Tuesday, January 11, 2011

Cosmology’s little wars: what’s a universe or two, or many?

Cosmic microwave background - the battleground
Some friends were talking about a recent story in Technology Review’s Physics ArXiv blog, “Astronomers Find First Evidence Of Other Universes” (12/13/2010).

The idea is that astronomers have found evidence that our cosmos was "bruised" in collisions with other universes:
Last month, Roger Penrose at the University of Oxford and Vahe Gurzadyan at Yerevan State University in Armenia announced that they had found patterns of concentric circles in the cosmic microwave background, the echo of the Big Bang.

This, they say, is exactly what you'd expect if the universe were eternally cyclical. By that, they mean that each cycle ends with a big bang that starts the next cycle. In this model, the universe is a kind of cosmic Russian Doll, with all previous universes contained within the current one.

That's an extraordinary discovery: evidence of something that occurred before the (conventional) Big Bang.

Today, another group says they've found something else in the echo of the Big Bang. These guys start with a different model of the universe called eternal inflation. In this way of thinking, the universe we see is merely a bubble in a much larger cosmos. This cosmos is filled with other bubbles, all of which are other universes where the laws of physics may be dramatically different to ours.
Tentative evidence for the latter proposition is said to have been found in the cosmic microwave background, though it might, researchers admit, be just a trick of the eye.

Indeed, for so momentous a discovery (evidence of other universes?), it attracted little attention.

Astrophysicist friend Rob Sheldon comments:
Penrose and Gurzadyan found these circles in the microwave background radiation (CMB) and attribute them to things that happened before the Big Bang (a time before time), using it to disprove inflation universe models. Well that got the inflation guys unhappy, who are, after all, the majority of cosmologists. So some young guy without a reputation to defend decides to take them on and claim that these circles are proof of inflation in a multiverse (a space beyond space), claiming instead that this disproves Penrose.

Neither Penrose's "aeons" require circles, nor multiverse "D-branes" require circles, so you're seeing a lot of post-facto theorizing here, ...
Yes, one had begun to wonder about that. The research is here.

Go here, here, and here for other responses, and here for Gurzadyan and Penrose’s response.