ASTR 1210 Quiz 3 Homework 7

Kepler's third law states that planet's orbital period, p, is related to its average (semimajor axis) orbital distance, a, according to the mathematical relationship p^2=a^3. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's third law? The Sun is located slightly off-center from the middle of each planet's orbit. Inner planets orbit the Sun at higher speed than outer planets. Earth is slightly closer to the Sun on one side of its orbit than on the other side. Pluto moves faster when it is closer to the Sun than when it is farther from the Sun. Venus orbits the Sun faster than Earth orbits the Sun. All the planets orbit the Sun in nearly the same plane.

Inner planets orbit the Sun at higher speeds than outer planets Venus orbits the Sun faster than Earth orbits the Sun From the relationship p^2=a^3, it follows that planets closer to the Sun must orbit at higher average speeds than planets farther from the Sun. For example, Venus must orbit the Sun faster than Earth because Venus is closer to the Sun

Galileo challenged the idea that objects in the heavens were perfect by _______.

observing sunspots on the Sun and mountains on the Moon

According to Kepler's second law, Pluto will be traveling fastest around the Sun when at ________.

perihelion

The mathematical form of Kepler's third law measures the period in years and the _________ _______ in astronomical units (AU).

semimajor axis

Although Kepler wrote his laws specifically to describe the orbits of the planets around the Sun, they apply more generally. Kepler's second law tells us that as an object moves around its orbit, it sweeps out equal areas in equal times. Because all the areas shown here are equal, the time it takes the comet to travel each segment must also be the same.

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You should now see the essence of Kepler's second law: Although the precise mathematical statement tells us that an object sweeps out equal areas in equal times, the key meaning lies in the idea that an object's orbital speed is faster when nearer to the Sun and slower when farther away. This idea explains why, for example, Earth moves faster in its orbit when it is near perihelion (its closest point to the Sun) in January than it does near aphelion (its farthest point from the Sun) in July.

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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?

1 year, which we know from Kepler's third law. Kepler's third law tells us that any object with the same average distance as Earth will orbit in the same time of 1 year

According to Kepler's third law (p2 = a3), how does a planet's mass affect its orbit around the Sun?

A planet's mass has no effect on its orbit around the sun. Kepler's third law makes no allowance for planetary mass, and the planet's mass has virtually no effect on its orbit of the Sun. The Sun's mass has a major effect, however.

Which of the following is not part of a good scientific theory? A scientific theory must make testable predictions that, if found to be incorrect, could lead to its own modification or demise. A scientific theory cannot be accepted until it has been proven true beyond all doubt. A scientific theory should be based on natural processes and should not invoke the supernatural or divine. A scientific theory must explain a wide variety of phenomena observed in the natural world.

A scientific theory cannot be accepted until has been proven beyond all doubt. Scientific theories can never be proven beyond all doubt; they can only be supported by a wide body of evidence.

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

A week would have eight days instead of seven. A week has seven days because seven naked-eye object appear to move among the stars: the Sun, the Moon, Mercury, Venus, Mars, Jupiter and Saturn. If Uranus had been an eight object visibly moving among the stars, a week very likely would have eight days.

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? Copernicus misjudged the distances between the planets. Copernicus used perfect circles for the orbits of the planets. Copernicus placed the Sun at the center, but did not realize that the Moon orbits the Earth. Copernicus placed the planets in the wrong order going outward from the Sun

Copernicus used perfect circles for the orbits of the planets. Because orbits are elliptical, his model did not make particularly accurate predictions

How does a 12-month lunar calendar differ from our 12 month solar calendar? It does not have seasons. It uses a 23-hour rather than a 24-hour day. It has about 11 fewer days. Its new year always occurs in February instead of on January 1.

It has about 11 fewer days. This is true because the lunar cycle averages about 29.5 days, so 12 of these cycles makes about 354 days, or 11 days short of our 365-day solar year.

Galileo observed all of the following. Which observation offered direct proof of a planet orbiting the Sun? The Milky Way is composed of many individual stars. Four moons of Jupiter. Phases of Venus. Patterns of shadow and sunlight near the dividing line between the light and dark portions of the Moon's face.

Phases of Venus. Galileo observed that Venus goes through all the phases, which cannot be explained unless Venus is orbiting the Sun

Kepler's Second law states that as a planet orbits the Sun, it sweeps out equal areas in equal times. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's second law? The Sun is located slightly off-center from the middle of each planet's orbit. Earth is slightly closer to the Sun on one side of its orbit than on the other side. Venus orbits the Sun faster than Earth orbits the Sun. Inner planets orbit the Sun at higher speed than outer planets. Pluto moves faster when it is closer to the Sun than when it is farther from the Sun. All the planets orbit the Sun in nearly the same plane.

Pluto moves faster when it is closer to the Sun than when it is farther from the Sun. The same ideas hold for any object orbiting the Sun: An object must move faster when it is closer to the Sun and slower when it is farther from the Sun.

Which of the following is not consistent with the major hallmarks of science? A scientific model must make testable predictions. Science consists of proven theories that are understood to be true explanations of reality. Scientific explanations should be based solely on natural causes. Science progresses through the creation and testing of models that explain observation as simply as possible.

Science consists of proven theories that are understood to be true explanations of reality. This statement is not consistent with the hallmarks of science, because scientific theories can never be proven beyond all doubt.

Kepler's 1st law states that the orbit of each planet is an ellipse with the Sun at one focus. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's first law? Inner planets orbit the Sun at higher speed than outer planets. All the planets orbit the Sun in nearly the same plane. The Sun is located slightly off-center from the middle of each planet's orbit. Earth is slightly closer to the Sun on one side of its orbit than on the other side. Pluto moves faster when it is closer to the Sun than when it is farther from the Sun. Venus orbits the Sun faster than Earth orbits the Sun.

The Sun is located slightly off-center from the middle of each planet's orbit Earth is slightly closer to the Sun on one side of its orbit than on the other side None of the planets have a perfectly circular orbit, which means that all planets are closer to the Sun on one side of their orbit than on the other. The Sun's off-center position arises because it is located at a focus of each planet's elliptical orbit, rather than at the center of the ellipse.

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

The planets moved along small circle that moved on larger circles around the Earth. This created a "loop-the-loop" motion that made the planets in the model appear to sometimes go backward as viewed from Earth.

Which of the following best describes a set of conditions under which archaeoastronomers would conclude that an ancient structure was used for astronomical purposes? The structure has holes in the ceiling that allow viewing the passage of constellations that figure prominently in the culture's folklore, and many other structures built by the same culture have ceiling holes placed in the same way. The structure has 29 straight lines pointing out from a center, just like there are 29 days in the lunar cycle. They find that, looking out from the center of the building, there are two windows that align with the rise and set points of two bright stars. The structure has the same dome shape as modern astronomical observatories.

The structure has holes in the ceiling that allow viewing the passage of constellations that figure prominently in the culture's folklore, and many other structures built by the same culture have ceiling holes placed in the same way. In fact, this answer describes the evidence for Pawnee lodges, as described in Section 3.1 of The Cosmic Perspective

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

Venus orbits the Sun at a slower average speed than Mercury. Kepler's third law tells us that orbital speed declines with distance, so venus must orbit the Sun at a slower speed than Mercury

Earth is farthest from the Sun in July and closest to the Sun in January. During which Northern Hemisphere season is Earth moving fastest in its orbit?

Winter Kepler's second law tells us that planets move fastest when they are nearest to the Sun. Since this is in January for Earth, it is Northern Hemisphere winter

According to Kepler's second law, Jupiter will be traveling most slowly around the sun when at ______.

aphelion

The extent to which Mars' orbit differs from a perfect circle is called its _________.

eccentricity

Earth orbits in the shape of a/an _______ around the Sun.

ellipse

Earth is located at one _____ of the Moon's orbit.

focus