Man and Universe

• Geocentric Model - Earth is the center of the Universe
• Heliocentric Model - Sun is the center of the universe
• Thales - flat earther; Earth is a disc floating on water
• Anaximander - Earth is a cylinder w/ a curved surface; Fire, Earth, Air, and Water are outside of Earth and supports the energy of Earth
• Anaximander - created the sundial (ancient watch for time)
• Pythagoras - first to originate a spherical Earth using observations; only observed, never went to space; geocentric
• Pythagoras' observations:

  1. North & South Constellation Planes
  2. Sinking Ships
  3. Lunar Eclipse
• Pythagoras - first to say that Earth is round
• North & South Constellation Planes - constellations are different for North and South poles
• Sinking Ships - if Earth was flat, ship will stay visible then gradually disappear; if not, ship will appear to sink until only top is visible.
• Lunar Eclipse - Pythagoras observed that the Earth's shadow on the moon is round, not flat.
• Music of Spheres - Pythagoras' term for the solar system; motion of planets are mathematically related to sounds and numbers
• Plato - elements (fire, water, air, earth, gaia/energy) are equally distributed around the planet
• Plato - Earth is a globe with elements in every direction equidistant from the center
• Plato - stars & universe is perfect, ethereal/divine, unchanging/eternal
• Eudoxus of Cnidus - homocentric model: celestial spheres share Earth as their common center; creator of the 1st geocentric model
• Eudoxus of Cnidus - According to him, there are 27 interconnected geocentric spheres.
• Aristotle - geocentrism believer; said that a prime mover drives the motion of planets
• Aristotle - believed that stars are fixed points, rotating on a single spherical sphere (56 spheres)
• Aristotle - added 3 spheres to Jupiter & Mars, 4 spheres to Sun, Moon, Venus, and Mercury (to Eudoxus' model)
• Eratosthenes - 1st to use math to measure the planet; gave the most accurate size during their time
• Claudius Ptolemy - Earth's a sphere; stars are fixed bodies; planets independently move and sometimes reverse; geocentrism believer
• Ptolemy - His model contained a deferent, epicycle, and equant
• Deferent - circular path in which planets move
• Epicycle - circles where planets move
• Equant - point close to the orbit's center (not the actual center)
• Aristarchus of Samos - 1st to place Sun at the center of the universe; Earth revolves around Sun in a circular orbit; also believed that stars and sun are fixed
• Nicolaus Copernicus - corrected geocentric theory and proposed heliocentric model with the following:

  1. Earth's the only planet that moves around the Sun
  2. Earth rotates daily on its axis and revolves around the Sun yearly
  3. Earth has yearly tilting of its axis
  4. Retrograde motion of planets is explained by Earth's motion
  5. Distance from Earth to sun is smaller than Earth to stars
• Retrograde Motion - point where planets are moving "closer" but actually just move faster on its orbit; rotational motion of an object in the direction opposite the rotation of its central/primary object (Earth)
• Tycho Brahe - 1st to design and build huge instruments to make precise measurements of planets' positions; geo-heliocentric proponent (planets revolve around the Sun, and the Sun revolves around the Earth)
• Tycho Brahe - discovered supernova in the constellation Cassiopeia (1572); witnessed and recorded 2 in total in his study of the heavens (contradicted Aristotle's idea that stars are unchanging)
• Tycho Brahe - Johannes Kepler's instructor/teacher
• Galileo Galilei - 1st to use telescope and discovered the following:

  • sunspots on the Sun
  • Lunar craters
  • phases of Venus
  • 4 moons of Jupiter
  • supernova
  • identical size of the Stars
• Sidereus Nuncius - i.e. The Starry Messenger; Galilei's book
• Johannes Kepler - created the 3 laws of Planetary motion
• First Law (Planetary Motion) - orbits of planets are elliptical w/ the sun as the focus; has aphelion (point farthest from Sun) and perihelion (point nearest to Sun)
• Second Law (Planetary Motion) - imaginary line drawn from the Sun to the planet sweeps out equal areas n equal time intervals (faster during perihelion, slower in aphelion)
• Third Law - cube of radius of the orbit of a planet around the sun is proportional to the square of its period of revolution.