Was the Big Bang a quantum mechanical vacuum fluctuation?

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  • #51
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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!
 
  • #52
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.
 
  • #53
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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.
 
  • #54
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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.
 
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  • #55
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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.
 
  • #56
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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 dont 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!!
 
  • #57
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I dont 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.
 
  • #58
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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!!"
 
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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?
 
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  • #60
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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.
 
  • #61
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).
 
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  • #62
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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
 
  • #63
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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.
 
  • #64
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My point one more time: GR is not the full picture
What is?
 
  • #65
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What is?
I believe a Quantum theory of gravity will give us a more complete picture.
 
  • #66
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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.
 
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  • #67
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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?
 
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  • #68
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Btw no conservation of energy in GR is a subject that is open to debate. See this paper:
[vixra link removed by moderator]
 
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  • #69
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vixra.org is NOT a reliable source. Instead of arguing with specialists and physicists you should rather think why they say what they say.
 
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  • #71
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I have question:

Is information conserved on universal scale?
 
  • #72
>> 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
I'm starting to think that discussion with you is ... unproductive. Last try. If you continue acting up, I'll stop replying. I have better things to do with my time.

You did say that GR has problems with dark energy and dark matter. Here, your words verbatim:

"""
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.
"""

The word "that" in last sentence refers to dark energy and dark matter "problems" allegedly plaguing GR. They aren't, so my reply was stating they are not. Now you are denying you said they are. What the actual F is going on?
 
  • #73
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Why you do not?
See:
https://arstechnica.com/science/201...-the-course-of-physics-but-couldnt-get-a-job/

Why it is usually conserved and the situations when its not was worked out by the great Emmy Noether.

There are various ways of having it conserved in those unusual situations by a suitable choice of the definition of energy - but we do not have agreement on those. We had a recent post from a research scientist on a slight generalization of Noether he thinks resolves it - but the whole thing is still a bit controversial and debatable:
http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html

Thanks
Bill
 
  • #74
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The word "that" in last sentence refers to dark energy and dark matter "problems" allegedly plaguing GR. They aren't, so my reply was stating they are not. Now you are denying you said they are. What the actual F is going on?
Frst, I am sorry for the confusion I caused in my replies.. maybe I was not able to deliver what I mean.
Second, have patience with me, I am trying to understand.. arguing is not my purpose.

What I meant in my last reply is that I know that dark energy and dark matter are mathematically consistent with GR, but GR will give wrong results without them.

So my final question to you is: lets say that scientists suddenly announced that Dark matter does not exist, how we can explain galaxies rotation speed with GR after that?
 
  • #75
So my final question to you is: lets say that scientists suddenly announced that Dark matter does not exist, how we can explain galaxies rotation speed with GR after that?
Rigorously proving negative is impossible. For example, sterile neutrinos, if they exist, are expected to interact with matter many orders of magnitude weaker than ordinary ones.

Therefore there will be no "sudden announcement" that DM does not exist.

The experiments will put more and more stringent limits on DM interaction cross-section (and other things, such as annihilation gamma-rays, if DM annihilates), while theorists, as always, will seek ways to explain observations by various new theories. Then either DM will be detected, or a new theory will explain observations without needing DM, and DM detection experiments will eventually fall out of favor.
 

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