Heliocentric
We orbit the sun
Geocentric
The sun orbits us
Aristotle
Geocentric
It doesn’t explain retrograde motion of Mars
Ptolemy
Copernicus
Heliocentric model
Galileo
- created compound telescope and looked up
Brahe
Kepler
Newton
You know him
Gravity
Distance between planets farther out
Gets way bigger
Gravity is weaker
Kepler’s 1st law
Law of ellipses
-elliptical orbits
(See diagram)
Kepler’s second
Law of equal areas
Kepler’s third
Law of periods -k•r^3 = p^2 k = constant p = period r = radius (mean distance to sun)
Orbital eccentricity
How much an orbit differs from a circle
Apogee
Point an object orbiting something is at its farthest point
Perigee
Point where an object orbiting something is closest to it
How big is the moon
27% earth’s size (about 1/4)
How far away is the moon
384 000km
Why do we always see the same face of the moon
Rotation and Revolution is the same length
Why do we have phases of the moon
Earth blocks the sun
Regolith (moon)
Dusty blanket of meteorites that landed on moon
Highlands (moon)
Mountains (rings around craters)
1000s of feet tall
Lowlands (moon)
Craters + Maria/seas (lava filled basins, hardened
Tides
- bay of Fundy has huge tides (55 feet)