THE SEASONS THE SEASONS

FIRST, dispel all myths about the seasons, the

Moon and other Astronomical errors by taking this 5-question

survey.

Private Universe - Surveys

SOME TERMINOLOGY…SOME TERMINOLOGY…

• ROTATION: the spinning of a body about it’s axis

• REVOLUTION: the spinning of a body about another body

SOME TERMINOLOGY…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…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…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…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 How Does the Earth Orbit the Sun?Orbit the Sun?

The Earth spins on its axisThis motion is called rotationIt takes the Earth 24 hours to

complete one rotationThis is what causes the Sun to rise

and set, and therefore defines a day

• 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 How Does the Earth Orbit the Sun?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 How Does the Earth Orbit the Sun?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

How Does the Earth How Does the Earth Orbit the Sun?Orbit the Sun?

THE SEASONSTHE 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.

SUMMERSUMMER• 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

SUMMERSUMMER

• 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

WINTERWINTER• 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.

WINTERWINTER

• 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