Aug 2, 2008

tweaking the constants

A while back, I linked to an article that, I figured, seriously undermined the Anthropic Principle's logic. Further monkeying with crucial constants reveals that, indeed, it's flawed to presume that we should test for "cosmic fine tuning" by changing only one variable at a time. [sub. req.]
[U of Michigan, Ann Arbor's Fred] Adams started with a simple definition of a star: a massive body held together by its own gravity that is stable, long-lived and generates energy through nuclear processes. Just three constants are involved in the formation of such stars. One is the gravitational constant. The second is alpha, the fine structure constant that determines the strength of interactions between radiation and matter. The third is a composite of constants that determines the reaction rates of nuclear processes.
Adams then cooked up a batch of virtual universes, computing a wide range of values for the three constants, each universe possessing laws of physics unlike our own. The results:
About a quarter of the resulting universes turned out to be populated by energy-generating stars. "You can change alpha or the gravitational constant by a factor of 100 and stars still form," Adams says, suggesting that stars can exist in universes in which at least some fundamental constants are wildly different than in our universe.
The possibility of life-supporting black holes, about as wild as you can get, cosmologically speaking, arose in Adams' simulations. CalTech's Sean Carroll comments:
"I don't know what it would look like or how it would work, but black holes radiate, just like stars do. Why couldn't you have life arise in the 'atmosphere' of a gently radiating black hole?"
Crazy stuff.

Those still clinging to the Anthropic Principle had better dig those fingernails in pretty tight.

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