| A | B |
|---|
| autumnal equinox | always in interval September 20-22 |
| vernal equinox | always in interval March 20-22 |
| winter solstice | always in interval December 20-22 |
| summer solstice | always in interval June 20-22 |
| 23.5 degrees | angle between earth's axis & its path of orbit around the sun |
| eliptical | an orbit that is not a perfect circle |
| summer in the Northern hemisphere | begins on longest day of year & ends on day w/ about 12 hours between sunrise & sunset |
| winter in the Northern hemisphere | begins on shortest day of year & ends on day w/ about 12 hours between sunrise & sunset |
| winter at North pole of earth | dark 24 hours/day |
| Summer at North pole of earth | light 24 hours/day |
| distance between earth and sun, on average | 93,000,000 miles or 1 astronomical unit (1 AU) |
| days of the year at the equator when the sun is directly overhead (90 degrees altitude) at its zenith | autumnal equinox AND vernal equinox |
| at equator, azimuth of sunrise on autumnal equinox or vernal equinox | due east, 90 degrees |
| at equator, azimuth of sunset of autumnal equinox and spring equinox | due west, 270 degrees |
| convection currents over water that is warmest over equator, then cools gradually at increasingly N or S latitudes | movement of winds away from the equator & control of moisture content at different latitudes |
