<p align="right">Last Update: <font color="#4f81bd">November 24, 2024</font></p> ## BIG IDEAS - Collection of gas, dust, and stars - A galaxy is a collection in [[space]], all held together by [[gravity]] and orbiting a common center. - [[Edwin Hubble|Hubble]] determined that galaxies are receding from us. - If galaxies are moving away from each other then there must have been a point in time in which they were near each other. [[Electromagnetic radiation|Light]] does not travel fast relative to the cosmological distances of galaxies. For example, the Andromeda galaxy (which can be seen by the naked eye) is approximately 2 million light years away; therefore, we "see" the galaxy as it was 2 million years ago. > [!NOTE] > > The Andromeda and Milky Way galaxies are expected to collide with each other in approximately 4-5 billion years. ### Related Topics --- [[Home|Home]] | [[The Universe]] | [[The Big Bang|The Big Bang Theory]] | [[Solar System]] | [[Galaxies]] | [[Star Clusters]] | [[Superclusters]] | [[Black Holes]]