24 NOVEMBER 2005
you
call a tail a leg, Abraham Lincoln once asked, how many legs does a dog
have?
Five? No, said Lincoln. Four. Calling a tail a leg doesn't make it a leg. It's still a tail.
In
a clearly similar way, calling "intelligent design" science doesn't make
it so. It's not science to say that life was constructed by an architect
who shall remain nameless. You might as well say the Earth is guided
in
its orbit by an invisible (but broad-shouldered) guy named Atlas. The
only way to make it "science" would be to change the definition of science
(which, oddly enough, is just what the Kansas 
Board of Education recently
did in its new public school science standards).
But no public body can dictate science's definition. That power resides solely within the scientific enterprise. And on rare occasion science does alter its self-identity, when progress requires a philosophical makeover.
"Most advances in the history of science," writes Nobel laureate physicist Steven Weinberg, "have been marked by discoveries about nature. But at certain turning points we have made discoveries about science itself."
These "turning points" typically signal drastic upheavals in human comprehension of the cosmos. Weinberg cites Einstein's relativity revolution, in which mathematical symmetry principles solved some mysteries of 19th century physics while destroying common-sense notions about motion. An earlier example, equally profound, was the Copernican revolution, which turned the universe inside-out, displacing humankind from its exalted status at the center of existence.
Today science may be on the verge of another transformation in the human mind's grasp on the nature of reality. "We may be at a new turning point," writes Weinberg, "a radical change in what we accept as a legitimate foundation for a physical theory."
Copernicus set the stage for Isaac Newton, who planted the idea in physicists' heads that theories describing the physical universe could be deduced from just a few basic principles. In Newton's case, the basics were the laws of motion and gravity. Einstein changed the rules, basing relativity on a symmetry -- the speed of light being the same no matter how you are moving (kind of like the way a circle is symmetric -- it looks the same no matter how you turn it).
Other symmetry principles have taken physics to the edge of explaining everything -- matter, forces, even gravity itself. But trying to tie it all together has stymied further progress. And the most fruitful approach so far to a "theory of everything" -- known as superstring theory -- has raised fears that humankind may be reclaiming special status as inhabitants of a preferred "location" in the cosmos.
For Copernicus, the Earth was not the center of the universe, but the sun was -- and it was, after all, our sun. But it turned out that the sun was only one of many stars, just an average inhabitant of a galaxy containing billions of others, many much brighter. Of course, it was our galaxy. But then it turned out that our galaxy was likewise just one speck of stardust among billions of others extending across a universe more vast than Copernicus could have imagined. Still, it was our universe.
Yet science refused to stop. Nowadays cosmic experts proclaim that our universe is only one of countless others, that reality comprises an unending web of spacetime bubbles beyond the realm of human senses but accessible to the equations describing space and time.
At least it's our reality.
But it turns out -- oh surely not. Reality is reality, right? Sorry. Superstring theory suggests that the reality we know may be a mere island in a sea of mathematical possibilities far greater than the number of stars in the galaxy or galaxies in the visible universe.
Perhaps those different realities correspond to different epochs of time, Weinberg suggests in a paper based on a recent talk. Or perhaps they just describe the multiple bubble universes -- the multiverse -- that cosmic math has already identified.
If so, our bubble must be the Goldilocks universe -- the part of reality where the laws of nature are "just right," producing conditions that are not too hot, too cold, or otherwise inhospitable for life to thrive.
Physicists have long sought a mathematical theory that specifies why the conditions in our Goldilocks universe are what they are. But superstring theory does not predict such a set of conditions -- it predicts a "landscape" of all the possible conditions you can imagine. In most of those universes, life would be impossible. But within a countless number of universes, sooner or later one will turn up with the proper Goldilocks features.
Consequently, says Weinberg, physicists might have to accept new forms of scientific explanation, abandoning their aversion to explaining the physical universe without regard to life's existence. And there is no need for design, intelligent or otherwise. "Just as Darwin and Wallace explained how the wonderful adaptations of living forms could arise without supernatural intervention," Weinberg notes, "so the string landscape may explain how the constants of nature that we observe can take values suitable for life without being fine-tuned by a benevolent creator."
E-mail: tsiegfried@nasw.org
