Parallel Worlds: A Journey Through Creation, Higher Dimensions, and the Future of the Cosmos

by Michio Kaku

Vera Rubin analyzed the blue stars in our galaxy, she found that the stars rotated around the galaxy at the same rate, independent of their distance from the galactic center (which is called a flat rotation curve), thereby violating the precepts of Newtonian mechanics. In fact, she found that the Milky Way galaxy was rotating so fast that, by rights, it should fly apart. But the galaxy has been quite stable for about 10 billion years; it was a mystery why the rotation curve was flat. To keep the galaxy from disintegrating, it had to be ten times heavier than scientists currently imagined. Apparently, 90 percent of the mass of the Milky Way galaxy was missing!

the reason why the night sky and the microwave radiation is so uniform is that the visible universe was once a tiny but uniform patch of the original fireball that suddenly inflated to become the universe.

By using Newton’s laws of motion, astronomers can calculate the mass of the central object by knowing the velocity of the stars orbiting around it. If the mass of the central object has an escape velocity equal to the speed of light, then even light itself cannot escape, providing indirect proof of the existence of a black hole.