I went to exactly the same post on Carroll's blog in response to the parent comment as well! Quite relevant I thought, given the comments about conservation la

I went to exactly the same post on Carroll's blog in response to the parent comment as well! Quite relevant I thought, given the comments about conservation laws and the especially the mention of dark energy that followed. -I elected not to post up there as I am studying GR - and not so confident with it! Thanks for dropping it in.