Early Models of the Universe

• Precession of the Equinoxes - This refers to a gradual shift in the orientation of earth's axis of rotation. (23.5 dgrees)
• Diurnal Motion - It is a 24 hours rotation and the earth sits inside a celestial sphere
• Oval - what is ecliptic
• Annual Motion - the earth revolves around the sun
• Geocentric -everything moved around the earth
• Heliocentric - stars and the planets revolves around the sun
• Geoheliocentric - Earth was the center, and the sun and the moon, revolved around it
• Homocentric and concentric sphere - the universe was composed of earth and 5 other planets which are mercury, venus, mars, jupiter, and saturn
• Plato , Aristotle and Pythagoras - Who proposed geocentric model
• Eudoxus - Who proposed homocentric and concentric sphere
• Aristarchus - who proposed heliocentric model
• Copernicus - Who revied the heliocentric model
• Ptolemy - who proposed that planets move around small circle which themselves move around larger circles
• small circles - epicycles
• larger circles - deferent
• Tycho Brahe who proposed geoheliocentric model
• Perihelion - fastest motion
• Aphelion - slowest motion
• Epicycles - small circles
• Deferent - large circle
• Kepler - Tycho's assistant
• kepler's 3 laws of planetary motion - law of ellipses , law of equal areas , law of harmonies
• Law of ellipses - focus situated at the sun
• Law of equal areas - planets moved around the sun in such a way that a line drawn from the sun to the planet sweeps out equal areas in intervals of time