Scientific Controversies No. 9: Dark Matter at Pioneer Works

Our observable universe shines with the light of hundreds of billions of galaxies, each with hundreds of billions of stars, vast clouds of gas and dust, nebula cast off in explosions — a zoo of luminous objects. And while that might sound like a lot of stuff, everything we have ever seen constitutes less than 5% of what’s out there. Nearly 25% of the universe’s content hides in an unknown form: Dark Matter. Despite decades of effort to detect dark matter, the substance eludes us.

Janna Levin, astrophysicist and writer, invites physicists Elena Aprile of Columbia and Peter Fisher of MIT to ask if we truly should look for a new fundamental constituent of nature, or could dark matter actually be microscopic black holes?