THE SEASONS

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

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

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

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.

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.

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

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

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 365.25 days This is what defines a year

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

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.

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

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

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.

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