Dark Matter and Why We Can't Measure It as Well as We Should

Dark matter is most of the stuff in the universe. Was discovered initially because we were looking at how galaxies rotate when galaxies spin, you might wonder, why don't the stars fly off into inter galactic space like ping pong balls would on a merry go round? And the answer is gravity. Gravity holds them into the galaxy. Because the galaxies are spinning wag too fast, there's not nearly enough gravity to hold them together. You just count the mass of the stars that we can see. This is a great kind of thing to do in science. It's just like double check that things make sense. But sometimes they reveal, like a cosmic mystery, a clue that there's something