| A | B |
|---|
| Geocentric | Earth Centered solar system |
| Ptolemy | Described the Solar System as Geocentric, with planets orbiting in epicycles. |
| Copernicus | Heliocentric solar system, planets orbit in perfect circles too. |
| Tycho Brahe | Mathematician who calculated the positions of planets and stars. Observed a Supernova in 1572; showing that the solar system can and does change. Lost his nose in a sword fight. |
| Johannes Kepler | Corrected the idea that planets orbit in perfect circles. He said they orbit elliptically or in Oval shaped paths. Each Planet has a different eccentricity. 3 Laws of Planetary motion. |
| Sir Isaac Newton | Put forth laws of Gravity and Inertia and said that these 2 forces keep planets in orbit around the sun. Also invented Calculus and showed that white light is actually all the colors of the spectrum. |
| Galileo Galilei | Using his modifed Telescope he discovered in 1609, 4 moons orbiting Jupiter. Proving that not everything orbits the earth. |
| Immanuel Kant | In 1755 he proposed a theory to explain how and when our solar system formed. He called it the Nebular Theory. |
| Inertia (inersha) | Objects at rest will stay at rest and objects in motion will stay in motion until a force acts on it to change that. It's is primarily the motion part that we consider to be inertia. |
| Gravity | The force that pulls everything towards the center. Newton said gravity is determined by the mass and distance between the objects. The more mass an object has the more gravity it posesses. The further away it is, the less gravitational effect the objects have on each other. |
| Heliocentric | Sun Centered solar system |
| Helios | Greek word for sun. That's where we get the word "Helium" |
| Eccentricity | The amount of ovalness. It is a number from 0 to 1. Zero being a perfect circle and 1 being the most elliptical. It's the shape or path a planet takes to go around the sun. |
| Aristarchus | 270 BC estimated the distance to and size of the sun. Proposed that the earth orbits the sun |
| Eratosthenes | 250 BC: estimated the size of the earth and that it was spherical-roundish by observing lunar eclipse |
| Aristotle | 150 BC: said the earth was at the center of the universe, it was round and it didn't move. |
| Hipparchus | 135 BC: Discovers the Equinoxes. Estimates the distance to the moon as 60 earth radii. |
| Hans Lippershey | invented the refracting telescope in 1608 |
| constellations | A group of stars that forms an imaginary Image. |
| Asterism | A group of stars within a constellation forming an imaginary image. Part of the constellation. |
| Kepler's first Law | Says that the shape of a planets orbit is elliptical. |
| Kepler's 2nd Law | Says that a planet will speed up as it get closer to the sun and slow down as it gets further away. |
| Kepler's 3rd Law | Says that the time it takes a planet to orbit the sun=T, depends on its distance from the sun =R. T2 = R3 |
| Apogee (aphelion) | means away. Because a planets orbit is elliptical at some point it is further fromthe sun than at other times. |
| Perigee (perihelion) | This describes the planet at its closest point to the sun. |
