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Transcript
The Earth in Space Solar System In the Milky Way Galaxy 100,000 light years wide 1 ly = 5,878,625,373,183 miles What does the sun provide for earth? Light and solar energy • Closest star = 4.22 ly The Earth • Voyager 1 = 14 light hours away; took 32 years (1977) to get there - .0017 ly away - 38,400 mph It is not a perfect sphere It’s fatter at the equator and the poles are squished: difference of 26.58 miles We 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: Sextillion 6,600,000,000,000,000,000,000 tons or 1,320,000,000,000,000,000,000,000 lbs Earth’s Rotation The Earth rotates on an axis One rotation = 23 hrs., 56 min., 4 sec. = 1 day Rotates eastward We rotate at more than 1000 mph! Why don’t we feel a 1000 mph wind? What would happen if we didn’t rotate? Earth’s Revolution The Earth revolves around the sun in an oval shaped orbit Closest to sun = in December! 1 revolution = 365¼ days = 1 year We add 1 day in February every 4 years = Leap Year Next one is 2012 We move at 66,700 mph around the sun! 147,000,000 km 152,000,000 km Not to scale! Earth’s Tilt The Earth is tilted 23½º off parallel from the sun The poles always point to the same spot in space North pole points to the North Star This tilt causes the seasons Seasons N Pole N Pole Solstice Longest / shortest day of the year When one pole is ‘pointing’ towards the sun Summer (June) and winter (Dec) Equinox Equal length day and night When both poles are equidistant from sun Spring/Vernal (March) and fall/Autumnal (Sept) 24 Atlanta 18/6 12/12 12/12 12 12/12 24 6/18 Solar Lines on Earth Arctic Circle Tropic of Cancer Equator Tropic of Capricorn Antarctic Circle 24 hrs. daylight Summer Direct Solar Energy Winter Not to scale! 24/0 12/12 12/12 12/12 24 12 24 At the North Pole 0/24 Svalbard, Norway: Daytime from April 19 to August 23!!! 3 hr time period Extremes: 20 hours at the Circles, 186 days at the poles Spring or Fall Winter Direct Solar Energy Summer 24 hrs. daylight Not to scale! Not to scale!