24.2 Sun and Seasons

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Earth Motions1. Earth moves in two major ways:– Rotation: spinning of earth on its axis – Revolution: earth orbits around the sun

What Causes Seasons?

1. 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

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

Seasons and Latitudes

1. Polar: Cold, don’t have 4 seasons – (66.4 N or S to poles)

2. Temperate: 4 seasons (23.5-66.5 N or S)

3. Tropics: Warm all year, no seasons (23.5 N or S)– Get intense rays all year long

• 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 =

VERNAL EQUINOX : March 211st day of springDays get longer and warmerSun’s direct & intense rays fall on the EQUATOR (and move north throughout spring)(equal day and night @ equator) SUMMER SOLSTICE: June 211ST day of SUMMERLongest day of the year – Shortest nightSun’s direct & intense rays are over 23.5 N (Tropic of Cancer) AUTUMNAL EQUINOX: Sept 231st day of FallSun’s direct & intense rays fall on the EQUATORDays get cooler and shorter(equal day and night @ equator) WINTER SOLSTICE: Dec 211ST day of WinterLongest night – shortest daySun’s direct & intense rays are over 23.5 S (Tropic of Capricorn)