So, dark matter is the stuff that scientists don’t even know what it is. It’s invisible. They can’t smell it.
They can’t touch it. It can’t be protons. It can’t be electrons.
It can’t be neutrons. I’m talking about non-baryonic particles. And it’s important because it’s the majority
of our universe. So when you’ve got something
that’s just plain weird like that, it’s invisible, it’s undetectable, it’s just hard to understand what it is,
it’s hard to get your mind around it. But you can get the gist of the idea just with some stuff you have lying around. The basic idea is simple. There’s stuff out in space
that’s not moving the way it should. The visible stuff is a lot like the crumbs
in my coffee cup. As I stir the coffee, the crumbs all float
around the center of the cup at different speeds, which is a lot like how the star should move
around the center of our galaxy. But there’s a problem. The stars actually spin together,
like one solid object. It would be pretty weird
if the crumbs in this coffee spun around in lockstep
like the words on that CD. God, that’s foul! For that make any sense, there would have
to be something in the coffee, something invisible,
holding the crumbs together. That’s what dark matter is. It’s the invisible stuff
that’s forcing the visible stuff to orbit around the galaxy in lockstep which it wouldn’t otherwise do. That wasn’t too bad, was it?