Tuesday, July 10, 2007

Two more articles

Because I have a lot of waiting to do today.

1) Big "bounce" hypothesis: Our expanding universe started not from a singularity, but from a very small, very heavy, particle existing at the end of a contracting universe. It makes me think of the universe being a sine wave, and also of the Doctor Who episode (The Satan Pit, I believe) where The Doctor says that you can't have anything "before time". Of course, it's a fairly blind guess. But pretty cool nonetheless.

2) Altruistic rats: When rats are done favors, they pay them back, or, failing that, they pay them forward.

(both were found on Monday.)

I get the feeling that no one much cares about the articles I find. However, I find them interesting, so I will be difficult and keep posting them.


Duff said...

I actually read most of the articles.

The idea of a cyclic process of expanding and contracting universes is quite old, at least from the 70's. What is interesting about this guy's work is a possibility of describing the gravitational singularity in a quantum mechanical fashion, which has been a huge question facing physics. String theory has also had some success with this as of late.

Though the "Big Bounce" article though did not address a fundamental issue that would be of concern to anyone hypothesisizing an earlier universe to our own (unless they were thinking of something along the lines of Susskind's Landscape Hypothesis, or the inflationary multiverse.) Namely, the dark energy phenomona seems to rule out the possibility that our own universe will ever start to contract, but much the opposite, it will expand into utter oblivion, with even the mean local density winding up at 0 after all the blackholes evaporate. Space expansion will start going so fast that atoms will be ripped apart, according to some analysis of Dark Energy.

The problem then would be that Dark Energy could not have existed in prior universes, otherwise how would it have contracted?

The earlier article on the many world's hypothesis I was also going to comment on, but it seems the article brought up what I was curious about, namely, decoherence. Really, the notion of quantum mechanical decoherence seems to be the first consistent way to tie quantum mechanics to classical physics. That is to say, not invoking any of the Copenhagen Mumble-jumble that I never particularly liked. Always seemed to me to make things too dependent on conscious agency, and there are plenty of areas of the universe where such agency is non-existent. Also decoherence makes testable claims, unlike the Copenhagen interpretation, which always seemed wishy-washy on that regard (Bohr and Heisenberg, a brilliant physicists, weren't very good metaphysicians). What I am unsure about is whether one has to accepts the many-worlds hypothesis if one believes decoherence.

Leah said...

Well I was going to comment but after reading Duff's comment I feel fear. I had read these myself and enjoyed them. I like the vision of a generous rat. Maybe you could make a movie about that.

Duff said...

Err, I don't mean to be scary. I'm just a physicist, and know a bit about this stuff.

Elizabeth said...

I think she was joking about the being scared? Slash more scared that she would show her great lack of knowledge than anything else.

I hadn't put the dark energy expanding/cyclic process of expanding+contracting universes thing together, and that adds something very interesting. Cool!

The article on the many worlds hypothesis seemed to say that with decoherence + quantum, you sort of did have to. But I am dubious? Because it seems like there should be other explanations for why the equations don't collapse; but as a biologist I hardly know.