Debunking the Big Bang Theory: Colliding Branes as a Possible Alternative

[stglyde]

Would you bet your life on it?

Big Bang proof supposedly came from:

1. Redshift
2. Cosmic Background Radiation
3. Deuterium and baryogenesis

what else?

Is there no other way for them to occur without the Big Bang? but there is this Colliding Branes Theory about two branes colliding and producing the Bang everywhere. Meaning it doesn't occur at a single point but at multiple points so not really Big Bang but Multiple Bangs. Is it a leading candidate against the Big Bang theory or does the colliding branes theory produced a singular Big Bang too?

Do you have list of all the evidences of the Big Bang in a site so any theory against it has to explain each point by point?

 

[bapowell]

Is there no other way for them to occur without the Big Bang? but there is this Colliding Branes Theory about two branes colliding and producing the Bang everywhere. Meaning it doesn't occur at a single point but at multiple points so not really Big Bang but Multiple Bangs. Is it a leading candidate against the Big Bang theory or does the colliding branes theory produced a singular Big Bang too?

The standard big bang model does not address the moment of the bang itself. It is instead a model that describes how the universe evolved from a hot and dense state in its youth to a cooler and less dense state at the present. The standard big bang model purports that the big bang happened everywhere at once, not at a single point. This is an important misconception to straighten out. The colliding branes theory is a proposal that seeks to explain the physical mechanism for the big bang itself. Therefore, it is not in opposition to the standard big bang model; rather, it seeks to extend it. The colliding branes theory is still only hypothesis. The colliding branes theory has the rather unfortunate name of "ekpyrosis" in case you wish to read more about it.

 

[stglyde]

The standard big bang model does not address the moment of the bang itself. It is instead a model that describes how the universe evolved from a hot and dense state in its youth to a cooler and less dense state at the present. The standard big bang model purports that the big bang happened everywhere at once, not at a single point. This is an important misconception to straighten out. The colliding branes theory is a proposal that seeks to explain the physical mechanism for the big bang itself. Therefore, it is not in opposition to the standard big bang model; rather, it seeks to extend it. The colliding branes theory is still only hypothesis. The colliding branes theory has the rather unfortunate name of "ekpyrosis" in case you wish to read more about it.

What I meant to say was the colliding branes just bang already existing spacetime. Whereas in original Big Bang theory, spacetime was expanded and created by the Big Bang. There's the important difference. When spacetime already exist and you bang every point of them. It's no longer Big Bang but some kind of Branes Bang (Ekpyrosis)

 

[BillSaltLake]

As to whether the Big Bang is 100% true, scientists now know that it is between 98.2% and 101.3% true, and it is believed that the error bar is constantly shrinking. However, philosophers keep saying, "We're going to need a bigger error bar."

 

[DaveC426913]

As to whether the Big Bang is 100% true, scientists now know that it is between 98.2% and 101.3% true, and it is believed that the error bar is constantly shrinking. However, philosophers keep saying, "We're going to need a bigger error bar."

We got a JimmySnyder contender here!

 

[stglyde]

Q. How many galaxies can fit on the head of a pin?

A. Billions and billions of them or all of them including billions of universes.

Modern physics exceed any unbelievableness that maybe fewer than 3% of the public is aware of Planck density. Anyone can share in a few sentences how to calculate the Planck density such that billions and billions of galaxies can fit into the Planck length?

 

[DaveC426913]

...the Planck density such that billions and billions of galaxies can fit into the Planck length?

Well, those galaxies are made of atoms. And I'm pretty sure "Pauli" would "exclude" them from fitting all on the same pin... in "principle".

 

[marcus]

...Whereas in original Big Bang theory, spacetime was expanded and created by the Big Bang...

Glyde, it sounds like you swallowed another popularization.

You could re-read what Brian Powell said, which I think is carefully worded, and he's a pro. As I understand it, the classic BB theory does not say anything about what was or what happened right at the start of expansion. So it does not say space was "created". The classic 1915-1923 theory would not know how to say that. It just breaks down and quits as it approaches that point.

Popularized accounts say things like that. But not to take seriously

Nowadays classic BB theory has been extended in various ways, which still have to be tested. They avoid "singularity", that is they do not break down and give meaningless results. They go back to the start of expansion and further back in time before start of expansion. There's always something there, some process being described.
I don't know any currently researched BB extension that says space or time are "created".
There may be such but that would not be typical of the majority of the research papers that model events/conditions around start of expansion.

In another thread you were talking about getting your ideas from Brian Greene books. One of the mods told you there that you have to choose between pop-sci and getting it straight.
I urge you to get the pop-sci stuff out of mind and start trying to get a grounding in contemporary cosmology concepts. We are reasonably well set up to offer that here...

For starters why don't you see what you can dig up in our local cosmo forum FAQ.

Or try the "einstein-online" link in my signature. It helps sort some of the misconceptions and confusion about BB out. It's the straight-dope public outreach website of a German federal research institute. Not commercial sell-a-lot-of-books hucksterism, or a go-for-the-ratings Telly series.

 

[e.bar.goum]

You seem to be missing the idea that there weren't billions of billions of galaxies at the BB. Hell, there weren't even quarks or gluons! They only appear after inflation (at about 10^-37 s, IIRC), you only start to get hadrons at about a microsecond after the BB.

I think you have some misunderstandings about the Big Bang.

ETA: My mistake, inflation occurs not at 10^-43 but at 10^-37 seconds. This is what I get when I don't verify things.

 

[stglyde]

You seem to be missing the idea that there weren't billions of billions of galaxies at the BB. Hell, there weren't even quarks or gluons! They only appear after inflation (at about 10^-43 s, IIRC), you only start to get hadrons at about a microsecond after the BB.

I think you have some misunderstandings about the Big Bang.

No. I mean I mentioned about Planck Density.. meaning since mass=energy.. then the potential energy of those billions and billions of galaxies are contained in Planck length.. after inflation.. the energy changed to mass as electron-anti electron pair is produced. I know all about it, but don't know if the calculations are proven that the energy of billions of galaxies can really be contained in a Planck length... and if so.. whether this proves the Big Bang or just an added support for it...

 

[Astronuc]

We are sure something happened. It was a long time ago.

 

[stglyde]

Glyde, it sounds like you swallowed another popularization.

You could re-read what Brian Powell said, which I think is carefully worded, and he's a pro. As I understand it, the classic BB theory does not say anything about what was or what happened right at the start of expansion. So it does not say space was "created". The classic 1915-1923 theory would not know how to say that. It just breaks down and quits as it approaches that point.

Popularized accounts say things like that. But not to take seriously

I've read so many references about the Big Bang from Steven Weinberg "The First Three Minutes" to Rees and other pros. So I'm well aware of the arguments. About space being created. Redshift occurs because space was being expanded.. so inflation is not an explosion inside spacetime.. it is spacetime being inflated... are you denying this?

Nowadays classic BB theory has been extended in various ways, which still have to be tested. They avoid "singularity", that is they do not break down and give meaningless results. They go back to the start of expansion and further back in time before start of expansion. There's always something there, some process being described.
I don't know any currently researched BB extension that says space or time are "created".
There may be such but that would not be typical of the majority of the research papers that model events/conditions around start of expansion.

In another thread you were talking about getting your ideas from Brian Greene books. One of the mods told you there that you have to choose between pop-sci and getting it straight.
I urge you to get the pop-sci stuff out of mind and start trying to get a grounding in contemporary cosmology concepts. We are reasonably well set up to offer that here...

For starters why don't you see what you can dig up in our local cosmo forum FAQ.

Or try the "einstein-online" link in my signature. It helps sort some of the misconceptions and confusion about BB out. It's the straight-dope public outreach website of a German federal research institute. Not commercial sell-a-lot-of-books hucksterism, or a go-for-the-ratings Telly series.

 

[e.bar.goum]

No. I mean I mentioned about Planck Density.. meaning since mass=energy.. then the potential energy of those billions and billions of galaxies are contained in Planck length.. after inflation.. the energy changed to mass as electron-anti electron pair is produced. I know all about it, but don't know if the calculations are proven that the energy of billions of galaxies can really be contained in a Planck length... and if so.. whether this proves the Big Bang or just an added support for it...

Ok, it seemed from your post that you meant actual atoms.

Well, the Planck density is the approximate density one Planck second after the big bang, not at the singularity. Approximately a microsecond of calculation, which I'm sure you could do yourself (why didn't you?), gives a Planck density of 5.1 × 10⁹⁶ kg/m³ - about 1023 solar masses squeezed into the space of a single atomic nucleus. But that's not at the singularity anyway, so I don't know why you're so hung up on it.

 

[stglyde]

Ok, it seemed from your post that you meant actual atoms.

Well, the Planck density is the approximate density one Planck second after the big bang, not at the singularity. Approximately a microsecond of calculation, which I'm sure you could do yourself (why didn't you?), gives a Planck density of 5.1 × 10⁹⁶ kg/m³ - about 1023 solar masses squeezed into the space of a single atomic nucleus. But that's not at the singularity anyway, so I don't know why you're so hung up on it.

From the site Marcus shared at http://www.einstein-online.info/spotlights/big_bangs
It says:

"At ultra-high densities, with the whole of the observable universe squeezed into a volume much smaller than that of an atom"

Of course I didn't say the atoms are squeezed inside the Planck area. But since energy=mass, just the energy. So it is true that the energy of billions and billions of galaxies can fit inside the Planck area. What is the calculations for it.. is it 100% true or subject to controversy?

 

[e.bar.goum]

I really don't see the problem with the energy densities required. It's not like energy is subject to Pauli exclusion, or takes up any space. It's energy, you could pack as much in as you want.

 

[stglyde]

I really don't see the problem with the energy densities required. It's not like energy is subject to Pauli exclusion, or takes up any space. It's energy, you could pack as much in as you want.

No problem with pressure? It really exceeds the imagination the energy of all existing galaxies can fit into the Planck area billions and billions of times smaller than an atom. So far. What experiments have showed that there is no limit to energy compression. So you are saying that it's possible billions of universes can also fit inside the Planck area (as far as energy is concerned)? There is just no limit??

 

[e.bar.goum]

It doesn't really stretch my imagination. Perhaps that's a sign I've done too much physics. But just because it exceeds the imagination doesn't mean it's not real. Try imagining 10^23 objects, for instance!

If I had no problem with energy density, I'd hardly have one with pressure, given that pressure is energy/volume. They're pretty much equivalent statements.

Edited to add.

There is no limit on energy density. To dive into some GR, local lorentz symmetry is enough to show that the energy density is not limited in GR.

The energy density is the T⁰⁰ component of the stress energy tensor. In GR the solution depends on the full stress-energy tensor, so we can't just consider T⁰⁰. Because the energy density is a component of a tensor, it is coordinate dependent. So, if we begin with a non black hole solution, with some energy somewhere, we can always choose a coordinate system to make the energy density as large as we like.

Now, how about over a finite area?

Consider the Roberston-Walker solution with a perfect fluid (not bad as an example, a QGP is a perfect fluid)

So, for a perfect fluid in the comoving frame:

T^ab =
ρ 0 0 0
0 p 0 0
0 0 p 0
0 0 0 p

(sorry, don't know how to do tensors on this site)Now if we change to a different coordinate system, using the coordinate transformation:
Λ_μν=
γ −βγ 0 0
−βγ γ 0 0
0 0 1 0
0 0 0 1

The energy density will transform as: ρ′=γ2(ρ+pβ2)

So, the energy density can be as large as we like!

Huzzah.

(You could have googled this: http://physics.stackexchange.com/questions/7771/is-there-an-energy-density-limit-in-gr)

Edited again: And this is with undergraduate general relativity. Not controversial.
Edited again again: However, you'd probably want QG to understand times that close to the BB. However, local lorentz symmetry would probably stick around in QG

 

[stglyde]

Wow. Before this. I thought it was already incredible that the energy of billions of galaxies can fit in the Planck area billions of times smaller than an atom. Now you are saying that an infinite number of universes can fit in the Planck area because there is no limit?? Hope others can second motion or verify this (that there is no limit.. or if there is.. how many billions of universes can fit in the Planck area.. of course in terms of energy of mass converted)).

 

[e.bar.goum]

It's right there in the maths! You don't need other peoples opinions - do you think the maths works out? If you don't, why? If you don't understand the maths, learn it!

I am saying that in GR, an arbitrary amount of energy can exist in an arbitrary volume.

Can I ask why you're so hung up on the Planck area thing?

Think of it another way - if you think of energy in terms of photons, which are bosons, then you can have an arbitrary amount of them in whatever volume you want, due to Bose enhancement. (AKA the lack of Pauli Blocking)

 

[pebbleanrock]

a book I read says the universe began as a bubble sitting in a liquid. The liquid is straight string energy at absolute zero with a quiver of waves moving through it. The first strings jumped into the bubble and went BANG and continued. This raised the temperature of the inside surface of the bubble which decayed the liquid into circular string inside the bubble forming all the particles. A black hole with lots of gravity is this energy trying to revert to it's previous liquid form. Dark energy is the gravitational pull of the surrounding liquid on all matter and is why it is accelerating. It would account for the even distribution of galaxies. Einstein's GR black hole centre defining space and energy as infinity + would also define the liquid.

 

[e.bar.goum]

a book I read says the universe began as a bubble sitting in a liquid. The liquid is straight string energy at absolute zero with a quiver of waves moving through it. The first strings jumped into the bubble and went BANG and continued. This raised the temperature of the inside surface of the bubble which decayed the liquid into circular string inside the bubble forming all the particles. A black hole with lots of gravity is this energy trying to revert to it's previous liquid form. Dark energy is the gravitational pull of the surrounding liquid on all matter and is why it is accelerating. It would account for the even distribution of galaxies. Einstein's GR black hole centre defining space and energy as infinity + would also define the liquid.

Well. That sounds ... either extremely fringe, or an analogy taken too far. Can I ask what book this was in?

 

[marcus]

Wow. Before this. I thought it was already incredible that the energy of billions of galaxies can fit in the Planck area billions of times smaller than an atom. .

Glyde, cool it and have a little skepticism will you? First, you mean Planck volume, not Planck area.

I can't believe you read a reputable account saying "billions of galaxies" energy fitting into a Planck volume. You have to be kidding or totally naive. In a standard discussion, you don't expect GR to apply when density is above Planck. Planck density is only a few micrograms of mass per Planck volume. A few millionths of a gram, nowhere near the mass of a planet or a galaxy, let alone billions of galaxies.

There is no need to take the online source quoted by BAR.GOUM seriously because it is talking about the density limit in general relativity. Nobody expects GR to apply at very high density so it does not matter what limit it has or does not have. I think bar.goum is sophisticated and realizes that a theoretical limit based on GR does not mean much. But a naive reader could get the idea that this is a real physical limit applicable to nature (not just something in a man-made theory).

What is far more relevant is what people calculate as the density limit in QUANTUM GR. Quantum effects are expected to be important at high density, so forget classical GR. There are several different approaches to getting a quantum theory of GR and in several of them something like the Heisenberg Uncertainty Principle (HUP) takes over at very high density.

HUP says quantum fields resist narrow constraint as to location. If you try to nail down position then momentum becomes highly uncertain. So as you might imagine, in a quantum theory of gravity the quantum corrections dominate and make gravity repel at high density.
So you never even get as high as Planck density.

A minor collapse like a stellar mass BH might just settle down into an equilibrium (we don;t know yet). A major collapse could conceivably bounce out the back door. Basically we don't know--stuff has to be tested observationally. An important item on the agenda is to examine the CMB for traces of a bounce, as described in one or more of the theoretical models.There is brief simple discussion of this and some links at the "einstein-online" essay I mentioned earlier. but current research papers dealing with the testing issue are more to the point. Here are 40-some recent research papers related to the observational testing of a type of quantum gravity big bounce model. I.e. was the expansion we see initiated by collapse of a prior space:
http://inspirehep.net/search?ln=en&...Search&sf=&so=d&rm=citation&rg=100&sc=0&of=hb

You really should look at actual peer-review research and not just exclaim "HOW INCREDIBLE!" about unverified secondhand gossip.

 

[e.bar.goum]

Ouch man, that's a bit harsh. I don't think I was using "unverified secondhand gossip" when I was talking about local Lorentz invariance. I was careful to point out that the above was only true in the limit where GR is OK, and you'd have to consider QG in the limit as t->0. It was to illustrate the point that even in classical theories, arbitrary energy densities are possible. I don't think there's any issue with my statements when taken in that light. If there is, do let me know.

Insofar as Glyde was asking whether arbitrary energy densities are possible, my reply was that "Yes, in GR, they are".

Since we have no theory of QG, it seems stupid to ask whether there would be a density limit in it. However, I must admit to some ignorance in this area - why is the HUP going to limit the possible energy density (by making gravity repel) in a QG situation? In classical QM arbitrary energy densities are possible, HUP or not. Nevertheless, it all seems rather speculative, since we have no theory of QG.

 

[marcus]

...Insofar as Glyde was asking whether arbitrary energy densities are possible, my reply was that "Yes, in GR, they are".

I have no quarrel with you, Bar.Goum. You choose your words carefully and you know a lot! But a naive reader could see that and think you were saying something about nature, or physical reality.

I wish it were customary for science popularizers to add a caveat. "this incredible thing I'm telling you is simply the mathematical consequence of a man-made theory which the experts are pretty sure does not apply here."

Like the myth of the "singularity", which is just the breakdown of a theory and shows it is not applicable. Not something one expects to exist in nature. This should be made carefully clear.

Since we have no theory of QG, it seems stupid to ask whether there would be a density limit in it.

Are kidding? We have several theories of QG. In cosmology we have both analytic (equation) models of the bounce and numerical (computer) models of the bounce. Why is it stupid to ask what the max density is achieved?

It is an interesting research task to relax assumptions of isotropy and homogeneity and vary parameters and see if the bounce still happens and see at what density. And what possible observable signatures in the CMB, from different cases.

It is not stupid, I expect you realize Bar.Goum. It is the way science is done. You get a model that fits current observation, you work back in time. It happens to show a bounce (which you did not put in) so you study various cases. Then you look for ways to test when we get higher resolution CMB data, what kinds of "footprint" if this bounce actually occurred. And maybe then you can falsify! So you can throw out the model which said there was a bounce and predicted the "footprint". It is pretty straightforward.

If you want to find out more about the early universe phenomenology related to QG cosmology you can look up papers on arxiv e.g. by
Aurelien Barrau
Julien Grain
Wen Zhao
Jakub Mielczarek
Here is a search that gets some of their papers and papers by others along related lines.
http://inspirehep.net/search?ln=en&...Search&sf=&so=d&rm=citation&rg=100&sc=0&of=hb
These are papers which appeared 2008-2011. You can change the dates in the search if you want to go back earlier, but most of this QG early universe phenomenology research is rather recent so you will not find much.

Don't bother to think about the HUP except as a preliminary analogy suggesting that quantum effects in geometry might resist collapse. Effects in quantum geometry that you can think of as in some sense analogous to how matter behaves. It's an intuitive handle people can relate to because they have heard of HUP. But if you want to see the actual math, look at a recent review paper by Abhay Ashtekar.

 

[e.bar.goum]

Fair enough. I would say that I was saying something about nature insofar as our theories correspond to nature, to the best of our ability. Certainly QM and GR have provided the most accurate correspondence to measurements of any theory. What are we up to, 14 sig fig in QM, or something crazy like that?

But, you are right, and caveats should be given. I still see no reason that energy densities of arbitrary values cannot exist in nature.

I should have perhaps said "we have no good theory of QG". But yes, there is no reason not to do research into the consequences of LQG on the CMB. Apart from the fact that it's using an unproven theory on as yet uncollected data.

Generally speaking, I do have reservations about the search for "signatures" of any kind in the CMB - remember that paper by Penrose a couple of years ago? It was widely regarded as pretty dodgy. I think that the search for signatures in the CMB needs to be *very carefully* done - you can find almost anything in noise if you look closely enough.

Thanks for the author links. I must admit, early universe QG cosmology isn't something I look into much, I mostly focus on experimental nuclear astrophysics, which is practically on the other side of the scale.

 

[stglyde]

Glyde, cool it and have a little skepticism will you? First, you mean Planck volume, not Planck area.

I can't believe you read a reputable account saying "billions of galaxies" energy fitting into a Planck volume. You have to be kidding or totally naive. In a standard discussion, you don't expect GR to apply when density is above Planck. Planck density is only a few micrograms of mass per Planck volume. A few millionths of a gram, nowhere near the mass of a planet or a galaxy, let alone billions of galaxies.

There is no need to take the online source quoted by BAR.GOUM seriously because it is talking about the density limit in general relativity. Nobody expects GR to apply at very high density so it does not matter what limit it has or does not have. I think bar.goum is sophisticated and realizes that a theoretical limit based on GR does not mean much. But a naive reader could get the idea that this is a real physical limit applicable to nature (not just something in a man-made theory).

What is far more relevant is what people calculate as the density limit in QUANTUM GR. Quantum effects are expected to be important at high density, so forget classical GR. There are several different approaches to getting a quantum theory of GR and in several of them something like the Heisenberg Uncertainty Principle (HUP) takes over at very high density.

HUP says quantum fields resist narrow constraint as to location. If you try to nail down position then momentum becomes highly uncertain. So as you might imagine, in a quantum theory of gravity the quantum corrections dominate and make gravity repel at high density.
So you never even get as high as Planck density.

A minor collapse like a stellar mass BH might just settle down into an equilibrium (we don;t know yet). A major collapse could conceivably bounce out the back door. Basically we don't know--stuff has to be tested observationally. An important item on the agenda is to examine the CMB for traces of a bounce, as described in one or more of the theoretical models.


There is brief simple discussion of this and some links at the "einstein-online" essay I mentioned earlier. but current research papers dealing with the testing issue are more to the point. Here are 40-some recent research papers related to the observational testing of a type of quantum gravity big bounce model. I.e. was the expansion we see initiated by collapse of a prior space:
http://inspirehep.net/search?ln=en&...Search&sf=&so=d&rm=citation&rg=100&sc=0&of=hb

You really should look at actual peer-review research and not just exclaim "HOW INCREDIBLE!" about unverified secondhand gossip.

But Marcus, from the site you shared at http://www.einstein-online.info/spotlights/big_bangs
It is stated:

"At ultra-high densities, with the whole of the observable universe squeezed into a volume much smaller than that of an atom"

In other words, billions and billions of galaxies in energy form can fit the volumn smaller than the size of a single atom? Do you agree? If so, then Planck volume can fit the energy of at least one galaxy like the milky way. Agree or disagree?

 

[Cosmo Novice]

But Marcus, from the site you shared at http://www.einstein-online.info/spotlights/big_bangs
It is stated:

"At ultra-high densities, with the whole of the observable universe squeezed into a volume much smaller than that of an atom"

In other words, billions and billions of galaxies in energy form can fit the volumn smaller than the size of a single atom? Do you agree? If so, then Planck volume can fit the energy of at least one galaxy like the milky way. Agree or disagree?

As I understand it in GR there is no classical limit to energy density. So by definition you can have infinite energy in any arbitrarily defined space. It was obviously permitted in other frameworks such as in frameworks for GM - why? - because that is the nature of the early U as can be seen by observation. (Extremely high and mostly uniform energy densities.)

Why does the Planck volume hold such significance in your opinion?

 

[bapowell]

No problem with pressure? It really exceeds the imagination the energy of all existing galaxies can fit into the Planck area billions and billions of times smaller than an atom. So far. What experiments have showed that there is no limit to energy compression. So you are saying that it's possible billions of universes can also fit inside the Planck area (as far as energy is concerned)? There is just no limit??

Science is a dispassionate pursuit that does not benefit from preconceived notions of what "exceeds the imagination". It is an incorrect picture to imagine Planckian energy densities somehow confined to a small region, fighting against this confinement with outward pressure. It is true that both density and pressure determine the gravitational properties of the stress-energy, and, when you place near-Planckian energy densities into the Friedmann equation, you get a perfectly well-behaved cosmological solution.

Sure, such high densities have not been tested in the lab. But we understand the equation of state of radiation, and we have lots of observational evidence that supports the Friedmann model. Extrapolation of these physical theories into untested regimes (as long as the theory is appropriate to these regimes) is a perfectly reasonable and substantiated practice.

 

[marcus]

But Marcus, from the site you shared at http://www.einstein-online.info/spotlights/big_bangs
It is stated:

"At ultra-high densities, with the whole of the observable universe squeezed into a volume much smaller than that of an atom"

In other words, billions and billions of galaxies in energy form can fit the volumn smaller than the size of a single atom? Do you agree? If so, then Planck volume can fit the energy of at least one galaxy like the milky way. Agree or disagree?

Two points. First, I disagree with the blue statement. In the hypothetical case where mass of observable U fits into volume of an atom (or even an atomic nucleus) you are only describing Planck density. That means each Planck volume contains only a few micrograms. Not the mass of a galaxy . Your arithmetic is way off.

But second and perhaps more significantly, what you quote from the article is exactly where it is explaining why cosmologists suspect that the classical model may not apply. There is NOT a professional consensus that a singularity actually can or did occur in nature. (E.g. because quantum effects may be expected to dominate.)
==quote==
Whether or not there really was a big bang singularity is a totally different question. Most cosmologists would be very surprised if it turned out that our universe really did have an infinitely dense, infinitely hot, infinitely curved beginning. Commonly, the fact that a model predicts infinite values for some physical quantity indicates that the model is too simple and fails to include some crucial aspect of the real world. In fact, we already know what the usual cosmological models fail to include: At ultra-high densities, with the whole of the observable universe squeezed into a volume much smaller than that of an atom, we would expect quantum effects to become crucially important. But the cosmological standard models do not include full quantum versions of space, time and geometry - they are not based on a quantum theory of gravity. However, at the present time we do not yet have a reliable theory of quantum gravity. While there are promising candidates for such a theory, none are developed far enough to yield reliable predictions for the very early universe.
==endquote==

Even this essay, which was written in 2006* or earlier, is now somewhat out of date. Unfortunately I don't happen to know a comparable more recent piece written for general audience.
(*I first saw it online in 2006, and there have been only minor changes. I see there is a new copyright date of 2011.)

 

[stglyde]

Two points. First, I disagree with the blue statement. In the hypothetical case where mass of observable U fits into volume of an atom (or even an atomic nucleus) you are only describing Planck density. That means each Planck volume contains only a few micrograms. Not the mass of a galaxy . Your arithmetic is way off.

Why, how many Planck volume can fit the volume of an atom such that when all the energy of the universe was concentrated on the volume of the atom, the Planck volume would only hold a few micrograms?? (this is assuming quantum gravity didn't take over in Planck scale or HUP in atomic scale that makes the Planck volume untouchable and let's assume classical model for sake of illustration of how many Planck volume are there in an atom)

Anyway. The head of a spin contains billions of atoms. So do you agree the following is correct:

"Q. How many galaxies (in energy form) can fit the head of a pin?

A. Billions and billions of galaxies or the entire universe (in energy form) assuming the detectable size of 43 billion light years"

But second and perhaps more significantly, what you quote from the article is exactly where it is explaining why cosmologists suspect that the classical model may not apply. There is NOT a professional consensus that a singularity actually can or did occur in nature. (E.g. because quantum effects may be expected to dominate.)
==quote==
Whether or not there really was a big bang singularity is a totally different question. Most cosmologists would be very surprised if it turned out that our universe really did have an infinitely dense, infinitely hot, infinitely curved beginning. Commonly, the fact that a model predicts infinite values for some physical quantity indicates that the model is too simple and fails to include some crucial aspect of the real world. In fact, we already know what the usual cosmological models fail to include: At ultra-high densities, with the whole of the observable universe squeezed into a volume much smaller than that of an atom, we would expect quantum effects to become crucially important. But the cosmological standard models do not include full quantum versions of space, time and geometry - they are not based on a quantum theory of gravity. However, at the present time we do not yet have a reliable theory of quantum gravity. While there are promising candidates for such a theory, none are developed far enough to yield reliable predictions for the very early universe.
==endquote==

Even this essay, which was written in 2006* or earlier, is now somewhat out of date. Unfortunately I don't happen to know a comparable more recent piece written for general audience.
(*I first saw it online in 2006, and there have been only minor changes. I see there is a new copyright date of 2011.)

 

[marcus]

Comments on this thread remind me that LQC has progressed quite a bit in the past 2 or 3 years and it is not so easy to keep abreast. So I want to call attention to a Abhay Ashtekar's recent review paper---a kind of status report---and quote some interesting passages just to get the latest stuff out on the table.
http://arxiv.org/abs/1108.0893
Loop Quantum Cosmology: A Status Report
Abhay Ashtekar, Parampreet Singh
(Submitted on 3 Aug 2011)
The goal of this article is to provide an overview of the current state of the art in loop quantum cosmology for three sets of audiences: young researchers interested in entering this area; the quantum gravity community in general; and, cosmologists who wish to apply loop quantum cosmology to probe modifications in the standard paradigm of the early universe. An effort has been made to streamline the material so that, as described at the end of section I, each of these communities can read only the sections they are most interested in, without a loss of continuity.
138 pages, 15 figures. Invited Topical Review, To appear in Classical and Quantum Gravity.

=======================

The paper is long and covers many topics. We already had a discussion here at PF forum of one of the key equations. Equation (5.7) as I recall. I forget who was asking about it.
Yes! It was (5.7) on page 73. This is the modified form of the Friedman equation which comes out of quantizing it and it shows clearly why you get gravity repelling at high density and causing a rebound (with an interval of super-exponential expansion called super-inflation).

That however is not new, one sees that modified Friedman derived already in 2007 basic LQC papers. (Together with a figure for the critical density at which the quantum corrections dominate.) So I won't copy that here.

What I want to take note of is some more recent stuff about generalizing and extending the model that they go into around page 67. Don't have time right now but hope to get back to this later today.

 

[marcus]

...
I should have perhaps said "we have no good theory of QG". But yes, there is no reason not to do research into the consequences of LQG on the CMB. Apart from the fact that it's using an unproven theory on as yet uncollected data. .

See the paper by Wen Zhao and two people at Cambridge which is in the search listing of LQC phenomenology-related papers which I gave earlier. In effect they confront LQC bounce cosmology with 7 years of WMAP data (using NASA's WMAP7 report to constrain).

It is as you know customary to make predictions which can be tested by FUTURE data and this on the whole is what is being done. I expect some more constraints to accrue from the European Planck spacecraft observations now in progress. But higher resolution (especially polarization of CMB) will be needed, again see Wen Zhao's paper. It's hardly a criticism to note that a lot of the testing literature is aimed at future possible data collection---although of course some relates to past and current.

Generally speaking, I do have reservations about the search for "signatures" of any kind in the CMB - remember that paper by Penrose a couple of years ago? It was widely regarded as pretty dodgy. I think that the search for signatures in the CMB needs to be *very carefully* done - you can find almost anything in noise if you look closely enough.

Yes indeed We should all be *very careful*. It also helps to have professional phenomenologists with no stake in your theory who see their job as testing it and will be just as happy if the data disprove as they would be if the data support the theory. (Penrose seems to have had just one guy who looked like he was collaborating with Sir Roger to find supportive evidence, rather than objectively putting the theory to the test.) I fail to see the analogy here. Perhaps you can discover some analogy if you take a critical look at some articles in the Inspire search list. By some of the people I mentioned.

Here is the link again.
http://inspirehep.net/search?ln=en&...Search&sf=&so=d&rm=citation&rg=100&sc=0&of=hb

The one by Wen Zhao I mentioned is as I recall #22 on the list.

 

[stglyde]

Markus, the universe in a grain of sand is assuming classing GR.. but quantum GR says the density can't be high so not only can all energy of the universe in Planck volume not possible, even atomic volume not possible. So based on your reading and experience, what is the surest bet of the minimize size of the initial universe. Do you think it was once maybe about a Ping Pong ball size or a baseball size or building size or the size of Texas? What is your estimate from non classical GR calculations and theoretical projection of rewinding the universe down to smaller and smaller size?

 

[marcus]

Markus, the universe in a grain of sand is assuming classing GR.. but quantum GR says the density can't be high so not only can all energy of the universe in Planck volume not possible, even atomic volume not possible. So based on your reading and experience, what is the surest bet of the minimize size of the initial universe. Do you think it was once maybe about a Ping Pong ball size or a baseball size or building size or the size of Texas? What is your estimate from non classical GR calculations and theoretical projection of rewinding the universe down to smaller and smaller size?

Glyde, it's nice of you to ask! I appreciate you asking my opinion. There was a Nasa report called WMAP5 (cosmology implications from the 5-year WMAP data) which said that in the simplest case where the U had a finite size, with 95% certainty it would be AT LEAST 10 times larger than the observable portion. (And it could just as well be 100 or 1000 times larger, the estimate was just a lower bound that it had to be at least that.)

Their number was more precise than 10. I am just speaking approximately. Their lower bound was roughly that. I can get the link to the report if you want. It's online.

Many cosmologists think of the U as spatially infinite, and therefore it would be spatially infinite at the start of expansion. And they do their calculations based on that assumption. You get approximately the same fit to the data whether you say infinite or finite-but-very-large.

So the first thing is always to remember that when people talk cosmology OBSERVABLE universe is just a small portion of the full universe that one has to model with the equations or the computer simulator. What one models is the full thing and this can be spatially infinite (even already at "bang" time) or in any case very large.

Don't confuse observable universe with the whole thing. I'm sure you know this, but people forget. It has to be made explicit to avoid confusion.

In standard cosmology, as you probably know, the universe has no edge or boundary, and matter is distributed approximately evenly throughout. So if space is infinite volume then matter must be infinite---because it is throughout all space.
===================

That is just preliminaries. Are you OK with all that?

 

[stglyde]

Glyde, it's nice of you to ask! I appreciate you asking my opinion. There was a Nasa report called WMAP5 (cosmology implications from the 5-year WMAP data) which said that in the simplest case where the U had a finite size, with 95% certainty it would be roughly 10 times larger than the observable portion.

But the universe could as well be 100 times larger than the observable universe. Their factor of 10 was just a lower bound.

Many cosmologists think of the U as spatially infinite, and therefore it would be spatially infinite at the start of expansion. And they do their calculations based on that assumption.

You get approximately the same fit to the data whether you say infinite or finite-but-very-large.

So the first thing is always to remember that when people talk cosmology OBSERVABLE universe is just a small portion of the full universe that one has to model with the equations or the computer simulator. What one models is the full thing and this can be spatially infinite (even at "bang" time) or in any case very large.

Don't confuse observable universe with the whole thing.

In standard cosmology, as you probably know, the universe has no edge or boundary, and matter is distributed approximately evenly throughout. So if space is infinite volume then matter must be infinite---because it is throughout all space.
===================

That is just preliminaries. Are you OK with all that?

Good you emphasize on the observable universe vs actual extent. Anyway. Do you know how many Planck volume can fit in say the hydrogen atom up to the electron orbital? You really think that if the observable universe energy were contained in the hydrogen atom. The Planck volume would merely hold a few micrograms. This would make the Planck scale unimaginably small. I wonder if your analogy is valid (ignoring quantum gravity and HUP).

Or for a radius of 40 Billion light years, how many meters or miles across would be the Planck length? Any ideas?

 

[marcus]

Good you emphasize on the observable universe vs actual extent. Anyway. Do you know how many Planck volume can fit in say the hydrogen atom up to the electron orbital? You really think that if the observable universe energy were contained in the hydrogen atom. The Planck volume would merely hold a few micrograms. This would make the Planck scale unimaginably small. I wonder if your analogy is valid (ignoring quantum gravity and HUP).

Or for a radius of 40 Billion light years, how many meters or miles across would be the Planck length? Any ideas?

Answer to blue question is yes. Actually much less than a few micrograms. A hydrogen atom is very big. To get PLANCK density you must compress observable down to something like the size of a proton, the nucleus of the hydrogen atom.

This is around 100 thousand times smaller than the atom, if I remember right.

 

[marcus]

BTW Glyde, Brian Powell said something useful a few posts back.

Science is a dispassionate pursuit that does not benefit from preconceived notions of what "exceeds the imagination". It is an incorrect picture to imagine Planckian energy densities somehow confined to a small region, fighting against this confinement with outward pressure. It is true that both density and pressure determine the gravitational properties of the stress-energy, and, when you place near-Planckian energy densities into the Friedmann equation, you get a perfectly well-behaved cosmological solution.

Sure, such high densities have not been tested in the lab. But we understand the equation of state of radiation, and we have lots of observational evidence that supports the Friedmann model. Extrapolation of these physical theories into untested regimes (as long as the theory is appropriate to these regimes) is a perfectly reasonable and substantiated practice.

I have to go. I want to remark on something in Brian's post. Back later.

OK I'm back. BTW the conventional ideas of the radii of proton and observable U differ by a factor of 10⁴¹. My feeling is that this is not so surprising. I wouldn't say a proton is very SMALL compared with the photons of highest energy light. Indeed a proton is kind of mediumsized as things go. But the observable U is very large. So between medium size and large there are these 41 powers of ten.

If you want to find out some about Planck scale----energy, volume, density, mass, length etc.----Wikipedia is not too bad.
http://en.wikipedia.org/wiki/Planck_units

The linear size associated with the proton is 10^-15 meters. You can read what the Plancklength is and see what their ratio is. The corresponding volumes would be related by the cube of that ratio, whatever you find it to be.

Ive got some other stuff to attend to, but see what you can find out meanwhile on your own.

 

[stglyde]

Answer to blue question is yes. Actually much less than a few micrograms. A hydrogen atom is very big. To get PLANCK density you must compress observable down to something like the size of a proton, the nucleus of the hydrogen atom.

This is around 100 thousand times smaller than the atom, if I remember right.

Energy units are electrovolts.. for example.. the possible mass of Higgs boson to be 125 TeV. I wonder what is the electron volts of the energy of the entire "observable" universe. Now it's still unbelievable that when you put it in the diameter of the nucleus. The Planck volume is almost negligible. But then energy doesn't have pauli exclusion so I wonder why a certain volume should hold certain energy or in what sense is the statement that the energy of the observable universe is put into the size of a hydrogen nucleus and the Planck volume holds only a few microgram since energy doesn't have spatial extension. Anyone else can explain? Thanks (this paragraph is ignoring quantum gravity and HUP for sake of discussion of energy Tev of the universe and containment of it in a limited spatial extension like in a hydrogen nucleus).

 

[Chronos]

I believe the most recent estimates on higgs mass are around 125 GeV.

 

[ThomasT]

... I wonder why a certain volume should hold certain energy ...

That would seem to me to depend on what's being talked about (ie., a certain volume of ... what?), and what it's assumed (or observed) to be doing.

... or in what sense is the statement that the energy of the observable universe is put into the size of a hydrogen nucleus ...

Why would anybody want to suppose that the energy of the observable universe was ever the "size of a hydrogen nucleus"?

Regarding the title question of the thread, and your OP, the standard 'big bang' theory accounts (in a necessarily limited way) for the evolution of our universe from a point (the 'big bang') beyond which (ie., further into the past) backward extrapolation from current observation and theory is impossible.

Whether it's 100% true is a question/consideration that can't be answered. But it makes sense and it's internally consistent (afaik), and (also afaik) it doesn't say or imply that the observable universe was ever the size of a hydrogen nucleus, or the head of a pin, or whatever (also just afaik).

Kudos to bapowell and marcus for their usual informative replies, and to Astronuc for putting the (sophisticated) cosmological speculation into (imo) the proper perspective.

Would I bet my life on the standard big bang theory being 100% true? No. But it certainly makes sense insofar as it's relevant. If somebody comes up with a better account, I feel sure that they'll publish it.

 

[marcus]

Glyde what you said about radiation energy (light, UV, gamma etc) not having Pauli exclusion is very important. The shorter the wavelength the more energy, too. There is no limit to how many photons fit in the box AND the smaller they are the more energy each one carries.

Can't you estimate how many Planck volumes are in a proton volume?

Planck length is about 10^-35 meters and proton scale is about 10^-15 meters. So cube their ratio.

Proton volume is about 10⁶⁰ times Planck volume. Like I said, the proton is kind of medium sized.

The standard metric unit of energy is a JOULE. It is the amount you expend if you lift a (kilogram) book about 10 centimeters off the table. It is the amount of thud you hear when you drop it back onto table.

The energy density of the U, with all matter converted to the common currency of light, is 0.22 nanojoules per cubic meter. What would density be if the volume of the observable were replaced by the proton volume but with same amount of energy. You know the linear size ratio (I gave it earlier).

I hope you get the hang of doing some simple physics arithmetic on your own soon if you have not already. Go ahead risk making mistakes. If you do someone will probably catch them, no harm done.

 

[stglyde]

Markus, I'll ponder on the above. But I need to know something now and the reason why I wrote this thread. Remember Lorentz when he tried to explain the reason for the null result of the Michelson-Morley Experiment. He claimed length can contract and time can shorten when something moving in the ether, that's why the MMX produced null result and all experiments up to the present can't distinguish between Lorentz Ether Theory and Special Relativity because they both use the Lorentz Transformation (which was invented by Lorentz before Einstein discovered SR). I think you are pretty familiar with LET. Now let's not debate about LET. What I want to know is whether the Big Bang is compatible with Lorentz Ether or how the Big Bang can give birth to Lorentz Ether. If no experiment can distinguish LET and SR. Can LET perhaps be refuted by strong evidence of the Big Bang.. assuming Big Bang and Lorentz Aether is totally incompatible. If not. Any papers or models of how the Big Bang can give rise or give birth to the Lorentz Ether?

 

[marcus]

Markus, I'll ponder on the above. But I need to know something now and the reason why I wrote this thread. Remember Lorentz when he tried to explain the reason for the null result of the Michelson-Morley Experiment. He claimed length can contract and time can shorten when something moving in the ether, that's why the MMX produced null result and all experiments up to the present can't distinguish between Lorentz Ether Theory and Special Relativity because they both use the Lorentz Transformation (which was invented by Lorentz before Einstein discovered SR). I think you are pretty familiar with LET. Now let's not debate about LET. What I want to know is whether the Big Bang is compatible with Lorentz Ether or how the Big Bang can give birth to Lorentz Ether. If no experiment can distinguish LET and SR. Can LET perhaps be refuted by strong evidence of the Big Bang.. assuming Big Bang and Lorentz Aether is totally incompatible. If not. Any papers or models of how the Big Bang can give rise or give birth to the Lorentz Ether?

Glyde, this is something of a new line of questioning. I will try to carry it along so we don't forget it. Maybe someone else will respond in a useful way, who knows more and has thought more about it than I have.

But before I try to understand the new I want to finish the discussion of Planck energy density and how to picture it.

People have different conjectures about the start of expansion---the actual start, that very moment, is not covered by classical GR and standard cosmology. So people are working on various models and they typically do involve densities around Planck.

One very concrete and definite model of the start of expansion is the (LQC) BOUNCE and when they study different cases and either solve the equations or run the computer simulations with various inputs it typically happens that the bounce occurs when the density is 41% of Planck.

In effect we always face the need to picture Planck energy density, with whichever model.
If you iike to picture stuff in your mind, as many do. The simplest is to think of that density of LIGHT filling the universe. Imagine that ordinary matter boiled away into light already at lower density. Nothing that occupies any space is left. Only photons. You know from LASERS that you can put as many photons as you want on top of each other like sardines without limit.

The typical photon in the mix has wavelength equal Planck length. (the smaller the more energetic, the hotter the light). That is wavelength equal to 10^-35 meter. So within the space of a proton sized 10^-15 meter he has room for a lot of ripples. A proton is a huge space for these photons because, being such hot and energetic light their wavelength is very small. And they have no Pauli territoriality, they welcome each other's company.

So let's put some numbers. The energy equivalent of 22 micrograms (i.e. Planck mass) is 1.9 billion joules or in round numbers 2 billion joules. It's like the energy equiv of a tank of gas. It is the Planck energy unit.
So at Planck density, or at 41% of Planck energy or whatever, everything is pure energy and we can picture the U filled with very hot bright light with about a billion joules in each Planck volume. Or two billion, if we are imagining Planck density instead of 41% of it.

...

...estimate how many Planck volumes are in a proton volume?

Planck length is about 10^-35 meters and proton scale is about 10^-15 meters. So cube their ratio.

Proton volume is about 10⁶⁰ times Planck volume...
The standard metric unit of energy is a JOULE. It is the amount you expend if you lift a (kilogram) book about 10 centimeters off the table. It is the amount of thud you hear when you drop it back onto table.

The energy density of the U, with all matter converted to the common currency of light, is 0.22 nanojoules per cubic meter...

So a proton volume has 10⁶⁰ Planck volumes each of which contains a two billion joules of light. So it contains 2x10⁶⁹ joules.

Lets compare that with (the energy equivalent of) the observable universe. The Hubble distance is about 13.8 billion light years. If you type that into google you get
1.3 x 10²⁶ meters. Radius of the observable is about 3.3 times Hubble distance so say 4x 10²⁶ meters. I think that makes the observable volume about 2.5 x 10⁸⁰ cubic meters. You might check that with a calculator.
So what do we get if each cubic meter of today's universe has on average the matter equivalent of 0.22 nanojoules? I get around 5 x 10⁷⁰ joules.

This has been quick and sloppy, it is not good enough to quote in another post. anyone who cares to do so could improve the accuracy and the result might change by up to an order of magnitude. But it gives the right idea. If you think of the proton volume as a room containing jillions of photons of very high temperature short wavelength light, and you imagine that the energy density is Planck,

then that proton volume contains about the same as the energy equivalent of the observable universe volume. This is admittedly kind of clunky. Anyone who wants is welcome to make it neater and more precise.

 

[Tanelorn]

Marcus, Re Proton energy ratios, that is very interesting that they are so close. It can't be any more than a mathemetical curiosity can it? Also how can all the protons in the observable universe have similar values of energy to just one proton?

 

[marcus]

Hi T., I did not see your post when I was typing this. Not sure how to respond to your question though. What I wanted to say was it's important to stress a point that Brian Powell made earlier. Not to think of the UNIVERSE as the size of a proton at the start of expansion.
We were talking about the observable and what is destined to expand to form the part that is currently observable to us.

The whole universe (at expansion start) is presumably quite a lot bigger than a proton!
And energy is all over the place. You cannot carve out and mentally isolate a little protonsized pocket of it and say "this energy in this pocket is what is going to make our observable universe".

You could only do that if everything held still and remained nicely compartmentalized. But it is all over the place.

So all this mental exercise with the proton volume does for us is give us practice imagining the ENERGY DENSITY we think the U had, as a whole, at the start of expansion. At that moment the "observable" part was not well defined and was all over the place without clear boundaries, so it had as yet no meaning. So the exercise is simply about visualizing a density.

There is no meaningful entity that had, at that time, "the size of a proton". So one cannot say that what is now our observable U started out as something the size of a proton. It is not so neat and compartmentalized.

The actual energy is all over the place and we can't lay claim to some definite chunk of it as ours. But we can talk about the density. In each protonsize volume there was at that time AFAIK enough to be equivalent to what now is in our observable region. That gives an idea how much is in any given volume at the time expansion started.

The whole universe should be pictured as (probably much) much larger than a proton. All of that same density. And of course boundaryless. No edge and no outside.

Particular bounce cosmology models would give you different estimates of the exact density (like LQG fairly consistently says 41% of Planck) but whatever the different models they tend to say something that is within an order of magnitude or so of Planck density. So that is what the mental exercise is really about imagining.
===========
Tanelorn AFAIK the proton is just an arbitrary choice to establish a visual image of a scale of size and volume. AFAIK it primarily comes up in cosmo popularizations where they have to give the reader something to visualize, like an atom, or the nucleus of an atom, or in this case the nucleus of a hydrogen atom (i.e. proton). To establish an idea of scale.

So it's probably just completely arbitrary. And as you know from the point of view of the three little quarks inside, a proton is just this big empty space with three flies buzzing around in it. The flies think that THEY are fundamental, not the big room they are buzzing around in. So the proton is here just a nice way to imagine a convenient amount of nearly empty space that has a definite size.

That's what I think anyway. Could be wrong.

 

[Tanelorn]

Hi Marcus, I just reread and saw that you said each cubic meter contains the same energy as a proton and not the whole observable universe. Thats what happens when you go speed reading!

Anyways seasons greetings to you and all at PF!

 

[Notwen7]

The standard big bang model purports that the big bang happened everywhere at once, not at a single point. This is an important misconception to straighten out. The colliding branes theory is a proposal that seeks to explain the physical mechanism for the big bang itself. Therefore, it is not in opposition to the standard big bang model; rather, it seeks to extend it. The colliding branes theory is still only hypothesis. The colliding branes theory has the rather unfortunate name of "ekpyrosis" in case you wish to read more about it.

Can you explain how it happened at multiple points at once? Also how do scientists arrive at these hypotheses?

 

[Tanelorn]

Notwen you are being misled by a bad name. I dislike Big Bang the name a great deal for that reason.
It is not an explosion from a point.
Inflation from a state of very high density and high temperature takes place everywhere at the same time.
The universe was almost infinite then and much much bigger now!

 

[Notwen7]

Notwen you are being misled by a bad name. I dislike Big Bang the name a great deal for that reason.
It is not an explosion from a point.
Inflation from a state of very high density and high temperature takes place everywhere at the same time.
The universe was almost infinite then and much much bigger now!

Indeed, I am. So in a sense it is almost like the dew point of a liquid? I'm imagining the small little vapor bubbles forming simultaneously being similar to the release of energy and matter from many places of the universe?

 

[Drakkith]

Indeed, I am. So in a sense it is almost like the dew point of a liquid? I'm imagining the small little vapor bubbles forming simultaneously being similar to the release of energy and matter from many places of the universe?

No. Imagine being a raisin inside a muffin in the oven. As the muffin starts to rise, all the other raisins seem to get further away from you as the muffin bakes. The muffin is like space and the raisins are like galaxies. The big difference is that a muffin occupies a finite volume. The universe is thought not to. Imagine being inside an infinitely large muffin mix. The raisins 10 miles from you would be receding from you at a much higher rate than the raisins next to you. This is all the "Big Bang" is. It is simply that the universe was once in a much denser state than we are now, similar to how the muffin mix is much thicker before cooked. No explosion, no bang.