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

[azureorb]

There IS no "boundary". You completely misunderstand the balloon analogy. I recommend the link in my signature.

Yes, I later got/remembered the 2D balloon view, unlike a 3D view of the universe/space expanding... I'm clicking on your link though...

 

[azureorb]

Okay, yes, I understand the 2D balloon view. It's focus is on how things (gravitationally bound) things move away from each other over time due to the expansion (and it's accelerating, too).

Questions from your link:

"NO CENTER there is NO center." - Okay. So if there is no center, then it'd have to be infinite, right? OR if not infinite, it'd have to wrap-around -- ie, no edges. Not necessarily wrap as a circle, but just, well, wrap around (in a sense) to the other point or whatnot, if it's to be finite & have no edges/boundaries -- hence, no center.

But how could the universe be literally infinite in size, in the full sense of the word (not merely from a practicality or speed of light standpoint) -- from a big bang -- unless that big bang had infinite energy?

I could see an infinite universe where expansion between two gravitationally bound sections always expands between each other, while being infinite before and after in it's overall size.

But if it's not infinite, then it's finite size is growing overall. And if it has no center, while being finite -- how could it not "wrap around" in some sense, since it can't have edges (otherwise that finite plane would have a center)?

"It is DISTANCE that is changing, not space."

Okay, just to make it clear: Yes, I understand that no, space is not "thinning out" like the rubber of a balloon. But the overall universe's space volume is changing, though -- as the distance is, right?

 

[Mordred]

Okay, yes, I understand the 2D balloon view. It's focus is on how things (gravitationally bound) things move away from each other over time due to the expansion (and it's accelerating, too).

gravitationally not bound, in other words the stars in a galaxy are not moving apart due to expansion. Neither is any large scale structure.

Questions from your link:

"NO CENTER there is NO center." - Okay. So if there is no center, then it'd have to be infinite, right? OR if not infinite, it'd have to wrap-around -- ie, no edges. Not necessarily wrap as a circle, but just, well, wrap around (in a sense) to the other point or whatnot, if it's to be finite & have no edges/boundaries -- hence, no center.

But how could the universe be literally infinite in size, in the full sense of the word (not merely from a practicality or speed of light standpoint) -- from a big bang -- unless that big bang had infinite energy?
I could see an infinite universe where expansion between two gravitationally bound sections always expands between each other, while being infinite before and after in it's overall size.
But if it's not infinite, then it's finite size is growing overall. And if it has no center, while being finite -- how could it not "wrap around" in some sense, since it can't have edges (otherwise that finite plane would have a center)?

Its unknown if the universe is infinite or finite, that may always be the case. If its infinite, then yes it would have infinite energy. If its infinite now then it was always infinite. A finite beginning cannot become infinite. Try to keep in mind, there is no preferred location or direction. Homogeneous (one location is the same as any other), Isotropic (there is no preferred direction.) If there is a center and expansion was radiating out from that center, that would be a preferred location and direction. Observations on the distance separations between ( for example multiple points forming a triangle) do not work out that way. Instead all separation distances between all points (not gravitationally bound are separating equally) and the angles between those points are maintained. This is not possible if space was radiating outward as per an explosion. Nor can this be possible if the universe has an overall rotation. So mathematically by measuring the expansion across multiple points we know with certainty that the universe has no center.

"It is DISTANCE that is changing, not space."

Okay, just to make it clear: Yes, I understand that no, space is not "thinning out" like the rubber of a balloon. But the overall universe's space volume is changing, though -- as the distance is, right?

correct

 

[bapowell]

But if it's not infinite, then it's finite size is growing overall. And if it has no center, while being finite -- how could it not "wrap around" in some sense, since it can't have edges (otherwise that finite plane would have a center)?

Precisely. A sphere "wraps around", right? If the universe is finite, its topology is compact and the surface is closed but unbounded, like the surface of a sphere or torus.

 

[Drakkith]

But how could the universe be literally infinite in size, in the full sense of the word (not merely from a practicality or speed of light standpoint) -- from a big bang -- unless that big bang had infinite energy?

The common view of the big bang, as an event that created the universe, is not real. It is a result of our current theories breaking down mathematically once the density of the universe rises to a certain point and giving us infinities as answers. The big bang theory does not explain the beginning of the universe, only the evolution of the universe from a very hot, very dense state about 13.7 billion years ago, to its present state now.

Also, it is very difficult to talk of energy in regards to the overall universe since global energy is not well defined in General Relativity. Just look at the article on energy conservation in GR here: http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html

But if it's not infinite, then it's finite size is growing overall. And if it has no center, while being finite -- how could it not "wrap around" in some sense, since it can't have edges (otherwise that finite plane would have a center)?

It can wrap around, just like the surface of a balloon wraps around on itself. We just don't know if this is true or not.

Okay, just to make it clear: Yes, I understand that no, space is not "thinning out" like the rubber of a balloon. But the overall universe's space volume is changing, though -- as the distance is, right?

The average density of the universe is getting lower as expansion causes all unbound objects to recede from each other, yes.

 

[PERFESSER]

However, we have measured the radius of the observable universe and it is indeed approximately 46 billion light years from Earth to the edge, making it about 92 billion light years in diameter.
CAN ANY-ONE TELL ME HOW THIS MEASUREMENT WAS DONE ?? I'M SKEPTICAL !

 

[Mordred]

Observations and redshift measurements, if your question is how is it bigger than light can travel in 13.7 Billion years, the answer is the universe expanded, which means the distance increases as the light approaches us.

http://cosmology101.wikidot.com/redshift-and-expansion

 

[Frank Weyl]

I have spent a great deal of pleasurable time reading all the scholarly answers to the original question.
Over time, certain scholars have meticulously taken the mathematics and topology out of the individual answers and rendered the complex explanation(s) in elegant and understandable English/American etc., (There are differences!)so that those who have an interest are not put off by the seemingly esoteric hieroglyphs. Although some are older and at a higher level, I can/have seen; and with some deep understanding of their own 'climb through' the complexities of the associated mathematics, astrophysics and cosmology,that they wish to steer the other 'students' along with them and, therefore, show them the fascinating nature of our universe and existence.
I cannot praise these people enough for your patience,diligence and 'translational' hard, difficult and philosophical work.
For those who follow the answers, the authors are not looking for praise or trying to gain ego. They do it simply because they are, intrinsically, seekers after the truths of the cosmos.
There are, off course, those pesky little 'Hidden Variables', which I am sure someone will explain in due course.
Thanks to everyone for their input(s) and it has been a fascinating journey, so far(!),,,even for an old cosmologist.

 

[Pranavarora]

Existence Of Space

In my opinion, space is neither created nor can be destroyed. The reason is that if we say that space is created, that means anything would have happened before creating space and the formation of space was its outcome. So another question arises that if anything would have happened before, then how does that thing came into existence before creating the space?? Similarly, if the space will destroy one day, then anything would definitely start one day, because the destruction of space would be the reason of creating another thing.

Lets think it in another way, we know that energy can neither be created nor can be destroyed but can be changed from one form to another. Also we know that space contains mass, and mass is the form of energy. So how can space be created or destroyed??

Lets take an example, Sun before coming into existence was not a sun but was a nebula, and after its destruction it will become either black hole or white dwarf. But don't you think that it was neither created nor destroyed, but it changed its form?

 

[Drakkith]

Pranavarora, have you read the rest of this thread?

 

[Mordred]

......
Thanks to everyone for their inputs) and it has been a fascinating journey, so far(!),,,even for an old cosmologist.

Your contribution to this thread on the aspects of strings is also a well needed contribution,I thank you for that as well

 

[Pranavarora]

Drakkith, But whatever i m saying, u think that its wrong, isn't it?

 

[Mordred]

In my opinion, space is neither created nor can be destroyed. The reason is that if we say that space is created, that means anything would have happened before creating space and the formation of space was its outcome. So another question arises that if anything would have happened before, then how does that thing came into existence before creating the space?? Similarly, if the space will destroy one day, then anything would definitely start one day, because the destruction of space would be the reason of creating another thing.

Ok I can tell English isn't your native language. Space is volume only, filled with matter and energy from the universe.

Lets think it in another way, we know that energy can neither be created nor can be destroyed but can be changed from one form to another. Also we know that space contains mass, and mass is the form of energy. So how can space be created or destroyed??

Space cannot be created or destroyed, it is volume only. Space itself has no energy or mass. What occupies space does.

Lets take an example, Sun before coming into existence was not a sun but was a nebula, and after its destruction it will become either black hole or white dwarf. But don't you think that it was neither created nor destroyed, but it changed its form?

yes, this is the only thing you stated that is correct, However the sun does not have the mass to become a black hole. E=Mc².

Please take the time to read the full thread, if you had you would see that space is volume, not a form of matter or energy. Matter and energy simply fills that volume.

 

[Chronos]

I prefer 'occupies' over 'fills'. I realize it's semantics, but, you must admit it's a frequent source of confusion.

 

[Drakkith]

I prefer 'occupies' over 'fills'. I realize it's semantics, but, you must admit it's a frequent source of confusion.

Well, they don't call it "cream filling" for nothing. And they most definitely don't call it "cream occupation". But if they did, it'd be the most delicious occupation ever...Mmmm...

 

[Mordred]

I prefer 'occupies' over 'fills'. I realize it's semantics, but, you must admit it's a frequent source of confusion.

Normally I use occupy as well, however I considered a language barrier, so I used both terms in my last post and LOL @Drakkith

 

[timmdeeg]

Space is volume only, filled with matter and energy from the universe.

... whereby the positive energy of matter/radiation is canceled by its negative gravitational potential energy according to the zero-energy universe hypothesis.

 

[julcab12]

In my opinion, space is neither created nor can be destroyed. The reason is that if we say that space is created, that means anything would have happened before creating space and the formation of space was its outcome. So another question arises that if anything would have happened before, then how does that thing came into existence before creating the space?? Similarly, if the space will destroy one day, then anything would definitely start one day, because the destruction of space would be the reason of creating another thing.

. Space itself has no energy or mass. What occupies space does.
.

...The space/nothing your referring pertains to a logic state/placeholder and volume (described by Mordred) is a proper descriptive constraint as part of an abstract mathematical map(space w/out energy). It is quite different when talking physical/realistic empty space. Space in relation to energy is inseparable (General Relativity) meaning, if you remove matter and energy. Spacetime will disappear along with it and what's beyond that event doesn't make sense. Same is slightly true to field and energy (Quantum Theory). If you try to destroy(or so we think) a 'thing'. It will be replaced by another 'thing'; abstract, you might want to check Particle physics for elaboration.

On a side note. This conventional thinking bothered me sometimes. Fundamentally we are not destroying things. Conversion, transformation and reshuffling of information is what took place at least to me or as far as being observed. I might be wrong or missing something but that's the way i picture reality.

 

[Mordred]

ah but that results in quantum vacuum zero-point energy which is the lowest possible energy state, there is still a higher than the minimal state due to the uncertainty principle. As a consequence at absolute zero, that volume of space would have a lowest energy potential of

\frac{1}{2}hv

which by the way is one point I mentioned during this thread is that there is always some energy-density, occupying space. You will always have either a positive or negative vacuum energy potential.

If I recall though this led to the biggest blunder, this process was once considered as a possible cause of the cosmological constant, however it was 120 orders of magnitude too large.

edit: this is in reply to Timmdeeg's post

 

[Mordred]

On a side note. This conventional thinking bothered me sometimes. Fundamentally we are not destroying things. Conversion, transformation and reshuffling of information is what took place at least to me or as far as being observed. I might be wrong or missing something but that's the way i picture reality.

basically correct, as far as my studies have shown, information loss is a huge issue, but that is another topic lol, by the way I think you got a better translation of what Pranavarora was asking, thanks for jumping in on that.

 

[timmdeeg]

ah but that results in quantum vacuum zero-point energy which is the lowest possible energy state, there is still a higher than the minimal state due to the uncertainty principle. As a consequence at absolute zero, that volume of space would have a lowest energy potential of

\frac{1}{2}hv

which by the way is one point I mentioned during this thread is that there is always some energy-density, occupying space. You will always have either a positive or negative vacuum energy potential.

If I recall though this led to the biggest blunder, this process was once considered as a possible cause of the cosmological constant, however it was 120 orders of magnitude too large.

edit: this is in reply to Timmdeeg's post

I am not sure, aren't you confusing the quantum mechanical zero point energy and the zero-energy universe hypothesis (s. Wikipedia)? That's something else.

 

[Mordred]

not really the zero-energy universe ( universe from nothing model is a zero-energy universe at the beginning and uses the zero-energy universe as a premise) uses quantum mechanics and the Heisenberg Uncertainty principle, to form the initial virtual particle production. The two are related.

Not to say that is the only treatment that uses the zero-energy universe. Allen Guth's original false vacuum also used the zero-energy universe.

http://arxiv.org/pdf/gr-qc/0605063.pdf

edit: forgot to mention a perfect zero-energy universe would be flat and static. Which would be unstable, I'm sure from that statement you can see the connection between the cosmological constant and the quantum zero point energy

 

[timmdeeg]

forgot to mention a perfect zero-energy universe would be flat and static.

Ah, that seems to be the misunderstanding. The negative gravitational energy
does not contribute to the stress energy tensor.

http://en.wikipedia.org/wiki/Zero-energy_universe

 

[Mordred]

you might be interested in this historical development of zero point energy.

"Preludes to dark energy:Zero-point energy and vacuum speculations." http://arxiv.org/ftp/arxiv/papers/1111/1111.4623.pdf. covers a lot of the historical aspects. Just figured you would find it interesting

 

[timmdeeg]

Thanks, interesting article.

However this statement

forgot to mention a perfect zero-energy universe would be flat and static.

isn't clear to me. Are you saying that the zero-energy universe hypothesis (matter energy canceled by gravitational potential energy) implies necessarily that the RW-universe is flat and static? If yes, how would you explain that? And saying flat you mean spatially flat (not flat space-time), right?

 

[Mordred]

... whereby the positive energy of matter/radiation is canceled by its negative gravitational potential energy according to the zero-energy universe hypothesis.

step back and think about this statement. Let's use GPE for total gravitational potential, let's use VPE for negative gravitational potential, (Vacuum gravitational potential)

if GPE+VPE=0 this equals a perfectly flat universe. One whose total energy densities is equal to the critical density.

Now we already know from the Einstein field equations that a static universe is unstable. The EFE predicts either a contracting or expanding universe.

1) So how is a zero-energy universe defined in a universe with curvature?
2) How does a zero-energy universe evolve or contract?

The solutions to question 1 is rather tricky, the paper I posted shows the use of pseudo tensors and states that you cannot use polar coordinates, or spherical coordinates. You must use Cartesian coordinates.
http://en.wikipedia.org/wiki/Pseudotensor
this tensor is also used
http://en.wikipedia.org/wiki/Stress–energy–momentum_pseudotensor

the answer to number 2 is also tricky, remember according to the zero energy universe, the only two parameters you need to describe the dynamics of the universe is GPE and VPE.

so in order to expand it follows that globally VPE>GPE, to contract GPE>VPE. The paper slices the global into local with pseudo tensors and cartesian coordinates,
http://en.wikipedia.org/wiki/Cartesian_coordinate_system

needless to say the model gets complex, compared to LCDM. You can see this from the above, and I haven't even included quantum effects such as particle pair creation and quantum tunneling. Inflation (False vacuum) like I said makes use of the zero energy universe, then adds those quantum effects. Which creates an imbalance between GPE and VPE. When inflation stops GPE=VPE once again.

There is numerous controversies on this model, and I haven't studied it in a while. However that's my understanding of it. The use of pseudo tensors itself is one source of controversy

 

[Discman]

Universe bigger?

The universe is only stretching, everything in it is co-moving with space. No new space is generated. Our visible universe is only a part of a much bigger universe, laid there by inflation. So the question is: do we see new structures while stretching? A couple of decennia ago that was possible when the horizon moving with the speed of light could catch a light ray from a galaxy behind the horizon who was decelerating with the universe. Than it was possible to see new structures.
But since the discovery of an accelerating universe we never again will see new structures.

 

[Mordred]

The universe is only stretching, everything in it is co-moving with space. No new space is generated. Our visible universe is only a part of a much bigger universe, laid there by inflation. So the question is: do we see new structures while stretching? A couple of decennia ago that was possible when the horizon moving with the speed of light could catch a light ray from a galaxy behind the horizon who was decelerating with the universe. Than it was possible to see new structures.
But since the discovery of an accelerating universe we never again will see new structures.

Welcome to the forum, However please read the entire thread before posting in that thread. In particular what we have repeatably said about the terminology stretching and how incorrect that term is. Also read the Redshift and expansion article posted earlier in the thread concerning how light can reach us in regards to expansion, and the Hubble sphere.

 

[bapowell]

He's talking about inflation, in which case objects beyond the event horizon are indeed never to be seen again...

 

[Discman]

event horizon

According to me is inflation a temporary event, it halted, so here is in principle not an event horizon. The accelerated universe will go on forever. The Hubble radius will be at one time forever lagging behind and there is the event horizon.

But I am quite new here so I will at the moment not interfere to much. I will accommodate at first. The aim of my first answer was to get on the main road again from the original question after being lost in all the side ways of the threads.