AST222H1 Lecture Notes - Lecture 31: Comoving And Proper Distances, Main Sequence, Big Bang

• School: UTSG
• Department: Astronomy and Astrophysics
• Course: AST222H1
• Professor: Jo Bovy

Document Summary

In milky way, globular clusters can be as old as up to 12 gyr. Neutral hydrogen comes about as universe cools, photons cool, move with no inhibition. In all places temperature will be identical by 1 part of 10,000. Helium"s mass fraction is around 25%, which is quite high, notifying that the big bang must have been extremely hot and dense (to create this much helium) Goal: simple understanding of expansion of the universe. How can the universe expand if it is only matter? (dark matter and regular matter) It would be expected for there to be a deceleration of the universe, but know from observing the supernovae discussed last week that the universe has to be accelerating. Consists of matter-gravity interaction, assumption that there is only the force of gravity that is involved in any interaction causing this model to have simplicity. Homogenous qualities, in all place"s density is on average the identical.