| A | B |
|---|
| Copernicus | proposed the heliocentric model of the solar system |
| Neptune | Coldest Planet |
| Big Bang Theory | Billion of years ago, the universe began expanding out from an enormous explosion |
| planets, moons, comets | Objects that are part of our solar system |
| Universe is expaanding | Galaxies are moving away from each other |
| Sun | the center of a solar system in the Milky Way Galaxy |
| Sun in Milky Way Galaxy | Sun is located on an outer rim (arm) of the Milky Way Galaxy |
| Galaxy | a large group of stars, gas and dust held together by gravity |
| Earth | located within one of the Milky Ways Galaxy's arm |
| Revolution | the yearly orbit of Earth around the Sun |
| Inner Planets | Mercury, Venus, Earth, Mars (these planets are more dense) |
| Outer Planets | Jupiter, Saturn, Uranus, Neptune (large and gaseous) |
| Shape of the orbit | similarity among the planets |
| The Earth's rotation | causes objects to appear to move acrros the sky |
| Earth | 56 degrees C |
| Venus | 470 degees C |
| Planets closer to the Sun | travel around the Sun faster; greater orbital speed |
| Objects closer to the Sun | have more of a gravitational pull |
| Comet | Large, dirty snowball; composed of dust and rock mixed with frozen water, methane, and ammonia |
| Meteor | Pieces of dust and rock that burn up in the Earth's atmosphere; considered harmless |
| Asteroid | Piece of rock similar to the material that forms planets; most located between the orbits of Mars and Jupiter |
| meteoroids | smaller pieces of rock broken from older comets |
| Mercury | many craters and high cliffs; smaller than Earth; no moons; no atmosphere; smallest in our Solar System |
| Venus | close the Earth's size; spins clockwise; hottest planet |
| Earth | one moon; only know planet with life |
| Mars | All water is now frozen; appears red because of rusted soil |
| Jupiter | Largest planet |
| Saturn | Large and most impressive ring system; Second largest planet in the Solar System |
| Uranus | Third largest planet |
| Geocentric Model | believed that the Earth was located at the center of the universe and planets revolved around the Earth |
