What do you already know?

What do you already know? The sun has the following effects on earth: Heats the earth’s surface & atmosphere Influences winds & water cycle. Lights half of the earth’s surface at a time.

ROTATION The spinning of Earth on its axis that causes day and night to occur

AXIS The imaginary line extending from the North Pole to the South Pole going through the center of Earth, which is the center of Earth’s rotation

ROTATION 24 HOURS • One complete spin/rotation takes 24 hrs

North Pole always faces Polaris, the North Star

23.5 DEGREES • The slant of Earth’s axis, which is 23.5° from vertical

NUMBER OF HOURS OF DAYLIGHT Depends on location on Earth • The number of hours of daylight received each day depends on the latitude. • The equator receives about 12 hours of daylight all year long

DAYLIGHT HOURS

The earth’s tilt on its axis remains constant throughout the year.

Seasons • As the Earth revolves around the Sun, the tilt sometimes points toward the Sun, sometimes away from the Sun, and sometimes neither away nor toward the Sun

Seasons: Summer(Northern Hemisphere • Position of the Earth is such that the northern hemisphere is tilted toward the Sun • Summer Solstice (1st day of summer) • Sun at highest point (over Tropic of Cancer) • Most hours of sunlight (longest day) • About June 21

Seasons: Winter(Northern Hemisphere) • Position of the Earth is such that the northern hemisphere is tilted away from the Sun • Winter Solstice (1st day of winter) • Sun at lowest point (over Tropic of Capricorn) • Fewest hours of sunlight (shortest day) • About December 21

Seasons: Spring(Northern Hemisphere) • Position of the Earth is such that the northern hemisphere is tilted neither towards nor away from the Sun • Vernal Equinox (1st day of spring) • About 12 hours of sunlight • About March 21

Summing Up: Winter - Earth tilted away from Sun, fewer hours of sunlight, less direct sunlight (insolation) Spring – Earth neither tilted away nor toward the Sun, equal hours of daylight and night Summer – Earth tilted toward the Sun, more hours of daylight, more direct sunlight (insolation) Fall - Spring – Earth neither tilted away nor toward the Sun, equal hours of daylight and night

Watch this animation:http://www.shsu.edu/%7Echm_tgc/sounds/flashfiles/earth.swf

What do you already know?