THE EARTH IN SPACE

Sphere

Round three – dimensional object Surface same distance from its center

point Earth

PROOF:○ Aristotle saw curved shadow of earth on moon○ Columbus – watched ship sail over horizon

and tops of ships sank over horizon last○ Today – pictures from satellites

Oblate Spheroid Flattened at poles Bulging at equator Why:

Speed of rotation causes the poles to pull in and the mass at the equator to bulge slightly out

Earth’s rotation Rotation – spinning

on an axis Axis – imaginary

pole through earthTilted 23 ½ ⁰

One spin= 1 dayActual 23hr 56 minRotation – clockwise

○ Why sun rises in the east and sets in the west

Earth’s magnetic field Created by;

RotationMovement of Fe Ni

coreMolten mantle

Protects us from solar radiation

Magnetic axis is not the same as the geographical axis

Solar ejections and earth’s magnetic field

Aurora borialis

Aurora australis

Earth’s revolution Revolution –

movement of earth in its orbit around the sun

365 ¼ days Orbit – ellipse

Elongated closed curve

Two foci pointsSun is one of the fociAverage 93 million

miles

2009 February 18

Perihelion – pt in orbit closest to sun

- Jan 2 -92 million mi Aphelion – pt in orbit

furthest from the sun - July 2 - 95 million mi

Cause of earth’s seasons Tilt of axis Position in orbit Curvature of earth’s

surface – amt of solar radiation

SummerTilt toward sunDirect rays on Tropic

of CancerMore concentration of

solar radiationSummer solstice –

June21 or 22Longest day of the

year

WinterTilt away from sun Direct rays on Tropic

of Capricorn less concentration of

solar radiationWinter solstice Dec

21 or 22Shortest day of the

year

Spring and Fall Direct rays fall on

the equator No tilt toward or

away from sun Equinox – equal

nights Fall – Sept 22 or 23 Spring – March 20

or 21