What is the Fabric of Spacetime Made Of?

[john 8]

GR suggests that any orbit around a massive body is caused due to the stretching and bending of trampoline (Space-Time).. right?
than such curvatures must essentially b perfectly circular in accordance with d GR..
Kepler laid down that orbiting bodies always orbit in elliptical paths with controlling body essentially at one of its focii.. that's what happens in actual practice..
So.. how do i relate that?

A trampoline made of what physical substance? Are you going to suggest that space or time are actual physical things that have an atomic structure? If so please describe this assumption.

 

[john 8]

The "fabric" of spacetime is simply a clever analogy to help imagine the merging of the 3 spatial dimensions, and the single time dimension. When you see picures of spheres bending a sheet that looks like a checkerboard, the checkeroard represents spacetime.

So, Spacetime is just what it implies; it's space and time.

So is this fabric an actual physical thing? If you say that it is, then is this fabric made of particles, waves or something else? What is it made out of?

 

[john 8]

This is incorrect. Orbits are geodesics in GR. In a Swarzschild spacetime they are essentially just distorted helixes. If you "flatten" the time dimension then you get the kind of precessing almost-ellipses that are actually observed.

What do you mean flatten? Are you talking about a physical occurrence? If so, are you saying time or dimensions are physical things? If so, time or a dimension are physical in what manner? Please be specific. Thank you.

 

[john 8]

If 4-D spacetime is curved doesn't that imply there must be a 5th physical dimension in which this, our 4-D spacetime, is curved?

What science are you using to make this statement?

 

[john 8]

I will factor in the idea of density into my growing definition of intrinsic curvature.

Space becomes more compressed, in a sense.

QUOTE]

Are you suggesting that space is a physical thing? If so that would mean that it is a form of energy, either a particle or a wave. Would you agree?

 

[john 8]

This argument is so curved, it's circular!

wot's a 'curved axis'?


Curvature of space or space-time is physical … parallel transport not working, or circles having the wrong circumference, are physical properties.

Please explain in what way either space or space-time are physcal things. I am using the term physical as it is defined in any dictionary or scientific reference book.

If you say space or space-time can physically be curved then that means that these things of which you speak are physical things that are being influeneced by exterior energy, which means that space or space-time come in contact with other forms of energy. So please give a scientific reference that describes how space or space-time are physical things.

 

[john 8]

But a change in a ruler (a change relative to what, btw? ) is a change in space itself … why else does the ruler change, if not because of where it is?

And similarly a change in a clock is a change in time itself.


Anything can be a measuring device …

a property of measuring devices is a property of everything!


"Physical" means that we can measure it …

what do you think it means? …

and we can measure parallel-transport and circumferences.

So are you saying that space-time is an actual physical thing? Yes/no.

If yes, please give a scientific reference that describes the physical structure of space-time. Remember that all things that we deem to be real physical things are made of energy. This energy either takes the form of a particle or a wave. if you know of a different way in which things exist please let me know. Otherwise, tell me and the rest of us participating on this discussion what form space-time exists as.

 

[granpa]

some scientists are now suggesting that 'information' is the fundamental thing that all things are made of. i'll try to find a reference.

edit:http://critical-path.itgo.com/Articlesanscover.html

http://en.wikipedia.org/wiki/Digital_physics

 

[Dale]

What do you mean flatten?

Hi john 8, it has certainly been a while, welcome back. Sorry about being imprecise, by "flatten the time dimension" I meant "take a projection along the time dimension". Specifically, a 3D projection of the 4D worldline of the satellite.

 

[I. N. Stine]

So are you saying that space-time is an actual physical thing? Yes/no.

If yes, please give a scientific reference that describes the physical structure of space-time. Remember that all things that we deem to be real physical things are made of energy. This energy either takes the form of a particle or a wave. if you know of a different way in which things exist please let me know. Otherwise, tell me and the rest of us participating on this discussion what form space-time exists as.

Wow. You have said my words exactly, if I could have ever thought of a good way to say my own questions about this. I love Relativity so much, but sometimes when I try to imagine it, the words people say about it just don't help me see it in my mind. I just can not imagine a thing that is not matter or energy that can be put into a curve or be flat or be anything, because it is nothing! It is not there! If nothing is there then there is no thing that can be curved!

Thanks for saying my question that I did not know how to say!

 

[john 8]

Hi john 8, it has certainly been a while, welcome back. Sorry about being imprecise, by "flatten the time dimension" I meant "take a projection along the time dimension". Specifically, a 3D projection of the 4D worldline of the satellite.

Hi DaleSpam.

I remember you from the thread regarding "Is time a dimension". We got into a discussion about if time was a real physical thing or not. I stated that time was not a real physical thing, you disagreed with me. We never resolved that issue, although I would like to.

Anyway, let's start off with a perfect understanding of each others ideas regarding this topic. I hope that you can agree that the only true way to understanding in communication is make sure that the people involved in the communication are familiar with and are using the same definitions of terms used in the communication.

In your above quote what exactly are you talking about? Are you talking about a physical action taking place or a concept in a math model? From the definitions of the terms that you are using it sounds like you are talking about a math model, something that only exists on paper or as a concept. Do I have this right?

 

[john 8]

Original quote by john 8 that is being referred to:

“So are you saying that space-time is an actual physical thing? Yes/no.

If yes, please give a scientific reference that describes the physical structure of space-time. Remember that all things that we deem to be real physical things are made of energy. This energy either takes the form of a particle or a wave. if you know of a different way in which things exist please let me know. Otherwise, tell me and the rest of us participating on this discussion what form space-time exists as.”

Wow. You have said my words exactly, if I could have ever thought of a good way to say my own questions about this. I love Relativity so much, but sometimes when I try to imagine it, the words people say about it just don't help me see it in my mind. I just can not imagine a thing that is not matter or energy that can be put into a curve or be flat or be anything, because it is nothing! It is not there! If nothing is there then there is no thing that can be curved!

Thanks for saying my question that I did not know how to say!

You are welcome, glad I could help.

 

[Dale]

In your above quote what exactly are you talking about? Are you talking about a physical action taking place or a concept in a math model? From the definitions of the terms that you are using it sounds like you are talking about a math model, something that only exists on paper or as a concept. Do I have this right?

A projection is an operation that you can perform in order to reduce the dimensionality of a higher-dimensional data set. It is usually used for visualization purposes. For example, a 3D rendering is a mathematical projection of a 3D scene onto a 2D image. An X-ray image is a physical projection from 3D onto 2D.

The projection I was talking about above was purely for visualization purposes and is neither something physical nor something that is part of the math of GR.

 

[A.T.]

So are you saying that space-time is an actual physical thing? Yes/no.

Remember that all things that we deem to be real physical things are made of energy. This energy either takes the form of a particle or a wave.

By this definition neither space-time, nor forces, nor EM-fields are physical things. They all are just useful concepts used in physics. Just like energy, particles and waves, which you use to define what "real physical things" are.

 

[Dale]

On that same note, john 8, I would still like to hear your time-free definition of energy or waves. If only matter and energy or particles and waves are "physical" according to you and time is not "physical", then you should be able to define energy and waves without any reference to time. Otherwise time is required for energy and waves and therefore every bit as "physical" as energy and waves.

 

[john 8]

Originally Posted by john 8

:So are you saying that space-time is an actual physical thing? Yes/no.

Remember that all things that we deem to be real physical things are made of energy. This energy either takes the form of a particle or a wave.”

By this definition neither space-time, nor forces, nor EM-fields are physical things. They all are just useful concepts used in physics. Just like energy, particles and waves, which you use to define what "real physical things" are.

These are not my definitions. They are standard scientific definitions.

By this definition force, EM fields, particles, waves, are physical things. Look up the definitions of physical, things, force, EM fields, energy, particles. Force or energy is the work done by a particle or wave, or the potential of work by a particle or wave.


Everything that exists in this universe that can be sensed, measured, or perceived is either made of a particle or a wave. There are no exceptions. These things that are made of particles or waves are classified as physical things, these things make up the physical universe.

Look, don’t just take my word for it. Learn, read, study, find out for yourself. After you have gotten some certainty on this, ask yourself are space, time, space-time physical things made of particles or waves.

If not then maybe they are just concepts.

This question goes out to all of you, is space-time a physical thing?

I am sure someone who thinks space-time is a physical thing can give an explanation or show a reference.

 

[Naty1]

at the largest scale the universe is flat to within 1 in 447,225,917,218,507,401,284,016?
If so, what would that mean?

According to theoretical physics, space thought to be EITHER flat or positively curved or negatively curved...experiments so far suggest it's flat...

 

[john 8]

On that same note, john 8, I would still like to hear your time-free definition of energy or waves. If only matter and energy or particles and waves are "physical" according to you and time is not "physical", then you should be able to define energy and waves without any reference to time. Otherwise time is required for energy and waves and therefore every bit as "physical" as energy and waves.

Right, time is not a physical thing. If you think that it is show me the reference. Currently there is no definition of time that defines it as a physical thing.

Time is not a physical thing due to lack of evidence to support a claim that it is a physical thing.

Science does not claim that time is a physical thing. There is nothing to support a claim that time is a physical thing. This is true.

If you want to say time is a physical thing than just show some evidence of this. Really, just put this to rest and show me that I am wrong.



Time either exists as a physical thing or it does not. If it is a physical thing then why doesn’t science recognize this. Find your evidence, a definition, observation, something. The fact that no one has provided any evidence that time is a physical thing just goes to strengthen my assertion that time is not a physical thing.

. If only matter and energy or particles and waves are "physical" according to you .

Not according to me, according to science. Do you even have an understanding of basic science?

I am not making up definitions. If you have a problem or disagreement with the definitions that I am using then you have a problem with the established empirical facts that are the basic building blocks of science.

You seem to want to deny what science has established as what is a physical thing and what is not.

Time is not a physical thing if you think that it is then you are in error and are in disagreement with science.

I am on the side of science.

Maybe you are having a problem accepting the fact that time is not a physical thing because you believe that SR and GR are explanations of the real physical workings of the universe and want to continue to prop up the belief that there is real phenomenon of time dilation, a big structure out in space that all of the planets are currently rolling around on. Is this what you believe. There is a big flat something in space that is just floating out there with planets rolling around on it? Maybe we are on the back of a big giant turtle. Maybe a big man named Atlas is holding us up.

The whole idea of a space-time fabric is not grounded in scientific reality. In order for SR and GR to be descriptions of real physical occurrences, time and space have to be real physical things that can interact with other physical things. If these things, time and space are real physical things then why hasn’t science stated this fact?

Sooner or later you are going to have to accept the fact that space and time are not physical things. There is no evidence that has ever existed to prove otherwise.

If you think time is a real physical thing then just show proof. Why do I have to keep asking this? Is it so difficult to do. Just participate in this discussion and support your claim with science and evidence.

 

[A.T.]

Force or energy is the work done by a particle or wave, or the potential of work by a particle or wave.

You need to learn the difference between force and energy.

Everything that exists in this universe that can be sensed, measured, or perceived is either made of a particle or a wave. There are no exceptions.

But space and time can be measured, yet they are neither particle nor wave.

I am on the side of science.

Who cares? Science is neither particle nor wave, so it is not a "real physical thing".

 

[Naty1]

John 8 posted...

I am sure someone who thinks space-time is a physical thing can give an explanation or show a reference.

Why limit your inquiry to space and time??

Is mass a physical thing? Is energy? Gravity?? Prove it! Nobody can...and how about dark mass and dark energy? Are they "a physical thing"...is 94% of the universe a "physical" thing that we have barely an understanding of at a basic level...seems that way...

Of course we take all those for granted, but nobody knows exactly...Keep in mind everybody assumed time and space were constant and unchanging until Einstein showed otherwise...so what we "know and understand" today is severely limited by our meager senses and limited evolutionary requirements for survival.

Nor do we know that exact constituents of space nor time...but that doesn't mean they are not physical...I posted similar thoughts very early in this thread... nobody can prove nor disprove physicality at this point...but we can begin to describe it in many ways...strings,branes, Penrose spin networks,spinfoam and on and on...so we have a start at understanding...

Mass, gravity, energy and space-time all appear to have emerged from an initally very unstable high energy environment where all were combined (unified) into one entity...those unstable initial conditions apparently resulted in the big bang, inflation and a lower energy more stable universe we inhabit...we have evidence, but not conclusive proof..for example certain forces can be unified: strong,weak, electromagnetic...but not so far gravity...so there is a belief that eventually we can unify all the forces under one mathematical construct...eventually that might include mass,time,etc...

 

[Naty1]

Time is not a physical thing due to lack of evidence to support a claim that it is a physical thing.

Where did you EVER get that thought??

You can't be reading on this forum and really believe THAT!

 

[john 8]

According to theoretical physics, space thought to be EITHER flat or positively curved or negatively curved...experiments so far suggest it's flat...

If space is flat then what is it existing in? What is outside the surface of this flat thing. This flat thing is made of what? The space between you and the computer monitor is that flat? There is the idea of space all around us what is flat about that.

This flat thing, is it above the Earth, below the Earth? Is the Earth in contact with it? If not then is there a distance between the Earth and this flat thing? If so what would you call the area that is between this flat thing and the Earth.

Do you see how absurd it is to believe that there is a flat thing called space .


Look, I am not trying to pick on you, but where has all the science and logic gone in this thread? The things that are being stated here are just silly. It is like being at some sort of science fantasy camp where the only requirement is to throw all logic and science out the window and just have fun with make believe.

Does anyone have the ability to think and not just repeat what they have been told? Think about what you are saying.

 

[john 8]

Originally posted by john 8

“Time is not a physical thing due to lack of evidence to support a claim that it is a physical thing.”

Where did you EVER get that thought??

You can't be reading on this forum and really believe THAT!

It is not a thought or belief. It is a statement of fact. There is no evidence to support the claim that time is a physical thing.

If you disagree, just show me a definition, or observation, or experiment that describes the physical structure of time.

All things that are considered to be physical are either made of a particle or a wave. This is according to science, not me.

If you think time is a physical thing then just provide some scientific evidence of this evidence of this.

 

[Dale]

I am not making up definitions.

Yes, you are. I have never heard anyone but you ever assert that all physical things are either particles or waves. It is entirely a definition made up by you. However, I have no problem with that definition. I just think that time and space are implied in the definition of a wave and therefore also "physical" by that definition.

So again, I ask how do you define a wave (or energy) without time? If you cannot then how can you assert that time is not "physical" according to your own definition of the term?

Re: http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html" that time is physical (of or pertaining to physics, not your "wave or particle" definition).

 

[john 8]

Yes, you are. I have never heard anyone but you ever assert that all physical things are either particles or waves. It is entirely a definition made up by you. However, I have no problem with that definition. I just think that time and space are implied in the definition of a wave and therefore also "physical" by that definition?).

All physical things are either a particle or a wave, that is what science says not me. Look for yourself, are you so unfamiliar with the basics of science? You are going to have to stop saying that I am making up definitions, it is an incorrect statement.

So again, I ask how do you define a wave (or energy) without time? If you cannot then how can you assert that time is not "physical" according to your own definition of the terms.?).

Again not my definitions.

So again, I ask how do you define a wave (or energy) without time? If you cannot then how can you assert that time is not "physical" according to your own definition of the term?).

This is a question. Not an definitive answer to the nature of time. You have used the term time in your question. What definition of the term time are you using? Is it "Of or pertaining to physics"? If so read your question using that definition and see if it makes sense or is what you are trying to communicate.

Re: http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html" that time is physical (of or pertaining to physics, not your "wave or particle" definition).

Again with this pertaining to physics. I am not asking that. We can all agree that the subject of time is used in physics. I am asking if time is a physical thing, something that is made of a particle or a wave.

If you do not think that time is made of either a particle or a wave then just say so, but you cannot then go on to say that time is something that dilates, or slows down, or was made at the Big Bang, or is a thing that has some type of existence. Time either exists or it doesn’t. if it exist as a physical thing then science would define it as such and time would have the qualities of all those other things that are considered to be physical.

In the link that you provided, did you find evidence of time being a physical thing? I have been referred to this link before and there is no evidence that time is a physical thing. If the link you provided has this evidence why don’t you just copy and paste this evidence and post it.

Here you are looking for evidence that time is a physical thing, but I notice that you did not send a definition of time to prove your point. Would not that be the quickest and easiest way to prove your point.

What! You did not find any scientific reference or definition to support your claim. How weird, yet you continue to assert that time is a physical thing. Why is that? Are we all just free to make up stuff and never have to back it up with facts. Is that what this form is all about?



Why is it that I seem to be the only one who notices that no one has provided any scientific evidence to back up their claims that time is a physical thing?

Still no evidence. How much longer can this go on until it is realized that time is not a physical thing?

 

[Dale]

Again with this pertaining to physics. I am not asking that. We can all agree that the subject of time is used in physics. I am asking if time is a physical thing, something that is made of a particle or a wave.

I think we are in agreement then. We both agree that time is used in physics and we both agree that time is not made of a particle or a wave.

This is a question. Not an definitive answer to the nature of time.

Yes, a question which you also avoided answering last time I asked it. I answered your question, so now you have no excuse to not answer mine.

The usual definition of a wave is:
{ \partial^2 u \over \partial t^2 } = c^2 \nabla^2 u
As you can see, time is part of this definition. So is this the definition of "wave" that you are using or not? If not, what is your definition of wave and is time part of it?

 

[p764rds]

Originally posted by john 8

“Time is not a physical thing due to lack of evidence to support a claim that it is a physical thing.”

I have just read this thread and am trying to show that 3D physical space is illogical.
A school teacher told me (I never forgot what he said) that the theories of space assume that it exists in the first place (and then go on to bend, shape it). He was annoyed and told that he thought this assumption (of space existing in the first place) to be fudged to fit 'the facts'!
I want to suggest its an unjustified assumption that real physical space is possible (and then offer another theory of 3d space - informational). Its empty - how can it hold up at all? Manifold or not.

I am trying to show that this space-time theory lies on shaky foundations (and that what we really see around us - is in information where 3D space is very, very easy to make).

Manifolds, bending by gravity - fine - no problems. Relativity, Lorentz invariance- no problems. But is it an initial assuption that it exists in the first place unproved?

 

[Dale]

There is no requirement that a physical theory start from no assumptions. Making such assumptions leads to theories that are consistent with observation. So I really don't see the value in what you are attempting.

 

[A.T.]

Manifolds, bending by gravity - fine - no problems. Relativity, Lorentz invariance- no problems. But is it an initial assuption that it exists in the first place unproved?

You cannot prove that anything exists. Do numbers really exist? They are just an abstract idea, quite useful though, aren't they? Space-time is no different.

 

[ThomasT]

... just show me a definition, or observation, or experiment that describes the physical structure of time.

Time refers to the configuration, or arrangement, or relative position of a set of physical objects.
So, time, in the most general sense, is any and all physical structure(s).

We 'keep time' or 'track time' or make 'time indexes' of a set of objects whose configuration is changing by associating the set of objects with the changing configurations of some other set of objects such as a conventional clock.

I want to suggest its an unjustified assumption that real physical space is possible.

Imho it's a justified assumption. There's lots of experimental evidence to suggest that there's activity in even the emptiest of empty spaces inside our universe, to vanishingly detectable energy scales.
For example, the observed effect on accelerated oscillators predicted by SR and GR.

The structure of the 'fabric of spacetime' is of course unknown. The fundamental medium of our universe might be effectively undectable, ie., nonphysical as far as we might be able to determine (even if it's particulate, but especially if it's nonparticulate). But it can still be used as a metaphysical framework from which a conceptually and mathematically unified theory of the physical (detectable by us) universe might be developed.

From the observational evidence and success of certain theoretical constructions it might be inferred that physical reality is fundamentally wavelike. Particulate structures, ie., more or less bounded, standing wave structures, and a hierarchy of particulate media might be formed via countless iterations of some (or a) fundamental wave dynamic(s) -- with the wave behavior in the particulate media being fundamentally governed by the same wave dynamics which produced the particles that define the media. It would also seem likely that higher order, scale dependent organizing principles would emerge as media interface and merge and wave interaction becomes increasingly complex.

GR's depiction of gravitational behavior is a mathematical simplification of increasingly intense and complex wave interaction. And, of course, a rather good and useful theory. However, the posts in this thread are evidence of how difficult it is to make a 'picture' of reality from a mathematical model that's, necessarily, somewhat removed from that reality. (The exchange particle 'picture' of gravity would be a step closer to the wave mechanical reality).

If this makes little sense, then I apologize. And I also apologize for the parts of this post that are out of place in this forum, but it seemed ok for this particular thread. Anyway, I do think of space and time as aspects of physical reality -- with space being the 'stuff' and time being how the 'stuff' is configured. And the posts have been interesting and fun to read.