Astronomy 2022A/B Lecture Notes - Lecture 6: Barred Spiral Galaxy, Lenticular Galaxy, Virgo Cluster

• School: Western University
• Department: Astronomy
• Course: Astronomy 2022A/B
• Professor: Chris Racknor

Document Summary

Lecture 6 large scale structure in the universe & energy. The first cosmologists (1940"s-50s) assumed that the universe was uniform and infinite in time and space and essentially unchanging. However, a lot of evidence has accumulated against this model. If the universe has a finite age, and light travels at a constant speed, then no light can have reached us from the most distant stars. In fact, since the universe is about 14 billion years old, we can"t see anything beyond about 14 billion light years away. This defines the observable universe which is finite. Universe itself is infinite, we will only ever be able to see a finite spherical region around us. Considering the largest scales in the universe, we make the following fundamental assumptions: 1) homogeneity: on the largest scales, the universe has the same physical properties everywhere. expansion rate, visible vs. dark matter, etc. : every region has the same physical properties (mass, density,