Light loosing frequency equals to a loss of energy as far as I understood. So where does this energy go, given that the law of conservation of energy is correct?
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In an expanding universe, energy is not conserved : http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/ – Sep 26 '16 at 08:44
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Not all redshifting means less energy of the photon only relatively. Redshifting due to expanding space is obviated by the work/energy of a bigger universe – Marijn Sep 26 '16 at 09:03
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Wich one is it then? Marijn's answer or CountTo10's answer? Or do the physicists still disagree? – Markus Appel Sep 26 '16 at 09:06
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Reading the other answers I'm probably wrong. But still wondering why the constant vacuumenergy is increasing by exapanding universe, couldn't this increase of energy comes from decreased energy of photons like CMB etc? – Marijn Sep 26 '16 at 09:32
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Hi Markus, please read the link to Sean Carroll's website. If that is not clear, then let me quote from Wikipedia, In general relativity conservation of energy-momentum is expressed with the aid of a stress-energy-momentum pseudotensor. The theory of general relativity leaves open the question of whether there is a conservation of energy for the entire universe. https://en.wikipedia.org/wiki/Conservation_of_energy – Sep 26 '16 at 11:42
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@CountTo10 I already did. Marijn's answer seems reasonable, too, but not in compliance with your blog article. – Markus Appel Sep 26 '16 at 11:46
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Ok, I won't give up just yet, one more link, especially the last three answers http://physics.stackexchange.com/questions/10398/why-is-global-conservation-of-energy-not-considered-a-tautology?rq=1 – Sep 26 '16 at 11:49