Question

1. the geocentric model of the solar system was proposed by the astronomers of ancient __________. 2. the planetary system of ptolemy had the planets moving in circular orbits around ________. 3. the ________ motion of planets is when they appear to move eastward among the stars, then stop and reverse direction. 4. the danish astronomer ________ made precise measurements of the locations of bodies in the solar system, especially mars. 5. the average distance between earth and the sun is about ________ million km, or one ________ unit. 6. the mass of an object is a measure of the total amount of ________ it contains. 7. the earth movement that causes night and day is called ________. 8. earth is closest to the sun on about january 3 at ________ and is farthest from the sun on about july 4 at ________. 9. because of ________, the north star will no longer be polaris in several thousand years. 10. the moon is closest to earth at ________ and farthest away at __________.

Explanation:

1. The geocentric model was a common view in ancient Greece.
2. Ptolemy's model had Earth at the center with planets orbiting it.
3. Retrograde motion is the apparent backward - motion of planets.
4. Tycho Brahe made accurate astronomical measurements.
5. The average Earth - Sun distance is about 150 million km or 1 astronomical unit.
6. Mass measures the amount of matter in an object.
7. Earth's rotation causes night and day.
8. Earth's closest point to the Sun is perihelion (around January 3) and farthest is aphelion (around July 4).
9. Precession causes the change in the position of the North Star over time.
10. The moon's closest point to Earth is perigee and farthest is apogee.

Answer:

1. Greece
2. Earth
3. Retrograde
4. Tycho Brahe
5. 150; astronomical
6. matter
7. rotation
8. perihelion; aphelion
9. precession
10. perigee; apogee