| Question | Answer |
| Showed that planets and moons stay in orbit due to gravity | Sir Isaac Newton |
| was one of the first perons to use a telescope to observe celestial bodies | Galileo Gallilei |
| developed a theory of a sun-centered universe | Copernicus |
| stated that planets move in elliptical orbits around the sun | Johannes Kepler |
| used a mural quadrant to measure the positions of planets and stars | Tycho Brahe |
| developed a theory of an Earth-centered universe in 140 CE | Ptolemy |
| proved the existenc ot galaxies other than the Milky Way | Edwin Hubble |
| the time required for the Earth to orbit once around the sun | Year |
| roughly the amound of time required for the moon to orbit once around the Earth | Month |
| the time required for the earth to rotate once on its axis | Day |
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