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The Earth in Space
Solar System
In the Milky Way Galaxy
What does the sun provide for earth? Light and solar energy
100,000 light years wide
1 ly = 5,878,625,373,183 miles
The Earth
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:6,600,000,000,000,000,000,000 tons or1,320,000,000,000,000,000,000,000 lbs
• Closest star = 4.22 ly
• Voyager 1 = 14 light hours away; took 32 years (1977) to get there - .0017 ly away - 38,400 mph
Sextillion
Earth’s Rotation
The Earth rotates on an axisOne 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?
Earth’s Revolution
The Earth revolves around the sun in an oval shaped orbit Closest to sun = in December!
1 revolution = 365¼ days = 1 yearWe 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
SeasonsSolstice 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)
N Pole
N Pole
Darkness
Dayligh
t
12
24
24
18/6
12/12
6/18
12/1212/12
AtlantAtlantaa
Solar Lines on EarthArctic Circle
Tropic of Cancer
Equator
Tropic of Capricorn
Antarctic Circle
66½º N
23½º N
23½º S
66½º S
0º
Not to scale!
Direct Solar Energy
24 hrs.
darkness
SummeSummerr
WinteWinterr
24 hrs. daylight
Darkness
12
24
24
24/0
12/12
0/24
12/1212/12
At the North At the North PolePole
Dayligh
t
Svalbard, Norway: Daytime from April 19 to August 23!!!
Extremes: 20 hours at the Circles, 186 days at the poles
3 hr time period
66½º N
23½º N
23½º S
66½º S
0º
SprinSpringg
oror
FallFall
66½º N
23½º N
23½º S
66½º S
0º
WinterWinter
SummeSummerr
Not to scale!
Direct Solar Energy
24 hr.
darkness
24 hrs. daylight
Not to scale!