Reasons for the seasons - Rebecca Kaplan

Transcription

1 Reasons for the seasons - Rebecca Kaplan /lunar-eclipse-supermoon-blood-moon/ /

2 Reasons for the seasons - Rebecca Kaplan Video Recap Johannes Kepler discovered the science behind the elliptical orbit of the Earth Earth s orbit is near a perfect circle Earth is closer to the sun in January, than in July Reasons for the seasons include tilt of the Earth, daylight hours and amount of solar energy

3 Earth Sun relations Earth motions Rotates on its axis Revolves around the Sun Earth rotates counter clockwise as seen from above the North Pole, which is why the sun, moon, planets, and stars all rise in the east and set in the west. Seasons Result of Changing Sun angle Changing length of daylight

4 Earth Sun relationships

5 Characteristics of the solstices and equinoxes

6 United Streaming Video: The Earth s Tilt Through the Seasons

7 Earth Sun relations Seasons Special days (Northern Hemisphere) Autumnal equinox Usually September Sun s vertical rays are located at the Equator (0º latitude)

8 Earth s Revolution Around the Sun Halfway in between the summer and winter solstices are the equinoxes. At these times the earth's axis is pointing neither toward nor away from the sun. On both equinoxes, all locations on earth receive exactly 12 hours of daylight and 12 hours of night.

9 September or Autumn Equinox Twilight zone/circle: area between the lighted and darkened halves

10 United Streaming: Autumnal Equinox

11 Due to differences between the calendar year and the tropical year, the September equinox can occur at any time from 9/21 9/24

12 A tropical year (also known as a solar year): the time that the sun takes to return to the same position in the cycle of seasons, as seen from Earth

13 the Sun rises directly in the east and sets directly in the west Before this point, the Sun rises and sets more to the north, afterwards, it rises and sets more to the south

14 Harvest Moon: Full moon closest to the Autumn Equinox

15 Earth Sun relations Seasons Special days (Northern Hemisphere) Winter solstice December Sun s vertical rays are located at the Tropic of Capricorn (23½º S latitude)

16 Relationship of Sun angle to the path of solar radiation

17 Winter solstice: the top of earth's axis is pointed away from the sun. Areas north of the equator experience the shortest day and longest night.

18 Earth Sun relations Seasons Special days (Northern Hemisphere) Spring (Vernal) equinox March Sun s vertical rays are located at the Equator (0º latitude)

19 Seasons Earth Sun relations Caused by Earth s changing orientation to the Sun Axis is inclined 23½º Axis is always pointed in the same direction Special days (Northern Hemisphere) Summer solstice June Sun s vertical rays are located at the Tropic of Cancer (23½º N latitude)

20 Summer Solstice Diagram of the Earth s seasons as seen from the north. Far left: summer solstice for the Northern Hemisphere. Front right: summer solstice for the Southern Hemisphere. the top of the axis (the North Pole) is pointed toward the sun. Areas north of the equator experience the longest day and shortest night. Sun's energy is now the strongest in the Northern Hemisphere, which is why it is warmer.

21 Summer Solstice Even though there are 24 hours of daylight at the north pole, it is still cold because the sun's rays are on such a slant! Arctic Circle is 23 1/2 degrees south of the North Pole. Everything within has 24 hours of light on June 21 The further north you travel on June 21, the longer the days are. Our maximum is about 15 hours of daylight.

22 Daily paths of the Sun at 40º N latitude The seasons have nothing to do with the Earth's distance from the sun, in fact the Earth is furthest from the Sun around July 1, and we are in the hottest part of the year. (APHELION)

23 The perihelion and aphelion are the nearest and farthest points respectively of a body's direct orbit around the sun.

24 Relationship of Sun angle and solar radiation received

25 Latitude and Length of Daylight

26 United Streaming: The Seasons

27 Gravitational pull of the Moon helps to ensure the stability of the Earth s spin axis tilt angle Too much deviation in the angle could send the Earth into a deep freeze or heated to dangerous levels Combination of Earth s almost circular orbit and large moon gives stability necessary for life on Earth 12% of sunlight is reflected at night Many species biological clocks are tied with the moon Gravitation pull lifts ocean tides circulation of nutrients necessary for ocean life to survive The Moon: Required For Life On Earth

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