Discussion:
Is spacetime really curved? Embedded somewhere?
(too old to reply)
Jarek Duda
2008-12-10 22:08:46 UTC
Permalink
When light goes through different materials, it chooses path to
locally minimalize distance - it's trajectory is geodesic of some
metric (usually diagonal - isotropic) . It is the result of that
microscopic structure of the material can reduce wave propagation
speed.

Microscopic models of physics usually assume that we have some field
everywhere and it's fluctuations transfer interactions/energy/
momentum.
So maybe these microscopic structure can reduce waves propagation
speeds?
Reciprocals of these velocities creates (anisotropic) metric tensor
(g) and so for example particles travel through geodesics like in
general relativity theory.

Standard interpretation of general relativity says that particles goes
through geodesics because of space time internal curvature: theory,
experiments suggest some equations, which looks like being a result of
internal curvature of spacetime.
But if we live on some curved manifold, it intuitively should be
embedded somewhere(?) (and for example black holes are some spikes)
So why our energy/matter is imprisoned on something infinitely flat?
Why we doesn't interact with the rest of this something?
What happen if our manifold will intersect with itself? (optimists say
that it would allow for time travel/hyperspace jumps?...)
And less philosophical, but most fundamental (to connect GR and QM)
question is: how energy/momentum density can create curvature?

Maybe it's not the only possible interpretation.
Maybe we live in flat R^4 and GR is only the result of reducing the
speed of wave propagation by microscopic structure of some field,
which somehow is ruled by similar equations to Einstein-Hilbert.
This interpretation doesn't allow for instant time/space travel, but
it get rid of some inconvenient questions ... and creates a chance to
answer to the last one.

So how should look such connection of QM(QFT?) and GR?
What are particles? From spacetime point of view, they are some
localized in some three dimensions and relatively long in the last
one, solutions of let say some field to some equations. These
solutions want to be more or less straight in four dimensions
(constant velocities), but they turn accordingly to interactions
transferred by the field.
Many of them were created in big bang (boundary conditions), so their
long dimension is similarly directed - creating local time arrow (GR).
Bolzman distribution among such trajectories, can purely classically
create QM like statistical behavior ( http://www.scienceforums.net/forum/showthread.php?t=36034
).

Are there any arguments for spacetime internal curvature other than
that the equations looks like being be a result of it?
What do you think about these interpretations?
If the curvature is the only option, is spacetime embedded
somewhere... ?
N:dlzc D:aol T:com (dlzc)
2008-12-11 00:00:21 UTC
Permalink
Post by Jarek Duda
When light goes through different materials, it chooses
path to locally minimalize distance -
How do you locally minimize distance ("distance" is a non-local
measurement in this Universe)? For that matter how does light
know it is about to enter a less dense medium in the case of
total internal rellection... if it had not already been there?
Post by Jarek Duda
it's trajectory is geodesic of some metric (usually
diagonal - isotropic) . It is the result of that
microscopic structure of the material can reduce
wave propagation speed.
Gamma and x-radiation do not refract, which effect is what you
are dancing around.
Post by Jarek Duda
Microscopic models of physics usually assume
that we have some field everywhere and it's
fluctuations transfer interactions/energy/
momentum.
That is a stretch...
Post by Jarek Duda
So maybe these microscopic structure can reduce
waves propagation speeds?
No.
Post by Jarek Duda
Reciprocals of these velocities creates (anisotropic)
metric tensor (g) and so for example particles travel
through geodesics like in general relativity theory.
Different tensors for different wavelengths? Better guess again.

...
Post by Jarek Duda
And less philosophical, but most fundamental (to
connect GR and QM) question is: how energy /
momentum density can create curvature?
Perhaps because spacetime is issue from said energy density, and
does not exist separate from it?

...
Post by Jarek Duda
Are there any arguments for spacetime internal
curvature other than that the equations looks like
being be a result of it?
Can you translate / reference: "*internal* curvature" and
"equations resulting from *it*"? Seems to me equations describe,
not drive curvature...
Post by Jarek Duda
What do you think about these interpretations?
Translate from Gibberese... then we can know.
Post by Jarek Duda
If the curvature is the only option, is spacetime
embedded somewhere... ?
How could we know? Do we have belief that spacetime exists
without the presence of mass / energy, or belief that objects in
a "higher order" spacetime have no presence in our spacetime?
Sounds like religion to me... unless you can measure something...

David A. Smith
xxein
2008-12-11 01:47:44 UTC
Permalink
Post by Jarek Duda
When light goes through different materials, it chooses path to
locally minimalize distance - it's trajectory is geodesic of some
metric (usually diagonal - isotropic) . It is the result of that
microscopic structure of the material can reduce wave propagation
speed.
Microscopic models of physics usually assume that we have some field
everywhere and it's fluctuations transfer interactions/energy/
momentum.
So maybe these microscopic structure can reduce waves propagation
speeds?
Reciprocals of these velocities creates (anisotropic) metric tensor
(g) and so for example particles travel through geodesics like in
general relativity theory.
Standard interpretation of general relativity says that particles goes
through geodesics because of space time internal curvature: theory,
experiments suggest some equations, which looks like being a result of
internal curvature of spacetime.
But if we live on some curved manifold, it intuitively should be
embedded somewhere(?) (and for example black holes are some spikes)
So why our energy/matter is imprisoned on something infinitely flat?
Why we doesn't interact with the rest of this something?
What happen if our manifold will intersect with itself? (optimists say
that it would allow for time travel/hyperspace jumps?...)
And less philosophical, but most fundamental (to connect GR and QM)
question is: how energy/momentum density can create curvature?
Maybe it's not the only possible interpretation.
Maybe we live in flat R^4 and GR is only the result of reducing the
speed of wave propagation by microscopic structure of some field,
which somehow is ruled by similar equations to Einstein-Hilbert.
This interpretation doesn't allow for instant time/space travel, but
it get rid of some inconvenient questions ... and creates a chance to
answer to the last one.
So how should look such connection of QM(QFT?) and GR?
What are particles? From spacetime point of view, they are some
localized in some three dimensions and relatively long in the last
one, solutions of let say some field to some equations. These
solutions want to be more or less straight in four dimensions
(constant velocities), but they turn accordingly to interactions
transferred by the field.
Many of them were created in big bang (boundary conditions), so their
long dimension is similarly directed - creating local time arrow (GR).
Bolzman distribution among such trajectories, can purely classically
create QM like statistical behavior (http://www.scienceforums.net/forum/showthread.php?t=36034
).
Are there any arguments for spacetime internal curvature other than
that the equations looks like being be a result of it?
What do you think about these interpretations?
If the curvature is the only option, is spacetime embedded
somewhere... ?
xxein: What holds an atom together? + and - charges? What
constrains a neutron? Quarks?

Where do they get their energy from? The external.

Why? Because they all create a void in the general energy by using
and requiring energy hold form. They have formed an energy trap.
Energy comes to them by means of a general energy equilibrium.
Gravity ensues.

I could suppose that a BB would not release energy in a truly
symmetrical expansion for several reasons, but that is not the point.
The point is that it hasn't been released in such a fashion.
Otherwise, we (nor any matter) would exist. It is a constrained
chaos. Still it cannot do anything it cannot do. Yet to be seen?

I don't mean to lose you with the connectivity of how a neutron,
proton or electron forms in the first place. Let's go back to the
BB. There is no true singularity. Something happened, however, to
trigger whatever we might call it. Should we say increasing pressure
or can we call it gravity?

Did it contain the whole universe (as we are used to calling
everything that exists in an infinite space)? We will never know.
But we know that stars and BH's can explode. We have no idea of where
we are in our sequential existence.

Even if we were the product of some initial BB, it would still be a
chaotic situation. Because:

Is there an infinite amount of energy that can occupy an infinite
space? No! Energy wouldn't be able to expand. Does energy create
space? It seems so, but then space would be limited to energy. A
conundrum of sorts. It conflicts with how we think of things. It
puts a boundary on space and yet allows for expansion. Into what?

If quasars are receding (Hubble) faster than light, what/when are we
seeing and how did they form? My guess is that they were dirty (had
some matter associated with them from a BB) and were (to us) the first
instance of a gravitation (besides the initial cause).

All of this is somewhat spherically symmetric and relates to what some
consider a curved space or spacetime. But it is not perfect (as
explained above). I might add that such a BB has to be formed somehow
from the outside. It has to be triggered by a continuous force. It
is not static, is it?

This leaves many questions to be answered, but I hope it leads to more
questions that have been ignored in favor of a particular scientific
theory that we call physics.

You have no idea, yet, of what we might be capable of thinking
tomorrow. Get off the math and use some logic.
Jarek Duda
2008-12-11 07:00:15 UTC
Permalink
N:dlzc,
There was this rule in optics that for example to calculate trajectory
of light going from air to water, we should minimalize optical path
length l_1/v_1+l_2/v_2 to find the trajectory. In fact light 'makes
such choices' on microscopic level
http://en.wikipedia.org/wiki/Optical_path_length
So because of interference with responses of local atoms, light
travels along geodesic of metric tensor being 'refractive
index'*'identity matrix'. If we would like to take this analogy to GR,
such refractive index has to be four-dimensional and usually
anisotropic (different tensors for different directions (not
wavelength)) and could be created for example by that interactions are
transferred by some waves of field, so large interactions should
create some periodic structure of the field - small differences
between being in different phase could make interference needed to
change propagation speed/direction of other waves.
Post by N:dlzc D:aol T:com (dlzc)
Perhaps because spacetime is issue from said energy density, and
does not exist separate from it?
Why? Is squeezed in something infinitely flat?
Post by N:dlzc D:aol T:com (dlzc)
Can you translate / reference: "*internal* curvature" and
"equations resulting from *it*"? Seems to me equations describe,
not drive curvature...
Internal curvature would create going on geodesics behavior - is it
the only argument for internal curvature?
Einstein - Hilbert equations connects internal curvature with energy/
momentum, but how physically is made this connection? Until we
understand it, these equations aren't argument for internal curvature.
Post by N:dlzc D:aol T:com (dlzc)
xxein: What holds an atom together? + and - charges? What
constrains a neutron? Quarks?
Here is even more essential question: what holds electron together?
Why it's density likes to form exactly one particle - no less, no
more? Why quantum numbers are integer multiplicities? Why proton and
electron has the same charge? Why particles are so extremely stable?
I cannot imagine different answer to these question than that it has
to have topological nature - they are some topological singularities
of some field... but such field shouldn't have zero value, why their
energy is finite, why electron is so extremely small... ???
The other question is if quantum numbers are really conserved - when
black holes evaporates are they really producing only photons? Why not
also other particles?

About BB - energy is some invariant of for example fields... I don't
know from where it comes from? It was stored in initial conditions...
how? Where the spacetime came from???? :)
But doesn't inflation theory - expanding faster than light, suggest
that something is wrong with curvature interpretation?
What I can believe in is that BB created local time arrows - time
doesn't came directly from laws of physics, but from their solutions.
OG
2008-12-11 09:33:01 UTC
Permalink
Post by Jarek Duda
N:dlzc,
There was this rule in optics that for example to calculate trajectory
of light going from air to water, we should minimalize optical path
length l_1/v_1+l_2/v_2 to find the trajectory. In fact light 'makes
such choices' on microscopic level
Quantum Theory does it better by integrating over all paths - and if you do
it that way, you automatically get the correct results taking into account
2nd order effects such as diffraction and interference as well as refraction
and reflection.

Take a look at the first and second Richard Feynman lectures available on
the web thanks to the Vega Science Trust
http://vega.org.uk/video/subseries/8
N:dlzc D:aol T:com (dlzc)
2008-12-11 13:39:59 UTC
Permalink
Post by Jarek Duda
N:dlzc,
There was this rule in optics
Not all light is visible, so the rules for visible light
('optics') canot be applied to the workings of the entire
Universe. Any light travels at c for the first few "atoms" in
path length, then "transmission" sets in. Gamma radiation and
X-rays always travel at c. Additionally, n is a function of
wavelenght, so for your musings to make sense, there must be an
infiinite number of curvatures for any small region of space.
Post by Jarek Duda
that for example to calculate trajectory of light going
from air to water, we should minimalize optical path
length l_1/v_1+l_2/v_2 to find the trajectory. In fact
light 'makes such choices' on microscopic level
http://en.wikipedia.org/wiki/Optical_path_length
Your application to all light is inappropriate.
Post by Jarek Duda
So because of interference with responses of local
atoms, light travels along geodesic of metric tensor
being 'refractive index'*'identity matrix'. If we would
like to take this analogy to GR,
We cannot.
Post by Jarek Duda
such refractive index has to be four-dimensional and
usually anisotropic (different tensors for different
directions (not wavelength)) and could be created for
example by that interactions are transferred by
some waves of field, so large interactions should
create some periodic structure of the field - small
differences between being in different phase could
make interference needed to change propagation
speed/direction of other waves.
Or not.
Post by Jarek Duda
Post by N:dlzc D:aol T:com (dlzc)
Perhaps because spacetime is issue from said
energy density, and does not exist separate from it?
Why? Is squeezed in something infinitely flat?
No. May only be "spreadsheet" where accounts of conservation of
momentum and net production of entropy are worked out. QM does
not "see" / require spacetime. It has to be spliced on.
Spacetime may have no more or less meaning than "population
mean"... the population must be large enough for it to make
sense. There is no place entirely devoid of effect from all the
matter / energy in the Universe. Pass light through any such
candidate place and say that it has no finite distance from any
other body, for single edge diffraction. Neglecting black holes
for the moment.
Post by Jarek Duda
Post by N:dlzc D:aol T:com (dlzc)
Can you translate / reference: "*internal* curvature" and
"equations resulting from *it*"? Seems to me equations
describe, not drive curvature...
Internal curvature would create going on geodesics
behavior - is it the only argument for internal curvature?
Translation insufficient. You even lost your original question.
Post by Jarek Duda
Einstein - Hilbert equations connects internal curvature
with energy / momentum, but how physically is made
this connection? Until we understand it, these equations
aren't argument for internal curvature.
You seem to think that we have access to underlying reality. We
don't. The equations describe curvature, and accurately describe
the Universe at certain scales. That is as real as we can ever
get.
Post by Jarek Duda
Post by N:dlzc D:aol T:com (dlzc)
xxein: What holds an atom together? + and - charges?
What constrains a neutron? Quarks?
Here is even more essential question: what holds electron
together?
It is not a composite particle.
Post by Jarek Duda
Why it's density likes to form exactly one particle - no
less, no more? Why quantum numbers are integer
multiplicities? Why proton and electron has the same
charge? Why particles are so extremely stable?
Neutron.
Post by Jarek Duda
I cannot imagine different answer to these question
than that it has to have topological nature - they are
some topological singularities of some field... but
such field shouldn't have zero value, why their
energy is finite, why electron is so extremely small... ???
The other question is if quantum numbers are really
conserved - when black holes evaporates are they
really producing only photons?
No. They are not expected to produce only photons.
Post by Jarek Duda
Why not also other particles?
They are expected to.
Post by Jarek Duda
About BB - energy is some invariant of for example
fields... I don't know from where it comes from? It was
stored in initial conditions... how? Where the spacetime
came from???? :)
Spacetime is not "stuff".
Post by Jarek Duda
But doesn't inflation theory - expanding faster than light,
suggest that something is wrong with curvature
interpretation?
Only if you insist on "fields" and "stuff".
Post by Jarek Duda
What I can believe in is that BB created local time
arrows - time doesn't came directly from laws of physics,
but from their solutions.
Is that an argument? You are saying the time's arrow does not
come from the postulates or the logical rules that arrive at the
answer. Is that a bad thing?

David A. Smith
Jarek Duda
2008-12-11 18:45:38 UTC
Permalink
OG - yes, the classical trajectory we are usually varying around to
calculate path integrals is just the geodesic.

N:dlzc,
Maybe You are right and x-rays has always n=1, I don't know. But it
only says about frequencies atom's operates on. I'm only suggesting
general mechanism which could connect GR and QM.

If You don't like it, please suggest a better connection, which
finally could result in Einstein-Hilbert equations.

I'm only suggesting that if something looks like curvature, it doesn't
mean that it's really true - like light 'thinks' that geometry changes
when it changes the material.
You believe that spacetime is embedded somewhere?
What would happen if it should meet with itself?
dlzc
2008-12-11 20:11:31 UTC
Permalink
Post by Jarek Duda
OG - yes, the classical trajectory we are usually
varying around to calculate path integrals is just
the geodesic.
N:dlzc,
Maybe You are right and x-rays has always n=1, I
don't know.
You can know, you can look.
Post by Jarek Duda
But it only says about frequencies atom's operates
on.
Atoms operate from fractions of an eV to thousands of eV for inner
electrons of heavy atoms. This includes both gamma and X-rays.
Post by Jarek Duda
I'm only suggesting general mechanism which
could connect GR and QM.
It cannot.
Post by Jarek Duda
If You don't like it, please suggest a better
connection, which finally could result in
Einstein-Hilbert equations.
How can you connect "sociology" and "psychoanalysis"? GM is a
classical theory based on infinite divisibility, that ignores
uncertainty. QM treats the entire Universe as some finite local
result. They *cannot* be "connected", because they mutually exclude
one another. Your destination is not on the map.
Post by Jarek Duda
I'm only suggesting that if something looks
like curvature, it doesn't mean that it's
really true -
No problem there... we don't have access to Truth. All we have are
guesses and experiment. Your "suggestion" has a hole that applies to
"wavelength", one which your "suggestion" does not address.
Post by Jarek Duda
like light 'thinks' that geometry changes
when it changes the material.
Different light then "sees" different geometry, and you end up with
different curvatures. How does mutiple reulsts describe a single
space?
Post by Jarek Duda
You believe that spacetime is embedded somewhere?
No. I believe spacetime is like "population mean". It is meaningless
without the population to define it.
Post by Jarek Duda
What would happen if it should meet with itself?
It is neither "stuff" nor "field". It does not exist except as
reflection / shadow of matter / energy. It is neither "it" nor "self"
nor "wrapable". What would happen if your credit history should meet
with itself? Or the credit histories of every intelligent being
everywhere in the Universe *now*, should they all meet with
themselves?

David A. Smith
Jarek Duda
2008-12-11 21:12:38 UTC
Permalink
Both GR and QM are some approximation of the reality. They works fine
in different scales.
So if we want to understand physics better, we have to find the
connection between them. Like sociology is a result of psychology, the
curvature-like behavior has to be somehow a result of the microscopic
structure, approximated quite well by QM, standard model...
I've calculated that bolzmanian distribution among trajectories gives
QM-like statistical behavior (details and papers are on the link from
the first post) - it allow to understand that QM can occurs just
naturally...
All physics looks to be ruled by some microscopic laws, so GR also
should ... but how?

I understand You like to criticize, but it would be more constructive
if You would propose some alternatives...
Ok - I understand You believe that we just cannot understand full
physics and I respect it.
But I also think that most physicist wouldn't be satisfied with such
answer...
Best,
Jarek
xxein
2008-12-12 03:32:08 UTC
Permalink
Post by Jarek Duda
Both GR and QM are some approximation of the reality. They works fine
in different scales.
So if we want to understand physics better, we have to find the
connection between them. Like sociology is a result of psychology, the
curvature-like behavior has to be somehow a result of the microscopic
structure, approximated quite well by QM, standard model...
I've calculated that bolzmanian distribution among trajectories gives
QM-like statistical behavior (details and papers are on the link from
the first post) - it allow to understand that QM can occurs just
naturally...
All physics looks to be ruled by some microscopic laws, so GR also
should ... but how?
I understand You like to criticize, but it would be more constructive
if You would propose some alternatives...
Ok - I understand You believe that we just cannot understand full
physics and I respect it.
But I also think that most physicist wouldn't be satisfied with such
answer...
Best,
Jarek
xxein: You are more intelligent than I originally thought. Thank
you.

Yes, we still have a cloudiness of how we attempt to understand what
is going on (the physic). We attempt to classify it into a 'physics'
when we know so little. It is a narcissism we all share to some
degree (our human nature). How we got this way is just as open as a
question as where the universe came from.

In our attempt to understand, we use some sort of a foothold. We
wouldn't attempt to lift a heavy object while standing on a slippery
slope. But yet we do so because we have the object in hand and think
only that we have grasped it. It's very subjective and logically
tricky depending upon how you "think" you "have" it in your mind. But
not all minds are alike (thank goodness).

Why aren't all minds alike? That should be the first clue for a
diversity in a universe. Do we want all minds to think alike? Not
hardly, but then again we wish all minds would work to get the same
description of things that any of our individual minds would make. It
is a selfish hope that we confuse with both a belief and a physics.

How do we obtain a logic? Let's say that flying saucer entities
exist. How could we relate to their logic? How could we relate to
even our next door neighbor's logic? We don't, and it's about time
that we admit such a diversity. But we try to get along and let
ourselves roll with the tide (so to speak).

But where does that get us? It is a form of comfort. We do
everything for comfort. Almost all of us think we have a rational
mind but even an irrational mind seeks a comfort. The universe acts
in the same way and is constrained in it's ability to achieve this
comfort just as we are. It cannot do everything --- only what it
can. We cannot force it by theory to step beyond those bounds.

An irrational mind is still within the bounds of nature/the physic.
Don't try to jump from a 10 story building with feathers attached to
your arms, though. If you do, nature/the physic will have it's say.

Enough fluff but you get my meaning, don't you?

Now here's the crux. Our comfort is subjective. The universe is
not. We can change local circumstances (in/to some extent) to suit
ourselves. The universe will follow it up. "Change" is the operative
word here. We can "peek and poke" but the universe will respond, of
course.

This is the difference. Nebulae manage to form as the birthplace of
stars. Can you make one? Of course not. This is the difference
between our subjective thoughts and measurements we use and the
objective and self-changing universe.

Objective and self-changing might give you a jolt. Well? There's no
way we cannot deny change. But is it only of a local receptive/
measurable nature?

We want to understand the properties of the universe as we measure
them instead of what they are.

Does that explain the/any difference beween how we think and how the
universe works?
Jarek Duda
2008-12-14 22:52:15 UTC
Permalink
I believe that we are quite near to understand most of physics using
some field theory
http://www.scienceforums.net/forum/showthread.php?p=452080
We should focus on understanding their consequences, solutions like
particles now.

The other thing is that these fields still doesn't look like being the
lowest level ... the field can be a result of something lower, which
for example makes topological singularities of the filed
possible... ?????

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