Origin of Modern Astronomy Who is Stan Hatfield and Ken Pinzke
Key Terms Geocentric Theory - Earth centered Universe Heliocentric Theory – Sun centered Universe
Geocentric Theory Ancient Greece
Geocentric Model: Ptolemy (87-150 AD) Used epicycles to explain planetary movements
Ptolemaic System • Ptolemy created a model of the universe that accounted for the movement of the planets. • Retrograde motion is the apparent westward motion of the planets with respect to the stars. Retrograde motion of Mars East West Sept. Aug. July June Dec. Jan. Feb. March April May
Retrograde Motion https://www.youtube.com/watch?v=72FrZz_zJFU
The Birth of Modern Astronomy Copernicus - 1473-1543 Argued that the motion of the Sun & planets could be equally described by a Sun centered system. This model explained the retrograde motion of planets better than the geocentric model.
Heliocentric Theory
The Birth of Modern Astronomy Tycho Brahe - 1546-1601 the greatest of the pre-telescope observers in Europe. His measurements about the , positions of Sun, Moon and planets, especially of Mars, were far more precise than any made previously. Tycho Brahe Johannes Kepler
Johannes Kepler - 1609 Kepler was an assistant to Tycho Brahe. He used Brahe’s observations to study the orbit of Mars Discovered three laws of planetary motion: predict with accuracy the motions of the planets.
Galileo - 1564-1642 first scientist to use a telescope to observe the sky. observed the phases of Venus and the moons of Jupiter. Both observations supported the heliocentric model.
Sir Isaac Newton – 1642-1727 English scientist explained gravity as the force that holds planets in orbit around the Sun.
Gravity’s Influence on Orbits Makes no sense without caption in book
Gravity Gravity is the force that holds us to the Earth causes a rock to fall towards the ground causes the Earth to go around the Sun causes the Sun to be pulled towards the center of the Milky Way galaxy Gravity acts between any two objects even if they are far apart.
Modern Universe Is the Sun the center of the Universe?
Final Question Final Question