8) Suppose the planet Uranus were much brighter in the sky, so that it was as ea

Question

8) Suppose the planet Uranus were much brighter in the sky, so that it was as easily visible to the naked eye as Jupiter or Saturn. Which one of the following statements would most likely be true in that case? A) Its slow motion through the sky would have led it to be named after the Goddess of Procrastination. B) Its gravity would cause the tides to be much higher than they actually are. C) The discovery that the Earth is a planet going around the Sun would have come hundreds of years earlier. D) Its brightness would make it possible to read by starlight at night. E) A week would have eight days instead of seven.

9) How did the Ptolemaic model explain the apparent retrograde motion of the planets? A) The planets moved along small circles that moved on larger circles around the Earth. B) The planets resided on giant spheres that sometimes turned clockwise and sometimes turned counterclockwise. C) The planets sometimes stopped moving and then reversed to move backward along their circular orbits. D) The model showed that apparent retrograde motion occurs as Earth passes by another planet in its orbit of the Sun.

10) When Copernicus first created his Sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model. Why not? A) Copernicus misjudged the distances between the planets. B) Copernicus placed the planets in the wrong order going outward from the Sun. C) Copernicus placed the Sun at the center, but did not realize that the Moon orbits the Earth. D) Copernicus used perfect circles for the orbits of the planets.

11) All the following statements are true. Which one follows directly from Kepler's third law ? A) Venus orbits the Sun at a slower average speed than Mercury. B) Venus takes longer to rotate than it does to orbit the Sun. C) Venus has a thicker atmosphere than Mercury. D) Venus is more massive than Mercury.

12) Galileo challenged the idea that objects in the heavens were perfect by ________. A) proving Kepler's laws were correct B) showing that heavy objects fall at the same rate as lighter objects C) inventing the telescope D) observing sunspots on the Sun and mountains on the Moon

13) Suppose a comet orbits the Sun on a highly eccentric orbit with an average (semimajor axis) distance of 1 AU. How long does it take to complete each orbit, and how do we know? A) It depends on the eccentricity of the orbit, as described by Kepler's first law. B) Each orbit takes about 1 year, which we know from Kepler's third law. C) Each orbit should take about 2 years, because the eccentricity is so large. D) It depends on the eccentricity of the orbit, as described by Kepler's second law

Explanation / Answer

8) E) A week would have eight days instead of seven.

9) A) Each planet was assumed to move around a small circle that turns upon a larger circle. The resulting path includes a loop in which the planet goes backward as seen from the earth.

10) D) Nowadays, we use ellipses to descibe the orbits of the planets around the sun.

11) A) Venus orbits the sun at a slower average speed is a direct consequence of Kepler's third law. If any of the others were a consequence it would have to involve the physics of the formation of the solar system, so it would not be something "direct'.

12) D)  observing sunspots on the Sun and mountains on the Moon.

13) B) Each orbit takes about 1 year, which we know from Kepler's third law.

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