Dark Matter: Radiation Would Have Washed Away Galaxies Without It, with Lisa Randall | Big Think

Dark Matter: Radiation Would Have Washed Away Galaxies Without

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Here's what we know about dark matter:

1. It's there.

2. Its gravity affects things around it.

3. Aside from those two, we don't really know much.

That doesn't mean there aren't plenty of people who would like to help out...

Physicist Lisa Randall steps up to the Big Think camera this week to share her thoughts on dark matter and space in general. She's just recently published a book about dark matter, called Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe.

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LISA RANDALL:

Lisa Randall studies theoretical particle physics and cosmology at Harvard University. Her research connects theoretical insights to puzzles in our current understanding of the properties and interactions of matter. She has developed and studied a wide variety of models to address these questions, the most prominent involving extra dimensions of space. Her work has involved improving our under-standing of the Standard Model of particle physics, supersymmetry, baryogenesis, cosmological inflation, and dark matter. Randall’s research also explores ways to experimentally test and verify ideas and her current research focuses in large part on the Large Hadron Collider and dark matter searches and models.

Randall has also had a public presence through her writing, lectures, and radio and TV appearances. Randall’s books, Warped Passages: Unraveling the Mysteries of the Universe’s Hidden Dimensions and Knocking on Heaven’s Door: How Physics and Scientific Thinking Illuminate the Universe and the Modern World were both on the New York Times’ list of 100 Notable Books of the Year. Higgs Discovery: The Power of Empty Space was released as a Kindle Single in the summer of 2012 as an update with recent particle physics developments.

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TRANSCRIPT:

Lisa Randall: Dark matter is just a form of matter, which is to say it acts like matter when it comes to gravity. So it clumps together like the matter we know about. It’s found in galaxies, for example, because of gravitational force. What distinguishes dark matter from ordinary matter is that it has no interaction as far as we know with light. So we see ordinary matter. It’s made up of atoms. Atoms are made up of charged particles. But so far as we know, dark matter is just an entirely new form of matter not made up of atoms, not made up of the stuff we’re familiar with. And the question we eventually have is what is it made up of exactly?

But as far as the physics of the universe goes, it’s just a form of matter. The reason we’re aware of dark matter is because of the gravitational effects. In fact, if you look at just the energy stored there’s five times as much dark matter as there is ordinary matter. So you observe this gravitational effects in galaxies for example. I mean one of the ways we first knew about dark matter was by looking at the motion of stars. The motion of stars responds to the gravitational force of all the matter around. It doesn’t care whether or not it interacts with light. The stars of course are bright because they interact with light. But they’re responding to the gravity of the matter including the dark matter. So that was evidence for dark matter. And now there’s lots of other evidence for dark matter too having to do with the way light bends or what galaxy clusters look like when they merge. So there’s really a lot of physical evidence that tells us dark matter is out there in the universe. Then the question for theoretical physicists like myself becomes: What is this stuff and what do we mean by that? Well, is it an elementary particle? Is it more than one elementary particle? If it is a particle, what is the mass of that particle? Does it have any interactions at all?

So far we haven’t seen any interactions with the light with which we’re familiar, but maybe there’s a small interaction that we just haven’t seen yet or maybe it attracts in an entirely different way. The only thing we know for sure is that there is this matter and it interacts via gravity. Dark matter was actually essential to the formation of structures we see in the lifetime of the universe. Now it’s important to say structures we see in the lifetime of the universe. Even without dark matter, structure would have formed. But the actual size of the galaxies that we see is only possible because dark matter was present....

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