Wow. TYVM On Mon, Nov 3, 2014 at 12:37 PM, H Veeder <[email protected]> wrote:
> Energy is not conserved > > > http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/ > > quote > > <<I like to think that, if I were not a professional cosmologist, I would > still find it hard to believe that hundreds of cosmologists around the > world have latched on to an idea that violates a bedrock principle of > physics, simply because they “forgot” it. If the idea of dark energy were > in conflict with some other much more fundamental principle, I suspect the > theory would be a lot less popular. > > But many people have just this reaction. It’s clear that cosmologists have > not done a very good job of spreading the word about something that’s been > well-understood since at least the 1920′s: energy is not conserved in > general relativity. (With caveats to be explained below.) > > The point is pretty simple: back when you thought energy was conserved, > there was areason why you thought that, namely time-translation invariance. > A fancy way of saying “the background on which particles and forces evolve, > as well as the dynamical rules governing their motions, are fixed, not > changing with time.” But in general relativity that’s simply no longer > true. Einstein tells us that space and time are dynamical, and in > particular that they can evolve with time. *When the space through which > particles move is changing, the total energy of those particles is not > conserved*. > >> > > Harry >
