1. THE SEASONS

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3. SOME TERMINOLOGY… ROTATION: the spinning of a body about it’s axis
REVOLUTION: the spinning of a body about another body

4. SOME TERMINOLOGY… AXIS: the center around which something rotates
SEASON: one of the natural periods into which the year is divided by the equinoxes and solstices or atmospheric conditions

5. SOME TERMINOLOGY…
SOLSTICE: either of the two times of the year when the sun is at its greatest distance from the celestial equator
EQUINOX: either of two times of the year when the sun crosses the plane of the earth's equator and day and night are of equal length

6. SOME TERMINOLOGY… TROPIC OF CANCER:
Parallel of latitude approximately 23°27¢ north of the terrestrial Equator.
Northern boundary of the tropics
Marks the northernmost latitude at which the Sun can be seen directly overhead at noon.

7. SOME TERMINOLOGY… TROPIC OF CAPRICORN:
Parallel of latitude approximately 23°27¢ south of the terrestrial Equator.
Southern boundary of the tropics
Marks the southernmost latitude at which the Sun can be seen directly overhead at noon.

9. How Does the Earth Orbit the Sun?
The Earth spins on its axis
This motion is called rotation
It takes the Earth 24 hours to complete one rotation
This is what causes the Sun to rise and set, and therefore defines a day

10. How Does the Earth Orbit the Sun?
The Earth rotates from West to East
Therefore, the Sun rises in the East and sets in the West
The stars move across the sky in a counterclockwise fashion

12. How Does the Earth Orbit the Sun?
The Earth also moves through space.
It is traveling, or revolving around the Sun
One complete revolution takes days
This is what defines a year

14. How Does the Earth Orbit the Sun?
The Earth travels 940,000,000 km in one year
Around January 2, the Earth is closest to the Sun (about 147 million km). This is called the PERIHELION
Around July 3, the Earth is farthest from the Sun (about 152 million km). This is called the APHELION

15. THE SEASONS The Earth’s axis is tilted 23.5° from vertical
This means that at times of the year, the Northern Hemisphere is oriented more towards or more away from the Sun.
The same goes for the Southern Hemisphere, but in the opposite way.

16. SUMMER
We experience SUMMER in the N. Hemisphere when the N. Hemisphere is oriented more towards the Sun
The Sun rises higher in the sky and is above the horizon longer, and the rays of the Sun strike the ground more directly
This raises the temperature of the ground and water

17. SUMMER The SUMMER SOLSTICE occurs on the 21st of June
This is the longest day of the year in the Northern Hemisphere
On this day, the Sun’s rays strike the Tropic of Cancer directly at Noon

18. WINTER
We experience WINTER in the N. Hemisphere when the N. Hemisphere is oriented more away from the Sun
The Sun only rises low in the sky, is above the horizon for a shorter period, and the rays of the Sun strike the ground more obliquely.

19. WINTER The WINTER SOLSTICE occurs on the 21st of December
This is the shortest day of the year in the Northern Hemisphere
On this day, the Sun’s rays strike the Tropic of Capricorn directly at Noon