Teach Astronomy - Newton's Cosmology

http://www.teachastronomy.com/ Newton's theory of gravity set the stage for physical cosmology, a study of the universe based on the idea of laws of physics that applied everywhere throughout space, and it gave rise to the idea of a clockwork universe, although we now know the universe is so complex that it is far from deterministic. Newton imagined the universe as infinite and filled with stars in random motion. This is essentially a static universe. Newton's rational was as follows. If the universe had an edge, then the stars near the edge would feel a greater force inside than outside where there are no stars, and so the stars would move inwards. Thus a universe with an edge would be forced to be in motion and collapse. The only way around this is to have an infinite universe filled with stars. Of course, an infinite universe has infinite gravity. This was a problem Newton couldn't address within his theory, so Newtonian cosmology had problems that were known even to Newton at the time.