'Dark matter' helped kill off the dinosaurs, new book theorizes

What killed off the dinosaurs 66 million years ago?

It’s one of the great mysteries of the universe. The best theory is that a massive, rogue comet slammed into the planet.

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But scientists have never been able to explain where this comet came from.

Harvard University particle physicist and cosmologist Lisa Randall has a theory, and it all has to do with another one of the great mysteries of the universe: dark matter.

Dark matter might sound odd or exotic, but as Randall explains in her new book, “Dark Matter and the Dinosaurs,” it’s really just ordinary stuff.

“Dark matter is one of the simpler things to understand,” she told CTV’s Canada AM Friday. “It’s just matter, but it’s not made up of the stuff we’re familiar with: atoms or charged particles.”

Dark matter is completely invisible and doesn’t interact with light; in fact, light passes right through it. But physicists know it exists because it interacts with gravity just like regular matter.

“We know it’s out there. We have seen its gravitational effects in many different ways,” Randall said.

In fact, it’s estimated that only about five per cent of the universe is composed of visible bits of ordinary matter; the rest is made up of dark energy and dark matter.

“In fact, billions of dark matter particles are passing through you this second and you don’t know about it because they just aren’t interacting with you,” Randall said.

Randall’s research team believes that dark matter tends to “clump” into galaxies and has formed a pancake-shaped disk inside the larger disk that is the Milky Way.

Our solar system, meanwhile, is rotating through the Milky Way every 240 million years, bringing with it the sun, the planets and an outer cloud of massive icy objects called the Oort cloud. As the solar system rotates, Randall theorizes that it bobs through this dark matter disk.

“Our idea is that when it crosses that disk, there is an extra gravitational tug on the solar system that could actually dislodge weakly bound objects very far away in… the Oort cloud,” she said.

Randall’s team believes that 66 million years ago, a large comet was dislodged from the Oort cloud, which hurtled through the solar system and collided directly with Earth.

When it did, it caused a massive cloud of debris that blocked out the sun, leading to the extinction of 75 per cent of the planet’s plant and animal species.

Now, Randall is quick to point out that this dark matter disk effect is just a theory -- and one that has been met with “a healthy degree of skepticism” from the astronomy community.

But she is hopeful that a satellite moving through the solar system right now might help to prove her theory.

That satellite is called Gaia and its mission is to measure the position and velocities of a billion stars to help chart a three-dimensional map of the Milky Way and reveal its composition.

Randall hopes the satellite will be able to spot this dark matter disk by noting the gravitational effects it’s having on our solar system and other stars in the Milky Way.

“So we’ll find out whether this disk exists or not.”


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