Cosmology, Page 87: [Previous Page] [Next Page] [Class Home Page] Textbook pages 439 - 450

Galaxies and our Expanding Universe

Soon after Hubble discovered galaxies existed outside of our own (see lecture notes Page 79), he soon came across another incredible discovery. He found a relationship between the radial velocity and distance of galaxies! The more distant a galaxy was, the higher its speed away from us was. (Doppler Shifted Spectrum) What could this mean?


What does it mean for the universe to be "expanding"?
Our universe is undergoing a continuous outward expansion as a function of time, so that as time goes by, distant galaxies move farther and farther away from us.



This leads to an obvious question: Are we the center of the Universe? No! This is because the distance between every galaxy is increasing, there is no central position in the universe about which things are moving outward from. If we go back in time, the Hubble relation suggests the universe was much smaller then.