Earth and Moon Notes

1. Earth and Moon Notes

2. Rotation vs. Revolution • Rotation- spinning of earth on its own axis: • 24 hours = 1 day = 1 rotation • What causes night and day.

3. Revolution • Earth’s movement around the sun is a revolution. • One complete revolution = 1 year = 365.25 days.

4. The Seasons • Equator does not experiences difference in temp. and daylight in seasons b/c it receives the most direct sunlight. • Poles = extreme temp. differences. • Winter in Alaska = 2 hrs of daylight, in summer = sun never sets. • Seasons caused by the tilt of the Earths axis – tilted 23.5 degrees

5. June in Northern Hemisphere • Axis tilted towards the sun. • Summer – longer days, warmer temperatures • NOT caused by the distance from the sun, caused by more direct sunlight.

6. December in the Northern Hemisphere • Earth’s axis pointed away from the sun. • Winter = shorter days, colder temperatures, due to less direct sunlight and fewer hours of daylight.

7. June and December Solstice • June 21st = longest day of the year, considered first day of summer. • December 21st, shortest day of the year, considered first day of winter.

8. Equinox in March and September • Equinox is halfway between each solstice. • Equinox – neither hemisphere is pointed towards or away from the sun. • Equinox = equal night = 12 hrs day/12 hrs. night • March 21st – spring equinox, September 22nd – fall equinox.

9. Gravity and Motion • Recall that gravity is a force that attracts all objects towards each other. • Universal Law of Gravitation – every object in the universe attracts every other object.

10. Gravity and Motion • The strength of gravity is dependent on 2 things: the mass of the objects, and the distance between them. • If mass increases, gravity increases. • If distance increases, gravity decreases. • Weight – the force of gravity on an objects mass.

11. Inertia and Orbital Motion • Two factors keep Earth and the moon in their orbits – inertia and gravity. • Earth’s gravity pulls the moon toward it, preventing the moon from traveling in a straight line. The moon keeps moving ahead because of it’s inertia.

12. Inertia – the tendency of an object to resist a change in motion.

13. The Moon • The positions of the moon, Earth, and sun causes the phases of the moon, eclipses, and tides.

14. Rotation vs. Revolution • A “day” and a “year” are the same length on the moon. • One day = 1 rotation of the moon= 29.5 earth days

15. Dark Side of the Moon • The ‘dark side’ is the side we never see. • The moons whole set of phases occurs in 29.5 days

16. Phases of the moon • Depends on how much of the sunlit side of the moon faces the Earth

17. Eclipses occur when…. • The moons shadow hits Earth or Earth’s shadow hits the moon • There are ‘solar’ eclipses, and ‘lunar’ eclipses

18. Solar Eclipse • Occurs when the moons shadow falls on the Earth. • Sun, moon and Earth aligned

19. Lunar eclipses occur when the earth’s shadow falls on the moon

20. View of Solar Eclipse

21. Tides • The tides are caused mainly by differences in how much the moon’s gravity pulls on different parts of the Earth

22. High vs. Low Tide • Tides occur in a daily cycle. • As the Earth rotates on its axis, any point on Earth goes through a cycle of high tide, low tide, high tide, low tide. • The moon’s gravity causes high tide on the side closest to the moon, • Low tide occurs when that part of the Earth is at a 90 degree angle to the moon. • Tide Schedule