What fuels accelerating expansion of our universe

[spicerack]

where does all the extra space come from ? ie... the stuff that is forcing objects to become further apart at speeds exceeding light particularly in the early universe stage

was it present at big bang ?... I don't think so cos that is what inflation is, rapidly expanding space

is it being pumped into our universe ?... by a white hole or bouncing back from a black hole

does it divide and multiply like a bacteria ?

please some help or links would be most appreciated

 

[moving finger]

where does all the extra space come from ? ie... the stuff that is forcing objects to become further apart at speeds exceeding light particularly in the early universe stage

was it present at big bang ?... I don't think so cos that is what inflation is, rapidly expanding space

is it being pumped into our universe ?... by a white hole or bouncing back from a black hole

does it divide and multiply like a bacteria ?

please some help or links would be most appreciated

I'm more worried about where all the energy is coming from. If it's correct that we have a positive cosmological constant then the vacuum energy is estimated to be around 6 x 10^-10 J/m^3. This is a very small energy density, but the exponential expansion (which is what our universe is apparently heading for) caused by the associated cosmological constant means that very soon our universe will be doubling in size roughly every 11 billion years - which means the total energy locked up in the vacuum is increasing by a factor of 8 every ~11 billion years?

MF

 

[SpaceTiger]

The answer to pretty much all of your questions is "nobody knows". There are a lot of theories, but unless you're an expert, I wouldn't recommend bothering with them. Ask again when there's more of a consensus.

 

[Mike2]

where does all the extra space come from ? ie... the stuff that is forcing objects to become further apart at speeds exceeding light particularly in the early universe stage

was it present at big bang ?... I don't think so cos that is what inflation is, rapidly expanding space

is it being pumped into our universe ?... by a white hole or bouncing back from a black hole

does it divide and multiply like a bacteria ?

please some help or links would be most appreciated

Consider the very first instant in the creation of spacetime. The very fact that it came into existence when before spacetime did not exist means that it is in the very nature of space to expand. Then just after the singularity, when there was a small differential region of spacetime, there could be no differences in any properties from one point to the next in that small region simply because it was so small no change in properties could occur. This means that initially every point of spacetime expanded in the same way and at the same rate as every other point in spacetime. The overall effect is an exponential expansion where the rate of growth of the universe is proportional to its size. So the key to why space expands is resolved by why it came into existence to begin with. We cannot know what happened before creation; we can only go back to a singularity, and perhaps that goes back to negative infinity in time.

I suppose such a process would be a purely mathematical consideration: what mathematical processes give rise to the growth of a manifold (or a space) from a singularity. There are homotopy classes that describe which kinds of manifolds (spaces) can be continuously shrunk down to a singularity, which manifolds can be continuously shrunk down to a closed line, a surface, etc. So no doubt there are some homotopy considerations involved with the possible spaces (manifolds) that can arise from a singularity.

Since we are talking about possible manifolds (spaces) that can continuously arise from singularity, it seems natural to construct a superposition of these possible manifolds from the same homotopy class. As I recall, Dynamical Triangulation is an attempt to construct our 3D+1D world from a quantum mechanical superposition various dimensional spaces. They found that such a construction expands with time. Where they got "time" I don't know. Maybe that is just the parameter that controls how the homotopy grows from a singularity. Is there a different parameter for each dimension of homotopy? Is there restrictions on these parameters (so that it forms our known time) since each additional point of added space forms a new point out of which new homotopy classes arise which must be consistent with prior existing growth? I don't know. It would be impossible to say which point was created first. So the parameters that control the shinkage of the homotopies would have to somehow form a consistency with the other parameters from other points. Does this spark any ideas from anyone else out there?

 

[spicerack]

interesting stuff guys but I'll have to mull it over cos I'm already feeling out of my depth.

Incidentally MF where does zero point energy fit into your equation ?

Is empty space devoid of matter/energy or is there no such thing and space comes loaded with energy so it begs your question as well ?

You know Mike, I can understand no space just compressed matter, but no time ?

Doesn't that imply that the initial singularity only existed from the time of the BB ?

It couldn't have been sitting round forever as there was no measurement to quantify how long forever or an instant was...

does that make sense ?

I guess i'll have to settle for "nobody knows" as an answer to where does all the space come from since it didn't exist before the BB and there seems to be more of it being constantly inputted into the system at a faster rate now than sometime before.

 

[moving finger]

Incidentally MF where does zero point energy fit into your equation ?

Dunno, but you may find interesting reading on the issue of ZPE and the Big Bang at :
http://www.ldolphin.org/zpe.html

MF

I realized that if I understood too clearly what I was doing, where I was going, then I probably wasn’t working on anything very interesting

 

[RoboSapien]

I believe that Universes Expansion is getting its energy from the same source that the moon is getting its energy to go away from Earth ( we will loose moon one day).

Its called Centrifugal Energy.

Please don't delete this post its Just a suggestion.

 

[Entropy]

I believe that Universes Expansion is getting its energy from the same source that the moon is getting its energy to go away from Earth ( we will loose moon one day).

Its called Centrifugal Energy.

The moon isn't getting any energy. You see gravitational orbits aren't exactly circular. It's orbits is slightly expanding. You see you can't really ever get a stable orbit, your orbit is either slightly decaying or slightly increasing. No energy is being added, it's just with the initial angular momentum the moon was originally given it takes X amount of time to travel Y distance from the Earth. Add actually the moon is decelerating. You see as it's orbitally distance increases it's angular velocity decreases as well. So the further away from the Earth it gets the slower it will become.

As for the expansion of the universe, matter in the universe appears to have a net linear acceleration away from the center of the universe. Unlike the moon, matter in the universe is gaining speed.

 

[SpaceTiger]

I believe that Universes Expansion is getting its energy from the same source that the moon is getting its energy to go away from Earth ( we will loose moon one day).

Its called Centrifugal Energy.

Science is not about "belief", it's about theory and experiment. A good scientist doesn't believe something until it has been satisfactorily demonstrated to them.

 

[Phobos]

I believe that Universes Expansion is getting its energy from the same source that the moon is getting its energy to go away from Earth

As noted above, that's a different mechanism. Here's a recent topic about the moon's orbit...
https://www.physicsforums.com/showthread.php?t=67691

( we will loose moon one day).

I seem to recall a past topic where Janus explained how this would not happen. You may want to try a search for it.

 

[spicerack]

As for the expansion of the universe, matter in the universe appears to have a net linear acceleration away from the center of the universe.

some people don't like it when others talk about a "centre" of the universe despite all the talk of bubbles, branes and curved space implying a spherical nature conventional wisdom would still have the centre as being everywhere if you rewind time back to the big bang

me, I like the idea

 

[Chronos]

I would be one of those people who discourage the notion of a center or edge to the universe. There would be distinct observational consequences if the universe had a topology that included these entities. No such evidence exists, and the mathematics we use to describe that topology [which seem to work nicely] admit to no such entities.

 

[hkhandrika]

I would be one of those people who discourage the notion of a center or edge to the universe. There would be distinct observational consequences if the universe had a topology that included these entities. No such evidence exists, and the mathematics we use to describe that topology [which seem to work nicely] admit to no such entities.

Wow, I was just about to say that though the thought of something outside of the universe, a boundary to the universe and what happened before the big bang exist, our maths and sciences may not be able to explain it, so scientists tend to stay away from those realms.

Very interesting question though.

 

[Mike2]

interesting stuff guys but I'll have to mull it over cos I'm already feeling out of my depth.

Incidentally MF where does zero point energy fit into your equation ?

Is empty space devoid of matter/energy or is there no such thing and space comes loaded with energy so it begs your question as well ?

You know Mike, I can understand no space just compressed matter, but no time ?

Doesn't that imply that the initial singularity only existed from the time of the BB ?

It just occurred to me: We believe that near the horizon of a black hole that some virtual pairs do not recombine because one member of the pair will slip behind the horizon, never to be recovered, so that there remains a surviving virtual particle that drifts away from the black hole to give the black hole a radiation. OK. So I suspect that the same thing is happening with the cosmological event horizon. QED tells us that virtual particle pairs are spontaneously formed, they travel apart for a brief time, then come together according to the uncertainty rule. And the path integral formulation says that some portion of these pairs can travel very far away before coming back together; they can even travel faster than light. So...

I wonder if anyone has studied the possibility that new particles are created in space due to the fact that some members of virtual pair productions are slipping behind the cosmological event horizon, only to leave behind the other member as a permanent particle? Would this process be responsible for particle creation to begin with? During inflation the universe expands exponentially. At first is expands slowly so that there is no event horizon, then as the universe begins to expand quite rapidly, the cosmological event horizon contracts. Then it would be very easy for members of virtual pair production to slip behind the cosmological event horizon, leaving many particles behind.

 

[selfAdjoint]

I wonder if anyone has studied the possibility that new particles are created in space due to the fact that some members of virtual pair productions are slipping behind the cosmological event horizon, only to leave behind the other member as a permanent particle? Would this process be responsible for particle creation to begin with? During inflation the universe expands exponentially. At first is expands slowly so that there is no event horizon, then as the universe begins to expand quite rapidly, the cosmological event horizon contracts. Then it would be very easy for members of virtual pair production to slip behind the cosmological event horizon, leaving many particles behind.

But unlike a BH event horizon, our cosmological horizon isn't a "thing" in spacetime, it's just an observer dependent appearance. As I believe Roger Bacon said, "Every eye sees a different rainbow". So there's nothing out there to keep the particles from recombining. Or have I missed something?

 

[marcus]

some people don't like it when others talk about a "centre" of the universe despite all the talk of bubbles, branes and curved space implying a spherical nature conventional wisdom would still have the centre as being everywhere if you rewind time back to the big bang

me, I like the idea

It is, I have to admit, a charming idea, like Santa Claus or the Tooth Fairy.

In big bang theory (the public's name for conventional cosmology) there is no centre.

but in popular imagination there is a centre

no scientific theory, that I know of, supposes a centre, no professional cosmologist talks about a centre, but large numbers of people seem to LIKE the idea

Me too. It is a delightful idea, which charms people so that they believe in a "centre of the universe" without needing any reasons. So I guess the best analogy is that

the centre of the universe (as per spicerack) IS A POEM

we all love poems, so let's all believe in the centre of the universe together because it is a satisfying image that you can't get out of your head or because it is instinctive in us to want this idea, or whatever makes poems memorable

(the only awkwardness comes when people inject it into the wrong context, like a quantitative discussion about the universe involving numbers, observation, tested theories etc)

 

[marcus]

I think it is important to recognize that people (scientist and nonscientist alike) have feelings.

feelings of attachment, like somebody or some thing is the center of your universe, can be TRANSFERED as you grow and go thru various of life's crises.

(for example people transfer feelings of love and dependency from mother or parent to teacher to shrink to spouse to grownup child etc. not necessarily in that order)

you find that professional cosmologists, deep down, feel about the CMB the way people who don't know anything about the real universe probably feel about "the centre of the universe"

if the CMB were suddenly turned off it would be a terrible psychological loss for cosmologists (analogous to what a religious person might feel if they found they could no longer pray or they had lost the sense of the divine presence)

the CMB is how many people relate, people who (because they have studied in school) have no "center of the universe"

 

[marcus]

I think the reason the CMB has such a profound hold on the astronomer's imagination
or anyway one of the reasons
is because it defines stillness

a cosmologist lives his or her mental life in a world with no center
in which (except for the CMB) you CANNOT EVEN SAY WHAT IT MEANS TO STAND STILL

in cosmology (for people who have been to school and studied it) there is no idea of "home base" that you can orient your mind towards

but the CMB is spread evenly throughout all space and it is not just something you IMAGINE, you can put up an antenna anywhere in the universe and point it in any direction and LISTEN TO IT

and it gives you a clear practical idea of what it means to be stationary with respect to it. You can say what our present motion is , relative to it. and you can change coordinates so you can map the universe
FROM THE STANDPOINT OF SOMEONE WHO IS NOT MOVING (relative of course to the CMB because there is no other marker)

there are other things that people get from the cosmic microwave background signal, but this practical concept of stillness is one of the chief things and most immediately accessible

Probably another reason the CMB has such a profound hold on astronomers' imaginations is because it is the oldest light----but the stillness thing has a practical everyday importance because one can base coordinates and orient relative to it. non-moving relative to Cmb is the same as non-moving relative to the Hubble flow (i.e. relative to the expansion of the universe).
When you have no center, then an idea of stillness (which is like the center of the velocity world, the zero velocity) can kind of take its place.

 

[marcus]

I'm more worried about where all the energy is coming from.

I agree! if the cosmological constant really does arise from a vacuum energy then where is it all coming from. Or do we toss out the conservation law? Apparently there is no energy conservation law in General Relativity (except locally or in some special cases). That whole
energy issue is a mystery.

And it's a severe mystery because a huge mass of evidence and argument points to there having been a brief moment of inflation, and that has the same non-conservation problem: a "scalarfield" constant energy density and a vast increase in volume, hence a vast creation of energy.

I'm more worried about where all the energy is coming from. If it's correct that we have a positive cosmological constant then the vacuum energy is estimated to be around 6 x 10^-10 J/m^3. This is a very small energy density, but the exponential expansion...

I agree with your estimate. I suppose maybe the cosmological constant might sometime be attributed to something else besides an energy, and worked into the theory some other way. The mysteries are staring us in the face.

and, at least for me, there is a big confusion about where did all the energy in the CMB go? there are essentially the same number of photons as there were in year 380,000 but they have been stretched out a thousand fold and have each lost 999/1000 of their original energy. Where did the energy go?

 

[turbo]

And it's a severe mystery because a huge mass of evidence and argument points to there having been a brief moment of inflation, and that has the same non-conservation problem: a "scalarfield" constant energy density and a vast increase in volume, hence a vast creation of energy.

The inflation is a problem, but there is another one that bothers me more: Where did the energy needed to stop inflation and transition to a relatively linear expansion come from? Assuming that inflation is needed to rapidly grow the BB Universe, how did every part of the now-spread-out Universe "decide" to stop inflating simultaneously and manage to avoid developing some really severe anisotropies? I have real trouble understanding how that process could occur.

 

[Mike2]

But unlike a BH event horizon, our cosmological horizon isn't a "thing" in spacetime, it's just an observer dependent appearance. As I believe Roger Bacon said, "Every eye sees a different rainbow". So there's nothing out there to keep the particles from recombining. Or have I missed something?

It would be the same effect as a BH. One of the pair enters a frame that is accelerated to the point of no return. Same with the cosmological event horizon. Problem is that with the cosmo event horizon, that one of the pair that slips behind the cosmo event horizon would have to travel faster than the speed of light to get there, and the path integral formulation suggests that this happens. But then if it is traveling faster than light, then it could travel that fast on its way back and overcome the speed of the expansion of the universe. Or could there be a small portion of pairs that travel there faster than light but travel back less than the speed of light? All paths are possible, right? Imagine during inflation that expansion is so fast that the cosmo event horizon is of the order of an inch or two. At that scale you can see how one of the pair could slip behind it, never to return, can't you? You might not even need faster than light speeds at that scale.

 

[RoboSapien]

Thanks Phobos. U r reasonable compared to others. Keep it up.

 

[moving finger]

there is a big confusion about where did all the energy in the CMB go? there are essentially the same number of photons as there were in year 380,000 but they have been stretched out a thousand fold and have each lost 999/1000 of their original energy. Where did the energy go?

Yep, there has been a lot of discussion on this topic too. See : Where did the energy in the CMB go to?

MF

 

[Garth]

There are several problems with energy in the standard model.

1. The loss of energy by the CMB photons. Integrated across any cosmological space-like hypersurface the total energy of the CMB photons steadily decreases with red-shift.

2. Inflation uses a massive 'cosmological constant', which then withers away to either nothing or a very small remnant value. However the nature of the cosmological constant is to be constant in order to preserve energy conservation, if the constant varies then energy conservation is thrown out of the window.

3. Dark energy may or may not be conserved depending on how it evolves. If it is invoked to exactly balance the books and keep the total mass-energy that of closure, then its equation of state (w = -1?) will not conserve energy. Its total energy must grow with the universe.

However GR never pretends to conserve energy in the first place, only energy-momentum (particle rest-mass), and that is different.

Either GR is correct and we are fools to worry about mass-energy conservation, or GR needs modifying.

For a concordant theory that modifies GR to conserve energy, and to include Mach's Principle, try Self Creation Cosmology - An Alternative Gravitational Theory .

Garth

 

[brightstar2005]

The accelerated expansion is fueled by lack of understanding.

 

[Mike2]

It would be the same effect as a BH. One of the pair enters a frame that is accelerated to the point of no return. Same with the cosmological event horizon. Problem is that with the cosmo event horizon, that one of the pair that slips behind the cosmo event horizon would have to travel faster than the speed of light to get there, and the path integral formulation suggests that this happens. But then if it is traveling faster than light, then it could travel that fast on its way back and overcome the speed of the expansion of the universe. Or could there be a small portion of pairs that travel there faster than light but travel back less than the speed of light? All paths are possible, right? Imagine during inflation that expansion is so fast that the cosmo event horizon is of the order of an inch or two. At that scale you can see how one of the pair could slip behind it, never to return, can't you? You might not even need faster than light speeds at that scale.

If this is the mechnism that created matter in the universe, then perhaps the density of matter created during inflation in a given amount of time can be used to find how big the whole universe really is. Or then again perhap the expansion rate has nothing to do with size, but only the density of matter. How does the Higgs mechanism relate to virtual pairs becoming separated to form permanent matter?

 

[spicerack]

The accelerated expansion is fueled by lack of understanding.

excellent, so once we understand enough it'll stop accelerating, expanding and...

...bang, slurp, boing ?

 

[Starship]

Doesn't the prediction of an inflaton scalar field imply the instability of the spacetime vacuum itself?

 

[moving finger]

I've just come across the super-Hubble-CDM model by Kolb et al, which attempts to explain present-day expansion based on the "after-effects" of primordial inflation, rather than on some kind of "dark energy"... anybody have any comments on this?

see

http://arxiv.org/PS_cache/hep-th/pdf/0503/0503117.pdf

MF

 

[Starship]

Well cosmic inflation and dark energy are hard to reconcile, because of the very different energy scales on which they occur.

 

[Uno Lee]

What if without things, space became infinite?

 

[turbo]

Here you can watch Sean Carroll's presentation on dark energy, the cosmological constant, and the energy of the vacuum. Go to the last video on the second day. He is quite open-minded about these concepts, including the possibilities that observed "coincidences" aren't coincidences, but poorly understood interrelations that would resolve in a proper theory.

http://www.slac.stanford.edu/econf/C0307282/top_program.html

 

[turbo]

I've just come across the super-Hubble-CDM model by Kolb et al, which attempts to explain present-day expansion based on the "after-effects" of primordial inflation, rather than on some kind of "dark energy"... anybody have any comments on this?

see

http://arxiv.org/PS_cache/hep-th/pdf/0503/0503117.pdf

MF

You may want to view these SLAC lectures. Rocky Kolb gave three lectures on Dark Matter and Dark Energy, August 4-6. Highly recommended. At one point, IIR he makes a comment to the effect that the popularity of a model is not important, its correctness is, and he points throughout to the very real dearth of knowledge and experimental evidence for DM and DE. You will notice very little smugness in the way he regards currently cosmology.

 

[moving finger]

the popularity of a model is not important, its correctness is,

I second that!

MF

 

[turbo]

Again at SLAC, a couple of great lectures by J. Patrick Henry on Clusters and Cosmology. Anybody here who thinks that standard model explains it all should at least listen starting at about 8 minutes into the second lecture. If this does not make you want to listen to his entire presentation, then you either already know way too much about cluster astrophysics, or you have been taken by the "dark side" of orthodox cosmolgy. Entertaining lectures, with a realistic view of "what we know" and what we assume.

http://www.slac.stanford.edu/econf/C0307282/lecture_program.html