1. 24.2 Sun and Seasons

3. Earth Motions 1. Earth moves in two major ways:
Rotation: spinning of earth on its axis
Revolution: earth orbits around the sun

4. What Causes Seasons? Tilt of the earth as it moves around the sun
Earth is tilted by 23.5 degrees
2. As the earth orbits, different parts of the earth get direct and intense solar radiation

8. Seasons
3. Opposite in the N and S hemisphere 4. When N tilted to the sun (summer), S tilted away (winter) 5. If the earth was not tilted= no seasons

10. Seasons and Latitudes 1. Polar: Cold, don’t have 4 seasons
(66.4 N or S to poles)
2. Temperate: 4 seasons ( N or S)
3. Tropics: Warm all year, no seasons (23.5 N or S)
Get intense rays all year long

14. Solstice: sun is directly overhead at latitude 23.5 N or S
Equinox: neither hemisphere is tilted toward the sun, and the lengths of daylight and darkness are =

15. VERNAL EQUINOX : March 21
1st day of spring
Days get longer and warmer
Sun’s direct & intense rays fall on the EQUATOR (and move north throughout spring)
(equal day and equator)
SUMMER SOLSTICE: June 21
1ST day of SUMMER
Longest day of the year – Shortest night
Sun’s direct & intense rays are over 23.5 N (Tropic of Cancer)
AUTUMNAL EQUINOX: Sept 23
1st day of Fall
Sun’s direct & intense rays fall on the EQUATOR
Days get cooler and shorter
WINTER SOLSTICE: Dec 21
1ST day of Winter
Longest night – shortest day
Sun’s direct & intense rays are over 23.5 S (Tropic of Capricorn)