Monday, March 16, 2015 A week ago, we changed our clocks one hour forward in order to save daylight at the end of the day. What effect does daylight savings have on the number of daylight hours? Write this question and your answer in your journal.

Monday, March 16, 2015 A week ago, we changed our clocks one hour forward in order to save daylight at the end of the day. What effect does daylight savings have on the number of daylight hours? NONE!!! The days continue to get longer because the northern hemisphere is starting to tilt towards the sun. Daylight savings is just causing it to be darker in the morning than in the evening. The days are continuing to get longer regardless of daylight savings time.

Weather Map High = Happy Weather (any temperature but no rain) Low = Lousy Weather (any temperature and rain) Precipitation before warm front Stormy weather before cold front

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

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

How fast does Earth rotate? 1,675 km/hour, 465 meters/second.

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

Earth is actually closer to the Sun when the Northern Hemisphere is experiencing winter!

Spring Summer Autumn (Fall) Winter March 21 June 21 September 21 December 21 SEASONS in NORTHERN HEMISPHERE

Summer vs. Winter

Seasons: Summer (Northern Hemisphere Position of the Earth is such that the northern hemisphere is tilted toward the Sun Summer Solstice (1 st 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 (1 st 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 (1 st 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

TEST on Thursday! Watch this animation: TEST on Thursday! Watch this animation: files/earth.swf files/earth.swf

Choices for your Table Event: Solstice or Equinox Seasons: Winter, Spring, Summer, or Fall (Autumn) # Daylight Hours (NH): Longest daylight hours, Shortest daylight hours, or Equal hours of day and night everywhere Latitude: 23.5 o N (Tropic of Cancer), Equator, or 23.5 o S (Tropic of Capricorn) Diagram: