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This is a false dichotomy. We have known energy is not (always) conserved since long before we began discussing dark energy. This is such a misunderstood topic

This is a false dichotomy. We have known energy is not (always) conserved since long before we began discussing dark energy. This is such a misunderstood topic vis a vis dark energy that Discovery specifically has an article on it: https://www.discovermagazine.com/the-sciences/energy-is-not-conserved https://www.discovermagazine.com/the-sciences/energy-is-not-...

ltbarcly3 7y ago
Nope. We have no actual evidence of a violation of the conservation of energy. What has happened here is that astrophysicists got way out on a branch. They were quite excited and came up with a theory that seemed to explain why there appeared to be increasing redshift with distance, and later that theory was shown to violate conservation of energy. Doubling down, they waved their hands and said that conservation of energy must not hold at 'cosmological scales', without any evidence to make such a claim.
- mr_mitm 7y ago
  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.
        7y ago
- cthalupa 7y ago
  >Doubling down, they waved their hands and said that conservation of energy must not hold at 'cosmological scales' Energy not being conserved has been experimentally verified, as noted in the article you were linked. This isn't a controversial topic, nor is it one where scientists have proposed it as a potential solution for a problem they can't conclusively solve. GR predicted it, we've verified it. >without any evidence to make such a claim. Light redshifts. The energy of a photon is in its wavelength. Light redshifting fundamentally means that energy isn't being conserved.
  - ltbarcly3 7y ago
    The example in the article is the exact thing that has been thrown into doubt. This entire thread is because a researcher has found evidence that contradicts the only evidence we have for expansion. I said of course there isn't expansion, the evidence is poor for it and that poor evidence is now disputed, plus expansion means a violation of energy conservation. You come back with "look at the article, energy conservation has been shown to be violated", but the example in the article is expansion. Circular reasoning at it's best.
    - cthalupa 7y ago
      You're totally misunderstanding this whole thing, unfortunately. I don't really know how to do a point by point rebuttal of every line here since each one is building on top of that misunderstanding. This article calls into question whether or not the expansion of the universe is accelerating - it does not call into question whether or not it is expanding. There is basically zero scientific debate on whether or not the universe is expanding - the evidence that it is huge. We know that light redshifts. We can observe it. It is experimentally verified. That means that we have verified that energy is not conserved. Dark energy is not required for the universe to expand and we knew that the universe was expanding long before we had any idea that it (might/might not) be expanding at dynamic rate. It is possible that our key indicator about the expansion accelerating was in error. It is not at all remotely an indicator that expansion is not happening. We have known the universe was expanding since 1929. Mountains of evidence have been piling up further confirming it ever since then. It wasn't until the 90s that we found evidence that that expansion was accelerating, and that is what ultimately lead to the hypothesis of dark energy. In fact, this new research wouldn't even be usable without taking into account expansion, and uses Cepheid variable stars as the control to figure out where we might have gotten things wrong when measuring supernova in distant parts of the universe. The Cepheid variable stars are exactly how we figured out the universe was expanding in the first place. And, to be clear, there's other evidence for dark energy, including the CMB and how galaxies cluster when we look at things on very very large scales. This is hardly a case of nailing up the coffin for dark energy, but if it pans out this is all accurate, it does call things into question. But it does not cast any doubt on if the universe is expanding, on light redshifting, or the idea that energy isn't always conserved - without those things being accepted as true this research couldn't even exist.

ltbarcly3 7y ago

Nope. We have no actual evidence of a violation of the conservation of energy. What has happened here is that astrophysicists got way out on a branch. They were quite excited and came up with a theory that seemed to explain why there appeared to be increasing redshift with distance, and later that theory was shown to violate conservation of energy. Doubling down, they waved their hands and said that conservation of energy must not hold at 'cosmological scales', without any evidence to make such a claim.

mr_mitm 7y ago
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.
        7y ago
cthalupa 7y ago
>Doubling down, they waved their hands and said that conservation of energy must not hold at 'cosmological scales' Energy not being conserved has been experimentally verified, as noted in the article you were linked. This isn't a controversial topic, nor is it one where scientists have proposed it as a potential solution for a problem they can't conclusively solve. GR predicted it, we've verified it. >without any evidence to make such a claim. Light redshifts. The energy of a photon is in its wavelength. Light redshifting fundamentally means that energy isn't being conserved.
- ltbarcly3 7y ago
  The example in the article is the exact thing that has been thrown into doubt. This entire thread is because a researcher has found evidence that contradicts the only evidence we have for expansion. I said of course there isn't expansion, the evidence is poor for it and that poor evidence is now disputed, plus expansion means a violation of energy conservation. You come back with "look at the article, energy conservation has been shown to be violated", but the example in the article is expansion. Circular reasoning at it's best.
  - cthalupa 7y ago
    You're totally misunderstanding this whole thing, unfortunately. I don't really know how to do a point by point rebuttal of every line here since each one is building on top of that misunderstanding. This article calls into question whether or not the expansion of the universe is accelerating - it does not call into question whether or not it is expanding. There is basically zero scientific debate on whether or not the universe is expanding - the evidence that it is huge. We know that light redshifts. We can observe it. It is experimentally verified. That means that we have verified that energy is not conserved. Dark energy is not required for the universe to expand and we knew that the universe was expanding long before we had any idea that it (might/might not) be expanding at dynamic rate. It is possible that our key indicator about the expansion accelerating was in error. It is not at all remotely an indicator that expansion is not happening. We have known the universe was expanding since 1929. Mountains of evidence have been piling up further confirming it ever since then. It wasn't until the 90s that we found evidence that that expansion was accelerating, and that is what ultimately lead to the hypothesis of dark energy. In fact, this new research wouldn't even be usable without taking into account expansion, and uses Cepheid variable stars as the control to figure out where we might have gotten things wrong when measuring supernova in distant parts of the universe. The Cepheid variable stars are exactly how we figured out the universe was expanding in the first place. And, to be clear, there's other evidence for dark energy, including the CMB and how galaxies cluster when we look at things on very very large scales. This is hardly a case of nailing up the coffin for dark energy, but if it pans out this is all accurate, it does call things into question. But it does not cast any doubt on if the universe is expanding, on light redshifting, or the idea that energy isn't always conserved - without those things being accepted as true this research couldn't even exist.