Discussion:
Is Inertia An Inherent Attribute Of An Object
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kefischer
2014-11-28 20:46:36 UTC
Permalink
Is Inertia An Inherent Attribute Of An Object


Now where have I heard something like
that before?

Oh, yeah, I remember now;

http://www.fourmilab.ch/etexts/einstein/E_mc2/e_mc2.pdf


DOES THE INERTIA OF A BODY DEPEND
UPON ITS ENERGY-CONTENT?
By A. EINSTEIN
September 27, 1905


If the answer is yes, why is space-time
or "field theory" needed?

If inertia is a property of an object,
all that is needed to explain gravity is that
matter expands, inertia then causes a reaction
previously called "Gravitational Force".

To arrive at the correct solution to
kinematic problems, the past history
of the motion of all nearby objects needs
to be included, but the math is then no
longer as simple as Newtonian Gravitation.
Y
2014-11-28 22:38:40 UTC
Permalink
Inertia in my opinion is a shared relation between spacetime, matter and energy.

It's precisely because of gravitation that I think this.

A body in inertial freefall is guided by the spacetime, so it doesn't make any sense that such accelerating objects are 'inertial' as an outcome of solely their mass.

The idea that inertia is a property of objects alone is a classical idea, and we know they knew very little of curved spacetime.

Don't confuse momentum with inertia, they are different. Inertia is a property or quality of an object, NOT a quantity. This quality of motion can show us that without any applied forces, the motion of a body can change. This way, tracking such inertial bodies, we can observe that spacetime has curvature in locally gravitational regions.

-y
kefischer
2014-11-28 23:25:07 UTC
Permalink
Post by Y
Inertia in my opinion is a shared relation between spacetime, matter and energy.
Well, think again.
Post by Y
It's precisely because of gravitation that I think this.
Einstein thought it was because of the
energy content.

DOES THE INERTIA OF A BODY DEPEND
UPON ITS ENERGY-CONTENT?
By A. EINSTEIN
September 27, 1905
Post by Y
A body in inertial freefall is guided by the spacetime,
No it is NOT, space-time is the math
construct that describes or predicts the
motion, thinking anything "guides" motion
in freefall is a mistake.
Post by Y
so it doesn't make any sense that such accelerating objects are 'inertial' as an outcome of solely their mass.
What "accelerating" objects, do you have
one foot in a Newtonian universe and the
other foot in as GR universe?

Freefall is just coordinate acceleration,
it can be because of either one of two
possible situations, either the ground
or surface is accelerating upward (that
is the least complex mechanism), or
the inertial reference frame of space-time
is accelerating downward.

Maybe the math is done in a small
local volume to avoid the issue of the
inertial reference frame not being
rectilinear, but if the inertial reference
frame is accelerating downward, it
also has to shrink horizontally and
expand vertically downward.
Post by Y
The idea that inertia is a property of objects alone is a classical idea, and we know they knew very little of curved spacetime.
And still know very little.
Post by Y
Don't confuse momentum with inertia, they are different. Inertia is a property or quality of an object, NOT a quantity. This quality of motion can show us that without any applied forces, the motion of a body can change. This way, tracking such inertial bodies, we can observe that spacetime has curvature in locally gravitational regions.
-y
You have no idea what momentum is,
it is just a math construct relating mass
and velocity, for comparison of two or
more objects moving, nothing else.

With the Divergent Matter model,
there is no need for space-time being
anything other than an anti-symmetric
reflection of the motions in the real
world we live in where gravity exists.
Y
2014-11-29 01:24:00 UTC
Permalink
Fischer.

An inertial body in freefall acelerates. Also it's momentum and energy increases relative to other bodies. Coordinate acceleration is mathematical, not what the actual body does and the potential it has to do work. So you have it backwards.

And yes, spacetime is a geometric representation. We use it to refer to the space in nature which corresponds nicely with spacetime.

-y
kefischer
2014-11-29 03:50:37 UTC
Permalink
Post by Y
Fischer.
An inertial body in freefall acelerates.
No, it doesn't, it appears to accelerate
relative to the surface, it appears to move
toward another object horizontally, and
it appears to move away from another
object vertically, all at the same time.
Post by Y
Also it's momentum and energy increases relative to other bodies.
Of course, but that is nothing new
to Newton or anybody else, but relative
to itself, it might as well be "at rest".
Post by Y
Coordinate acceleration is mathematical, not what the actual body does and the potential it has to do work. So you have it backwards.
Actually, you are over your head,
and need to study coordinate frame
mechanics.
Post by Y
And yes, spacetime is a geometric representation. We use it to refer to the space in nature which corresponds nicely with spacetime.
-y
You are trying to BS me, it won't work,
your limited knowledge is obvious.
Poutnik
2014-11-29 07:24:27 UTC
Permalink
Post by kefischer
Post by Y
An inertial body in freefall acelerates.
No, it doesn't, it appears to accelerate
relative to the surface, it appears to move
toward another object horizontally, and
it appears to move away from another
object vertically, all at the same time.
And if you jumped from the Pisa tower,
your body would just appear to splash
when it appeared to hit the ground.... :-)
--
Poutnik
Tom Roberts
2014-11-29 01:09:38 UTC
Permalink
Post by kefischer
Is Inertia An Inherent Attribute Of An Object
First you must define what you mean by "inertia". I think you will have great
difficulty formulating a sensible definition that is not intrinsic to objects.

There is no quantity in any theory of modern physics that can be called
"inertia". The quantity that comes closest is mass, and that is indeed intrinsic
to each object.
Post by kefischer
If the answer is yes, why is space-time
or "field theory" needed?
Because "inertia" is not the whole story.
Post by kefischer
If inertia is a property of an object,
all that is needed to explain gravity is that
matter expands, [...]
You also need to invoke MAGIC so that spatial relationships, such as orbits, can
be preserved.

You also need to explain why Lorentz invariance is so pervasive -- you cannot
possibly "expand" objects in a Lorentz-invariant way.

And if you want anyone else to take notice, you need to formulate this as a
physical theory, not just as a set of unconnected "just so" stories. Nobody else
cases about your personal fantasies, hopes, and dreams (which is all you seem to
have).


Tom Roberts
Y
2014-11-29 01:17:57 UTC
Permalink
Roberts

Mass isn't inertia. Inertia is a quality of a body which has no forces acting upon it. Mass is a quantity.

-y
Tom Roberts
2014-11-29 03:37:26 UTC
Permalink
Post by Tom Roberts
Roberts
Mass isn't inertia.
I didn't say it is.
Post by Tom Roberts
Inertia is a quality of a body which has no forces acting upon it.
As I said: First you have to define what you mean by "inertia". There is no
quantity in any theory of modern physics that can be called "inertia".


Tom Roberts
Y
2014-11-29 05:33:09 UTC
Permalink
Roberts

I didn't say you said mass was inertia. You did say the closest thing to inertia is mass. I woud disagree with this also. Whie mass is an invariant quantity, inertia is a quality, so there is no closeness at all between inertia and mass. A body with mass can have forces acting upon it without any change in mass. A body that is inertial has no forces acting on it.

Btw. Inertia does have a closely correspnding quantitative measure, and guess what, it isn't mass it's weight. When the body is weightless it is inertial.

-y
Poutnik
2014-11-29 07:25:38 UTC
Permalink
Post by Tom Roberts
Roberts
Mass isn't inertia. Inertia is a quality of a body which has no forces acting upon it. Mass is a quantity.
Closest is not IS.
--
Poutnik
Y
2014-11-29 09:22:23 UTC
Permalink
Poutnik.

Mass is not the closest definition to inertial. Weight is the closest. More specifically zero weight. Where m.g=0, mass can be any invariant value (rest mass), but the resultant of any reaction forces is zero. Literally, to be inertial means that no reaction forces are acting on a body. So no, the inertia is not intrinsic to the mass. It is a shared relation between mass and any forces applied to that body. This is why again and again it must be stressed; Freefall is. NOT "forced fall". In this regard, the momentum of a body in motion can vary, while m.g=0.

So in a very simplistic mathematical relation inertia can be defined m.g=0. Also, where F=ma=0=inertial.

I used to be satisfied with a definition of inertia that; a body resisting motion change. This fails in a gravitationally curved space where masses induce motion change inertially. The better unification definition is simply; Inertial is zero forces acting on a body. Once you get a fully functioning mental rotation for how this applies in both a flat as well as a gravitationally curved spacetime, physics will be more simple for you.

-y

kefischer
2014-11-29 03:42:00 UTC
Permalink
On Fri, 28 Nov 2014 19:09:38 -0600, Tom Roberts
Post by Tom Roberts
Post by kefischer
Is Inertia An Inherent Attribute Of An Object
First you must define what you mean by "inertia". I think you will have great
difficulty formulating a sensible definition that is not intrinsic to objects.
I don't see why, many books I have are
about gravity and inertia.
Post by Tom Roberts
There is no quantity in any theory of modern physics that can be called
"inertia". The quantity that comes closest is mass, and that is indeed intrinsic
to each object.
http://phun.physics.virginia.edu/topics/inertia.html

It seems to be a good word.
Post by Tom Roberts
Post by kefischer
If the answer is yes, why is space-time
or "field theory" needed?
Because "inertia" is not the whole story.
It is half, if the other half is matter
expanding, another way to view gravity.
Post by Tom Roberts
Post by kefischer
If inertia is a property of an object,
all that is needed to explain gravity is that
matter expands, [...]
You also need to invoke MAGIC so that spatial relationships, such as orbits, can
be preserved.
That is what Gary said, but he is wrong,
I may be on the verge of being able to show
it with animated videos.
Post by Tom Roberts
You also need to explain why Lorentz invariance is so pervasive -- you cannot
possibly "expand" objects in a Lorentz-invariant way.
I do think it is possible, there has to
be a hidden outward velocity if matter is
expanding, something I am not aware
of being in the literature before, anything
that accelerates has to produce a velocity.
Post by Tom Roberts
And if you want anyone else to take notice, you need to formulate this as a
physical theory, not just as a set of unconnected "just so" stories. Nobody else
cases about your personal fantasies, hopes, and dreams (which is all you seem to
have).
Tom Roberts
I don't expect to actually formalize the
model, I would have to study math for a
couple of months to do that, and chances
are, it won't happen.

These are not "just so" stories, they
are the only possible result of the premise
of matter expanding with an acceleration,
I do not stipulate, the model does.
Tom Roberts
2014-11-29 05:43:41 UTC
Permalink
Post by kefischer
On Fri, 28 Nov 2014 19:09:38 -0600, Tom Roberts
Post by Tom Roberts
Post by kefischer
Is Inertia An Inherent Attribute Of An Object
First you must define what you mean by "inertia". I think you will have great
difficulty formulating a sensible definition that is not intrinsic to objects.
I don't see why, many books I have are
about gravity and inertia.
So what is "inertia"?
Show the symbol that represents it in any equation of modern physics.
Post by kefischer
Post by Tom Roberts
There is no quantity in any theory of modern physics that can be called
"inertia". The quantity that comes closest is mass, and that is indeed intrinsic
to each object.
http://phun.physics.virginia.edu/topics/inertia.html
It seems to be a good word.
That page discusses related issues, but gives no definition of the word. And
displays no symbol in any equation of modern physics.


THAT'S MY POINT: people discuss related issues, but never actually define the
word, and never display any equation of modern physics that contains or defines it.

Without an equation it is NOT well defined (no matter how many words might be
used to describe it).


The notion of "inertia" as a definite quantity has disappeared from modern
physics; the only remnant is as "(locally) inertial frame".

One could point to it in equations of Newtonian mechanics: the
"m" in f=ma. But there is no such equation in relativity, and
no quantity that takes the place of "m" in that equation
("relativistic mass" is woefully inadequate, as is "mass").
Another equation of NM is p=mv [3-vectors] (again "m") -- the
corresponding equation of relativity is P=mV [4-vectors] and
"m" is mass.

That's basically why I said that mass is the closest quantity in modern physics
(but it does NOT have all the aspects one expects from NM). So all of the
aspects of "inertia" that can be subsumed in a single quantity are aspects of
"mass", but not all of the expected aspects can be captured at all -- including
that most people consider the most important one: "resistance to acceleration".

Bottom line: physics is more complicated than the vocabulary of Newtonian
mechanics; "inertia" came from the latter and does NOT carry over into modern
physics.


Tom Roberts
Y
2014-11-29 06:06:02 UTC
Permalink
Roberts...

In principle, Inertia can be defined mathematically as m.g=0

So you can have a body with a positive value for mass, but the reaction force on that body is zero (i.e. no surface forcing against that body).

Assuming you were an astronaut pulled into a black hole, you wouldn't die till you actually hit something (assuming you could). Freefall into a bh would have about as much an impact on your body as skydiving (minus wind resistance).

-y
Y
2014-11-29 06:49:18 UTC
Permalink
Fischer

Regarding m.g=0=inertia=F=W

This is basically a proof that inertia isn't an intrinsic attribute of mass. To understand inertia mathematically requires the demonstration of zero reaction forces where g=0 or F=0 or W=0.

This equation can be used to prove (that in order to define inertia) the reaction forces must be zero, and the only way this can be shown is by making force part of the equation. This also shows how mass on its own says nothing of inertia.

In short, to understand inertia you have to throw force in as a product with mass and this product must be zero. Sheemples.

-y
kefischer
2014-11-29 08:23:08 UTC
Permalink
Post by Y
Fischer
Regarding m.g=0=inertia=F=W
This is basically a proof that inertia isn't an intrinsic attribute of mass. To understand inertia mathematically requires the demonstration of zero reaction forces where g=0 or F=0 or W=0.
This equation can be used to prove (that in order to define inertia) the reaction forces must be zero, and the only way this can be shown is by making force part of the equation. This also shows how mass on its own says nothing of inertia.
In short, to understand inertia you have to throw force in as a product with mass and this product must be zero. Sheemples.
-y
I think you are confusing yourself,
I just printed dozens of pages with the
sub-titles containing inertia from;

http://www.mathpages.com/rr/rrtoc.htm

and I suggest you read them instead
of making stuff up with your wild imagination.
Y
2014-11-29 09:01:42 UTC
Permalink
Fischer.

You are obviously a severely deluded old codger. Inertia doesn't require a symbol.

Inertia = m.g = 0

I think even Roberts would agree with this (both that you're a severely deluded old codger and that inertial means weightlessness [zero weight])

-y
kefischer
2014-11-29 07:32:50 UTC
Permalink
On Fri, 28 Nov 2014 23:43:41 -0600, Tom Roberts
Post by Tom Roberts
Post by kefischer
On Fri, 28 Nov 2014 19:09:38 -0600, Tom Roberts
Post by Tom Roberts
Post by kefischer
Is Inertia An Inherent Attribute Of An Object
First you must define what you mean by "inertia". I think you will have great
difficulty formulating a sensible definition that is not intrinsic to objects.
I don't see why, many books I have are
about gravity and inertia.
So what is "inertia"?
Show the symbol that represents it in any equation of modern physics.
I am not sure a symbol is needed, as "inertia"
plays no part in the kinematics, in free space, all
free moving bodies follow geodesics, not because
anything guides them, but simply because there
is no other path can follow in the absence of any
external forces.
If there is a collision, or an external force
acting, mass will have to be in the equation, not
inertia, the term inertia is just the name of the
impetus provided when mass is involved in any
kind of collision or interaction where real forces
are involved.


I just found this, I don't know what level
it is written at, I can't see any math with the
colors set the way I have them set, I only see
a flat gray background if I highlight the area
between text where I think math may be,
I will be getting another computer running
so I can see the math, but I don't want to
change the colors on this computer, I will
print this url and maybe I will be able to
see the math.
Please let me know if the below has any
merit, in your opinion;

http://www.mathpages.com/home/kmath588/kmath588.htm

"So, despite Einstein’s hopes, general relativity does not in any way
explain or obviate the principle of inertia. Granted, if the field
equations didn’t include the trace term (so that the covariant
divergence didn’t vanish), the resulting theory would have many problems
and be subject to many objections, but this goes without saying. No one
disputes that the principle of inertia is extremely well-founded in
observation. It is an extremely well-justified postulate – but it is
still a postulate. General relativity does not explain inertia, nor does
it dispense with the need to organize our spatio-temporal theories on
the topology and morphology implicit in the principle of inertia and the
associated distinguished coordinate systems."
Post by Tom Roberts
Post by kefischer
Post by Tom Roberts
There is no quantity in any theory of modern physics that can be called
"inertia". The quantity that comes closest is mass, and that is indeed intrinsic
to each object.
http://phun.physics.virginia.edu/topics/inertia.html
It seems to be a good word.
That page discusses related issues, but gives no definition of the word. And
displays no symbol in any equation of modern physics.
I am trying to figure out a way to describe
the kinematics of motion in space without and
forces acting (in the Divergent Matter model),
the math for collisions does not need any new
explanation or description.
Post by Tom Roberts
THAT'S MY POINT: people discuss related issues, but never actually define the
word, and never display any equation of modern physics that contains or defines it.
I did never infer it was involved in the
kinematics, it only comes into play when
there is a collision or interaction (in the
model).
Post by Tom Roberts
Without an equation it is NOT well defined (no matter how many words might be
used to describe it).
Perhaps I use the word too much
without specifying that it is only needed
for such things as "weight" on the surface.

The motion of any object (in the model)
becomes a result of all the other bodies
present and their mass and density, which
determines their contribution to the geometry.
The model uses this geometry to create
an apparent "field" when viewed by an
observer, but no "field" exists, and none
is needed because the kinematics is just
"apparent motion" only referenced to the
positions of bodies having mass.
Post by Tom Roberts
The notion of "inertia" as a definite quantity has disappeared from modern
physics; the only remnant is as "(locally) inertial frame".
Which works for the math, but (in the
model), an inertial frame can be indexed
to the most massive bodies, there is no
reason to construct arbitrary inertial frames.
Post by Tom Roberts
One could point to it in equations of Newtonian mechanics: the
"m" in f=ma. But there is no such equation in relativity, and
no quantity that takes the place of "m" in that equation
("relativistic mass" is woefully inadequate, as is "mass").
Another equation of NM is p=mv [3-vectors] (again "m") -- the
corresponding equation of relativity is P=mV [4-vectors] and
"m" is mass.
That's basically why I said that mass is the closest quantity in modern physics
(but it does NOT have all the aspects one expects from NM). So all of the
aspects of "inertia" that can be subsumed in a single quantity are aspects of
"mass", but not all of the expected aspects can be captured at all -- including
that most people consider the most important one: "resistance to acceleration".
Which is only needed (in the model)
to explain "weight", or the kinetic energy
in interactions amongst bodies.
Post by Tom Roberts
Bottom line: physics is more complicated than the vocabulary of Newtonian
mechanics; "inertia" came from the latter and does NOT carry over into modern
physics.
Tom Roberts
I will print out the url I posted above,
and see if it seems agreeable with the model,
the kinematics without the need for any type
of interaction with "space-time" may make
the model different from GR, except that
it seems to me the model is just the
inverse view of GR.
Since I think I have seen the constant G
in Einstein GR field equations, I could us an
expert explanation why that would ever be
for the kinematics in free space, if it is used
for that, I haven't examined the math.

I do think the model has great merit,
I would hope others with the talent and
ability to develop the math treatment
of the model, that is my only goal.
Joel Rhea
2014-11-29 09:04:14 UTC
Permalink
Post by Tom Roberts
The notion of "inertia" as a definite quantity has disappeared from
modern physics; the only remnant is as "(locally) inertial frame".
I=2, inertia is frequently used in static mechanics, if you need to build
a bridge for instance, you need to know the load distribution.
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