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Member (Idle past 3853 days) Posts: 390 From: Irvine, CA, United States Joined: |
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Author | Topic: Does the universe have total net energy of zero? | |||||||||||||||||||||||
kbertsche Member (Idle past 2152 days) Posts: 1427 From: San Jose, CA, USA Joined: |
quote: I'm interested in this question, too. I hope Cavediver or someone else who really understands it can explain it to us. The popular "history of the universe" graphic on NASA's WMAP site has the universe starting with a "quantum fluctuation". By Heisenberg's uncertainty principle, this would only be possible for a 13.7 billion year old universe if the total energy of the universe were almost exactly zero. As Designtheorist says, the mass energy is large, and dark matter makes it even larger. Gravitational energy is negative, but is it enough to balance the mass energy? And what about dark energy? Since it is repulsive rather than attractive, it should add more positive energy that would have to be balance by gravity. Can someone explain how the total mass-energy can be zero?"Science without religion is lame, religion without science is blind." — Albert Einstein I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously. — Erwin Schroedinger
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kbertsche Member (Idle past 2152 days) Posts: 1427 From: San Jose, CA, USA Joined: |
Cavediver,
Thanks for the explanations. This is another of the times that I wish I had taken the GR course in grad school! As far as I know, the experimental data is consistent with a flat universe (reference; see Fig 5). Apparently, the claim of zero net energy is equivalent to the claim of perfect flatness to the universe? Can you explain this relationship to us a bit better? (BTW, the claim that the universe arose from an initial "quantum fluctuation" has the same problems (but worse, IMO) as the claims that the universe "began to exist". A fluctuation is something that occurs in time; how can a "fluctuation" occur if time and space do not yet exist?) Edited by kbertsche, : No reason given."Science without religion is lame, religion without science is blind." — Albert Einstein I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously. — Erwin Schroedinger
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kbertsche Member (Idle past 2152 days) Posts: 1427 From: San Jose, CA, USA Joined: |
Cavediver--any answer or comments to my earlier question of how flatness is related to zero net energy? We have experimental evidence of flatness, so if there's a relationship to zero net energy, this would help to give zero net energy some experimental grounding.
"Science without religion is lame, religion without science is blind." — Albert Einstein I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously. — Erwin Schroedinger
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kbertsche Member (Idle past 2152 days) Posts: 1427 From: San Jose, CA, USA Joined: |
quote:This is called a "thought experiment" and has a grand tradition in physics. Thought experiments are very helpful in figuring out how to think about a problem. The basic idea is that gravity "wants" to pull things together. If no other forces counteract it, gravity will do so. In principle, this gravitational force could be harnessed to do work on an external device such as a generator. (Force times distance equals work or energy). This extracts energy from the gravitational field. Thus the gravitational field loses energy. Imagine two masses that are infinitely far apart. There is no gravitational force between them, and no gravitational energy in the system. As they move closer together, they can do work on (supply energy to) an external device like a generator. But since energy is conserved, and positive energy has been extracted to the generator, the gravitational field must contain negative energy. Edited by kbertsche, : Add last paragraph"Science without religion is lame, religion without science is blind." — Albert Einstein I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously. — Erwin Schroedinger
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kbertsche Member (Idle past 2152 days) Posts: 1427 From: San Jose, CA, USA Joined: |
I'll try again to answer your questions, but I'm not sure that I can explain it any better than I've already tried to do.
quote:Yes, really. If energy is conserved, and positive energy was extracted from the gravitational field, then the gravitational field energy must have become more negative. quote:If the mass is held constant, then as it shrinks to a smaller and smaller volume, the gravitational field becomes stronger and the gravitational field energy becomes more negative. As your wiki article said, if the mass were to shrink to a size of zero the gravitational field energy would become infinite. quote:No, the volume is reduced, but the mass remains fixed. The mass does not reduce. quote:Then you haven't quite grasped the arguments yet. Guth's and wikipedia's arguments should be persuasive. quote:Good points. I agree that it seems incredible that gravitational energy can offset the mass energy of the universe. I don't have a simple explanation or illustration for this. But I have no solid reason to doubt or deny it, either. It may well be true. Physics offers many examples of things which challenge our intuition until we learn how to think about them correctly. "Science without religion is lame, religion without science is blind." — Albert Einstein I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously. — Erwin Schroedinger
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kbertsche Member (Idle past 2152 days) Posts: 1427 From: San Jose, CA, USA Joined: |
quote:Yes, that's the claim. They are offsetting the positive mass energy of the universe with the negative, potential gravitational energy. (Note: both are equally "real" and physical). Dark matter and dark energy must also be added into the equation. "Science without religion is lame, religion without science is blind." — Albert Einstein I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously. — Erwin Schroedinger
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kbertsche Member (Idle past 2152 days) Posts: 1427 From: San Jose, CA, USA Joined: |
quote:This is a reasonable example. As in Guth's example, if the ropes and generators were absent and the mass shell were allowed to freely contract, then the elements of the mass shell would be accelerated toward the center and would gain kinetic energy. This kinetic energy comes from the gravitational field, the energy of which becomes more negative. "Science without religion is lame, religion without science is blind." — Albert Einstein I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously. — Erwin Schroedinger
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