NATS 1740 Lecture Notes - Lecture 2: Milky Way, Bertrand Russell, Virgo Supercluster

• School: York University
• Department: Natural Science
• Course: NATS 1740
• Professor: Michael De Robertis, Alireza Rafiee

Document Summary

Universe: the sum of everything (all matter, energy, space) within and between galaxies. + some people suggest universe is more than this => philosophy. + bertrand russell the universe is just there, and that"s all . Some pp think there is an infinite number of universe. Light travels at a finite speed (300,000km/s), light travel 1 thousand times faster than sound on. Our universe is 14 billion years old. => we see objects nowadays as they were in the past. => the farther away we look at a distance of a planet (object), the further back we look in time. Ex: the star we see now, is what it looked like in the past. => universe is a time machine (andromeda galaxy is 2. 5 million years light time travel, so what we see this galaxy now, is what it looked in the past 2. 5 million years ago) Definition: light year => the distance light can travel in 1 year.