Earth in Space

Rotation• Rotation is the Earth turning on its axis• Rotation is responsible for day and night• The Earth rotates in a counter-clockwise

direction • 1 rotation takes 24 hours• Earth rotates at a speed of 1670 km/hr

or 1035 mph (circumference of the Earth at the Equator is 40,000km) (Speed=distance/time)

• We do not feel the speed of Earth’s rotation due to Newton’s First Law of Motion (object in motion stays in motion unless acted upon by an outside force)

Revolution

• Revolution is the movement of the Earth around the sun

• It takes 365.25 days (1 year) for the Earth to complete one revolution

• The Earth revolves around the sun in an elliptical shaped orbit

• To make up for the extra ¼ day that is takes the Earth to revolve around the sun, an extra day is added to February every 4 years

• This is called a Leap Year

• February 29, 2012 is our next Leap Year

Revolution

Seasons(Seasons described relative to the Northern Hemisphere)

• Seasons are caused by the Earth’s 23.5o tilt on its axis.

• Earth is tilted toward the sun in the summer and away from the sun in winter.

• http://www.classzone.com/books/earth_science/terc/content/visualizations/es0408/es0408page01.cfm?chapter_no=04

• www.brainpop.com (seasons)

Summer

• We experience the season of summer when the North Pole is directed a full 23.5o toward the sun

• Due to the positioning of the North, more direct rays of the sun are present in the summer

• There are longer periods of daylight and shorter nights in the summer

Summer• Due to the longer days and more direct rays,

the temperatures in summer are hottest.

• The Earth is actually furthest from the sun in our elliptical orbit in the summer

Winter

• In the winter, the North Pole is directed a full 23.5o away from the Sun

• There are shorter days and longer nights in the winter

• The Earth is further from the sun in its elliptical orbit in the winter

• Due to the shorter days and less direct rays of the Sun, the temperatures in winter are coldest

Northern and Southern Hemispheres• The seasons are different in the Northern and

Southern Hemispheres because of Earth’s tilt on its axis

• In June, the Northern Hemisphere is tilted toward the sun and people are experiencing summer and the Southern Hemisphere is tilted away from the sun and people are experiencing winter

Solstice

• Solstice means Sun and stop• The solstice is the time when the sun stops moving

higher or lower in the sky each day• The Summer Solstice is the first day of summer

(June 20 or 21)• The Summer Solstice is the longest day of the year

and the Sun reaches its highest point in the sky• The North Pole is at “full tilt” toward the sun

Solstice

• The Winter Solstice is the first day of winter (December 21 or 22)

• The Winter Solstice is the shortest day of the year. The sun appears at its lowest point in the sky.

• The North Pole is at “full tilt” away from sun

Equinox

• Equinox is Latin for equal night

• The Vernal Equinox is the first day of spring (March 20 or 21)

• Day and night are of equal length all over the world during the Equinox

Equinox

• The Autumnal Equinox is the first day of fall (September 22 or 23)

http://www.windows.ucar.edu/tour/link=/the_universe/uts/equinox_gif.html

http://www.windows.ucar.edu/tour/link=/the_universe/uts/seasons_orbit.5x7_jpg_image.html

Websites

• http://www.usatoday.com/weather/tg/wseason/wseason.htm (Earth’s tilt creates the 4 seasons)

• http://esminfo.prenhall.com/science/geoanimations/animations/01_EarthSun_E2.html

Earth and Seasons Quiz

• 1. Name the four seasons. ___• spring,summer, fall,winter• 2. Are the Earth's seasons caused by the

differences in the distance from the Sun throughout the year or the tilt of the Earth's axis?

• Tilt of Earth’s axis• 3. What is the tilt of the Earth's axis (in degrees)?• 23.5*

• 4. During which season do the Sun's rays hit the Earth at the most direct angle?

• Summer• 5. During which season are the days the shortest?

• Winter• 6. What is the name of the shortest day of the year

(and the beginning of winter)? • Winter Solstice

• 7. What is the name of the longest day of the year (and the beginning of summer)? Summer solstice

• 8. What is the name of a day in which the day and night are of equal duration? Equinox

• 9. How many times each year do we have days in which the day and night are of equal duration? 2 times

• 10. What are the names of each of these days? the vernal equinox and the autumnal equinox