Where does new space come from as the universe gets bigger?

[CosmicVoyager]

Greetings,

How is new space created?

There was no space before the big bang, correct? And the universe is still getting bigger? So the amount of space is increasing.

Where did and does it come from? Space is something not nothing correct? It can be stretched, compressed, and curved.

Is something being converted into space? I heard mention somewhere that gravity was being converted into space.

Thanks

 

[Mordred]

A common mistake is to apply a physical nature to space. Space is simply volume or distance. the volume is filled with other things such as energy and matter. google metric expansion.

 

[CosmicVoyager]

"google metric expansion."

I had read that.

So the countless illustrations of space being warped by mass are incorrect? And the idea that you could travel faster than light by contracting and expanding space? And wormholes shown and described as distorted space. Space is constantly referred to as a fabric. That all indicates space is something.

 

[Bandersnatch]

In your opening post, try and replace every instance of the word "space" with the word "distance". Read the altered text and ask yourself whether it seems sensible to you to ask such questions.

Space is of course not equivalent to distance, but it is a very similar concept.

 

[Matterwave]

"google metric expansion."

I had read that.

So the countless illustrations of space being warped by mass are incorrect? And the idea that you could travel faster than light by contracting and expanding space? And wormholes shown and described as distorted space. Space is constantly referred to as a fabric. That all indicates space is something.

The picture of space-time as a "fabric" is an analogy, not to be taken seriously. It has its uses, but must be abandoned when it's no longer useful. Space-time is made up of all the events that take place in it, it is not its own separate entity.

 

[CosmicVoyager]

In your opening post, try and replace every instance of the word "space" with the word "distance". Read the altered text and ask yourself whether it seems sensible to you to ask such questions.

Space is of course not equivalent to distance, but it is a very similar concept.

Well this is big news. As in my last post...scientists are constantly describing it as as a thing not distance. I mean every time cosmology and physics is talked about. I could spend forever citing scientists saying something incorrect about space then, assuming they continue to make the mistakes. I can probably search these forums and find experts doing it. They are then misinforming millions of people. Most science books are wrong. Space is not curved. Mass/gravity does not curve space. Wormholes are not as illustrated. You can't expand and compress space to bypass the speed of light. It is all wrong then.

I have been trying to understand universe for years based on these endless false statements. Darnit. This changes everything. No I need to reread everything on cosmology, relativity, and quantum physics *without* thinking of space like that. They really screwed up.

 

[Bandersnatch]

I did not write any of that. Why are you saying so?

Scientists are describing space as space. It's a mathematical concept with certain well-defined properties. It's not a "thing" any more than distance is.

 

[Matterwave]

It's not as bad as it seems. People have to use words to describe things to other people. We can't just say to the masses "hey, look at the Einstein field equations - That's spacetime - that's gravity!" because nobody would know what we were talking about. The use of analogies is appropriate where they are appropriate. You don't have to "reread" everything or relearn everything just because you found out a new piece of information. Incorporate this new information into what you know.

 

[CosmicVoyager]

Scientists are describing space as space. It's a mathematical concept with certain well-defined properties. It's not a "thing" any more than distance is.

I will begin compiling a list of examples of space described and illustrated as a thing with shape stretched, compressed, curved, twisted. Grids showing space itself as having shape.

 

[Mordred]

"I will begin compiling a list of examples of space described and illustrated as a thing with shape stretched, compressed, curved, twisted. Grids showing space itself as having shape."

no need we have all seen them numerous times lol. As mentioned they are a visual aid. To describe GR influences on the energy-mass filling space.

"According to the general theory of relativity, the geometrical properties of space are not
independent, but they are determined by matter. Thus we can draw conclusions about the
geometrical structure of the universe only if we base our considerations on the state of the
matter as being something that is known."

Part of the confusion derives from statements like the one I posted, coincidentally that one is from Einstein himself lol. Remember that space itself is simply volume filled with energy/mass. So in a way its more accurate to say that gravity affects the energy/mass contained within space rather than space itself. However cosmologist tend to gloss over that as they expect the public to already understand that. Even a total vacuum has energy. So once there is more volume, that volume will always contain some form of energy potential or matter. Terms such as space is created or stretched often are in cosmology literature. Its part of the limitations of lanquage. The mathematics itself shows that its simply an increase in volume or distance between two or more points.

This article shows the geometric aspects in terms of simple distance measures with the pressure relation influences of matter and the cosmological constant.

https://www.physicsforums.com/showpost.php?p=4697773&postcount=30

the article is based largely on Barbera Ryden's "Introductory to cosmology"

 

[Chronos]

Space is merely the emptiness between objects in the universe. Emptiness has no metric, so it is unbounded.

 

[Mordred]

define emptiness, even a void has energy density implications in quantum mechanics as the lowest possible energy state.

 

[CosmicVoyager]

"According to the general theory of relativity, the geometrical properties of space are not independent, but they are determined by matter. Thus we can draw conclusions about the geometrical structure of the universe only if we base our considerations on the state of the
matter as being something that is known."

Part of the confusion derives from statements like the one I posted, coincidentally that one is from Einstein himself lol. Remember that space itself is simply volume filled with energy/mass. So in a way its more accurate to say that gravity affects the energy/mass contained within space rather than space itself. However cosmologist tend to gloss over that as they expect the public to already understand that.

That is completely the opposite of what the general public understands. I am far more scientifically literate and knowledgeable than the general public. That quote from Einstein clearly states the opposite. It says space has geometry. That space itself has shape.

In beginning to complie my list of examples I found further confirmation of physicists currently statng that space in actually a thing like a fabric and not just volume or distance. This raises the concern to me that the problem is that only one of the current views is being represented in the replies in this forum. A dangerous state of affairs. I will seek to determine whether or not this is the case with the following example.

Are you aware of the physicist, Brian Green, and his books and PBS series'? One of which is titled "The Fabric of the Cosmos" in which one of the questions he addresses is "Is space a human abstraction or a physical entity?". Are you claiming his view is that space is not an actual thing just as you have stated? It is essential that this be made clear. It is my understanding that his view is that space itself actually has shape. That is is something like a fabric. If I am mistaken about that, then my original question was based on false assumptions. If i am correct, it was not and there should be people here who can answer the question. If there are not, this forum is extrmely limited and lacking.

 

[bapowell]

CosmicVoyager -- are you sure you aren't just getting caught up in semantics?

When we talk about the curvature of space -- we are quite literally referring to its geometry: how points in this space relate to one another. This geometry can be probed empirically -- by measuring physical objects within the universe. For example, the global curvature of the observable universe is measured by looking at the cosmic microwave background: in effect, by drawing a giant triangle through space (the sides being the size of the horizon when the CMB was generated and the distance in space out to when this happened). We then measure the opening angle of this triangle and compare it with that expected from Euclidean trigonometry, given the length of the two sides. If the universe has appreciable curvature, we expect that the angle will not follow the Euclidean rule. In what sense then, is space not curved?

Note that this is different from saying that space is a material thing, like a "fabric". (Yes, shame on Brian Greene for putting this into people's heads.)

 

[Bandersnatch]

In beginning to complie my list of examples I found further confirmation of physicists currently statng that space in actually a thing like a fabric and not just volume or distance. This raises the concern to me that the problem is that only one of the current views is being represented in the replies in this forum. A dangerous state of affairs. I will seek to determine whether or not this is the case with the following example.

This objection is similar to saying that many scientists refer to the universe as an expanding balloon in their public outreach book and talks, and then complaining that they are misleading the public by not teaching the 'alternative theory' that the universe is not in fact a balloon, or that actual scientists dogmatically reject the 'balloonness' of the universe instead of giving it equal time in their work.

It's been said many times that using the word 'fabric' is an analogy. A convenient shorthand for visualising some properties of space, exactly because talking about space having geometry, being stretched and curved, flies over most people's heads.

Are you aware of the physicist, Brian Green, and his books and PBS series'? One of which is titled "The Fabric of the Cosmos" in which one of the questions he addresses is "Is space a human abstraction or a physical entity?". Are you claiming his view is that space is not an actual thing just as you have stated? It is essential that this be made clear. It is my understanding that his view is that space itself actually has shape. That is is something like a fabric. If I am mistaken about that, then my original question was based on false assumptions. If i am correct, it was not and there should be people here who can answer the question. If there are not, this forum is extrmely limited and lacking.

You're presenting a false dillema: either space is made of something(fabric, whatever), or it is not curved, stretched etc.
There is nothing contradictory in saying that something can have a shape and not be a 'thing'. An orbit has got a shape, a bullet's trajectory has got a shape, a galactic plane has got a shape. Borders between countries have got a shape.
These are all not made of anything either.

So, no, space is not made of fabric, dough nor rubber. Yes, it does curve, stretch etc.

 

[Chronos]

The concept of zero point energy implies empty space has intrinsic 'properties'. This has captured the imagination of the lay public, and inspired more than a few cranks to make a leap of faith off the bridge of reality into an ocean of ignorance. The thermos bottle is a wonderful demonstration of the 'properties' of empty space. It does not conduct heat, yet occupies volume. The vacuum, is however, very accommodating to fields as it neither impedes or amplifies their propagation in any meaningful sense. A magnet place inside a thermos will still attract iron filings external to the container. The magnetic field is unaffected by the vacuum layer, it is only attenuated by distance interposed between the field source. Would that inspire an argument that distance has intrinsic properties? Nothing is nothing, and the supply of nothing in the universe is mathematically unlimited.

 

[julcab12]

space is a dynamic thingy? It is modeled on 2 accounts GR and QM. If combined we have Curved Space Vacuum or something.. I hope it wouldn't end up in a hole argument.. Just my 2 cents.^^

 

[Mordred]

I'm sorry Chronos this time you lost me lol.

Your example shows that due to no impediment, there is in fact energy present in the vacuum region. The source may be your magnet but it is present in that region. In every unit of volume of space there is always a pressure value. Pressure has energy potential. Whether or not you describe that truism via quantum or classical means its no less true. I do however agree that far too much mysticism oft gets implied by that simple fact.

 

[Ogg Yggdryzzle]

after the big bang

"google metric expansion."

I had read that.

So the countless illustrations of space being warped by mass are incorrect? And the idea that you could travel faster than light by contracting and expanding space? And wormholes shown and described as distorted space. Space is constantly referred to as a fabric. That all indicates space is something.

according to standard inflation theory the universe began with about 25 kilograms of matter
before inflation. the inflation of space seems to have warped matter and it increased the mass of the universe exponentially. can somebody explain that? why EXPANSION OF SPACE TIME WOULD INCREASE THE AMOUNT OF MATTER IN THE UNIVERSE?

 

[Drakkith]

according to standard inflation theory the universe began with about 25 kilograms of matter before inflation.

Can you provide a link to this? I've never heard this before.

 

[Mordred]

Welcome to the forum, I'm almost afraid to ask where you heard that statement lol. Its certainly not what the hot big bang nor the \LambdaCDM model teaches.

The model tells us that the Observable universe started at a hot dense state, of undetermined size and origin. Here is some recommended reading materials.

http://arxiv.org/pdf/hep-ph/0004188v1.pdf :"ASTROPHYSICS AND COSMOLOGY"- A compilation of cosmology by Juan Garcıa-Bellido

http://arxiv.org/abs/1304.4446 :"What we have leaned from Observational Cosmology." -A handy write up on observational cosmology in accordance with the LambdaCDM model.

http://arxiv.org/abs/astro-ph/0310808 :"Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe" Lineweaver and Davies

the first article is rather lengthy but it shows the FLRW metrics in a textbook style

 

[Ogg Yggdryzzle]

I think Steven Weinberg said it in the first three minutes. The primordial vacuum fluctuation supposedly generated a 25 kg "primordial egg" that grew into the known universe.

If nature abhors a vacuum how did space get bigger instead of contracting around the "primordial egg?" The universe sucks and that made the egg grow bigger?

 

[Ogg Yggdryzzle]

A friend recommended David Lerner's book "the big bang never happened." I have never read it. Does anyone know what its about?

 

[phinds]

A friend recommended David Lerner's book "the big bang never happened." I have never read it. Does anyone know what its about?

Based on the title, my guess is it's about 5 beers short of a six-pack.

 

[craigi]

A friend recommended David Lerner's book "the big bang never happened." I have never read it. Does anyone know what its about?

Eric Lerner has a website with the same title, arguing that plasma cosmology contradicts the big bang theory and is better supported by the evidence. I won't link it because I think it falls short of the forum standards.

You can find an overview of his academic career on the wikipedia page about him along with a number of references from serious cosmologists who dismissed his book.

 

[Mordred]

I think Steven Weinberg said it in the first three minutes. The primordial vacuum fluctuation supposedly generated a 25 kg "primordial egg" that grew into the known universe.

If nature abhors a vacuum how did space get bigger instead of contracting around the "primordial egg?" The universe sucks and that made the egg grow bigger?

I had to look in my copy of the first 3 minutes, I couldn't find that line anywhere lol not that I expected to. I always enjoy reading the book even though a lot has changed since the time of its writing

 

[Nugatory]

Are you aware of the physicist, Brian Green...

Somewhere north of two thousand hits between the google queries for "Brian greene site:www.physicsforums.com" and "Brian green site:www.physicsforums.com" suggests that we are. Those are small numbers for the Internet as a whole , but not for a single specialist web site.

 

[Romulo Binuya]

space is a dynamic thingy? It is modeled on 2 accounts GR and QM. If combined we have Curved Space Vacuum or something.. I hope it wouldn't end up in a hole argument.. Just my 2 cents.^^

That's how I understood it too, the big bangis mathematically allowed by the Heisenberg Uncertainty Principle and upheld by the General Theory of Relativity.

Our universe emerged from vibrant nothingness, nothing as is not even empty space where time could exist. Nevertheless, henceforth the big bang we have a dynamic universe because of gravity.

Learning Topology is not enough to comprehend the universe, though it could explain the expanding space.

Our universe consists of four dimensions, the three space dimensions and one that is not exactly time but is related to time it is in fact time multiplied by the square root of minus 1. Which means we are discussing the concepts behind the equations and our language is inadequate.

 

[timmdeeg]

according to standard inflation theory the universe began with about 25 kilograms of matter
before inflation. the inflation of space seems to have warped matter and it increased the mass of the universe exponentially. can somebody explain that? why EXPANSION OF SPACE TIME WOULD INCREASE THE AMOUNT OF MATTER IN THE UNIVERSE?

During inflation space expanded exponentially, not matter. Matter was created after the inflation stopped. The mass then didn't increase anymore due to the conservation of baryon and lepton number.

 

[CosmicVoyager]

CosmicVoyager -- are you sure you aren't just getting caught up in semantics?

When we talk about the curvature of space -- we are quite literally referring to its geometry: how points in this space relate to one another. This geometry can be probed empirically -- by measuring physical objects within the universe. For example, the global curvature of the observable universe is measured by looking at the cosmic microwave background: in effect, by drawing a giant triangle through space (the sides being the size of the horizon when the CMB was generated and the distance in space out to when this happened). We then measure the opening angle of this triangle and compare it with that expected from Euclidean trigonometry, given the length of the two sides. If the universe has positive curvature, we expect that the angle will not follow the Euclidean rule. In what sense then, is space not curved?

Note that this is different from saying that space is a material thing, like a "fabric". (Yes, shame on Brian Greene for putting this into people's heads.)

It is unclear to me if you are saying 1) Brian Greene is not saying what he means or if 2) you disagree with what he means?

By material, I do not mean has mass. I mean it is physical. It is something as real matter and energy.

Quoting Brian Greene referring to the frame dragging detected by Gravity Probe B, "Space is something real, a physical entity like a fabric. If space were nothing there would be nothing to twist."

It seems to me he is emphasizing over and over again that space is something more than what repliers are saying.

Bandersnatch, are you also saying that by "a physical entity" Brian Greene means the same thing you are saying? I do not see how much clearer he can say it.

I am asking those who think space is something, a physical entity, as the universe gets bigger and there is more of this something, where does it come from? Is it being converted from something? Some kind of dark energy?

 

[timmdeeg]

Einstein said: "Space-time does not claim existence in its own right, but only as a structural quality of the [gravitational] field".

Whoever claims that space itself has truly physical properties should suggest how this idea could be verified experimentally, at least in principle.

 

[Bill_K]

Quoting Brian Greene referring to the frame dragging detected by Gravity Probe B, "Space is something real, a physical entity like a fabric. If space were nothing there would be nothing to twist."

If that's accurate, it's another example of a Brian Greene statement that is patently false and misleading. Frame dragging, once again, is nothing more than an alteration of distances and directions. Nothing physical like a "fabric" is involved. Empty space does not have a coefficient of viscosity, or a Young's modulus.

 

[Nugatory]

Quoting Brian Greene...

Brian Greene is to physics as pentecostal snake handling is to herpetology... Interesting, but not a foundation upon which you can build any deep understanding of the subject.

 

[Mordred]

It is unclear to me if you are saying 1) Brian Greene is not saying what he means or if 2) you disagree with what he means?

By material, I do not mean has mass. I mean it is physical. It is something as real matter and energy.

Quoting Brian Greene referring to the frame dragging detected by Gravity Probe B, "Space is something real, a physical entity like a fabric. If space were nothing there would be nothing to twist."

It seems to me he is emphasizing over and over again that space is something more than what repliers are saying.

Bandersnatch, are you also saying that by "a physical entity" Brian Greene means the same thing you are saying? I do not see how much clearer he can say it.

I am asking those who think space is something, a physical entity, as the universe gets bigger and there is more of this something, where does it come from? Is it being converted from something? Some kind of dark energy?

Space is simply volume filled with matter and energy, we have tried explaining that to you numerous times. Space itself is not a material. It is simply volume filled with matter and energy. The geometry of space is a relationship of how gravity and the cosmological constant influences the matter and energy content occupying space. In terms of expansion its a relation of the universes actual energy-matter density compared to its critical density.

The critical density is a calculated value that would result in a static universe.

GR is essentially the same, its a description of how gravity influences observations via light paths occupying the volume of space-time due to the same geometric properties of the matter-energy distributions.

Gravity does not act upon space itself, it influences the matter content residing in its volume.

those lines you see in visual images showing twists and curls etc, is simply a visual representation describing the influences on the matter-energy content residing in the volume of space.

As mentioned numerous times if you have a unit of space in the universe it will have pressure, pressure has energy potential, according to QM there will be virtual particles occupying that same volume. In QFT there will be fields influencing the matter-energy content occupying the volume of space.

However space itself does not have a fabric and is not a form of energy or matter, it is simply volume filled with the matter and energy content of the universe.

 

[WannabeNewton]

Quoting Brian Greene referring to the frame dragging detected by Gravity Probe B, "Space is something real, a physical entity like a fabric. If space were nothing there would be nothing to twist."

Why are you quoting a popularizer instead of a textbook? Granted, many textbooks often make such inaccurate claims about frame dragging as well so that won't necessarily help you. Space is not twisting and neither is space-time. The space-time of an isolated spinning body itself possesses angular momentum but that doesn't imply some kind of material twisting. What's twisting are the world-lines of observers fixed with respect to the distant stars due to the spin of the source and this is where frame dragging comes from because this twisting is proportional to the precession of a gyroscope relative to the distant stars.

 

[CosmicVoyager]

Space is simply volume filled with matter and energy, we have tried explaining that to you numerous times.

Please read that again. I am asking whether or not you agree or disagree with what Brian Greene said. That is perfectly clear in the post you quoated, and you still did not answer the question. Yes or no?

The initial responses to my question of where new space comes from claimed that the decriptions and illustrations of space as a physical entity were only analogies, so I gave one (of countless) example(s) that seems to me to be not just an analogy, disproving those replies. So, I have been pullling teeth trying to get an answer as to whether or not those repliers think Brian Greene is using it only as an anology or not. If not, then those replies are wrong. I could give countless more examples but it would be like pulling countless more teeth due to not being able to get an answer.

Once it has been established what physicists such as Brian Greene are claiming, then we can proceed further.

 

[CosmicVoyager]

Why are you quoting a popularizer instead of a textbook? Granted, many textbooks often make such inaccurate claims about frame dragging as well so that won't necessarily help you. Space is not twisting and neither is space-time. The space-time of an isolated spinning body itself possesses angular momentum but that doesn't imply some kind of material twisting. What's twisting are the world-lines of observers fixed with respect to the distant stars due to the spin of the source and this is where frame dragging comes from because this twisting is proportional to the precession of a gyroscope relative to the distant stars.

Please read my previous reply. I am not citing it as evidence. I am asking whether or not you agree with it.

 

[craigi]

Read that again! I am asking whether or not you agree or disagree with what Brian Greene said. That is perfectly clear in the post you quoated, and you have *failed* yet again to answer the question. Yes or no?

The initial responses to my question of where new space comes from claimed that the decriptions and illustrations of space as a physical entity were only analogies, so I gave one (of countless) example(s) that seems to me to be not just an analogy, disproving those replies. So, I have been pullling teeth trying to get an answer as to whether or not those repliers think Brian Greene is using it only as an anology or not. If not, then those replies are wrong. I could give countless more examples but it would be like pulling countless more teeth due to the apparent density of the people who can't answer a yes or no question!

Once it has been established what physicists such as Brian Greene are claiming, then we can proceed further.

Part of the problem here, is that we really don't know the true nature of space-time. For that we would need a working theory of quantum gravity, but we don't. Brian Greene, is one of many, who have spent many years searching for it with little success. Some argue that there's been no signifiant progress, in that direction. He's also written a book (or books) which attempt to explain complex mathematical ideas to non-physicists and as such need to use colourful descriptions to convey them.

You started your thread in the comology sub-section of the forum, which is largely concerned with the well established theory of general relativity and you've been given answers based upon that. Brian Greene's work is concerned with the speculative attempt to unite general relativity with quantum mechanics, that is string theory. If you'd asked your question in the 'beyond the standard model' sub section, you'd have probably been given different responses, but what you're asking amounts to the same thing - do we agree that the colourful language which one physicist uses to describe an unproven speculative, mathematical theory, to non-physicists, is an accurate description of nature? The answer to that has got to be no, but it was probably not incorrect for him to offer it, in the context that he did.

There's a peculiar thing about the way we learn physics. We learn it through white lies. We need over simplifications to help us create a framework in order to learn more complex things. Then we need to cast off the simplified theories as either approximations, limiting cases, or learning aids. Physicists accept this as implicit as soon as they come to terms with undergrad physics. Analogously, mathematics carefully delinates the domain of each formalism. When physicists, speak to non-physicists, they often forget to be clear that they are talking about a specific model, while the non-physicist is usually in pursuit of an absolute truth.

 

[Mordred]

Read that again! I am asking whether or not you agree or disagree with what Brian Greene said. That is perfectly clear in the post you quoated, and you have *failed* yet again to answer the question. Yes or no?

The initial responses to my question of where new space comes from claimed that the decriptions and illustrations of space as a physical entity were only analogies, so I gave one (of countless) example(s) that seems to me to be not just an analogy, disproving those replies. So, I have been pullling teeth trying to get an answer as to whether or not those repliers think Brian Greene is using it only as an anology or not. If not, then those replies are wrong. I could give countless more examples but it would be like pulling countless more teeth due to the apparent density of the people who can't answer a yes or no question!

Once it has been established what physicists such as Brian Greene are claiming, then we can proceed further.

fair enough if your just asking if we agree with Brian Greene's descriptive use the answer is NO as its misleading

 

[Bill_K]

Part of the problem here, is that we really don't know the true nature of space-time.

Nevertheless, the premises that the OP raised are out of the question - That, as the universe expands, part of space is newly created (which part??) and must "come from somewhere."

This is only true in the sense that all of space at time t + dt is "newly created."

More generally, one could write down the Cauchy initial value problem with an arbitrary initial spacelike hypersurface. The evolution is not volume-preserving, so as we step to the next hypersurface, space may expand (or contract), giving the impression that something is being newly created. But space is a continuum, and nothing is really "new," every point in that hypersurface in fact arose from a point in the initial one. (Or from more than one point, or from a singularity.)

 

[CosmicVoyager]

Matterwave - "The picture of space-time as a "fabric" is an analogy, not to be taken seriously."Bandersnatch - "Scientists are describing space as space. It's a mathematical concept with certain well-defined properties."Matterwave - "People have to use words to describe things to other people. We can't just say to the masses "hey, look at the Einstein field equations - That's spacetime - that's gravity!" because nobody would know what we were talking about. The use of analogies is appropriate where they are appropriate."CosmicVoyager (me) - "I will begin compiling a list of examples of space described and illustrated as a thing with shape stretched, compressed, curved, twisted. Grids showing space itself as having shape."Mordred - "no need we have all seen them numerous times lol. As mentioned they are a visual aid."CosmicVoyager (me) - "In beginning to complie my list of examples I found further confirmation of physicists currently statng that space in actually a thing like a fabric and not just volume or distance...Are you aware of the physicist, Brian Green, and his books and PBS series'? One of which is titled "The Fabric of the Cosmos" in which one of the questions he addresses is "Is space a human abstraction or a physical entity?". Are you claiming his view is that space is not an actual thing just as you have stated? It is essential that this be made clear..."No one answers the question. They keep talking about what space is, but they never answer the question of whether what Brian Greene is saying is an example of a physicist using analogies.

I keep asking, they keep not answeringCosmicVoyager (me) - "It is unclear to me if you are saying 1) Brian Greene is not saying what he means or if 2) you disagree with what he means?

Quoting Brian Greene referring to the frame dragging detected by Gravity Probe B, 'Space is something real, a physical entity like a fabric. If space were nothing there would be nothing to twist.'

It seems to me he is emphasizing over and over again that space is something more than what repliers are saying.

Bandersnatch, are you also saying that by 'a physical entity' Brian Greene means the same thing you are saying? I do not see how much clearer he can say it."People keep replying but still not answering the question. I have a fit.Then finally I get an answer saying they do not agree with Brian Greene, that he is not just using analogies as multiple people stated. So what they should have said is there are multiple views as there are multiple interpretations of quantum decorehence, and stated what *their* view is.

My original question is directed at physicists whose view it is space is a physical entity. Who think Gravity Probe B's measurement of frame dragging is direct evidence that it is, because if space were nothing there would be nothing to twist.

I am *not* asking whether or not one agrees with that view of space.

 

[CosmicVoyager]

Looking for an answer I found a lecture on inflation by Dr. Paul J. Steinhardt. I do not know if it is related. I do not fully understand it.

An excerpt, "The inflation process obviously does not conserve inflationary energy because we are creating more and more space. It is an energy generating process. It is a space generating process. Where is the energy coming from? It is coming from gravity. Is there a limit to how much energy I can draw from a gravitational field and convert it into inflationary energy? The answer is no. There is something special about gravity. All the other forms of energy we know of have a bottom to them. If you draw the energy down eventually it gets to zero or some minimum. That is not true for gravity. Gravity is a unique form of energy that is bottomless. The gravitational potential energy curve gradually goes toward negative infinity as two objects are brought closer together. If you can find some way of tapping that energy continuously there is no end to how long you can do it, and inflation is a mechanism that does it automatically. So energy is conserved. You can always find more negative gravitational energy and balance it with positive inflationary energy."

That is at 33 minutes. http://youtu.be/IcxptIJS7kQ

 

[craigi]

Nevertheless, the premises that the OP raised are out of the question...

Agreed. My comment was specifically directed at the latter section of the thread pertaining to the Brian Greene reference from post #13.

To be clear, neither Greene nor any other proponent of any theory, that I'm aware of, at least, suggest that the volume of space is a property that should be conserved either in itself or as converted from another quantity.

 

[Ken G]

There's a peculiar thing about the way we learn physics. We learn it through white lies.

That is wonderfully said, I often try to make that same point.

When physicists, speak to non-physicists, they often forget to be clear that they are talking about a specific model, while the non-physicist is usually in pursuit of an absolute truth.

Again I completely agree. Indeed on another thread I critiqued a famous physicist who said words to the effect that the search to understand space was a search to find out if Aristotle "was right" that space is absolute, or if Einstein "was right" that space is relative. I said they were both right if we understand what they (and what all scientists) were actually saying, which is no more than "here is the insight that will propel the advance of science forward to the next step." Science is not a quest for absolute truth, it is a process of discovery. To set it up as something that it is not only sets us up for ultimate disappointment in it, and also sells short its exquisite mixture of doubting, testing, and grabbing at the insights that propel it along.

To be clear, neither Greene nor any other proponent of any theory, that I'm aware of, at least, suggest that the volume of space is a property that should be conserved either in itself or as converted from another quantity.

CosmicVoyager, if that does not answer your question, then I don't know what would. I would just add one point. The only empirically demonstrable fact we can point to to say that space is expanding is that the number of rigid meter sticks that would fit between the galaxy clusters now is more than in the past (we can't really lay rigid rulers between them, but we think we have tests that are the equivalent). Thus we cannot even say that space actually is expanding, it is just as possible that rulers are shrinking (and all gravitationally bound systems as well). No law of physics is violated by that picture, and no observational test comes out any different. Hence, we cannot say that space is a physical thing, as we have no theory that says it is. Frame dragging doesn't say it is either, as we equally have no specific mechanism that would make space twist, than we have a specific mechanism that can make a gyroscope precess relative to that space. In the absence of theories that give demonstrable meanings to our words, all our words should be regarded as interpretational pictures.

 

[chill_factor]

I do not think that shrinking matter is equivalent to expanding distances, as shrinking matter should be detectable through changes in the moment of inertia of a gyroscope which scales as the radius squared.

 

[Ken G]

I do not think that shrinking matter is equivalent to expanding distances, as shrinking matter should be detectable through changes in the moment of inertia of a gyroscope which scales as the radius squared.

The radius of a shrinking object does not change, if the rulers you'd use measure it shrink too. That is not to say the object may unambiguously be said to be shrinking if the rulers shrink too, indeed the whole point is, one cannot actually tell if an object is shrinking or not, any more than you can tell if space is expanding. General relativity is a theory of the dynamics of a metric, and a metric always involves ratios of lengths or ratios of times, where the numerator is the quantity you are measuring and the denominator is your standard of measurement. The theory only tells you the ratio is changing, it doesn't tell you why the ratio changed, or whether it was a change in the numerator or the denominator. A metric theory does not even distinguish such changes as different things. You would need a deeper theory for that, just like you would need a deeper theory to give space any physical attributes or mechanisms by which it can be expanded. GR doesn't do either of those things, it is purely a metric theory. But framing it as shrinking matter, rather than expanding space, sure makes the question "where does the new space come from" go away!

 

[Chronos]

Ken G, you know full well we have observational evidence that refutes your 'proposition'. Stirring the pot only serves crank views.

 

[Ken G]

No, there is no such evidence, and no stirring. Crank views are not assisted by the truth, they will find their own path, ignoring the truth, the truth never matters to them. But it should matter to the scientist, so the scientist must know the difference between what is an observed fact, and what is simple convention of language. We have evidence that GR works. GR is a metric theory. Metric theories tell you how ratios between measurements and standards evolve. That's what a metric does.

It's the same with time, by the way-- the proper time between two events can be predicted and tested. What are you predicting, what are you testing? Clearly, just look, you are predicting and testing the number of times some standard clock will tick between the two events. Let the two events be the arrival of successive wave fronts of the observed CMB. GR tells us that as the universe ages, that number increases. It certainly does not tell us, and this is quite important, if some absolute time between the wave fronts is increasing, or if the clocks are ticking faster. To claim otherwise is both to ignore the central lessons of relativity, and to mistake simple pedagogical conventions for statements of physical fact.

Now, of course the convention is fine. We choose to say space is expanding, we say light is redshifting, it's a standard language and we all know what we mean. But it becomes dogma if we really believe that we think we know that is true, and if we think we know objects are not shrinking and clocks are not ticking faster. It's not even what we do in SR, for crying out loud-- there we tend to make the opposite choice and say that objects are shrinking and clocks are ticking differently as we change our frame of reference! But all physics tells us, in either case, is what we will measure, that's it-- and all measurements are ratios between some physical quantity and some standard, so we have no idea which one is responsible for the change, or if it even makes sense to ask which one is responsible.

The point is clearly true, but why bother making it? Because people ask questions like, where does the space come from? And the truth is, we have no idea if there is any more space in there in the first place, that's just not something that GR tells us, it's a convention of language.

 

[Frank Weyl]

Riemann Sphere

Think of the universe as created from a Planck-like object some 1.6160X10^-33cm diameter.
Imagine now, as an example, a mobius curve or strip which has only one side. Now imagine this object as an inner tube to a bicycle and cut it opposite the valve and give it a twist and glue the two ends together. Again, imagine that the inner tube is made of a special material which will not flex or distort as it is filled with air/energy. As the inner tube expands, the internal diameter decreases until it its size becomes Planck length, the shortest distance that has any meaning in quantum mechanics, and we then have a sphere which has only one side. As there is absolutely nothing external to the expanding sphere, the expanding edge, or 'event horizon', creates space and time continuously as it increases in size. The actual name for this theoretical topological object is a Riemann sphere.
There is no doubt that the creation of the universe from its expansion has spawned many theories and this is only a small attempt to explain in words, in analogous form, the imagined shape which would explain the nothingness in which the universe is expanding into.

 

[phinds]

... which would explain the nothingness in which the universe is expanding into.

You're just making this up, right? There is zero evidence that the universe is expanding INTO anything and if it were, there would be a boundary which would cause serious problems in physics. The consensus among cosmologists is solidly that there is no such thing.