A Wild Way to Look for Dark Matter
For decades, scientists have been speculating about a tantalizing dark horse in the race to understand the nature of dark matter, the invisible substance that binds together galaxies and larger cosmic structures. Rather than being made of undiscovered subatomic particles or arising from oversights in theorists' equations, dark matter could be a bizarre class of black holes that may have arisen shortly after the big bang. Such "primordial" black holes could be about as heavy as an asteroid yet as small as an atom. And according to a new study, if they are indeed dark matter, they should be so prevalent as to pass through our solar system about once per decade, causing subtle-but-detectable shifts in the motions of some planets, moons and asteroids.
Is this wild idea plausible? Remarkably so. Is it probable? That's a thornier question. But as scientists' increasingly thorough searches leave whatever's behind dark matter with ever-fewer ways to hide, the possibilities that remain must be carefully considered—no matter how unlikely they may seem.
--Lee Billings
