Physical Characteristics of Earth 1.Spherical shape -satellite photos -curved shadow on moon during a lunar eclipse. -approaching ships “rise” over the horizon
Physical Characteristics of Earth 2. Rotation -Earth spins on its axis (an imaginary vertical line) causing night and day. -24 hours to rotate once on its axis -rotates 365 times in a year Foucault’s Pendulum shows the Earth’s rotation as it swings http://www.classzone.com/books/earth_science/terc/content/visual izations/es0403/es0403page01.cfm?chapter_no=visualization
Physical Characteristics of Earth 3. Magnetic Field -Movement of liquid iron inside Earth and its rotation create a magnetic field. -Helps protect Earth from harmful CME’s from the sun.
Physical Characteristics of Earth 4. Revolution -Earth’s yearly orbit around the sun. (365 ¼ days) -Path is elliptical in shape. Farthest away from sun in July Closest to sun in January
What do you know about the Seasons? Summer –NJ-warm, longer days, June-August –Hawaii-80’s, 12 hours of light –Alaska- up to 24 hours of light –Australia-Dec-Feb Winter –NJ-cold, longer nights, Dec-Feb –Hawaii- 70’s, 12 hrs of light –Alaska-up to 24 hours of darkness –Australia-June-Sept.
Distance from the sun does NOT cause our seasons. If it did, we would all feel winter in July and summer in January. Even Hawaii would have a cold winter!
Physical Characteristics of Earth 5. A Tilted Axis 23.5˚ tilt -The Earth is always tilted the same direction during its yearly revolution around the sun.
So what causes the seasons? The Earth’s tilt causes the seasons! http://www.y outube.com /watch?v=p 0wk4qG2mI g
Solstice The day when the sun reaches its greatest distance north or south of the equator. Northern Hemisphere- (opposite of S. Hemi) –Summer solstice: June 21 or 22 (longest period of daylight of the year) –Winter solstice: December 21 or 22 (shortest period of daylight of the year)
The sun’s path across the sky is higher in the summer and lower in the winter http://www.newscientist.com/blogs/shortsharpscience/2011/10/about-time-beer-can-freezes-ti-1.html
Equinox When the sun is directly above the Earth’s equator. Daylight hours are nearly equal all over Earth. –Neither the N. or S. Hemisphere is tilted towards the sun. –Spring equinox-March 20 or 21 –Fall equinox-September 22 or 23 http:// news.national geographic.com/news/ 2009/09/090922- autumnal-equinox- 2009-fall-equinox.html
Northern Hemisphere Solstice and Equinox positions Seasons are opposite for the Southern Hemisphere