ASTRON 2B03 Lecture Notes - Lecture 12: Large Hadron Collider, Baryon, Subatomic Particle
6 Dec 2017
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In 1933, fritz zwicky made the first estimates of the masses of clusters of galaxies. Without extra mass the galaxies would have velocities too high to stay in the cluster! All subsequent studies have confirmed zwicky"s result. What did zwicky find? total mass / mass in stars + gas = ~ few hundred. His estimate was a little high, but the idea was a good one! and in 1933! Today we can repeat zwicky"s measurement and find the exact ratio of dark matter to luminous matter. Andromeda galaxy m31 closest big galaxy to the milky way. The best, early evidence for large amounts of dark matter came from the rotating motions of spiral galaxies like the milky way or m31 (early 1970"s) A spiral galaxy keeps its size and shape by rotating. Each star in it is orbiting around the centre of the galaxy. The speed of rotation depends on the amount of mass inside the orbit.
