Lisa Randall: evaluation

Transcript context

…In theory, it behaves just like any other matter, it just doesn’t interact with light. When we say it interacts just like any other form of matter, we have to be careful because gravitationally, it interacts like other forms of matter, but it doesn’t experience electromagnetism, which is why it has a different distribution. In our galaxy, it’s roughly spherical unless it has its own interactions, that’s another story. We know that it’s roughly spherical, whereas ordinary matter can radiate and clumps into a disk. That’s why we see the Milky Way disk. On large scales, in some sense, yes, all the matter is similar in some sense. In fact, dark matter is in some sense more important because it can collapse more readily than ordinary matter because ordinary matter has radiative forces, which makes it hard to collapse on small scales. Actually it’s dark matter that drives galaxy formation and then ordinary matter comes along with it. There’s also just more of it, and because there’s more of it can start collapsing sooner. That is to say the energy density in dark matter dominates over radiation earlier than you would if you just had an ordinary matter. It’s part of the story of the origin of the galaxy, part of the story of the end of the galaxy, and part of the story of all the various interactions throughout.…

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