| A | B |
|---|
| solar system | a group of planets and thousands of other bodies that revolve around the sun |
| leap year | a year of 366 days that occurs every four years because it combines the extra one-fourth days in the earth's revolution around the sun into a full day |
| revolution | one complete orbit of a planet around the sun |
| atmosphere | layer of air surrounding the Earth |
| orbit | path planets follow in revolving around the sun |
| axis | imaginary line that runs through the earth's center between the North and South Poles |
| winter solstice | the day in December when the sun appears directly over the Tropic of Capricorn |
| December 22 | the day with the fewest hours of sunlight in the northern hemisphere |
| summer solstice | the day in June when the sun appears directly over the Tropic of Cancer |
| Tropic of Cancer | 23 1/2 degree North latitude |
| Tropic of Capricorn | 23 1/2 degree South latitude |
| equinox | the day in March and September when the sun appears directly over the Equator |
| equinox | when day and night are of equal length |
| vernal | spring |
| autumnal | fall |
| June 21 | the day with the most hours of sunlight in the northern hemisphere |
| rotation | spin |
