Sun-Earth System Investigation 3, Part 2 Seasons and Sun Sun-Earth System Investigation 3, Part 2 TG-P.97-98

Review Review the following questions from “Wendy and Her Worldwide Weather Watchers”: Which locations have the greatest number of hours of daylight on June 21? The fewest hours of daylight? Which locations have the greatest number of hours of daylight on December 21? The fewest hours of daylight? TG-P.99

Review Alpena, Michigan is located 45 degrees north of the equator. How much daylight do you estimate they have on June 21? December 21? Boulder, Colorado has a latitude of 40 degrees north. Wellington, New Zealand has a latitude of 41 degrees south. Which city has the longest amount of daylight on June 21? TG-P.99

What ideas do you have to explain why daylight hours change over a year? TG-P.99

Sun-Earth Model Represent the Earth and the Sun How should I set up the model? TG-P.99

Sun-Earth System TG-P.99

Revolution The movement of one object around another TG-P.99 *This takes 365 days (1 year) *The Earth revolves around the Sun

Rotation The Earth turning on its axis *One rotation on it axis takes 24 hours (1day) Earth has a North and South Pole Axis is the imaginary line that if you connect the North and South Pole TG-P.99 *The axis is tipped over at an angle of 23.5˚

Rotation How do we know where it is day and where it is night on this globe? Day Night TG-P.100 How much of the globe is in daylight at any given time? Always exactly half illuminated and half dark

North Star (called Polaris) Always positioned directly over Earth’s North Pole Used as a navigation aid to seafarers and explorers for centuries TG-P.100

Summary Is there a part of Earth that experiences only daylight or only darkness during the year? Above the Arctic Circle TG-P.101 Below the Antarctic Circle

Equinox Two days during the year that day and night hours are equal Comes from Latin meaning “equal night” TG-P.101

Fall Equinox Spring Equinox (Autumnal equinox) occurs around September 21 Fall Equinox TG P. 101 (Vernal equinox) occurs around March 21 Spring Equinox

Longest Day in the Northern Hemisphere? TG-P.101 Which way is the North Pole tilted? Toward the Sun

Solstices Summer Solstice Winter Solstice Around June 21 TG-P.101 Winter Solstice Around June 21 The longest day of the year Solstice means “sun stands still” Around December 21 The shortest day of the year

North Pole is tilted neither toward nor away from the Sun At fall equinox North Pole is tilted neither toward nor away from the Sun Sun is directly over the equator Half in daylight and half in darkness At winter solstice North Pole is now tilted away from the Sun Shortest day of the year TG-P.101 At summer solstice North Pole is tilted toward the Sun Northern Hemisphere receives more sunlight At summer solstice North Pole is tilted toward the Sun Northern Hemisphere receives more sunlight At summer solstice North Pole is tilted toward the Sun Northern Hemisphere receives more sunlight At spring equinox Sun is directly over the equator Day and night are equal

Seasons At winter solstice Days are shortest At fall equinox Less exposure to light, lower temperatures Snow, ice, frost, etc At fall equinox Days are getting shorter Less exposure to light, lower temperatures At summer solstice Days are longer Longer exposure to light produces the effects of summer Warmer temperatures, plant growth Seasons At spring equinox Days are getting longer Exposure to light is increasing, raising temperatures TG-P.102

Reading Read “Seasons” starting on page 17 of your green resource book. TG. P.102 Student Resource Book P.17-19

Multimedia Turn to “Seasonal Changes” You will use the Sun-Earth program on the CD-ROM to answer the questions on page 9 of your lab book. The questions are difficult, so make careful observations and concentrate TG-P.102

Response Sheet After you finish the Multimedia, turn to pg 11 in your Lab Notebook – Seasons and Sun Complete the assignment TG-P.102 Student Lab Notebooks P.11 TG -Teacher Assessment Master p. 383/p. 426