Modern Astronomy

4. Earth centered universe
6. a large, level basalt plain on the surface of the moon, appearing dark by contrast with highland areas.
9. a fissure or narrow channel on the moon's surface.
11. a unit of measurement equal to 149.6 million kilometers, the mean distance from the center of the earth to the center of the sun
12. a regular oval path
13. Sun centered universe
15. an eclipse in which the sun is obscured by the moon.
20. the action of rotating around an axis or center

1. a large, bowl-shaped hole in the ground or on the surface of a planet or the moon
2. an eclipse in which the moon appears darkened as it passes into the earth's shadow.
3. the point in the orbit of a planet, asteroid, or comet at which it is closest to the sun
5. each of the lines in which light (and heat) may seem to stream from the sun or any luminous body, or pass through a small opening.
7. Study of the universe
8. refers to the backwards motion of planets
10. is composed in part of rock and mineral fragments that were broken apart from underlying bedrock by the impact of meteorites
14. the point in the orbit of the moon or a satellite at which it is nearest to the earth.
16. a single orbit of one object around another or about an axis or center
17. the slow movement of the axis of a spinning body around another axis due to a torque (such as gravitational influence) acting to change the direction of the first axis
18. the curved path of a celestial object or spacecraft around a star, planet, or moon, especially a periodic elliptical revolution
19. the point in the orbit of the moon or a satellite at which it is furthest from the earth.
21. the point in the orbit of a planet, asteroid, or comet at which it is furthest from the sun.