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

[Drakkith]

If this is the case then why does space expand faster than the speed of light?

A few things about this. First, expansion is measured by a RATE, not a speed. By that I mean that it doesn't make sense to talk about the speed of expansion because that speed will change depending on how far away your two points of comparison are. For example, galaxies recede from each other at an increasing velocity of about 70 km/s for every megaparsec (Mpc) they are apart. So two galaxies 10 Mpc's apart will be receding from each other at approximately 700 km/s.

However, the RATE of expansion does not change in this manner. The time it takes for the distance between them to double is the same whether they are 10 Mpc's apart or 10,000 Mpc's apart.

Also, it gets us nowhere by talking about the expansion of "space itself". In reality, expansion is measured by comparing actual objects that exist within spacetime.

If the Universe is 13.8 billion years old we should only see back in time to 13.8 billion light years. Yet the visible Universe is roughly 46 billion light years.

There is no contradiction here. We CANNOT see back further than 13.8 billion years because light has not had time to travel any longer than that. (A little shorter than 13.8 billion years actually. Light wasn't free to travel until after Recombination occurred around 378,000 years after the big bang and the universe became transparent to EM radiation)

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. Note that years is a measurement of time, while light years is a measurement of distance.

Understand that to measure the radius of the observable universe requires us to understand how expansion works, otherwise we would get the wrong value. In a non-expanding, static universe, the diameter of the observable universe would only be about 13.8 billion light years, increasing by one light year ever year. However, in an expanding universe, the galaxies we see now have actually receded from us since their light left them, making the observable universe larger than it would appear to be if you only consider the time that light has had to travel.

The argument is that space can expand faster than light because it is nothingness. Nothingness does not follow the laws of physics. But you said space includes matter and energy. Which is it?

That is not the argument. Our primary theory for understanding the universe on its largest scales is General Relativity. Under the rules of GR, the expansion is the result of dynamic geometry, not the result of space expanding as if space were something that was actually moving. Space is not moving. The concept of space being something that can move does not even apply under GR. We can set up frames of reference at different points within spacetime and watch the effects that this dynamic geometry has on them, but we cannot see "spacetime itself" nor can we assign a frame of reference to it since it is the underlying framework upon which everything occurs.

 

[Ken G]

Also note that, once again, just imagining that matter shrinks makes that question go away as well. Poof, no "where does the space come from," no "how can objects move away from each other faster than c." This doesn't mean matter "really does" shrink, any more than space "really expands", it just makes the point that these are all just pictures and cannot be taken seriously enough to worry about questions like these. Questions that persist in all perspectives are the "real" questions-- questions that stem from a particular picture, but go away in a different picture, are seen to stem from the pictures, not the physics.

 

[craigi]

The rebuttal, as I understand it, is that space can expand faster than light because it is nothingness. Nothingness does not follow the laws of physics.

Not quite. The laws of physics are models and we do model nothingness. In fact, it's important to explain the expansion of the universe.

There's a common misconception that claims that there is nothing that can travel faster than the speed of light. In the model of special relativity, information and matter can't travel faster than the speed of light, but that isn't to say that there isn't anything that can. To illustrate this, if you project an image off into the distance and rotate your projector, there is a distance beyond which the projected image is traveling faster than the speed of light. The image is still constructed from the interaction of matter and information is still transmitted, but no matter or information moves faster than the speed of light, nevertheless the projected image can travel at unbounded speeds.

 

[bapowell]

If this is the case then why does space expand faster than the speed of light? If the Universe is 13.8 billion years old we should only see back in time to 13.8 billion light years. Yet the visible Universe is roughly 46 billion light years. The rebuttal, as I understand it, is that space can expand faster than light because it is nothingness. Nothingness does not follow the laws of physics.

No, the observable universe is 46 byl across because it is expanding. Simple as that. As space expands, it brings photons along with it: as they recede from Earth they have a velocity v_{\rm rec} + c: the first term is that due to the Hubble expansion, and the second, c, is the local speed of light. Of course, as the universe expands v_{\rm rec} continuously changes. If you integrate this speed over the time the universe has existed (13.6 by), you get something larger than 13.6 bly because photons recede with speeds surpassing that of light the whole time. The universe itself "expanding faster than light speed" has nothing to do with it, and as Drakkith has explained, is not a correct way to think of expansion.

 

[Mordred]

If this is the case then why does space expand faster than the speed of light? If the Universe is 13.8 billion years old we should only see back in time to 13.8 billion light years. Yet the visible Universe is roughly 46 billion light years. The rebuttal, as I understand it, is that space can expand faster than light because it is nothingness. Nothingness does not follow the laws of physics.

But it was said above that space, essentially, includes matter and energy. So it is not nothingness. Is not this matter and energy subject to the speed of light limitation, or is the universe expanding (creating space) into an existing space of matter and energy? Not clear to me. Or are we alluding to Dark Energy and Dark Matter which is called Dark because we do not understand it yet. But then I am just a lowly mechanical engineer. But I absolutely enjoy reading these threads. I do get a lot of insight from them.

The others have already answered the majority of your questions. However I would add the term "dark" in both dark energy and dark matter are kind of stuck to science. Although we do not completely understand them. There is a lot we do. We may not know what dark matter is, however we know how it influences the universe mass density calculations. In fact dark matter is the larger gravitational influence. Baryonic (what stars etc are made of) matter is a small fraction of the gravitational influence. In Dark energy the mystery is more that we do not know what mechanism that keeps the density of dark energy constant. As a negative pressure influence its effects are easily understood in regards to expansion. Dark energy is a contributor to the cosmological constant. Matter influence is positive vacuum, the cosmological constant is a negative influence.

Due to the ratio of dark matter and baryonic matter, dark matter is the largest contributor to positive vacuum. Due to the sheer volume of space the cosmological constant is the largest contributor to the negative vacuum pressure. So yes much of the dynamics of expansion is primarily due to the pressure relations of the cosmological constant and dark matter. More so than other forms of energy and baryonic matter

P.S I'm just a lowly Electronic controls tech, I simply spent several years studying cosmology textbooks, and asking questions on PF. Cosmology is my favorite hobby lol. Although some of the posters on this thread are physicists. I won't say who, that is their privilege to divulge

hint the tools and links to understand basic cosmology have already been posted throughout this one thread. So they don't need to be reposted. However my signature also contains many of those tools on the http://cosmology101.wikidot.com/main link. The http://www.einsteins-theory-of-relativity-4engineers.com/LightCone7/LightCone.html. Provides a handy calculator to understand the history and future expansion history. http://cosmocalc.wikidot.com/start is where to find the information on how to use that calculator

 

[ptalar]

Thanks to all for providing input and insight.

 

[azureorb]

Back to the OP's original concern... Brian Greene, no, was not talking purely analogy. He LITERALLY meant that space IS a "thing", and not a complete void at all. Not in the sense of the geometry or boundaries of "nothingness", but that it's not a complete void -- there is a something -- not of mass, not of standard energy, but it's a "something" of a different sort.

OP's question was whether people agree with this. The argument seemed to shift into "what he really meant".

Physics programs/documentaries do use analogies all the time. It's great. And yes, there will be little white lies that pass through and instructors/writers/presenters will forget to put an asterisk next to certain things they say because they're actually being analogous and not literal.

BUT with Brian Greene as an example, among others, they go out of their way -- loud and clear -- to make it clear as a bell that they Literally mean that space is SOMETHING -- not complete nothingness in and of itself. And others point out things very loud & clear -- not in analogy -- that space LITERALLY bends & twists with the mass residing in it.

So the question is -- do you believe that, or do you think they're mistaken themselves and that's all just a hypothesis and has no grounding (but it great for selling books and videos)?

 

[phinds]

So the question is -- ... do you think they're mistaken themselves and that's all just a hypothesis and has no grounding (but it great for selling books and videos)?

Yes.

 

[Mordred]

So the question is -- do you believe that, or do you think they're mistaken themselves and that's all just a hypothesis and has no grounding (but it great for selling books and videos)?

Yes its great for selling books, and is not scientifically accurate, its great for grabbing attention though. See the reasons posted throughout this thread.

 

[Ken G]

So the question is -- do you believe that, or do you think they're mistaken themselves and that's all just a hypothesis and has no grounding (but it great for selling books and videos)?

I'm going to go with neither of the choices, even though on the surface they seem to cover the possibilities! But there's a third possibility which I think is more the truth here, which is that science simply does not make any important distinction between a working hypothesis/theory, and a statement of "what is," such that it could ever "mistake itself" by using the latter language as a kind of rhetorical shortcut. We forget this all the time-- we have a theory that talks about protons and electrons, so we tend to imagine the protons and electrons "are," but then someone like Heisenberg comes along and says its time to stop thinking in terms of elementary particles and start to think in terms of elementary symmetries. So much for what is! It seems "what is" is very much in the eye of the beholder, the laboratory observer thinks "what is" is their apparatus, a theorist thinks "what is" is an abstract mathematical structure, and Brian Greene thinks "what is" is a twisting expanding space. These are all just pictures, we don't get to know "what is," but the language of science is more direct if we all kind of pretend like we are talking about "what is." We can even make non-scientists think that's what we are talking about, which can be a slippery slope but is still more or less unavoidable. We just don't need to really believe it ourselves.

 

[azureorb]

Yes its great for selling books, and is not scientifically accurate, its great for grabbing attention though. See the reasons posted throughout this thread.

But you didn't directly answer the question. :) And they aren't dancing around words to make something clearer to the masses. You could pick apart some things they're saying of course and say "Well, technically, this doesn't Really work this way, it actually works This way, but you can think about it that way because it makes more sense to understand." Sure, there's lots of that.

But the concept of space being Literally, in all aspects in all ways 100% *nothing*, nada, zip, zilch on every level from the macroscopic to the quantum level -- they're literally saying essentially "No, we used to think it was truly nothing, but it's not. It IS something in and of itself." That's Very different than forgetting to make it clear "It's not literally like this, but you can think of it this way."

So it should be of no argument that that is their claim -- not just for the masses but to physics world as well. The closest thing you could say is that they're forgetting to say that it's merely a modern-day theory, and not validated enough to say it so strongly. But it'd be silly to think "Oh, they don't Really mean that, they're just being analagous." THAT would be an incorrect observation.

So are they correct (do you share the belief) in literally saying that space in and of itself, IS in fact, something?

We forget this all the time-- we have a theory that talks about protons and electrons, so we tend to imagine the protons and electrons "are," but then someone like Heisenberg comes along and says its time to stop thinking in terms of elementary particles and start to think in terms of elementary symmetries. So much for what is!

True -- in some sense something exists in a very different way -- but presenters/instructors/writers draw it out to make it understandable even though No -- an electron doesn't exist at all (like that), but it exists in a totally different way (and can be of a totally different type of existence in another state/situation, etc).

But in the Brian Greene example (among others), it's not about exactly what space is -- it's actually a bit of a simpler, basic concept. Does it in some way, exist as something? Some type of different type of existence as a 'something', a field of sorts, as they claim it Literally is?

Again, they go out of their way to make it very clear that we used to believe space was absolutely nothing in every sense, in every dimension from the macro->quantum and in every sense of the word -- NOTHING. BUT NOW, it is shown to be something in and of itself. WHAT that is gets more complex of course. WHAT that is would easily fit the mold of language misuse and an incorrect vision of what it actually is...

... but to distinctly say that it's no longer absolutely nothing, but in and of itself it IS something -- that does not fall victim to language misuse where you can say "Oh, they don't mean it literally is something -- they're just trying to get you to understand some concepts about this and that." No, that's not what they're doing. :)

 

[Mordred]

well you can believe whatever makes you most comfortable, personally I studied enough to prove to myself that space isn't created, or have a substance. Its merely a change in geometric volume filled with the contents of the universe. Even my studies into strings hasn't shown me any difference in that understanding. Nor has reading Brian Greene's papers. Some articles he refers to it as a volume change, other string articles he refers to it as a space curvature. However his metrics show the geometry relations. Even in his string articles.

for example he is clear in this article, "It is the volume that grows and signals a transition to a radiation phase" page 19 section 38

http://arxiv.org/pdf/0809.1704v3.pdf
even when he discusses branes and phase space his metrics and descriptives refer to the geometric aspects and energy-density relations and distributions.

opening page he refers to toroidal volume.
http://arxiv.org/abs/0707.1062
down further he defines shape as
"As the universe cools, different species contribute to the energy density in non-relativistic matter leading to an alteration in the shape of the potential" nice accurate descriptive of topography in Cosmology applications. Very appropriate definition of space curvature if you include the potential affects of all energy density contributors, such as dark energy

 

[azureorb]

Its merely a change in geometric volume filled with the contents of the universe. Even my studies into strings hasn't shown me any difference in that understanding. Nor has reading Brian Greene's papers.

I'm sure geometric changes in it and focuses on that and such don't mean that's All there is (as he points out quite literally elsewhere in other circles that space is a substance of sorts).

However, it'd be a separate argument to say space would be a substance in the same sense that we interact with "substance". And if it's some form of field, well, that's not the same as a fabric in the sense of what we think... but again, the OP's original question was is it "something" in ANY sense of word -- which is what many uber-modern analysts will claim (like Greene).

I mean, to us, in which we directly interact with it, it could literally mean nothing -- absolutely nothing -- but still be "something".

And here's an off-shoot of the question. Whether or not space itself in any way is a 'something' ... and let's say it's not at all in any sense of the word: The boundaries, like a balloon expanding -- is that 'something'?

In a balloon, there is "nothing" (as far as the balloon itself is concerned; just air; not rubber). But the boundaries of that balloon is something (rubber).

So in that analogy of the universe (space) being like a balloon expanding -- are the edges of it 'something'?

 

[phinds]

... The boundaries, like a balloon expanding -- is that 'something'?

In a balloon, there is "nothing" (as far as the balloon itself is concerned; just air; not rubber). But the boundaries of that balloon is something (rubber).

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

 

[Drakkith]

So in that analogy of the universe (space) being like a balloon expanding -- are the edges of it 'something'?

The surface of the balloon is a 2d boundless, edge-less, finite surface.

 

[Mordred]

I'm sure geometric changes in it and focuses on that and such don't mean that's All there is (as he points out quite literally elsewhere in other circles that space is a substance of sorts). However, it'd be a separate argument to say space would be a substance in the same sense that we interact with "substance". And if it's some form of field, well, that's not the same as a fabric in the sense of what we think... but again, the OP's original question was is it "something" in ANY sense of word -- which is what many uber-modern analysts will claim (like Greene).

I mean, to us, in which we directly interact with it, it could literally mean nothing -- absolutely nothing -- but still be "something". ?

The something is the contents of the universe, that fills the volume. Just like if you increase a volume of a container containing gases, those gases will fill that volume. The universe is treated as a fluid, or ideal gas, defined by its energy-density relations. One unit of volume, even if it has no particles or fields within it, will have negative pressure. Energy-density has a pressure relation. Matter exerts negligible pressure. see the equations of state Cosmology.

and I quote from the wiki page, though I rarely like using wiki as a reference.

"The equation of state may be used in Friedmann–Lemaître–Robertson–Walker equations to describe the evolution of an isotropic universe filled with a perfect fluid"

http://en.wikipedia.org/wiki/Equation_of_state_(cosmology)

if you increase the volume, the effective pressure and temperature drops. Just as the ideal gas laws tells us with its corresponding equations of state.

A pressure is an energy-density relation, so an absolute nothing is never possible, within a fluid. There is always an energy-density present. However that "never means space itself.. Even one quanta of a perfect (theoretical) vacuum, will have energy potential. If you were to have a theoretical toy model universe, and were to remove all matter, all forms of radiation, and the only thing left is vacuum. That Universe has energy-density. The same as it would if it had a positive vacuum. Those universes would expand and contract according to its pressure relations between positive pressure and negative pressure.

the curvature or shape of space is a description of the energy-density relations between all the species of particles and energy contained within the measurable volume of the universe.

There is no container or walls of some mysterious substance or fabric, defining an edge of the universe

 

[guywithdoubts]

The something is the contents of the universe, that fills the volume.

I'm still trying to understand this, aren't we simply replacing "space" by "volume" here? What is this volume, then? I'm always coming back to this very concept; even after all the critical density talk and your article about geometry, eventually one word seems to be replaced by another and I keep getting the impression "space" or "volume" is some sort of entity whose existence as such is objected. "It's not something, it's just the distance between things in a volume." (not quoting anyone here)

Am I being a victim of semantics?

 

[craigi]

...

BUT with Brian Greene as an example, among others, they go out of their way -- loud and clear -- to make it clear as a bell that they Literally mean that space is SOMETHING -- not complete nothingness in and of itself. And others point out things very loud & clear -- not in analogy -- that space LITERALLY bends & twists with the mass residing in it.

...

Space is something and it's not nothing. It's the dimensions in which objects have relative position, in exactly the same way that flat Euclidean space is. It's how we define it, so what else could it possibly be?

How can anything be nothing anyway? It's logically impossible.

General relativity is visualised as a curvature of space and time, and string theory, for example, incorporates extra dimensions, but they still just represent relationships between objects.

I think the confusion arises form the popular visualisation of the "fabric" of space. It's a useful prop for learning but as others have said, don't start believing the "fabric" somehow exists. It's just a way to describe the notion that space and time aren't always "flat", in the same way that fabric isn't always flat.

Space itself can never be observed directly. We observe objects in space. Again this is the same for flat Euclidean space.

So what is "empty" space filled with? The quantum vacuum. That's something and not nothing either and again, we can't observe it directly, but we need it for our models to work.

 

[Mordred]

From wiki

"Volume is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance (solid, liquid, gas, or plasma) or shape occupies or contains"

for the universe ignore the closed boundary, defining volume of an ideal gas can get tricky in Cosmology applications. I tend to think of it as the area or region that is in thermal equilibrium or can be described by the same conditions

"In differential geometry, volume is expressed by means of the volume form, and is an important global Riemannian invariant. In thermodynamics, volume is a fundamental parameter, and is a conjugate variable to pressure."

edit for example if I want to describe one gas floating in the intergalactic medium, surrounded by another gas in the same medium. I can set the volume as the measurable region occupied by the gas I wish to study. Then set the boundary where the outer gas meets the gas under study or where there is no interactions between the two. However I can then define the volume of the region of interactions as well, as the area of interactions whose boundary is the area that interactions do not occur encompassing it.

please note I do not need some "fabric" separating the two

 

[Mordred]

If you take the last post, and wish to apply it to the volume of the universe, a simple translation would be. The universe is the region of measurable influences. (Observable Universe). The Cosmic event horizon is the boundary separating the region we cannot measure and has no measurable interactions, within our observable universe. Again no fabric is needed to separate the two.

 

[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 Heisenburg 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.