The Earth in Space

1. The Earth in Space

2. 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

3. 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

4. Earth’s rotation • Rotation – spinning on an axis • Axis – imaginary pole through earth • Tilted 23 ½⁰ • One spin= 1 day • Actual 23hr 56 min • Rotation – clockwise • Why sun rises in the east and sets in the west

5. Earth’s magnetic field • Created by; • Rotation • Movement of Fe Ni core • Molten mantle • Protects us from solar radiation • Magnetic axis is not the same as the geographical axis

6. Solar ejections and earth’s magnetic field

7. Aurora borialis

10. Aurora australis

13. Earth’s revolution • Revolution – movement of earth in its orbit around the sun • 365 ¼ days • Orbit – ellipse • Elongated closed curve • Two foci points • Sun is one of the foci • Average 93 million miles

14. 2009 February 18

15. 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

16. Cause of earth’s seasons • Tilt of axis • Position in orbit • Curvature of earth’s surface – amt of solar radiation

17. Summer • Tilt toward sun • Direct rays on Tropic of Cancer • More concentration of solar radiation • Summer solstice – June21 or 22 • Longest day of the year

18. Winter • Tilt away from sun • Direct rays on Tropic of Capricorn • less concentration of solar radiation • Winter solstice Dec 21 or 22 • Shortest day of the year

19. 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