00:01
In this question, we're going to look at dark matter and why scientists hypothesize that 90 % of the matter in the universe is actually made of this dark matter that we don't actually know too much about and aren't able to actually see with our eyes.
00:23
So the first evidence for dark matter came from an astrophysicist named fritz zwick.
00:30
And in 1933, zwicki was observing the coma cluster, which is a cluster of galaxies.
00:43
So you've got galaxies all around each other, and sort of like the way that you'd have planets around a star and stars orbiting around the center of a galaxy.
01:02
And so this is a cluster of galaxies, and they're all orbiting around.
01:07
A massive center.
01:11
And what zwicki saw was that the galaxies at the edge of the cluster, they're moving with a much greater velocity than you would have expected based on the amount of matter between them and the center.
01:29
So it's sort of like the earth revolving around the sun, right? in the center, we have the sun, which has a certain mass, and the earth with another smaller mass orbits around it.
01:46
We can figure out what this velocity must be based on the radius and the mass within that radius...