question

In Ptolemy's Earth-centered model for the solar system, Venus's phase is never full as viewed from Earth because it always lies between Earth and the Sun. In reality, as Galileo first recognized, Venus is __________.

answer

full whenever it is on the opposite side of the Sun from Earth, although we cannot see the full Venus because it is close to the Sun in the sky

question

Imagine that Venus is in its full phase today. If we could see it, at what time would the full Venus be highest in the sky?

answer

at noon

question

When would a new Venus be highest in the sky?

answer

at noon

question

When would you expect to see Venus high in the sky at midnight?

answer

never

question

In Ptolemy's Earth-centered model for the solar system, Venus always stays close to the Sun in the sky and, because it always stays between Earth and the Sun, its phases range only between new and crescent. The following statements are all true and were all observed by Galileo. Which one provides evidence that Venus orbits the Sun and not Earth?

answer

We sometimes see gibbous (nearly but not quite full) Venus.

question

The place in a planet's orbit that is closest to the Sun is called:

answer

perihelion.

question

Kepler's second law implies what about planetary motion?

answer

A planet moves faster when it is closer to the Sun.

question

It was the Chinese who provided critical ancient data on supernovae and comets.

answer

True

question

The principal culture that transferred Greek astronomical knowledge to Renaissance Europe was:

answer

Islamic

question

The most accurate Greek attempt to explain planetary motion was the model of:

answer

Ptolemy

question

The Ptolemaic model probably persisted for all these reasons EXCEPT:

answer

it accounted well for Galileo's observations of the phase cycle of Venus.

question

The greatest contribution of the Greeks to modern thought was:

answer

the development of scientific inquiry and model building.

question

The Ptolemaic model of the universe:

answer

explained and predicted the motions of the planets with deferents and epicycles.

question

According to Copernicus, retrograde motion for Venus must occur around:

answer

inferior conjunction, when it passes between us and the Sun.

question

Combining Newton's and Kepler's laws, we can weigh the Sun, provided we know:

answer

the size of the A.U. and exact length of the year.

question

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

answer

True

question

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

answer

True

question

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

answer

True

question

Scientists today do not accept the Ptolemaic model because:

answer

the work of Tycho and Kepler showed the heliocentric model was more accurate.

question

On which of these assumptions do Ptolemy and Copernicus agree?

answer

All orbits must be perfect circles.

question

The heliocentric model was actually first proposed by:

answer

Aristarchus.

question

According to Copernicus, the retrograde motion for Mars must occur:

answer

at opposition, when the Earth overtakes Mars and passes between Mars and the Sun.

question

Which was a contribution to astronomy made by Copernicus?

answer

He laid out the order and relative motion of the known solar system.

question

Which of these was NOT a part of the original Copernican model?

answer

Mercury speeds up at perihelion, and slows down at aphelion.

question

Which of the statements below is part of both the Ptolemaic and Copernican models?

answer

The Moon orbits the Earth once a month.

question

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

answer

True

question

Which of these was NOT seen telescopically by Galileo?

answer

Stellar parallax

question

Which of the following was NOT a contribution of Galileo to astronomy?

answer

The changing appearance of Saturn's rings corresponds to our seasons.

question

Which of the following is a contribution to astronomy made by Galileo?

answer

All of the above.

question

Which of these observations of Galileo refuted Ptolemy's epicycles?

answer

the complete cycle of Venus' phases

question

Which of these was NOT a telescopic discovery of Galileo?

answer

the moons of Saturn

question

A fatal flaw with Ptolemy's model is its inability to predict the observed phases of:

answer

Mercury and Venus.

question

It took two centuries for the Copernican model to replace the Ptolemaic model because:

answer

there was no scientific evidence to support either model until Galileo made his observations.

question

Galileo found the rotation period of the Sun was approximately:

answer

a month.

question

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.

answer

True

question

Galileo's observations of sunspots proved the Sun was rotating, like the Earth.

answer

True

question

Kepler's first law worked, where Copernicus' original heliocentric model failed, because Kepler described the orbits as:

answer

elliptical, not circular.

question

Tycho Brahe's contribution to Kepler's Laws of Planetary Motion was:

answer

his detailed and accurate observations of the planet's position.

question

The most famous prehistoric astronomical observatory is:

answer

Stonehenge

question

A circular orbit would have an eccentricity of:

answer

0.

question

Upon which point do Copernicus and Kepler disagree?

answer

The orbits of the planets are ellipses, with one focus at the Sun.

question

What contribution to astronomy was made by Tycho Brahe?

answer

His observations of planetary motion with great accuracy proved circular orbits could not work.

question

Which concept was NOT a part of Kepler's Laws of Planetary Motion?

answer

Epicycles are needed to explain the varying brightness of the planets.

question

According to Kepler's third law, the square of the planet's period in years is:

answer

proportional to the cube of its semimajor axis in A.U.

question

What does Kepler's third law imply about planetary motion?

answer

Planets further from the Sun orbit at a slower speed than planets closer to the Sun.

question

A planet whose distance from the Sun is 3 A.U. would have an orbital period of how many Earth-years?

answer

Square root of 27

question

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

answer

True

question

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

answer

True

question

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

answer

True

question

The eccentricity of a perfectly circular orbit is 1.

answer

False

question

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.

answer

True

question

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

answer

True

question

A planet (or comet) will speed up as it approaches the Sun.

answer

True

question

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

answer

True

question

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

answer

True

question

During the eighteenth and nineteenth centuries, attempts to precisely measure the astronomical unit relied largely on rare:

answer

transits of the inferior planets across the Sun.

question

Today we rely largely on what technique to precisely measure distances in the solar system?

answer

radar echo timings

question

The force of gravity varies with the:

answer

Both A and C are correct.

question

The Law of Universal Gravitation was developed by:

answer

Newton.

question

The force of gravity between two objects:

answer

increases with the masses of the bodies, but decreases with the square of the distances between them.

question

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:

answer

decrease by a factor of 9.

question

How much stronger is the gravitational pull of the Sun on Earth, at 1 AU, than it is on Saturn at 10 AU?

answer

100X

question

Which of these was a contribution of Newton to astronomy?

answer

All of these were due to Newton's work.

question

Geosynchronous satellites orbit at about four Earth radii, where the Earth's gravitational pull is:

answer

1/16 g.

question

Jupiter lies about 5 A.U. from the Sun, so at its distance:

answer

the Sun's gravity is 25 times weaker than its pull on the Earth.

question

How does Newton's Universal Law of Gravitation explain Kepler's laws?

answer

Both C and D are correct.

question

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:

answer

the same as you do here.

question

If the distance between two asteroids is doubled, the gravitational force they exert on each other will:

answer

be one fourth as great.

question

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

answer

True

question

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

answer

False

question

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

answer

True

question

Compared to orbital velocity, escape velocity is about:

answer

40% more.

question

Orbital speed is the speed with which a planet moves around the Sun. This speed is determined by:

answer

the mass of both the planet and the Sun and the distance between the two.

question

Escape velocity is the speed required to:

answer

overcome the gravitational pull of an object.

question

Modern scientific theories are NOT:

answer

perfect.

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