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Please read this and let me know if you are still convinced that energy must be conserved in General Relativity: https://www.preposterousuniverse.com/blog/2010/

Please read this and let me know if you are still convinced that energy must be conserved in General Relativity: https://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/ https://www.preposterousuniverse.com/blog/2010/02/22/energy-... (edit: Nevermind, this is the same content as the Discovery article linked above, except with better formatting). In short: conservation of energy is a result from the Noether theorem, which says it must be conserved iff the laws of physics are invariant under time translations. That's the case in Newtonian physics where we also have plenty of experiments supporting it, but not in GR. Precisely because of the expansion of the universe, the metric is time dependent and thus there can not be an associated conserved quantity. This has been known before we knew about dark energy or even the expansion of the universe.

ltbarcly3 7y ago
You are using circular reasoning. Energy is not conserved if the universe is expanding. I am saying of course that isn't happening, the evidence for expansion is poor and now has been shown to be unreliable. Without expansion energy is conserved. The example from your article is expansion, which it assumes to be a fact based on the poor evidence that is now invalidated.
- cthalupa 7y ago
  I covered this in more depth in my other comment, but quite simply, your entire premise here is wrong. This research was about whether or not the expansion of the universe is accelerating, and it casts some doubt on our belief that it is. It does not invalidate all of the evidence, potentially just that of measuring supernovas. Not only does this research not cast doubt on whether or not expansion is occurring, it would be nonsensical and couldn't exist in a meaningful way without taking expansion as a fact.
- mr_mitm 7y ago
  I don't know what you are talking about. The expansion of the universe is an observational fact. The evidence is overwhelming and you'll be hard pressed to find a single professional cosmologist who won't agree. Now whether the expansion is accelerating is another question, which is what the article of this thread is about. That's something that is still considered a fact, but the evidence is not quite as overwhelming. It's still strong, but questions about the validity of standard candles should be taken seriously.
  - ltbarcly3 7y ago
    The expansion of the universe is consistent with our best astronomical observations. Saying it is a 'fact' is just wordplay.
    - cthalupa 7y ago
      It is a fact in as real a sense as most anything is a fact when it comes to science. Arguing against the expansion of the universe without providing any evidence whatsoever to show it isn’t expanding is a waste of time. Questioning things is fine, when productive - you are not presenting any evidence to the contrary or even a hypothesis to explain even a portion of what expansion explains, shortly after showing that your understanding of the subject matter is not solid. Please do further research on these subjects before putting yourself in a position to mislead others.
      - ltbarcly3 7y ago
        To what end? If someone is mislead about the interpretation of astronomical observations on a cosmological scale there is absolutely no consequence. Your sensitivity to any suggestion that the most popular interpretation may be incorrect is, to be blunt, inappropriate. It's not my burden to prove that expansion isn't well founded. It is consistent with the best data available, however it is, in the best possible light, still a post-hoc interpretation of that data. It requires significant assumptions that do not have any basis. So lets unpack that. Given the assumption that the universe his homogeneous, what we observe isn't different from what would be observed from any other position in the universe. Given the assumption that the universe is isotropic, the universe should be the same no matter which direction we look. There is no evidence for either of these assumptions. Since we can only observe the portion of the universe that we are able to observe, we can only assume that our cosmological observations are (in the ways we are debating here) not a function of our position in the universe. This is no different from whom we may consider a less sophisticated observer on Earth who looks around and decides that the universe is full of breathable air. After all, the universe is homogeneous and isotropic, therefore it must be entirely full of air and no matter where you look you would see air. Obviously this is not consistent with our observations, but to someone without telescopes and a modern understanding of physics it would be the logical conclusion given the same assumptions you are making. The point is that these assumptions are assumptions. We have no evidence for them, except that the best observations we can make do not currently contradict our most recent version of the conclusions we take from those assumptions when combined with the best data we have. The problem is that this is always true, even for the unsophisticated observer who just sees air everywhere they are able to look with their primitive technology. If you can't see why it is not valid to make these assumptions at this point you should sit and think a bit.

ltbarcly3 7y ago

You are using circular reasoning. Energy is not conserved if the universe is expanding. I am saying of course that isn't happening, the evidence for expansion is poor and now has been shown to be unreliable. Without expansion energy is conserved. The example from your article is expansion, which it assumes to be a fact based on the poor evidence that is now invalidated.

cthalupa 7y ago
I covered this in more depth in my other comment, but quite simply, your entire premise here is wrong. This research was about whether or not the expansion of the universe is accelerating, and it casts some doubt on our belief that it is. It does not invalidate all of the evidence, potentially just that of measuring supernovas. Not only does this research not cast doubt on whether or not expansion is occurring, it would be nonsensical and couldn't exist in a meaningful way without taking expansion as a fact.
mr_mitm 7y ago
I don't know what you are talking about. The expansion of the universe is an observational fact. The evidence is overwhelming and you'll be hard pressed to find a single professional cosmologist who won't agree. Now whether the expansion is accelerating is another question, which is what the article of this thread is about. That's something that is still considered a fact, but the evidence is not quite as overwhelming. It's still strong, but questions about the validity of standard candles should be taken seriously.
- ltbarcly3 7y ago
  The expansion of the universe is consistent with our best astronomical observations. Saying it is a 'fact' is just wordplay.
  - cthalupa 7y ago
    It is a fact in as real a sense as most anything is a fact when it comes to science. Arguing against the expansion of the universe without providing any evidence whatsoever to show it isn’t expanding is a waste of time. Questioning things is fine, when productive - you are not presenting any evidence to the contrary or even a hypothesis to explain even a portion of what expansion explains, shortly after showing that your understanding of the subject matter is not solid. Please do further research on these subjects before putting yourself in a position to mislead others.
    - ltbarcly3 7y ago
      To what end? If someone is mislead about the interpretation of astronomical observations on a cosmological scale there is absolutely no consequence. Your sensitivity to any suggestion that the most popular interpretation may be incorrect is, to be blunt, inappropriate. It's not my burden to prove that expansion isn't well founded. It is consistent with the best data available, however it is, in the best possible light, still a post-hoc interpretation of that data. It requires significant assumptions that do not have any basis. So lets unpack that. Given the assumption that the universe his homogeneous, what we observe isn't different from what would be observed from any other position in the universe. Given the assumption that the universe is isotropic, the universe should be the same no matter which direction we look. There is no evidence for either of these assumptions. Since we can only observe the portion of the universe that we are able to observe, we can only assume that our cosmological observations are (in the ways we are debating here) not a function of our position in the universe. This is no different from whom we may consider a less sophisticated observer on Earth who looks around and decides that the universe is full of breathable air. After all, the universe is homogeneous and isotropic, therefore it must be entirely full of air and no matter where you look you would see air. Obviously this is not consistent with our observations, but to someone without telescopes and a modern understanding of physics it would be the logical conclusion given the same assumptions you are making. The point is that these assumptions are assumptions. We have no evidence for them, except that the best observations we can make do not currently contradict our most recent version of the conclusions we take from those assumptions when combined with the best data we have. The problem is that this is always true, even for the unsophisticated observer who just sees air everywhere they are able to look with their primitive technology. If you can't see why it is not valid to make these assumptions at this point you should sit and think a bit.