| A | B |
|---|
| Heliocentric Theory | A description of the solar system in which all of the planets revolve around the sun. |
| Geocentric Theory | A description of the solar system in which all of the planets revolve around the earth. |
| Big Bang Theory | The initial explosion that resulted in the formation and expansion of the universe. |
| Universe | All of space and everything in it. |
| Light Year | The distance that light travels in one year. |
| Galaxy | A giant structure that contains hundreds of billions of stars. |
| Milky Way | The name of the galaxy in which we are a part of. |
| Solar System | A group of planets orbiting around a central star or star group. |
| Astronomical Unit | The distance from the Earth to the Sun. |
| Constellation | A pattern of stars in the sky. |
| Altitude | Elevation above sea level. |
| Gravity | The attractive force between two objects |
| Gravity | Its magnitude depends on their masses and the distance between them. |
| Meteor | A streak of light in the sky produced by the burning of a meteoroid in Earth's atmosphere. |
| Asteroid | Objects revolving around the sun that are too small and too numerous to be considered planets. |
| Asteroid Belt | The region of the solar system between the orbits of Mars and Jupiter, where many asteroids are found. |
| Meteorite | A meteoroid that has hit Earth's surface. |
| Comet | A ball of ice and dust whose orbit is usually a long, narrow ellipse. |
| Ellipse | An elongated circle, or oval shape; the shape of the planets' orbits. |
| Meteoroid | A chunk of rock or dust in space. |
| Hypothesis | A possible explanation for a set of observations or an answer to a scientific question. |
| Mass | The amount of material in an object. |
| Density | The mass divided by the volume of an object. |
| Ellipse | The shape created by objects as they orbit the sun. |
| Lunar Eclipse | The blocking of sunlight to the moon that occurs when Earth is directly between the sun and moon. |
| Solar Eclipse | The blocking of sunlight to Earth that occurs when the moon is between the sun and the Earth. |
| Eclipse | The partial or total blocking of one object by another. |
| Phase | One of the different shapes of the moon as seen from the earth. |
| Revolution | The movement of an object around another object. |
| Rotation | The spinning motion of an object about its axis. |
| Climate | The average, year-after-year conditions of temperature, precipitation, winds, and clouds in an area. |
| Tropical Zone | The area near the equator, between about 23.5 degrees north and south latitudes. |
| Temperate Zone | The area between the tropical and polar zones, from about 23.5 degrees to 66.5 degrees North and South latitudes. |
| Polar Zones | The areas near both poles, from about 66.5 degrees to 90 degrees north and south. |
| Hemisphere | One half of the sphere that makes up Earth's surface. |
| Equator | The imaginary line that runs around the center of the earth. |
