What is space made out of?

[AlphaBeta]

Aren't atoms only in matter? If so, what does space consist of? I know there are gases, but that's not the actual space itself. I mean, does space contain anything in and of itself? I'm referring to outer space and/or any space you may experience on Earth.

 

If you look out into a room and observe all of the empty areas without objects, what does that space consist of? Besides any gases, the space itself is just nothingness, right? There are no atoms etc. contained within empty space, correct?

 

I know this may sound like a dumb question, but it's something I've ever thought of before.

[YT2095]

space is made out of Distance.

[AlphaBeta]

space is made out of Distance.

 

What maintains the distance? Why doesn't space collapse in on itself?

[Klaynos]

Space has properties...

 

And most regions at least have afew atoms/m. All space will have alot of neutrinos and photons in it.

 

So I don't think it's fair to say space is nothingness.

 

It doesn't collapse because of the big bang and now dark energy, what ever that is is causing it to expand faster than previously.

[AlphaBeta]

"All space will have alot of neutrinos and photons in it."

 

You are saying these things are IN the space... they're not the actual space itself. I'm talking about just the space. Space doesn't contain anything in and of itself, right?

 

Also... look at the room you are in. Notice the space in between the walls. What is holding that space there i.e. what keeps the walls from closing up til there is no space inbetween them?

 

If I said... what keeps an object from flying into the sky, you would say gravity... so what keeps things from moving side to side and eliminating space? How can space expand? Is that saying, new space is being created?

[Radical Edward]

good question. We know space has properties like electrical permittivity, permeability and curvature, but as to what it is, well it could just be an artefact of how things work. The problem is that at the moment we don't have a background independent description of the universe.

[Klaynos]

Space is a thing itself sortof, it's a very special thing like time. Because they're so special you can't settup a good analogy for them.

[ydoaPs]

Space is the separation between objects. Time is the separation between states of a system. Time and space are very related. You can see from what is said that they are similar, but not identical ideas. The magnitude of the separations are relative and dependent on the energy of the system in a reference frame.

[Radical Edward]

Space is the separation between objects. Time is the separation between states of a system. Time and space are very related. You can see from what is said that they are similar, but not identical ideas. The magnitude of the separations are relative and dependent on the energy of the system in a reference frame.

 

well a better way to put it is to say that space and time are dimensions. separation in space and time are described by spacetime vectors.

[AlphaBeta]

Okay... say I just bought a goldfish and I had it in one of those clear, plastic bags filled with water. And let's say the sides of the bag represents the walls in a room... and the water in the bag represents the area in between the walls. If I remove the water from the bag, the bag will close in on itself, because the water is what gives the bag shape and holds the sides apart. So in the room... what is holding the walls apart?

[ydoaPs]

well a better way to put it is to say that space and time are dimensions. separation in space and time are described by spacetime vectors.

 

I thought my reply was basically how space and time were defined in Gravitation. I guess I'll have to re-read it.

 

Okay... say I just bought a goldfish and I had it in one of those clear, plastic bags filled with water. And let's say the sides of the bag represents the walls in a room... and the water in the bag represents the area in between the walls. If I remove the water from the bag, the bag will close in on itself, because the water is what gives the bag shape and holds the sides apart. So in the room... what is holding the walls apart?

 

When you remove the water, you lower the pressure on the inside of the bag. This means the pressure on the outside of the bag is much larger. The outer pressure wins and causes the bag to collapse.

 

In the case of the room, however, the pressure inside and outside are nearly equal unless made to be otherwise.

 

I'm not sure what this has to do with the thread, though.

[AlphaBeta]

Well, if space isn't made of anything... I want to know what gives it shape... that's how it was related to the thread.

[Kyrisch]

Nothing actually gives it shape. It just sort of exists, just a property of the universe. In order to describe it, the metaphor of the 'fabric' of space-time is used in order to conceptualise gravitation wells as 'bending of the fabric and stuff' but I doubt its actual nature is much like that at all.

[stevo247]

Aren't atoms only in matter? If so' date=' what does space consist of? I know there are gases, but that's not the actual space itself. I mean, does space contain anything in and of itself? I'm referring to outer space and/or any space you may experience on Earth.

 

If you look out into a room and observe all of the empty areas without objects, what does that space consist of? Besides any gases, the space itself is just nothingness, right? There are no atoms etc. contained within empty space, correct?[/quote']

 

 

Isn't vacuum energy (whatever that is) somehow related to the structure of space?

[Kyrisch]

It could be. Too bad we don't know much about that one either xP.

[Mr Skeptic]

I think that this question is still an unsolved question in science. No one knows exactly what empty space is.

 

Doesn't empty space also contain virtual particles? It certainly has length/volume, electrical permittivity and permeability (which are linked to length, somewhat, by the speed of light). In special relativity, space and time are linked so that what looks like a distance in one reference frame might seem like a smaller distance plus a time separation in a different reference frame. In general relativity, spacetime has curvature, which is related to gravity. In the Big Bang model, spacetime has a rate of expansion.

[Martin]

good question. We know space has properties like electrical permittivity, permeability and curvature, but as to what it is, well it could just be an artefact of how things work. The problem is that at the moment we don't have a background independent description of the universe.

 

this is a major idea that is floating around these days, that you hear a lot.

different people say it different ways.

one way to put it is to say that space and time are emergent features

not fundamental, but sort of macroscopic scale illusions that you see if you back off from the very microscopic planck scale (nittygritty "atomic" ) fundamental descriptors.

 

people talk about the macro space, time, and matter that we see, all being emergent from more fundamental degrees of freedom (descriptors, microscopic interactions) which themselves do not know about space and time.

 

this is not philosophy. I am talking about people's mathematical modeling and their attempts at mathematical modeling fundamental degrees of freedom without spacetime, without putting spacetime in at the start, and having overall spacetime emerge from it

 

the most advanced research team in this kind of endeavor is at Utrecht holland. They clearly HAVE a background independent fundamental picture from which a common vanilla spacetime (deSitter) emerges as a quantum average. it "self-organizes" in the course of humongous computer runs. they don't put the spacetime in at the start. they put in a bee-hive, or be-hive, of micro descriptors, which self-organize.

the number of dimensions that will emerge is not predetermined and can differ from place to place, run to run, and over different scales of measurement-----in other words, chaos.

the remarkable thing is that a smooth 4D geometry emerges at large scale average, and one sees quantum fluctuations around it.

 

this is s step towards the goal of background independent quantum geometry.

As of December 2007, they only just got this far, they still need to put matter in and get it to work.

so far they just got a vanilla empty universe.

 

probably the papers to read about this are the ones by Renate Loll and team.

just google Renate Loll and go to website and it gives links to papers.

one just came out this month----it is a lightreading version of something that came out December 2007

 

it gives a tentative answer to the thread question

What is space made of?

It is made of the little micro thingies that Loll team puts into the computer and gets to self-organize and become spacetime

 

but in the limit as the size of them goes to zero. Loll team doesn't propose a minimal size, the description is consistent if you let the size of the thingies go down arbitrarily small---which is a bit strange. so it is easier on the brain to think of a fixed stage and a fixed size

 

like the infinitesimals in calculus. as small as they need to be. little dx

things that interconnect with each other to make the illusion of a world.

 

I guess the point is that if you can get it to run in the computer and look at the result and study and measure it at any arbitrary point, then it is not just philosophy

 

Loll has raised the bar for background independent quantum geometry

if anyone wants links to read, please say

[D H]

this is not philosophy. I am talking about people's mathematical modeling and their attempts at mathematical modeling fundamental degrees of freedom without spacetime, without putting spacetime in at the start, and having overall spacetime emerge from it

 

the most advanced research team in this kind of endeavor is at Utrecht holland. They clearly HAVE a background independent fundamental picture from which a common vanilla spacetime (deSitter) emerges as a quantum average. it "self-organizes" in the course of humongous computer runs. they don't put the spacetime in at the start. they put in a bee-hive, or be-hive, of micro descriptors, which self-organize.

The July 2008 Scientific American has a good lay article on this very topic. A free preview is at sciam.com. Preprints of articles of a more technical nature are at arxiv. One is http://arxiv.org/abs/0712.2485. Clicking on any of the authors' names will lead to several more papers on the same subject.

[Martin]

The July 2008 Scientific American has a good lay article on this very topic. A free preview is at sciam.com.

 

Yes DH, you're right! Thanks for the link to the preview of the SciAm article.

Fortunately I came across a site where you can read the whole article free, as well, but it is set up so it cannot be copied or printed out (afaics).

 

The graphic illustrations are well-done and intuitive, so I find the whole thing is very helpful

http://www.scribd.com/doc/3366486/SelfOrganizing-Quantum-Universe-SCIAM-June-08

[ydoaPs]

Thanks DH & Martin. You expert types can be helpful at times.

[whap2005]

The thing that keeps space from colapsing on itself is of course time. So in a sense, "empty space" is actually made of time.

[ydoaPs]

The thing that keeps space from colapsing on itself is of course time. So in a sense, "empty space" is actually made of time.

 

Yes, of course!

[Martin]

good question. We know space has properties like electrical permittivity, permeability and curvature, but as to what it is, well it could just be an artefact of how things work. The problem is that at the moment we don't have a background independent description of the universe.

 

 

this is a major idea that is floating around these days, that you hear a lot.

different people say it different ways.

one way to put it is to say that space and time are emergent features

 

 

The July 2008 Scientific American has a good lay article on this very topic. A free preview is at sciam.com. Preprints of articles of a more technical nature are at arxiv. One is http://arxiv.org/abs/0712.2485. Clicking on any of the authors' names will lead to several more papers on the same subject.

 

I like this thread. Lots of people got interested and contributed. The ideas are presented in a way that isn't too technical or hard to understand. Some deep issues are raised (background independent description of the universe, one that doesn't depend on putting some prescribed spaceandtime geometry in by hand at the start)

 

I hope everybody who is at all interested in these issues of what fundamental descriptors, from which macroscopic space and time arise or emerge, what is the quantum dynamics of spacetime at small scale. I hope everybody interested in this thread's topics will read that SciAm article that DH mentioned.

 

I'll give the link to the free version again.

 

http://www.scribd.com/doc/3366486/SelfOrganizing-Quantum-Universe-SCIAM-June-08

 

If this scribd link stops working, please let me know. I'll try to find an alternative. This SciAm article is clear and accessible and non-mathematical as anything I can recall seeing at this level. This is the basic stuff underlying space and time they are trying to computer-model----and ultimately the basic stuff of matter, but they havent got matter included yet in their published results.

 

their description is indeed background independent, which is crucial. But Radical Edward is right in saying we don't have a [FULL] background independent description yet. what Renate Loll and Jan Ambjorn and their group have is a first step, the dynamics of an EMPTY quantum universe. It will be an important first step, if it proves to be right, but there's still a ways to go.

 

A big international conference on this kind of stuff (the 2008 Quantum Geometry and Quantum Gravity conference "QG2") starts 30 June, in about a week from now. Renate Loll will be giving a talk about this at the conference.

http://www.maths.nottingham.ac.uk/research/conferences/qg2_2008_quantum_geometry_and_quantum_gravity_conference/

 

This site has the QG2 schedule and participants and titles and brief abstracts of sixty-some talks, including Loll's, so if you're interested you can see roughly where the field is at, currently, and what some different approaches are. Basically they are all trying to help answer the question that the original poster AlphaBeta raised in this thread. Which everybody knows is a hard problem and most approaches are almost certain to turn out wrong, but it is a kick to see them try for it. If you are in Nottingham UK during first week of July, consider dropping in and checking out some of the talks.

Edited June 22, 2008 by Martin