Energy, general relativity, and the Big Bang

[mmcirvin]

Sean Carroll dissects an anti-Big-Bang petition in New Scientist, and explains why energy isn't conserved in general-relativistic cosmology. He's right on both counts, and his explanations are well worth reading. When I first read, in Edward Harrison's great and thoughtful (if rather out-of-date by now) textbook Cosmology: The Science of the Universe, that energy wasn't conserved in general relativity, I thought he was nuts. It's true, though; energy conservation is best seen as a special case of something more general that holds in GR. That's why a universe with a vacuum energy density, such as exists in inflationary cosmology and in dark-energy scenarios, can keep on inflating.

Comments

[partiallyclips.livejournal.com]

What does it mean for those of us in the crowd who are kind of rooting for extropy (http://www.extropy.com)? A little ray of hope for opposing our old nemesis the Second Law of Thermodynamics?

Or is cosmic inflation simply an even bleaker picture for the survival/triumph of intelligence at the far end of the Universe's natural lifespan?

[mmcirvin.livejournal.com]

Well, as far as anyone knows, it doesn't particuarly mean that there's a bonanza of energy-from-nothing waiting to be usefully tapped.

Except in one way: back in the 1980s, Alan Guth figured out that, if inflationary cosmology is correct, it's quite possible that a future civilization (maybe even with technology not too many centuries advanced beyond ours) could exploit this fact to create new universes. A new universe created by artificial means would pinch off completely from ours (possibly leaving a small, explosive black hole behind) and Big Bang all by itself... we'd be left with nothing but the satisfaction of having done it.

Some, such as Andrei Linde, have even suggested that the new universe could have physical constants slightly modified from the parent's, and that there could therefore be a kind of Darwinian process selecting out universes particularly favorable to intelligent life, with technological civilization serving as the reproductive organ.

[ronebofh.livejournal.com]

Who is that Douglas Bundy fellow that Carroll is so pointedly ignoring?

[mmcirvin.livejournal.com]

Somebody who doesn't know what he's talking about.