The velocity of the wind relative to the water is crucial to sailboats. Suppose a

Astronomy 103 Chapter 3: Motion of Astronomical Bodies  Motions in the sky o From our perspective on earth, it appears that everything in the sky moves and orbits around us o Early astronomers and philosophers therefore crafted mostly geocentric models of the universe to reflect this o These models became greatly fixed in the minds of astronomers for millennia o Politics and science can clash when cultural minds refuse to be changed o Another point unwilling to be conceded was the idea of “uniform circular motion” o Objects moved imperfect circles at uniform speeds o As astronomers viewed the motions of the planets, the models did not match the observations  Retrograde motion o Complicated models were needed to explain phenomena such as retrograde motion o Ptolemy developed a system with epicycles in 150 CE that remained accepted for about 1,500 years  Heliocentric Model o Copernicus was the first to create a mathematical model with the sun at the center and circular planet orbits o Could estimate relative distances of the planets from the sun and each other o Copernicus was able to use right-triangle trigonometry and observations of planets at opposition or conjunction to very accurately find their distances relative to the earth-sun distance o He was not able to discern our distan