2Solar System In the Milky Way Galaxy What does the sun provide for earth?Light and solar energy100,000 light years wide1 ly = 5,878,625,373,183 miles
3The Earth It is not a perfect sphere Closest star = 4.22 lyVoyager 1 = 14 light hours away; took 32 years (1977) to get there ly away ,400 mphThe EarthIt is not a perfect sphereIt’s fatter at the equator and the poles are squished: difference of milesWe are about 93,000,000 miles from the sun (it takes 8 minutes for sunlight to reach us!)The Earth weighs 6,600 billion billion tons:6,600,000,000,000,000,000,000 tons or1,320,000,000,000,000,000,000,000 lbsSextillion
4Earth’s Rotation The Earth rotates on an axis One rotation = 23 hrs., 56 min., 4 sec. = 1 dayRotates eastwardWe rotate at more than 1000 mph!Why don’t we feel a 1000 mph wind?What would happen if we didn’t rotate?
5Earth’s RevolutionThe Earth revolves around the sun in an oval shaped orbitClosest to sun = in December!1 revolution = 365¼ days = 1 yearWe add 1 day in February every 4 years= Leap YearNext one is 2012We move at 66,700 mph around the sun!
7Earth’s Tilt The Earth is tilted 23½º off parallel from the sun The poles always point to the same spot in spaceNorth pole points to the North StarThis tilt causes the seasons
8Seasons Solstice Equinox Longest / shortest day of the year N PoleSolsticeLongest / shortest day of the yearWhen one pole is ‘pointing’ towards the sunSummer (June) and winter (Dec)EquinoxEqual length day and nightWhen both poles are equidistant from sunSpring/Vernal (March) and fall/Autumnal (Sept)