The Earth spins around an axis. The Earth takes (a bit more than) one day to go around once. This axis is pointing off somewhere in space. This axis (mostly) doesn’t move. At the same time, the Earth is orbiting the Sun. It takes (a bit more than) one year to go around once. The plane of the Earth’s orbit (mostly) doesn’t move. The spin axis of the Earth’s daily rotation is not perpendicular to the plane of the Earth’s orbit.It is tilted (approximately) 23.4 degrees. The angle of tilt (mostly) doesn’t change.
Earth does not spin perpendicular to the plane it is tilted, the reason earth is tilted is because it got hit by meteoroids and other stuff when the planets first formed.
Also it takes about 24 hours for one period of earth rotate. From that we get sunlight, half of our days.
We can calculate easily how fast earth is spinning by 2πR(radius of the ...view middle of the document...
"the day 40 years ago was longer than today by about 8 millionths of a second." More significant, he said, is the fact that the sporadic spacing of water reservoirs has changed the Earth's axis. Since 1940, water impoundment has pushed the axis of rotation about 60 centimeters away from the North Pole toward western Canada, said by Chao
Also it effect on the direction of the wind and movement of the clouds.
"Stars and planets form as a result of the gravitational collapse of accreting material. Any net translational motion of that initial material is accelerated as its radius of rotation decreases. Once an initial spin was established for the Earth, the same conservation principle says that its angular momentum will continue unless it can be transferred to another object. With no significant frictional forces to allow that to happen, the Earth can continue to spin indefinitely without any further prodding" said by Paul Walorski.
If earth stop there would be no season and no day and light. It would change to half of earth side desert and other side for the ice desert. There will be sunlight 24 hours on half of the side and night for half of other side.
If it happens like that there would no life would form; it would be a dead planet.
Serway Jewett "Physics for scientists and Engineers" 6th Ed.
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"Motion of the earth" http://www.tigerwave.com/spaceflight/EarthMotion.htm (24/11/2004)
"What's The Deal With The Tilt of The Earth" http://www.weathersavvy.com/Seasons2.html (24/11/2004)
Nasa Gov "Space science gallery" 2002 http://www.gsfc.nasa.gov/gsfc/newsroom/tv%20page/G02-023_space.htm (24/11/2004)
U.S. Water News Online "Construction of water reservoirs alters Earth's spin" March 1996 http://www.uswaternews.com/archives/arcglobal/6earth.html (24/11/2004)
Physic Link "Physic Link.Com" http://www.physlink.com/Education/AskExperts/ae201.cfm (24/11/2004)
National online "Earth 2" http://faculty.ucc.edu/egh-damerow/earth_2.htm (24/11/2004)