| A | B |
|---|
| rotates | what the earth does on its axis |
| planet's rotation | turns into night and day |
| 24 hours | time it takes for earth to rotate |
| 12 hours | amount of daylight and darkness at the equator |
| revolves | what the earth does around the sun as it rotates |
| year | a planet's revolution around the sun once |
| 365 days | the amount of days it takes the earth to revolve around the sun |
| orbit | the path a planet travels around the sun |
| atmosphere | this surrounds and protects earth from meteors |
| mists and gases | the atmosphere consists of this |
| oxygen | the most important thing in the earth's atmosphere -- we wouldn't be able to breathe without it |
| invisible green house | what the earth's atmosphere is like -- helps protect us from very high and low temperatures |
| about 800 miles high | how high our atmosphere goes up in the sky |
| meteors | falling rocks |
| burn up | most of the meteors do this before they reach the ground |
| meteorites | meteors that survive and hit the ground |
| 23 1/2 degrees | amount earth is tilted on its axis |
| seasons | earth's tilt causes these |
| summer | we are tilted toward the sun -- we get more direct light from sun |
| winter | we are tilted away from the sun -- light is more spread out |
| equator | imaginary line that divides the entire earth in half |
| Northern Hemisphere | top half of the earth |
| Southern Hemisphere | bottom half of the earth |
| warm | at the equator since sun shines almost directly on this line |
| cold | north and south poles -- sun never shines directly on top and bottom of earth |
| solstice | June 21 and December 21 |
| June 21 | first day of summer |
| December 21 | first day of winter |
| equinox | March 21 and September 21 |
| March 21 | first day of spring |
| September 21 | first day of autumn |
| equinoxes | sun is directly over the equator so daytime and nighttime hours are the same all over the world |
| layers | our planet has many of these |
| crust | top layer of the earth -- contains oceans, dirt, rocks & mountains |
| 20 miles thick | earth's crust is approximately this size |
| mantle | the layer of the earth under the crust -- made of soft, hot semisolid rock |
| thousands of miles thick | size of mantle |
| core | below the mantle -- solid iron surrounded by a layer liquid iron |
