Sean Carroll in Preposterous Universe:
The past few centuries of scientific progress have displaced humanity from the center of it all: the Earth is not at the middle of the Solar System, the Sun is but one star in a large galaxy, there are trillions of galaxies, and so on. Now we know that we’re not even made of the same stuff as most of the universe; for every amount of ordinary atoms and other known particles, there is five times as much dark matter, some kind of stuff we haven’t identified in laboratory experiments. But we do know a great deal about the behavior of dark matter. I talk with Lina Necib about why we think there’s dark matter, what it might be, and how it’s distributed in the galaxy. The latter question has seen enormous recent progress, especially from high-precision measurements of the distribution of stars in the Milky Way.