Chapter 22.1 Early Astronomy

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Across
  1. 4. He designed and built instruments to measure the locations of the heavenly bodies. His observations, especially of Mars, were far more precise than any made previously.
  2. 6. Gravitational force _________ as mass of an object increases.
  3. 7. Orbits of the planets are __________.
  4. 10. Concluded that Earth is a planet. He proposed a model of the solar system with the sun at the center.
  5. 11. An ellipse is an _______ shaped path.
  6. 12. The apparent westward motion of the planets with respect to the stars.
  7. 15. The three laws of planetary motion
Down
  1. 1. The average distance between Earth and the sun; it is about 150 million kilometers.
  2. 2. Developed his own telescope and made important discoveries.
  3. 3. Ancient
  4. 5. Earth and the other planets orbit the sun.
  5. 8. The science that studies the universe. It includes the observation and interpretation of celestial bodies and phenomena.
  6. 9. Law of universal gravitation
  7. 13. Model in which the moon, sun, and the known planets—Mercury, Venus, Mars, and Jupiter—orbit Earth.
  8. 14. Gravitational force _________ as distance increases between two objects.