Conceptual Quiz
Chapter 3

Part A
Suppose that 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?
Hint A.1
What is named for planets visible to the naked eye?

The discovery that the Earth is a planet going around the Sun would have come hundreds of years earlier. A week would have eight days instead of seven. Its gravity would cause the tides to be much higher than they actually are. Its brightness would make it possible to read by starlight at night. Its slow motion through the sky would have led it to be named after the Goddess of Procrastination.
Part B
How does a 12-month lunar calendar differ from our 12-month solar calendar?
Hint B.1
Study Section 3.1.

It does not have seasons. It has about 11 fewer days. Its new year always occurs in February instead of on January 1. It uses a 23-hour rather than a 24-hour day.
Part C
Which of the following best describes a set of conditions under which archaeaoastronomers would conclude that an ancient structure was used for astronomical purposes?
Hint C.1
Study Section 3.1.

They find that, looking out from the center of the building, the building has 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 find that a particular culture built many similar structures, all of which have holes in the ceiling placed the same way, and these holes allow viewing the passage of constellations that figure prominently in the culture's folklore. The structure has 29 straight lines pointing out from a center, just like there are 29 days in a month.
Part D
How did the Ptolemaic model explain the apparent retrograde motion of the planets?
Hint D.1
Study Section 3.2.

It held that the planets moved along small circles that moved on larger circles around the Earth, and that the combined motion sometimes resulted in backward motion. It held that the planets resided on giant spheres that sometimes turned clockwise and sometimes turned counterclockwise. It held that sometimes the planets moved backwards along their circular orbits. It held that this motion occurs as Earth passes by another planet in its orbit of the Sun.
Part E
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?
Hint E.1
Study Section 3.3.

Copernicus misjudged the distances between the planets. Copernicus placed the Sun at the center, but did not realize that the Moon orbits the Earth. Copernicus used perfect circles for the orbits of the planets. Copernicus placed the planets in the wrong order going outward from the Sun.
Part F
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?
Hint F.1
Consider Kepler's second law.

Summer Fall Winter Spring
Part G
According to Kepler's third law (p 2 = a 3), how does a planet's mass affect its orbit around the Sun?
Hint G.1
Study Section 3.3.

A planet's mass has no effect on its orbit around the Sun. More massive planets must have more circular orbits. More massive planets orbit the Sun at higher average speed. A more massive planet must have a larger semimajor axis.
Part H
All the following statements are true. Which one follows directly from Kepler's third law (p 2 = a 3)?
Hint H.1
Study Section 3.3.

Venus takes longer to rotate than it does to orbit the Sun. Venus has a thicker atmosphere than Mercury. Venus is more massive than Mercury. Venus orbits the Sun at a slower average speed than Mercury.
Part I
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?
Hint I.1
Study Section 3.3.

It depends on the eccentricity of the orbit, as described by Kepler's first law. It depends on the eccentricity of the orbit, as described by Kepler's second law. 1 year, which we know from Kepler's third law. Each orbit should take about 2 years, because the eccentricity is so large.
Part J

What, if anything, is wrong with the planetary orbit shown?
Hint J.1
Study Kepler's laws.

There is nothing wrong with this orbit; it is fine as shown. The Sun is not at one focus, as Kepler's first law requires. The shape of the orbit is not an ellipse, as Kepler's first law requires. The orbital path violates Kepler's third law.
Part K
Galileo challenged the idea that objects in the heavens were perfect by _________.
Hint K.1
Study Section 3.3.

inventing the telescope showing that heavy objects fall at the same rate as lighter objects observing sunspots on the Sun and mountains on the Moon proving Kepler's laws were correct
Part L
Galileo observed all of the following. Which observation offered direct proof of a planet orbiting the Sun?
Hint L.1
Study Section 3.3.

The Milky Way is composed of many individual stars. Patterns of shadow and sunlight near the dividing line between the light and dark portions of the Moon's face Phases of Venus Four moons of Jupiter.
Part M
Which of the following is NOT consistent with the major hallmarks of science?
Hint M.1
Study Section 3.4.

Scientific explanations should be based solely on natural causes. A scientific model must make testable predictions. Science consists of proven theories that are understood to be true explanations of reality. Science progresses through the creation and testing of models that explain observation as simply as possible.
Part N
Which of the following is NOT part of a good scientific theory?
Hint N.1
Study Section 3.4.

A scientific theory must explain a wide variety of phenomena observed in the natural world. A scientific theory should be based on natural processes and should not invoke the supernatural or divine. A scientific theory cannot be accepted until it has been proven true beyond all doubt. A scientific theory must make testable predictions that, if found to be incorrect, could lead to its own modification or demise.
Part O
Only one of the statements below uses the term theory in its correct, scientific sense. Which one?
Hint O.1
Study Section 3.4.

I have a new theory about the cause of earthquakes, and I plan to start testing it soon. Evolution is only a theory, so there's no reason to think it really happened. I wrote a theory that is 152 pages long. Einstein's theory of relativity has been tested and verified thousands of times.
Part P
Which of the following best describes how modern astronomers view astrology?
Hint P.1
Study the box in Section 3.4.

Astrology is new age mumbo-jumbo that was a waste of time when it was invented thousands of years ago and remains a waste of time today. Astrology played an important part in the development of astronomy in ancient times, but it is not a science by modern standards. Astrology was a great idea until it was disproved by the work of Copernicus, Tycho, Kepler, and Galileo. Astrology is a synonym for astronomy.
Part Q
The astrology practiced by those who cast predictive horoscopes can be tested by __________
Hint Q.1
Study Section 3.5.

counting how many times the predictions come true. polling people to find out what percentage believe their horoscopes to be accurate. comparing how often the predictions come true to what would be expected by pure chance. asking astrologers if it works.