杏吧原创

IN THIS , NASA physicist tackles the question of whether the universe requires a supernatural 鈥渄esigner鈥� or whether our cosmological theories can explain the wondrous reality around us.

The standard model of cosmology, in which a tiny piece of inflating 鈥渇alse vacuum鈥� decays into a fireball, and stars and galaxies congeal out of the cooling debris, has passed many tests, but problems remain. Where did the false vacuum come from in the first place? And how do the supposedly enormous quantum convulsions of our current vacuum manage to cancel out to almost 鈥� but not exactly 鈥� zero, leaving behind a piddling 鈥渄ark energy鈥� that lies in the tiny range of values that allow life to exist?

Physics and cosmology alone may have the answers, says Calle. Combine eternal inflation, in which the primordial false vacuum continuously grows and decays, with string theory and you end up with a multiverse 鈥� a vast collection of universes, each of which has a different amount of dark energy. We find ourselves in one where it has just the right value for stars, planets and life because鈥� well, we couldn鈥檛 find ourselves anywhere else.

Another cosmological model that has emerged from string theory has our universe living on the surface of a 鈥渂rane鈥� floating in a higher-dimensional space. Our brane collides with a nearby brane over and over again for eternity, triggering an endless sequence of big bangs. This cyclic model may home in on the exact value of the dark energy we measure.

The model doesn鈥檛 require a beginning, and some theorists suspect that eternal inflation may not either. Certainly, neither requires a designer. Cosmology still has a lot to figure out, Calle contends, but it is in good shape.