Chapter 2 Terms Flashcards
Angular Size
A measure of how large an object looks to you
Ellipse
A geometric figure related to a circle but flattened into an oval shape
Epicycle
Where each planet moved on one small circle, when in turn moved onto a large one
Focus
A point within an ellipse used to generate the eliptical shape and an optical system in which light rays are brought together
Geoncentric Model
That the Earth was the center of the Solar System, not the Sun
Heliocentric Moel
That the Sun is the center of the Solar System
Kepler’s Three Laws
1st Law is that planets move in an elliptical orbit. 2nd Law is when a planet is near the sun, It orbits more rapidly. The 3rd law is the mass of the planet is = to the amount it takes it to orbit the sun.
Moon Illusion
Illusion that the moon appears larger when near the Horizon
Parallax
The shift in an object’s position caused by the observer’s motion
Retrograde Motion
The drift of a planet westward against the background stars
Semimajor Axis
Half the long dimension of an ellipse
