| A | B |
|---|
| vernal equinox | On this day, March 20 there is an equal number of daylight and night time hours. |
| autumnal equinox | ON this day, September22 there is an equal number of daylight and night time hours. |
| winter solstice | On this day, December 21, in the northern hemisphere, there is the shortest number of daylight hours and the longest number of night time hours. |
| summer solstice | June 21, in the northern hemisphere, there is the longest number of daylight hours and the shortest number of night time hours. |
| revolution | Motion of the earth around the sun-takes 365.25 days. |
| rotation | spinning of thge earth on its axis, causes day and night, takes 24 hours. |
| seasons | Regular change in temperature that repeats every year. |
| northern hemisphere | The half of the earth above the equator. |
| southern hemisphere | The half of the earth below the equator. |
| orbit | curved path of the earth around the sun |
| axis | imagnary line which the earth turns around causing day and night. |
| earth's tilt | tilted by 23.5 degrees |
| aphelion | The earth's revolution around the sun is an ellipse; this is the point in the revolution when the earth is farthest from the sun, July 5th |
| Perihelion | The earth's revolution around the sun is an ellipse; this is the point in the revolution when the earth is closest to the sun, Jan 3rd |
