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Robert100
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What do we mean by "Is the universe losing energy"?
In recent posts it has been proposed that, on a large scale, the law of conservation of energy just may not be true. Some analyses of the cosmic microwave background (CMB) are interrepted as meaning that energy has been lost over time. However, are all people using the same definitions for the same phrase?
If I understand this correctlly, then are you saying that these photons have really not lost energy? In "Expanding Space: the Root of all Evil?", by Matthew J. Francis et. al., we read:
On the surface, at least, this seems to contradict the brief discussion given here (http://www.gravityfromthegroundup.org/pdf/timeenergy.pdf ) in which the energy of the universe is said to decrease over time. But I may be mistaken. The way in which the author is considering energy to be lost over time may come from a different phenomenon? Anyone?
Also, this seems to contradict Marcus's analysis, which he comments on in post #27 in the thread "Is energy conserved in an expanding universe?"
https://www.physicsforums.com/showthread.php?t=179051&page=2
Marcus writes:
I have tried to find out what the consensus of the physics community is on this issue, only to get nowhere. There doesn't seem to be a consensus yet. If I understand correctly, the problem is worse: the total energy of the universe is being defined differently by different people.
Sound familiar? When people talked about "the expansion of space", it turned out that people used significantly different definitions for the same phrase, and worse, they were often unaware of this. It took years before someone finally wrote "The Root of all Evil" paper, in which this terminology mess was straightened out.
I think someone needs to write a similar paper for this issue. When talking about the energy of the universe, we need to look at the different ways that people have loosely used this term. We also need to look at all the analyses of the CMB, and analyses of the increase in volume of the universe, and subsequent contribution that is made by vacuum energy.
If there are any papers that do this, please let me know!
Robert
In recent posts it has been proposed that, on a large scale, the law of conservation of energy just may not be true. Some analyses of the cosmic microwave background (CMB) are interrepted as meaning that energy has been lost over time. However, are all people using the same definitions for the same phrase?
Wallace said:The CMB photons 'cool' simply due to redshift, which is caused by expansion alone (ignoring the Reese-Sciama effect).
If I understand this correctlly, then are you saying that these photons have really not lost energy? In "Expanding Space: the Root of all Evil?", by Matthew J. Francis et. al., we read:
"The key is to make it clear that cosmological redshift is not, as is often implied, a gradual process caused by the stretching of the space a photon is traveling through. Rather cosmological redshift is caused by the photon being observed in a different frame to that which it is emitted. In this way it is not as dissimilar to a Doppler shift as is often implied. The difference between frames relates to a changing background metric rather than a differing velocity."
On the surface, at least, this seems to contradict the brief discussion given here (http://www.gravityfromthegroundup.org/pdf/timeenergy.pdf ) in which the energy of the universe is said to decrease over time. But I may be mistaken. The way in which the author is considering energy to be lost over time may come from a different phenomenon? Anyone?
Also, this seems to contradict Marcus's analysis, which he comments on in post #27 in the thread "Is energy conserved in an expanding universe?"
https://www.physicsforums.com/showthread.php?t=179051&page=2
Marcus writes:
I calculated the energy lost by the redshifting of CMB photons starting out in some volume of space----as that space expanded (the calculation is simple and would be somewhere in PF archives I suppose)
I calculated the energy gained just by the expansion of that same volume of space, assuming a constant darkenergy density of 0.6 joules per cubic kilometer (the present measured value)
The amount lost and the amount gained were same order magnitude. Maybe they differed by a factor of 2. I don't recall. they didnt exactly match but they were same ballpark.
I have tried to find out what the consensus of the physics community is on this issue, only to get nowhere. There doesn't seem to be a consensus yet. If I understand correctly, the problem is worse: the total energy of the universe is being defined differently by different people.
Sound familiar? When people talked about "the expansion of space", it turned out that people used significantly different definitions for the same phrase, and worse, they were often unaware of this. It took years before someone finally wrote "The Root of all Evil" paper, in which this terminology mess was straightened out.
I think someone needs to write a similar paper for this issue. When talking about the energy of the universe, we need to look at the different ways that people have loosely used this term. We also need to look at all the analyses of the CMB, and analyses of the increase in volume of the universe, and subsequent contribution that is made by vacuum energy.
If there are any papers that do this, please let me know!
Robert