Sun, Earth, Moon System

The Earth Spherical Shaped… …with a slight bulge at the equator and slightly flattened poles Humans first believed the Earth was flat Aristotle first suspected that Earth was a sphere based on observations made during an eclipse Sailors also thought Earth was spherical based on observations at sea of other boats and of the stars "Nasa blue marble" by NASA/ GSFC/ NOAA/ USGS - http://antwrp.gsfc.nasa.gov/apod/image/0304/bluemarble2k_big.jpg. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Nasa_blue_marble.jpg#mediaviewer/File:Nasa_blue_marble.jpg

The Earth Rotates Rotation: Earth rotates on its axis, an imaginary line on which it spins Causes night and day Rotates every 23 hrs. 56 min. 4 sec. (sidereal day) A solar day is 24 hours

Magnetic Poles Thought to be created by a combination of the Earth’s core and rotation The magnetic north pole is different from the geographical north pole (where the earth rotates) The magnetic north pole is 11.5° off from the geographical north pole

Seasons The Earth’s yearly orbit around the sun: Revolution Earth’s orbit is NOT a circle, it is an ellipse (elongated, closed curve) The Earth is closest to the sun on January 4 and furthest from the sun on July 4. The tilt of the Earth’s axis, in combination with its orbit, causes the seasons When the Earth is tilted toward the sun, it is summer When the Earth is tilted away from the sun, it is winter It is the opposite season in the southern hemisphere because when we’re pointed toward the sun, they are pointed away, and vice versa

Seasons

Solstices The solstices occur when the Earth is pointed completely toward or away from the sun The summer solstice (around June 21) is the longest day in the northern hemisphere. This is the day that the Earth is pointed most toward the sun. The sun travels directly over the Tropic of Cancer, located at 23.5° north latitude. The winter solstice (around December 21) is the shortest day in the northern hemisphere. This is the day that the Earth is pointed most away from the sun. The sun travels directly over the Tropic of Capricorn, located at 23.5° south latitude.

Summer Solstice "Earth-lighting-summer-solstice EN". Licensed under CC BY-SA 2.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Earth-lighting-summer-solstice_EN.png#mediaviewer/File:Earth-lighting-summer-solstice_EN.png

Winter Solstice "Earth-lighting-winter-solstice EN". Licensed under CC BY-SA 2.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Earth-lighting-winter-solstice_EN.png#mediaviewer/File:Earth-lighting-winter-solstice_EN.png

Equinox The spring (around March 21) and fall (around September 21) equinox occurs when the sun travels directly above the Earth’s equator. On these days, the equator receives exactly 12 hours of daylight and 12 hours of darkness. The solstices and equinoxes begin each season.

Equinox "Earth-lighting-equinox EN". Licensed under CC BY-SA 2.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Earth-lighting-equinox_EN.png#mediaviewer/File:Earth-lighting-equinox_EN.png