9 June 2005
It may be that you don’t
spend a lot of your time wondering why the speed of light is as fast as it
is, or the gravitaty is as weak as it is. But for
physicists these are ultimate questions, necessary to explain the nature of
the universe. It may be that someday physicists will come up with a theory
so complete and that these fundamental constants of nature can be calculated from some
simple idea; but for now the mystery has inspired some to entertain a
controversial, intriguing possibility: Perhaps there are ‘many universes’
but only a few of them are ‘interesting’, while most are simple or too homogeneous. It is no accident that we live in an ‘interesting’
universe, because the boring ones don’t support enough complexity that
life could ever evolve, so there's no one there to look at them.
The evidence for this
hypothesis is that the world we know seems so sensitive to the physical constants.
Were these constants just a bit different from what they are, there would be
no stars, no chemistry – certainly no life.
One example: if the charge on
each proton were just a bit bigger, then multiple neutrons
and protons would not be able to stick together to form nuclei of different
kinds of atoms. The whole universe would be made of hydrogen. No nuclear
fusion; no stars; no chemical elements; probably, no life.
Another example: if the
gravitational constant were just a bit weaker than it is, then no galaxies
would ever form, and no stars would form out of the galaxies. Matter would
remain pretty uniformly dispersed through the universe. No clumps. No stars
or planets. How interesting is that? But if the gravitational constant were
just a bit stronger than it is, then gas and stars in a galaxy would pull too hard
on one another, would collide too frequently, and whole galaxies would collapse into black holes, perhaps
too quickly for the stately pace of biological evolution that has engendered
us.
Thin book on the subject:
Just Six Numbers, by Martin Rees
And a thick one: The Anthropic Cosmological
Principle, by John Barrow and
Frank Tipler
"And that which sings and contemplates in you is still dwelling
within the bounds of that first moment which scattered the stars into
space."
–Kahlil Gibran, The Prophet
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