Movement of the Earth Seasons & Movemements

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

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

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

 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)

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

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

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

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

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

Movement #2 … REVOLUTION Earths movement around the sun

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

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

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

APHELION Ap=away Helio=Sun Earth’s farthest point from sun at: 152 million km = 94.45 million miles And occurs on: July 4th Ap=away Helio=Sun

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

… The SEASONS

The SEASONS are caused by Earth’s tilted axis

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

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.

Seasons Simulator: http://www. learner Seasons Simulator: http://www.learner.org/jnorth/tm/mclass/eclipticsimulator.swf Seasons Interactive (SEPUP) http://www.sepuplhs.org/students/iaes/simulations/SEPUP_Seasons_Interactive.swf

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

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

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

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!

Antarctic Circle has 24 hrs of daylight!

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

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

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

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

Precession:The axis points in different directions!

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

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

http://www.youtube.com/watch?v=1iSR3Yw6FXo

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