NATS 1880 Lecture Notes - Milky Way, Baryon, Observable Universe
17 May 2013
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Document Summary
The universe is vast and old: vastness implies many planets on which life may arise, age means there was lots of time for life to start and evolve. The elements of life are widespread: organic building blocks have been found throughout the galaxy, basic chemicals that make up earth are present through the universe. The same physical laws that operate on earth operate throughout the universe: the process that evolved life on earth can happen anywhere. 3. 2 the structure, scale, and history of the universe. Earth is a planet on our solar system: our solar system consists of the sun and its orbiting objects, including the planets, their moons, and rocky asteroids and icy comets. Our sun is only one of about 200 billion stars in the milky way galaxy: a galaxy is an island of stars in space. Our milky way galaxy is part of the local group: billions of galaxies are found in groups.
