Chapter 1: The Copernican Revolution - Homework

According to Newton's first law, an object traveling in a circle does not have a force acting on it

False

Aristotle was the first to propose that all planets revolve around the Sun.

False

Copernicus believed the Earth was the center of all celestial motion.

False

During retrograde motion, planets actually stop and move backward in space.

False

Galileo's observations of the sky were made with the naked eye.

False

In Ptolemy's geocentric model, the planet's motion along its deferent is all that is needed to understand retrograde motion.

False

Kepler relied heavily on the telescopic observations of Galileo in developing his laws of planetary motion.

False

Kepler's laws hold only for the six planets known at the time.

False

The heliocentric model of the universe holds that Earth is at the center and everything else moves around it.

False

The speed of a planet orbiting the Sun is independent of the planet's position in its orbit.

False

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

Mercury and Venus.

In the geocentric Greek model, which of the following objects did not require an epicycle?

Sun

Both Geocentric and Heliocentric

The brightness of a planet increases when the planet is closest to Earth, Epicycles and deferents help explain planetary motion, Planets move in circular orbits and with uniform motion. Predicted planetary positions accurately over relatively short time periods, Planetary orbits and motions based on Greek ideologies of perfect for, and motion.

The geocentric model, in all of its complexity, survived scientific scrutiny for almost 1,400 years. However, in modern astronomy, scientists seek to explain the natural and physical world we live in as simply as possible. The complexity of Ptolemy's model was an indicator that his theory was inherently flawed. Why, then, was the geocentric model the leading theory for such a long time, even though the heliocentric model more simply explained the observed motions and brightness of the planets?

The heliocentric model did not make noticeably better predictions than the geocentric model. Ancient astronomers did not observe stellar parallax, which would have provided evidence in favor of the heliocentric model. The geocentric model conformed to both the philosophical and religious doctrines of the time. From Earth, all heavenly bodies appeared to circle around a stationary Earth.

Geocentric

This model is Earth-centered, Retrograde motion is explained by epicycles. Rooted in widely accepted religious beliefs regarding Earth's place in the universe.

Heliocentric

This model is Sun-centered, Retrograde is explained by the orbital speeds of planets. Explained planetary motions and brightness changes most simply.

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

True

According to Kepler's third law, if you know the planet's orbital period, you can find its average distance from the Sun.

True

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

True

According to Newton's third law, when the Voyager probes passed Jupiter in 1979, they exerted force of exactly the same magnitude on Jupiter as the giant planet did on them.

True

Among Galileo's discoveries with his telescope were sunspots.

True

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.

True

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

True

Kepler's third law relates to the square of the planet's orbital period in years to the cube of its average distance from the Sun in astronomical units.

True

You throw a baseball to someone; before the ball is caught, it is temporarily in orbit around Earth's center.

True

Which of the following is the best summary of Galileo's observations of the phases of Venus that directly refuted the Ptolemaic (geocentric) model?

Venus can be seen to exhibit a full phase, which is predicted not to happen in the geocentric model.

Copernicus' heliocentric theory explains that

Venus retrogrades when she overtakes us at inferior conjunction.

Galileo found the rotation period of the Sun was approximately

a month.

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

aphelion.

According to Copernicus, the retrograde motion for Mars must occur

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

The force of gravity varies with

both product of the two masses and inverse square of the distance separating the two bodies.

A major flaw in Copernicus's model was that it still had

circular orbits.

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

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

elliptical, not circular.

In Ptolemy's geocentric model, retrograde motion occurs when the planet is closest to us, on the inside portion of the

epicycle.

Retrograde motion was explained by the Greeks by inventing which of the following?

epicycles

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

focus

An asteroid with an orbit lying entirely inside Earth's

has an orbital semimajor axis of less than 1 AU.

Tycho Brahe's contribution to Kepler's Laws of Planetary Motion were

his detailed and accurate observations of the planets' positions.

If Earth's orbit around the Sun were twice as large as it is now, the orbit would take

more than two times longer to traverse.

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

perihelion.

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

perihelion.

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

semimajor axis

Which of these was NOT seen telescopically by Galileo?

stellar parallax

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

the complete cycle of Venus' phases

A calculation of how long it takes a planet to orbit the Sun would be most closely related to Kepler's

third law of planetary motion.