1. The Reasons for the Seasons

2. Rotation Earth spins on axis (imaginary line through center of Earth from North to South Pole) Earth spins on axis (imaginary line through center of Earth from North to South Pole) Rotation is counter clockwise as seen from North Pole Rotation is counter clockwise as seen from North Pole Earth spins on its axis like a top Earth spins on its axis like a top

3. Rotation - Axis Earth tilt = 23.5 ° Earth tilt = 23.5 ° Axis currently pointed at Polaris (the North Star) Axis currently pointed at Polaris (the North Star) Polaris

4. Rotation Earth rotates once every 24 hrs Earth rotates once every 24 hrs The rotation causes day & night The rotation causes day & night Earth’s rotation causes celestial objects to appear to move from east to west in Northern Hemisphere Earth’s rotation causes celestial objects to appear to move from east to west in Northern Hemisphere

5. Night and Day Map

6. Just Checking… THINK…PAIR…SHARE What does it mean when we say the Earth rotates? What does it mean when we say the Earth rotates? How would you define or explain the concept of Earth’s axis? How would you define or explain the concept of Earth’s axis?

7. Revolution Movement of one object around another Movement of one object around another Earth revolves around our Sun Earth revolves around our Sun counterclockwise counterclockwise Earth’s orbit is almost circular rather than oval shaped but is still referred to as an elliptical orbit Earth’s orbit is almost circular rather than oval shaped but is still referred to as an elliptical orbit 365 ¼ days to revolve once around the Sun (~ a year) 365 ¼ days to revolve once around the Sun (~ a year)

8. CPS Quiz The imaginary line that runs through the north and south poles of the Earth is called the The imaginary line that runs through the north and south poles of the Earth is called the A. Equator B. Axis C. Longitude D. Latitude

9. CPS Quiz – Decide weather each example is of A. Rotation or B. Revolution The Earth spinning on it’s axis. The Earth spinning on it’s axis. A baseball player running around the infield. A baseball player running around the infield. Takes 1 year Takes 1 year A top spinning A top spinning Causes day and night. Causes day and night. Takes 24 hours Takes 24 hours The moon circling the Earth The moon circling the Earth

10. Location and Distance in Orbit

11. http://www.uwm.edu/~kahl/CoVis/Seasons/Handout available at 1.angle of Sun in the sky at a given time and latitude 2.number of hours of daylight at a given time and latitude. Two Primary Reasons for the Seasons (on Earth)

12. Seasons

13. Seasons Northern hemisphere tilts towards Sun = warmer (Summer) Northern hemisphere tilts towards Sun = warmer (Summer)

14. Seasons Northern hemisphere tilts away from Sun = cooler (winter) Northern hemisphere tilts away from Sun = cooler (winter)

15. Seasons In the Spring and the Fall, the tilt of the Earth is such that the spread of sunlight shines on the Earth approximately equally In the Spring and the Fall, the tilt of the Earth is such that the spread of sunlight shines on the Earth approximately equally

16. Seasons Southern hemisphere seasons are opposite Northern hemisphere seasons Southern hemisphere seasons are opposite Northern hemisphere seasons If its Winter here, then Australia is having _?_. If its Winter here, then Australia is having _?_.

17. Solstices Occur twice yearly when the Sun is directly over “Tropics” (23.5°N and 23.5°S Latitude) Occur twice yearly when the Sun is directly over “Tropics” (23.5°N and 23.5°S Latitude) Summer Solstice is the longest day of the year in the Northern Hemisphere (Sun directly over Tropic of Cancer- 23.5°N -at noon) Summer Solstice is the longest day of the year in the Northern Hemisphere (Sun directly over Tropic of Cancer- 23.5°N -at noon) Winter solstice = shortest day of the year for Northern Hemisphere (Sun directly over Tropic of Capricorn- 23.5°S -at noon) Winter solstice = shortest day of the year for Northern Hemisphere (Sun directly over Tropic of Capricorn- 23.5°S -at noon)

18. Equinox equal night & day equal night & day Occurs twice each year Occurs twice each year Half-way between solstices Half-way between solstices noon sun directly over equator noon sun directly over equator Sun will be at its highest point in our sky at noon but never directly overhead in Texas… why do you think this is true? Sun will be at its highest point in our sky at noon but never directly overhead in Texas… why do you think this is true?

19. CPS Quiz – Your answer should refer to Carrollton TX. This occurs because the Earth’s axis is tilted as it moves around the sun. This occurs because the Earth’s axis is tilted as it moves around the sun. This occurs when the Northern hemisphere is tilted towards the sun. This occurs when the Northern hemisphere is tilted towards the sun. This is when the length of day and night are equal. This is when the length of day and night are equal. The shortest and longest days of the year when the noon sun is directly overhead at 23.5 degrees. The shortest and longest days of the year when the noon sun is directly overhead at 23.5 degrees. This occurs when the Northern hemisphere is tilted away from the sun. This occurs when the Northern hemisphere is tilted away from the sun. A. Winter B. Summer C. Solstice D. Equinox E. All of the above

20. Based on this Night and Day Map… What season do you think it is in Carrollton? What season do you think it is in Carrollton? What time do you think it is in Carrollton? What time do you think it is in Carrollton?