1. Movement of the Earth
Seasons
&
Movemements

2. The Reason for the Seasons
1. The longest day of the year for us (in the Northern Hemisphere) occurs on:
B) June 21
The Summer Solstice

3. The Reason for the Seasons
2. The hottest month(s) of the year for us in the Northern Hemisphere are usually:
B) July & August

4. The Reason for the Seasons
3. Planet Earth is closest to the Sun during the month of:
B) January !

5.  Date
Earth-Sun Distance
 Earth-Sun Distance
 January 12
 147,122,000 km
(91,417,000 miles)
 July 12:
 152,076,000 km
(94,496,000 miles)
 February 11:
 147,623,000 km
(91,729,000 miles)
 August 17
 151,470,000 km
(94,119,000 miles)
 March 26:
 149,206,000 km
(92,712,000 miles)
 September 14:
 150,499,000 km
(93,516,000 miles)
 April 10:
 149,891,000 km
(93,198,000 miles)
 October 15:
 149,194,000 km
(92,705,000 miles)
 May 23
 151,452,000 km
(94,108,000 miles)
 November 16
 147,534,000 km
(91,673,000 miles)
 June 15
 151,947,000 km
(94,415,000 miles)
 December 15:
 147,249,000 km
(91496,000 miles)
Perihelion
Aphelion
Jan 4
 147,097,641 km
(91,402,237 miles)
 July 4:
 152,087,478 km
(94,502,778 miles)

6. D) Exactly opposite Of Northern Hemisphere
The Reason for the Seasons
4. Seasons in the Southern Hemisphere are:
D) Exactly opposite
Of Northern Hemisphere

7. The Reason for the Seasons
5. Summer for us in the Northern Hemisphere occurs because:
C) The Earth’s Tilt
towards The Sun!

8. Earth has 2 Movements: Rotation & Revolution
Rotation: 2. The turning or spinning of a body on its axis
1 rotation = 24 hours = 1 day

9. What effect (that we see daily) does rotation cause??
DAY
&
NIGHT

10. Earth’s rotation is in the direction from West to East…
Sun appears to be moving East to West
Sunrise in East & sunset in West

11. Movement #2 … REVOLUTION
Earths movement around the sun

12. Revolution cont. 1 Revolution= 365.24 days = 1 year
.24 x4 = 1 day  Leap Year!
Speed of Revolution =30km/s=70,000 mph
ORBIT: path the Earth follows

13. Earth’s Orbit Slightly elliptical (not a perfect circle)
Earth is NOT always the same distance from the sun

14. PERIHELION PERI=near Helio=Sun Earth’s closest point to the sun at:
147 million km = (91.34 million miles)
and occurs on:
January 3rd
PERI=near Helio=Sun

15. APHELION Ap=away Helio=Sun Earth’s farthest point from sun at:
152 million km = million miles
And occurs on:
July 4th
Ap=away Helio=Sun

16. Always pointed toward North Star
Tilt of Earth’s Axis
is 23.5 degrees
Always pointed toward North Star
What effect does this cause??

17. … The SEASONS

18. The SEASONS are caused by Earth’s tilted axis

19. As North Pole tilts toward the sun, the Northern Hemisphere has longer days and shorter nights… & vise versa
Longest Days & Most Direct Sunlight = SUMMER
Shortest Days & Least Direct Sunlight = WINTER

20. Summer is warmer than winter because the Sun's rays hit the Earth at a more direct angle and also because the days are much longer. During the winter, the Sun's rays hit the Earth at an extreme angle, and the days are very short. These effects are due to the tilt of the Earth's axis.

21. Seasons Simulator: http://www. learner
Seasons Simulator: Seasons Interactive (SEPUP)

22. Summer Solstice Is the longest day of the year in Northern Hemisphere
Occurs when North Pole tilts toward the sun and the sun rays hit the Tropic of Cancer at 90 ° angle
Sun is highest in sky
Occurs on June 21-22

23. Arctic Circle has 24 hrs of daylight!
Rays
Antarctic Circle has 24 hrs of night!

24. Winter Solstice Is the shortest day of the year in Northern Hemisphere
Occurs when North Pole tilts away from the sun and sunrays hit the Tropic of Capricorn at 90 ° angle
Sun is the lowest in sky
Occurs on December 21-22

25. Arctic Circle has 24 hrs of night! Antarctic Circle has 24 hrs of day!
Rays
Arctic Circle has 24 hrs of night!
Antarctic Circle has 24 hrs of day!

26. Antarctic Circle has 24 hrs of daylight!

27. Autumnal (Fall) Equinox
Equal hours of day and night (12 and 12)
Sunrays hit the equator at 90 ° angle
North Pole does NOT tilt to or away from Sun
Occurs on September 22-23

28. Vernal Equinox
March 21-22
Autumn Equinox
September 22-23

29. Vernal (Spring)Equinox
Same info as Fall except it occurs on March 21-22
Sunrays strike equator at 90 ° angle
North Pole does NOT tilt to or away from Sun
Equal hours of day and night

30. Earth’s other movements
Precession
Gravitational pull of moon causes axis wobble and to spin like a top
Earth makes 1 full turn every 26,000 years
North Star will NOT always be where North Pole points

31. Precession:The axis points in different directions!

32. Nutation – the rocking or wiggling motion on the axis of rotation
Earth’s nutation period is 18.6 years
The effect is a small change in Earth’s tilt towards the sun
- Result is a slight shift in location of: Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle

34. Barycenter – the point between 2 objects where they balance each other
- The center of mass between 2 or more celestial bodies that orbit each other
- Both bodies orbit around a point that is NOT the center of the larger body

36. Earth’s Circumference
Video: Shape of Earth
Earth’s circumference
Video: Earth’s Equatorial Bulge