…is wholly incompatible with the standard earth centered universe with everything else laid out there was a pathetic compromise proposed by Tycho Brahe, in which the sun goes around the earth but mercury and venus go around the sun in order to explain the…

…in the earth's atmosphere, as almost everybody thought, or is it something astronomical? In the 16th century the Danish Astronomer Tycho Brahe, Johannes Kepler's Teacher, realized that there was a way to answer that question. Next slide, please. If you had…

…it works quantitatively by the relative shift against the background stars you can tell, in fact how far away it was. Well Brahe organized a cooperative international program to examine a comet and found beyond any doubt that the comet was beyond the moon,…

…wanted comets to be down in the atmosphere. But it's mathematics hard to say no to. What a comet in fact was was not for Tycho Brahe to figure out, and this was I'll come to it in a moment an insight provided by Edmund Halley. But let me show you…