Vocabulary List
1) Geocentric- earth-centered
2) Heliocentric-sun-centered
3) Retrograde Motion-apparent periodic reversal motion of some planets as viewed from the earth
4) Ellipse-oval whose shape is determined by two points within the figure
5) Focus-one of two points within an ellipse that determines the shape of the figure
6) Inertia-tendency of a moving body to remain in motion or a stationary body to remain at rest until an outside force acts on it
7) Astronomical Unit-average distance between the earth and the sun, approximately 149.5 million km
8) Epicycles- small circular motion of the planets within their orbits proposed as an explanation for Retrograde Motion
9) Orbit Period-time required for a planet to make one revolution around the sun
2) Heliocentric-sun-centered
3) Retrograde Motion-apparent periodic reversal motion of some planets as viewed from the earth
4) Ellipse-oval whose shape is determined by two points within the figure
5) Focus-one of two points within an ellipse that determines the shape of the figure
6) Inertia-tendency of a moving body to remain in motion or a stationary body to remain at rest until an outside force acts on it
7) Astronomical Unit-average distance between the earth and the sun, approximately 149.5 million km
8) Epicycles- small circular motion of the planets within their orbits proposed as an explanation for Retrograde Motion
9) Orbit Period-time required for a planet to make one revolution around the sun