1. Earth’s relative motion
Motion in the Universe
Earth’s relative motion

2. Daily Review
Kepler’s 1st law states that planetary orbits are _________________ shapes?
Kepler’s 2nd law states that 2 equal intervals of time an imaginary line connecting a planet and the sun will sweep an equal amount of ___________?
Kepler’s third law states that the innermost planets orbit ______________________ than the outermost planets.
Rotation is the earth spinning on it’s _________________.
One trip around the ______________ is called a revolution.

3. Essential Standard
EEn.1.1 Explain the Earth’s role as a body in space.
EEn Explain the Earth’s motion through space, including precession, nutation, the barycenter, and its path about the galaxy.
Explain relative motion of the Earth in the solar system, the solar system in the galaxy, and the galaxy in the universe—including the expanding nature of the universe; Orbital motion (Earth around the Sun- once/year, seasons depend upon an approximate 23.5 degree tilt); Rotation around our axis (day/night,)

4. Essential Question
How do galaxies and planets move in the universe?

5. Motions of Earth Rotation Revolution Precession
Turning or spinning of a body on its axis
Revolution
Motion of a body along a path around some point in space
Precession
Slight movement of Earth’s axis
26,000 years

6. Rotation Results in day and night 24 hours 1,667 km/hr (1,036 mi/hr)
Prove Earth is Rotating? OK!
Rotation
Results in day and night
24 hours
1,667 km/hr (1,036 mi/hr)

7. revolution Earth moves around the sun in an elliptical orbit
Speeds around 107,000 km/hr (66,500 mph)
Average distance is 150 million kilometers
Perihelion is the point where earth is closest to the sun
Aphelion is the point where earth is farthest from the sun

8. Earth’s axis and Seasons
Earth's Seasons
Earth’s axis and Seasons
Earth’s axis is tilted about 23.5º on its axis
This tilt brings the sun 23.5º south of the equator on the winter solstace
This tilt bring the sun 23.5º north of the equator on the summer solstace

9. Precession and polar shift
Direction which earth’s axis points changes very slowly over time without a change in tilt
Takes about 26,000 years to complete one period
Currently the axis points toward Polaris making it the North Star, in 14,000 years Vega will be the North Star.

10. Earth's not orbiting the sun?!
Earth-Sun Motion
Earth accompanies the sun as the entire solar system speeds toward a distant star, Vega
The sun revolves around the galaxy
Over 230 million years
At 250 km/sec
Now Earth is approaching our nearest galactic neighbor, Andromeda

11. Motions of the Earth-moon system
Earth’s only natural satellite
Orbit’s Earth in one month
When viewed from the North Pole, the orbit is counterclockwise
Average distance is 384,401 kilometers
Point close to the Earth is Perigee
Point farthest from Earth is Apogee

12. Phases of the Moon Phases are the amount of moon that appears lit
supermoon
Phases are the amount of moon that appears lit
Half of the moon is always illuminated
Phases result from the motion of the moon and the sunlight reflected from its surface
Every 29.5 days

13. Tides (pg 458) Daily elevation changes of the ocean surface. Rhythmic
tidal mystery
bay of fundy
Daily elevation changes of the ocean surface.
Rhythmic
Caused by gravitational pull of the moon
Atmosphere and ocean are fluids and free to move due to this force.
The sun is further away resulting in less tug

14. Nutation The moon pulls on Earth and Earth pulls on the moon
gyroscope demo
The moon pulls on Earth and Earth pulls on the moon
This pull causes the Earth to wobble on its axis by about ½ a degree.
Changing in the tilt of the Earth’s axis
How does this differ from precession?

15. Barycenter
barycenter animation
barycenter
Point between 2 or more objects where they balance each other
Point where 2 celestial bodies orbit each other

16. More Barycenter
When a moon orbits a planet or a planet orbits a star, both are actually orbiting a point outside the center of the larger body.
The moon and earth actually orbit a spot about 1,710 km below earth’s surface.

17. Earth’s shape

18. Earth’s shape Not a true sphere
Called an oblate spheroid, geoid, or ellipsoid

19. Circumference and diameter
Not equal throughout
Poles are squished making a bulge at the equator
Diameter and circumference are greater at the equator than at the poles.

20. Why? Earth’s rotation and gravity
Gravity pulls on the mass causing it to contract
Rotation causes earth to flatten due to centrifugal force
The force that causes objects to move outward, away from the center of gravity
We call this the coriolis effect
coriolis effect

21. Local Topography Topography- study of surface shape and feature
On a global scale this difference is very small
Mt. Everest is about 8,850 m above sea level
The Mariana Trench is about 10,900 m below sea level
The difference is only about 19,000 m or 12 mi