CHAPTER 2

Which was a contribution to astronomy made by Copernicus? A. The planets move around the Sun in elliptical orbits. B. He discovered the Sun was not at the center of the Milky Way. C. He laid out the order and relative motion of the known solar system. D. His telescope revealed the four moons of Jupiter, a model solar system. E. His theory of gravity accounted for the variable speeds of the planets.

Which of these was NOT a part of the original Copernican model? A. The Sun lies at the center of the solar system. B. The Earth rotates on its axis once a day. C. Venus can go all the way around the Sun. D. Mercury speeds up at perihelion, and slows down at aphelion. E. Mercury must move faster in its orbit than any other planet.

Which of the statements below is part of both the Ptolemaic and Copernican models? A. The Moon orbits the Earth once a month. B. Venus' epicycle must always lie between us and the Sun. C. The Sun lies in the center of the Cosmos. D. Epicycles are needed to explain retrograde motion of the planets. E. The Earth orbits the Sun once a year.

A fatal flaw with Ptolemy's model is its inability to predict the observed phases of: A. Mercury and Venus. B. the Moon in its monthly cycle. C. Jupiter and Saturn. D. the Sun during an eclipse. E. Mars and Jupiter.

It took two centuries for the Copernican model to replace the Ptolemaic model because: A. there was no scientific evidence to support either model until Galileo made his observations. B. in Copernicus' time, there were no telescopes. C. the Ptolemaic model was simpler and more aesthetically pleasing. D. the Church wouldn't let anyone talk about Copernicus' model for 200 years. E. the Copernican model required complicated new terms to explain it correctly.

The most accurate Greek attempt to explain planetary motion was the model of: A. Erastothenes. B. Hipparchus. C. Aristotle. D. Ptolemy. E. Pythagoras.

Kepler's first law worked, where Copernicus' original heliocentric model failed, because Kepler described the orbits as: A. much larger than Copernicus had envisioned. B. elliptical, not circular. C. around the Sun, not the Earth. D. being on equants instead of epicycles. E. complex, with epicycles to account for retrograde motions.

Tycho Brahe's contribution to Kepler's Laws of Planetary Motion was: A. his observations of Jupiter's moons. B. his detailed and accurate observations of the planet's position. C. a precise lunar calendar. D. the correct explanation of lunar phases. E. a mathematical explanation of epicycles.

The most famous prehistoric astronomical observatory is: A. the Sphinx. B. Mount Rushmore. C. Carcacol. D. Big Horn stone circle. E. Stonehenge.

A circular orbit would have an eccentricity of: Select one: A. exactly 1.0. B. between 0.5 and 1. C. between 0 and 0.5. D. infinity. E. 0.

Upon which point do Copernicus and Kepler disagree? A. Retrograde motion occurs when one planet overtakes another. B. The orbits of the planets are ellipses, with one focus at the Sun. C. The Moon orbits the Earth. D. Venus will appear as a crescent when she retrogrades between us and the Sun. E. The Earth orbits the Sun.

What contribution to astronomy was made by Tycho Brahe? A. The Earth is not the center of the Universe. B. His telescope revealed the moons of Jupiter before Galileo noted them. C. The planets' orbits around the Sun are ellipses, not circles. D. Retrograde motion must be explained by epicycles larger than those of Ptolemy. E. His observations of planetary motion with great accuracy proved circular orbits could not work.

Which concept was NOT a part of Kepler's Laws of Planetary Motion? A. A planet must move fastest in its orbit at perihelion. B. The square of the planet's period is equal to the cube of its average distance. C. Epicycles are needed to explain the varying brightness of the planets. D. All planetary orbits are ellipses.

According to Kepler's third law, the square of the planet's period in years is: A. proportional to the cube of its semimajor axis in A.U. B. equal to the fourth power of its average temperature in degrees Kelvin. C. equal to the square of its aphelion distance in A.U. D. inversely proportional to its mass in kilograms. E. equal to its perihelion distance from the Sun in A.U.

What does Kepler's third law imply about planetary motion? A. Planets further from the Sun orbit at a faster speed than planets closer to the Sun. B. Planets further from the Sun orbit at a slower speed than planets closer to the Sun. C. Planets closer to the Sun orbit at a slower speed than planets further from the Sun. D. All planets orbit the Sun at the same speed. E. This law implies nothing about a planet's motion.

The Ptolemaic model probably persisted for all these reasons EXCEPT: A. it had the authority of Aristotle behind it. B. it accounted well for Galileo's observations of the phase cycle of Venus. C. it was consistent with the doctrines of the Catholic Church. D. it used perfect circles, which appealed to geometry. E. it explain why stellar parallax was not observed by the Greeks.

A planet whose distance from the Sun is 3 A.U. would have an orbital period of how many Earth-years? Select one: A. √3 B. 3 C. 81 D. 9 E. √27

The place in a planet's orbit that is closest to the Sun is called: A. perihelion. B. crossing the ecliptic. C. vernal equinox. D. aphelion. E. None of these; a planet's distance from the Sun never changes.

The force of gravity varies with the: A. product of the two masses. B. inverse of the distance separating the two bodies. C. inverse square of the distance separating the two bodies. D. Both A and B are correct. E. Both A and C are correct.

The Law of Universal Gravitation was developed by:

The force of gravity between two objects: A. increases with the masses of the bodies, but decreases with the square of the distances between them. B. increases with the square of their masses, but decreases with the cube of their periods of orbit about the Sun. C. depends on the temperature, density, and size of the bodies. D. increases with the masses of the bodies, but decreases with their separations. E. depends on the density, not the mass of the bodies.

According to Newton's Law of Universal Gravitation, if the Moon were three times further from Earth, the force by Earth on the Moon would: A. increase by a factor of 3. B. stay the same. C. decrease by a factor of 9. D. decrease by a factor of 3. E. increase by a factor of 9.

How much stronger is the gravitational pull of the Sun on Earth, at 1 AU, than it is on Saturn at 10 AU? A. 25X B. 100X C. 250X D. 5X E. 10X

Which of these was a contribution of Newton to astronomy? A. His differential calculus lets us calculate planetary motions more accurately. B. The Sun's gravity is greatest on a planet at perihelion, so the planet must speed up. C. Artificial satellites could be put into orbit about the Earth. D. The Moon pulls as strongly on us as we do on it. E. All of these were due to Newton's work.

Geosynchronous satellites orbit at about four Earth radii, where the Earth's gravitational pull is: A. 1 g. B. 2 g. C. 1/4 g. D. 1/2 g. E. 1/16 g.

Jupiter lies about 5 A.U. from the Sun, so at its distance: A. the Sun's gravity is five times weaker there than at one A.U. distance. B. the Sun's gravity is just as strong as it is here at Earth. C. the Sun's gravity is 25 times weaker than its pull on the Earth. D. the Sun's gravity is so weak that ultimately Jupiter will escape the solar system. E. the Sun's gravity must be five times stronger to hold massive Jupiter in orbit.

How does Newton's Universal Law of Gravitation explain Kepler's laws? A. Universal gravitation implies that the planets will sweep out equal areas in equal times (Kepler's second law). B. Universal gravitation implies that the orbits of the planets must be elliptical (Kepler's first law). C. Universal gravitation implies that the planets further from the Sun will move more slowly than the planets closer to the Sun (Kepler's third law). D. Universal gravitation implies that when a planet is closer to the Sun in its orbit, it will move faster than when it is farther from the Sun (Kepler's second law). E. Both C and D are correct.

Given that the planet orbiting the nearby star 51 Pegasi is about 20X larger than the Earth, but 400X more massive, on that world you would weigh: A. half as much as you do here. B. 20X more that you do here. C. 400X more than you do here. D. the same as you do here. E. twice as much as you do here.

If the distance between two asteroids is doubled, the gravitational force they exert on each other will: A. be four times greater. B. be half as great. C. also be doubled. D. be 1/16 as great. E. be one fourth as great.

According to Copernicus, retrograde motion for Venus must occur around: A. inferior conjunction, when it passes between us and the Sun. B. greatest elongation, when the planet is farthest from the Sun. C. quadrature, when the planet is 90 degrees away from the Sun. D. superior conjunction, when the planet is on the far side of the Sun. E. opposition, when the planet lies opposite the Sun in the sky.

Combining Newton's and Kepler's laws, we can weigh the Sun, provided we know: A. the exact timings of the transits of Venus and its diameter. B. its density as found by spectroscopy. C. its temperature as found by Wien's Law. D. the size of the A.U. and exact length of the year. E. the Earth's mass and circumference.

The Ptolemaic model of the universe: A. always kept Mars and Mercury between the Earth and Sun. B. explained and predicted the motions of the planets with deferents and epicycles. C. describes the orbits of the planets as being ellipses, not circles. D. could not account for the stellar parallax observed by Hipparchus. E. is the basis of our modern cosmology.

Kepler's second law implies what about planetary motion? A. A planet moves faster when it is closer to the Sun. B. A planet moves faster when it is farther from the Sun. C. A planet moves slower when it is closer to the Sun. D. A planet moves at a constant speed during its orbit of the Sun. E. This law implies nothing about a planet's motion.

Scientists today do not accept the Ptolemaic model because: A. it was too complicated, compared to Copernicus' heliocentric model. B. it had no explanation for retrograde motion. C. it has been shown that Ptolemy faked his data. D. the work of Tycho and Kepler showed the heliocentric model was more accurate. E. it is ancient history. Check

On which of these assumptions do Ptolemy and Copernicus agree? A. All orbits must be perfect circles. B. The Sun was bigger than the Earth. C. The Sun must orbit us, but the planets do orbit the Sun. D. The Earth must be the center of all motion in the Cosmos. E. Venus must always stay between us and the Sun. Check

The heliocentric model was actually first proposed by: A. Aristarchus. B. Aristotle. C. Archimedes. D. Alexander the Great. E. Hipparchus. Check

According to Copernicus, the retrograde motion for Mars must occur: A. at inferior conjunction, when Mars laps the Earth and passes between us and the Sun. B. at greatest elongation, when Mars can get up to 47 degrees from the Sun. C. at superior conjunction, when Mars lies on the far side of the Sun. D. at quadrature, when Mars lies exactly 90 degrees east or west of the Sun. E. at opposition, when the Earth overtakes Mars and passes between Mars and the Sun.

Kepler based his theories on the precise planetary observations of Tycho Brahe.

The eccentricity of a perfectly circular orbit is 1.

Kepler determined the shape of each planet's orbit by triangulation from different points on Earth's orbit, using observations made at many different times of the year.

Mercury, with a higher eccentricity orbit, should change its orbital speed more than do Venus or Earth.

Transits of Venus were critical in early determinations of the A.U.

Newton's Laws completely replaced the incorrect work of Kepler.

Newton's modification of Kepler's Third Law lets us measure the mass of the Sun.

Newton's Law of Gravity would explain why Saturn, so far from the Sun, moves so slowly across the sky.

If the mass of a body were doubled, its gravity would become 4 times stronger.

When a planet retrogrades, it appears to move westward for weeks at a time.

According to Newton's second law, if you double the force acting on a body, the acceleration will double.

Like the Sun and the Moon, the planets appear to move from west to east from one day to the next.

Like the Sun and the Moon, the stars appear to move from west to east from one day to the next.

As originally stated, the Copernican model did no better job of predicting planetary behavior than did the Ptolemaic one.

Galileo's observations of the entire phase cycle of Venus proved that Ptolemy's epicycles could not be correct in keeping Venus between us and the Sun.

Kepler found the orbits of planets are ellipses, not circles.

The orbits of most of the planets in our solar system have eccentricities close to zero.