,000 times longer than its
radius, which is very close to a straight line. (That
aspect ratio corresponds to a human hair about 6 meters
long.)]

General Relativity is a fascinating subject that is VASTLY more
complicated than I have alluded to above. To get a general understanding
of its basic concepts I recommend:

Geroch, _General_Relativity_from_A_to_B_.
This is a non-mathematical introduction to GR.

[Perhaps later I'll describe how "gravitational force" in GR is only
distantly related to "gravitational time dilation" -- they are simply
different manifestations of the same aspect of GR.]

Tom Roberts
Maciej Wozniak
2021-05-08 18:11:09 UTC
Post by Tom Roberts
[There has been much confusion and misinformation in this thread, as
well as a few sensible responses. I will answer the original question,
but cannot follow the many side issues raised.]
I've been trying to understand how gravity acts like a force.
Our best model of gravity is General Relativity.
The Shit isn't even providing a consistent system of
coordinates and Tom is admitting it.
He only says it's "best" because he is a fanatic religious
crank.
mitchr...@gmail.com
2021-05-12 16:16:03 UTC
I've been trying to understand how gravity acts like a force.
I'm sure the math works out but I don't understand the logic.
On the net are many rubber trampoline examples which imply that you have to
bend (toward the south pole in those 2D examples).
I don't see what is moving.
I realize EVERYTHING is moving (at half a millions miles per second or so,
given rotation, orbit around the sun, the sun spinning up and around the
galaxy, the galaxy moving, etc.).
But if I think about gravity in the frame of reference from the earth I'm
not moving with respect to the earth. Am I?
I'm standing still with respect to the earth, aren't I?
So what's moving?
When I dig further I find out that it's more the curvature in time than in
space that causes this effect we call gravity. Most explain this feeling of