Was the Big Bang a quantum mechanical vacuum fluctuation?

[nikkkom]

If you insist that energy exits the universe, when all you can show is that it became no longer to you findable, while I insist that it must be somewhere, when all I can show is that historically, energy once reported as missing usually turns up somewhere else

It's not a "he said, she said" competition. Energy conservation is a theorem. For time-translation invariant spacetime, energy must be conserved.

Since our local conditions, to a very high precision, are time-translation invariant, we should, and we are, observing that energy is conserved in all processes.

At the same time, on a cosmological scale, we observe that Universe is not time-translation invariant. Therefore, energy conservation on that scale is not required by any theorem.

 

[fresh_42]

I cut off the discussion about energy conservation at this point, because this post summarizes it all:

It's not a "he said, she said" competition. Energy conservation is a theorem. For time-translation invariant spacetime, energy must be conserved.

Since our local conditions, to a very high precision, are time-translation invariant, we should, and we are, observing that energy is conserved in all processes.

At the same time, on a cosmological scale, we observe that Universe is not time-translation invariant. Therefore, energy conservation on that scale is not required by any theorem.

Everything else I've read so far is an argumentation about phrasing it. It is furthermore off topic, resp. will become off topic if we go on with it. So please return to the question, whether the big bang can be considered a quantum fluctuation, on which scale ever, i.e. possibly a real giant one. Otherwise we will be forced to close the thread, as personal debates about wordings won't help anybody to understand what has been going on before inflation.

Thank you.

 

[Deepblu]

To expand on that a bit, conservation of energy is universally true LOCALLY. That is, everywhere in the universe energy is conserved on small scales (~ within glactic clusters) but over cosmological distances it is not.

That is true in General Relativity which is not the full picture .. maybe energy will be conserved in a quantum theory of gravity.

 

[phinds]

That is true in General Relativity which is not the full picture .. maybe energy will be conserved in a quantum theory of gravity.

Nothing about a quantum theory of gravity would change the fact that photons lose energy as they travel in an expanding universe, so no, it would not.

 

[Deepblu]

Nothing about a quantum theory of gravity would change the fact that photons lose energy as they travel in an expanding universe, so no, it would not.

It might explain where that energy goes.

 

[phinds]

It might explain where that energy goes.

That was just one example. Another is that you can't even DEFINE kinetic energy between two objects separated by cosmological distances. You really should read this:

http://math.ucr.edu/home/baez/physic...energy_gr.html

or this:

http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/

 

[Deepblu]

That was just one example. Another is that you can't even DEFINE kinetic energy between two objects separated by cosmological distances.

Yes I know that.

My point is that our current theories are not complete.. what appears to us as violation to the law of conservation of energy, and what makes it appear to only work "localy", could be our lack of knowledge on the complete picture.

Thats why we need a more complete theory such as a quantum gravity theory.

 

[haushofer]

Yes I know that.

My point is that our current theories are not complete.. what appears to us as violation to the law of conservation of energy, and what makes it appear to only work "localy", could be our lack of knowledge on the complete picture.

Thats why we need a more complete theory such as a quantum gravity theory.

I think that these "pseudoproblems" are because we try to impose Newtonian concepts (e.g. energy conservation in fixed backgrounds) into general relativistic frameworks. It has nothing to do with a "lack of the complete picture". It's just a matter of oversymplifying, based on Newtonian intuition.

 

[PeroK]

It might explain where that energy goes.

Why do you think energy must be conserved?

 

[Deepblu]

I think that these "pseudoproblems" are because we try to impose Newtonian concepts (e.g. energy conservation in fixed backgrounds) into general relativistic frameworks. It has nothing to do with a "lack of the complete picture". It's just a matter of oversymplifying, based on Newtonian intuition.

Conservation of energy is not Newtonian concept! It is a law of physics.
In my view it is as fundamental as 2nd law of thermodynamics.

 

[PeroK]

Conservation of energy is not Newtonian concept! It is a law of physics.
In my view it is as fundamental as 2nd law of thermodynamics.

Why do you think it's a law of physics?

 

[Deepblu]

Why do you think energy must be conserved?

Why you do not?

 

[fresh_42]

Conservation of energy is not Newtonian concept! It is a law of physics.
In my view it is as fundamental as 2nd law of thermodynamics.

I always thought it is Newtonian and the consequence of Noether's local theorem about invariant Lagrangians. I cannot see a system of differential equations for some particles be extended on the entire universe. That would result in serious problems with the atlas.

 

[PeroK]

Why you do not?

Because I've studied GR.

 

[nikkkom]

Conservation of energy is not Newtonian concept! It is a law of physics. In my view it is as fundamental as 2nd law of thermodynamics.

"Laws of physics" are proposed by people, then tested against experiments. If experiments match, then the corresponding law might be true; if experiments contradict them, they are out. No law is secure against refuting by future developments.

In this case, conservation of energy fell victim to the discovery of expansion of the Universe, especially accelerating one.

Mathematically speaking, conservation of energy is consequence of time translation invariance ("the same experiment tomorrow has the same result as today"). Our local part of Universe on the scale of, say, our Galaxy, is very nearly time translation invariant. That causes conservation of energy to be not violated in our experiments.

As it turns out, most global solutions of GR are not globally time translation invariant. Therefore, globally, no mathematical logic exists for conservation of energy.

 

[Deepblu]

Because I've studied GR.

GR is not complete to describe universe on large scale.. GR is not reality it is a good approximation to reality!

And no energy does not just evaporize into nothing, we are still far from completely understanding how the universe work on cosmological scale, to jump to a definitive conclusion that energy is not conserved.

Btw "no energy conservation" is troublesome, imagine if we lived in a universe that is contracting instead of expanding? We will see as if energy is being created from nothing!

 

[nikkkom]

GR is not complete to describe universe on large scale..

Wrong. GR's problems lie elsewhere. Its description of large-scale Universe works just fine.

 

[Deepblu]

Wrong. GR's problems lie elsewhere. Its description of large-scale Universe works just fine.

I said "it is not complete" i didnt say "is wrong".
The Standard Model is not complete too ..you know that.

Not seeing the full puctures gives the illusion that energy is not conserved.

 

[PeroK]

GR is not complete to describe universe on large scale.. GR is not reality it is a good approximation to reality!

And no energy does not just evaporize into nothing, we are still far from completely understanding how the universe work on cosmological scale, to jump to a definitive conclusion that energy is not conserved.

Btw "no energy conservation" is troublesome, imagine if we lived in a universe that is contracting instead of expanding? We will see as if energy is being created from nothing!

You didn't answer my question, so let me try to answer it for you.

Someone told you once that energy conservation is a law of physics. And, for the physics you were learning at the time, this was true. But, it wasn't true in general and in particular for an expanding universe.

And, because you learned conservation of energy before you heard about GR, you are inclined to reject the latter.

 

[PeroK]

I said "it is not complete" i didnt say "is wrong".
The Standard Model is not complete too ..you know that.

Not seeing the full puctures gives the illusion that energy is not conserved.

And the classical physics that suggested the conservation of energy in the first place is a complete theory?

Conservation of energy arises from theories with less applicability than GR, not more. You may as well argue for Newtonian absolute time and space.

 

[Deepblu]

You didn't answer my question, so let me try to answer it for you.

Someone told you once that energy conservation is a law of physics. And, for the physics you were learning at the time, this was true. But, it wasn't true in general and in particular for an expanding universe.

And, because you learned conservation of energy before you heard about GR, you are inclined to reject the latter.

I don't reject GR! ofcourse not!

GR does not state that energy should or should not be conserved. Our current expansion model suggess that it is not. GR is not even compatible with our expansion model in first place!

 

[PeroK]

I don't reject GR! ofcourse not!

GR does not state that energy should or should not be conserved. Our current expansion model suggess that it is not. GR is not even compatible with our expansion model in first place!

You're the second person today to suggest that. It's an extraordinary idea. Modern cosmology is entirely based on GR!

The Einstein field equations do not naturally admit a steady state solution but imply an expanding universe.

 

[Deepblu]

You're the second person today to suggest that. It's an extraordinary idea. Modern cosmology is entirely based on GR!

The Einstein field equations do not naturally admit a steady state solution but imply an expanding universe.

Correction:
"GR is not even compatible with our accelerating expansion model in first place!"

 

[PeroK]

Correction:
"GR is not even compatible with our accelerating expansion model in first place!"

Not true. Having a non-zero vacuum energy explains that.

Where are you getting your misinformation?

 

[Deepblu]

Not true. Having a non-zero vacuum energy explains that.

Where are you getting your misinformation?

We need dark energy to make GR work for current expansion model, dark energy is theorized but never proven to actually exist. Thats why there are many alternative theories with and without dark energy.

Dark matter is also needed to explain observed galaxies rotation speed that do not match what is predicted by GR, dark matter also has never been observed.

That does not mean GR is wrong, it means that it is not the final ultimate theory.

 

[nikkkom]

We need dark energy to make GR work for current expansion model, dark energy is theorized but never proven to actually exist. Thats why there are many alternative theories with and without dark energy.

Dark matter is also needed to explain observed galaxies rotation speed that do not match what is predicted by GR, dark matter also has never been observed.

That does not mean GR is wrong, it means that it is not the final ultimate theory.

No. THESE particular issues do not disqualify GR from being completely correct and consistent. Dark energy is not a "bolted-on" crutch in GR, it is mathematically consistent with GR (and actually rather simple). Same with dark matter.

There are issues which disqualify GR, but they are completely different (classical theories are fundamentally not compatible with quantum physics, so we need some sort of quantum gravity theory).

 

[Deepblu]

What

No. THESE particular issues do not disqualify GR from being completely correct and consistent. Dark energy is not a "bolted-on" crutch in GR, it is mathematically consistent with GR (and actually rather simple). Same with dark matter.

There are issues which disqualify GR, but they are completely different (classical theories are fundamentally not compatible with quantum physics, so we need some sort of quantum gravity theory).

Again I never said something about disqualifying GR nor I mentioned anything about math inconsistency!

My point one more time: GR is not the full picture

 

[Deepblu]

Lets go back to conservation of energy:

No conservation of energy not only means energy can be destroyed, but also means energy can be created from nothing.

 

[PeroK]

My point one more time: GR is not the full picture

What is?

 

[Deepblu]

What is?

I believe a Quantum theory of gravity will give us a more complete picture.

 

[PeroK]

Lets go back to conservation of energy:

No conservation of energy not only means energy can be destroyed, but also means energy can be created from nothing.

In order to believe that fundamentally conservation of energy is an absolute law of physics, you need a full understanding of energy and a watertight physical model that shows why it is conserved.

For example, pre Einstein you could have said the same about mass. Remember that? Mass can be neither created or destroyed. How can mass be created out of nothing?

But, that turned out not to be a law of physics. As a result of SR, which certainly wasn't the full picture.

Then GR came along and conservation of energy was modified as a law of physics.

QM also shook previously accepted laws.

Interestingly, you seem to be willing advances in physics not to further modify what we know but to return a pre-GR status quo.

Who knows what golden rule Quantum Gravity might revise! Personally, I think it's a forlorn hope that it will restore a universal conservation of energy.

 

[weirdoguy]

Well, probably quantum gravity will not change that our Universe is not symmetric under time translations... @Deepblu you are familiar with the definition of energy and its connection with Noether theorem, aren't you?

 

[Deepblu]

Btw no conservation of energy in GR is a subject that is open to debate. See this paper:
[vixra link removed by moderator]

 

[weirdoguy]

vixra.org is NOT a reliable source. Instead of arguing with specialists and physicists you should rather think why they say what they say.

 

[Deepblu]

vixra.org is NOT a reliable source.

I expected that answer :)

Here is another paper from arxiv.org:
https://arxiv.org/abs/physics/0407077