| A | B |
|---|
| revolution | The earth's complete trip around the sun |
| solstice | first day of summer and of winter |
| equinox | when day and night in both hemispheres are of equal length |
| orbit | a planet's elliptical path around the sun |
| solar system | the sun, planets, and other smaller bodies that revolve around the sun |
| sun | the earth's most important companion in space; all the planets in the solar system revolve around it |
| axis | The earth rotates on this imaginary line running through earth from the North Pole to the South Pole |
| seasons | The tilt of the earth and its travel around the sun causes changes in the... |
| day and night | The earth's turning toward and away from the sun every 24 hours causes this |
| galaxy | A huge system of stars |
| leap year | every four years there is an extra day in the calendar |
| Earth | Third rock from the sun; Mr. Hobb's favorite planet. |
| moon | cold, rocky sphere that orbits the earth |
| inner planets | small and solid, these "earth-like" planets rotate slowly |
| outer planets | large and gaseous, these "Jovian" planets spin rapidly |
| atmosphere | layer of air surrounding the earth |
| 365 1/4 days | time it takes for the earth to make one complete revolution around the sun |
| 23 1/2 degrees | How many degrees is the earth tilted its axis? |
