Did Dark Matter Murder the Dinosaurs?

We may care a lot about dinosaurs, but you know what doesn’t give a fig about them? The entire rest of the universe, that’s what. The great thunder lizards that once ruled Earth are beasts of no consequence in the great sweep of everything. Unless, of course, something in that sweep of everything is what set loose the object that collided with Earth 65 million years ago, causing the dinosaur die-off in the first place.

That’s the premise of Dark Matter and the Dinosaurs, by Harvard particle physicist Lisa Randall–and she makes a compelling case. Dark matter is the not-fully-explained stuff that makes up 85% of all matter and is believed to surround galaxies in a sort of sphere, holding them together. In 2014, Randall and her colleagues developed a model of a different type of dark matter, which interacts electromagnetically and exists in a thin layer in the middle of the Milky Way, sandwiched between its top and bottom halves.

Most of the time, that would have no consequence for Earth. But every 35 million years, as our sun orbits the center of the galaxy, it would cross that dark-matter equator, creating a disturbance that could jostle the comets that hover at the fringes of our solar system, sending one plunging toward Earth. Geological records do suggest heavy cratering on Earth at about those intervals, and fossil records suggest corresponding die-offs.

All this matters for reasons that go beyond merely closing a very cold case file. The universe, Randall elegantly argues, is an organic thing, a symphonic thing, with all its myriad parts contributing their own notes. Pluck a string billions of light-years away and a single leaf on a single tree may vibrate on Earth. The dinosaurs paid with their lives for that fact, but the universe–as it has for so long–just played on.

–JEFFREY KLUGER