The ancient Greek thinker whose model of the universe came to dominate the medieval world was
Ptolemy
The Ptolemaic model of the universe included each of the following features,except one. Which one is the exception?
The apparent daily motion of the stars is due to the rotation of Earth.
A major theme of Ancient Greek philosophy was that stars and planets in the sky
followed patterns that could be described logically.
The correct order of"appearance"of the following"actors"on the"stage"of scientific discovery is
Ptolemy,Copernicus,Kepler,Newton,Einstein.
Before the invention of the telescope,the known planets were
Mercury, Venus, Mars, Jupiter, and Saturn.
Planets move past the background stars as seen by someone on Earth.What is the normal direction of this motion?
west to east because of the motion of the planet along its orbit
When observing planetary motions from Earth,the phrase"retrograde motion"refers to
a slow westward motion of the planet from night to night against the back ground stars.
Ptolemy's model for the solar system was
Earth-centered,with epicyclic planetary orbits.
In the geocentric model of the solar system developed by Ptolemy,planets move
in circular epicycles while the centers of the epicycles move in circular orbits around
Earth.
The primary purpose of describing planetary orbits in terms of epicycles and deferents was to account for the
pattern of direct and retrograde motion of a planet as it moved slowly against the background of stars.
In the geocentric model for the solar system developed by Ptolemy,to what does the word "epicycle" refer?
a small circle around which a planet moves while the center of this circle moves around Earth
In Ptolemy's description of the solar system, the deferent is
a circular path (aroundEarth) along which the center of a planet's epicycle moves.
The concept called Occam's Razor tells us that
when two theories describe the same phenomena equally accurately,choose the simpler
theory.
Retrograde motion of a planet when viewed from Earth is caused by the fact that the
Earth is moving.
The early Copernican system for planetary motions is
Sun-centered,with planets moving in perfect circles around the Sun.
Copernicus used the fact that Mars can sometimes be seen high in our sky at midnight to conclude that
Earth can come between Mars and the Sun.
When Venus is at inferior conjunction,
it is at its smallest distance from Earth.
When Venus is at superior conjunction
it is at its greatest distance from Earth.
In which direction is Venus moving when it is at greatest elongation?
directly toward or away from Earth
How will the illuminated side of Venus appear to us when it is at its greatest eastern elongation?
half-illuminated or quarter-phase
When Jupiter is at opposition, it rises at
sunset.
Where and when would Venus be seen from Earth when it is at greatest eastern elongation?
just after sunset, in the west
What is the difference between the synodic and sidereal periods of a planet?
The synodic period refers to the planet's period with respect to Earth's motion, while
the sidereal period is the true period with respect to the background stars.
An imaginary planet is orbiting the Sun in a circle at precisely the same average orbital distance as Earth (i.e., one AU). What is its sidereal period?
1year
The greatest inaccuracy in Copernicus' theory of the solar system was that he
placed the planets in circular orbits.
Which one of the following statements about Copernicus' system of planetary motion is correct?
It used uniform circular motion.
The reason why Copernicus' heliocentric theory eventually came to be regarded as preferable to the geocentric theory of Ptolemy is that the heliocentric theory
accounted for the same observed motions of the planets as the geocentric theory but did
so in a much simpler way.
The phenomenon of parallax is the
change in apparent position of a nearby object as the observer moves.
Tycho Brahe demonstrated that the supernova of 1572 was not a nearby (close to Earth) event by
proving that it did not show parallax over the course of one night.
Tycho Brahe
made accurate measurements of planetary positions,which Kepler later used to find the
shapes of planetary orbits.
The Kepler model of the solar system is
Sun-centered,with elliptical planetary orbits.
Kepler's first law states that the orbit of a planet about
the Sun is an ellipse with the Sun at one focus.
To which point in a planetary orbit does the word "perihelion"refer?
the point closest to the Sun
To which point in a planetary orbit does the word"aphelion"refer?
the point farthest from the Sun
If an object's orbit around the Sun has an eccentricity of 0.1,then the orbit is
almost circular.
If an object's orbit around the Sun has an eccentricity of 0.8,then the orbit is
along,thin ellipse.
The semimajor axis of an ellipse is
the distance from the center of the ellipse to one end along the largest diameter of the ellipse.
Kepler's second law states that a line joining a planet to the Sun
sweeps out equal areas in equal times.
Kepler's second law states that a planet moves fastest when it
is closest to the Sun.
Kepler's third law states that
the square of the orbital period is directly proportional to the cube of its mean distance
from the Sun.
Which of the following statements is true,according to Kepler's third law?
The larger the orbit,the longer it takes for the planet to complete one revolution.
Kepler's third law in general applies
to all situations where two objects orbit each other solely under the influence of their
mutual gravitational attraction.
If a new planet (tentatively predicted to exist on the basis of perturbations in the orbits of Uranus and Neptune) were to be discovered with a sidereal period of 200 years, what would be the radius of its orbit (assumed to be circular)?
34.2 AU
Suppose an asteroid is discovered in an elliptical orbit with a period of exactly one year and at perihelion it is 0.5 AU from the Sun. Using Kepler's third law, how far from the Sun is this asteroid when at aphelion? (Drawing a diagram of the orbit, incl
1.5 AU
An asteroid orbits the Sun in a circle with a sidereal period of 11.9years.Compare this with the orbital characteristics of the planets. At what equivalent distance will this asteroid orbit the Sun?
at the same orbital distance as Jupiter
Halley's Comet returns to the Sun's vicinity every 76 years in an elliptical orbit.(SeeFig.4- 23, Freedman and Kaufmann, Universe, 8th ed.) What is the semimajor axis of this orbit?
17.5 AU
If Halley's Comet has an elliptical orbit with a semi major axis of 17.5AU,approximately how far out into the planetary system does it reach at its furthest point (aphelion)? (Assume that perihelion distance from the Sun is negligible; be careful. The que
between the orbits of Neptune and Pluto
Galileo's early observations of the sky with his newly made telescope included the
fact that Venus showed phases similar to those of the Moon.
What did Galileo see when he observed Jupiter through his telescope?
four satellites(moons)orbiting Jupiter
What did Galileo see when he observed Venus through his telescope?
phases like those of the Moon
Which of the following statements correctly states the significance of Galileo's observation that Venus shows phases?
The phases were correlated with angular size in a way that supported the heliocentric
theory.
In the heliocentric model of the solar system,which one of the following phases of Venus should not be visible from Earth?
none of these They are all visible.
What was the most important difference in development between Isaac Newton's theory of planetary motion and that of Johannes Kepler?
Newton developed his theory from basic physical assumptions, whereas Kepler simply
adjusted his theory to fit the data.
Why were Newton's three laws so important to astronomy?
They showed that planets can move around the Sun by themselves forever,without
coming to rest.
Careful description of the velocity of a moving object at a particular time requires that one define
the speed and the direction of the moving object.
To specify an object's speed, we need to specify
only how fast it is moving.
Acceleration of a moving body is defined as the rate of change of
velocity with time.
A body whose velocity is constant
has zero acceleration.
According to Newton's first law
if no force is acting on an object,then the object's speed and direction of travel will both
be constant.
Newton's second law of motion states that a
body acted on by a force will accelerate constantly while the force is applied.
Newton's second law states that acceleration produced by a force is
inversely proportional to the mass on which the force acts.
Which of the following statements is a correct version of Newton's third law?
When ever object Aexerts a force on some other object B,B must exert a force of equal
magnitude on A in the opposite direction.
A person standing on a bathroom scale sees a reading on the scale of 148pounds.This person is acted on by
two forces of equal size acting in opposite directions.
In which direction would Earth move if the Sun's gravitational force were suddenly removed from it?
in a straight line along at angent to its circular orbit
When an object moves uniformly at a constant speed in a circle,the acceleration of the object is always
inward,toward the center of the circle.
Which one of the following statements describes the Newtonian understanding of the mechanics of the solar system?
The natural motion of the planets is motion in a straight line. They are prevented from
straight line motion by the gravitational force of the Sun.
In Newton's law of universa lgravitation,F=GMm/R2,which defines the force between Earth with mass M and an orbiting satellite of mass m at a distance R from Earth, G
is a constant,through out all measured space and time.
The law of gravitation expounded by Newton for the force F between two objects of masses M and m with separation (between centers) of R is given, with G being a constant,
F=GMm/R2
If the mass of the Sun were doubled,the gravitational force on Jupiter due to the Sun would
be twice its present value.
Suppose that a planet of 10 times the mass of Earth were orbiting the Sun at the same distance as Earth (1 AU). The gravitational force on this planet due to the Sun would be
10times that on Earth due to the Sun.
If Earth were to be moved to a distance of 10AU from the Sun,how much stronger or weaker would be the Sun's gravitational force on Earth?
100times weaker
The first major astronomical prediction of Newton's theory of gravitation to be confirmed
return of Halley's comet.
The main characteristics of our solar system are
four small planets close to the Sun and four large planets far from the Sun.
In our solar system,which of the following planets is not a member of the terrestrial group?
Jupiter
In our solar system,which of the following planets is not a member of the Jovian group?
Mars
Orbital eccentricity is a number that describes the
shape of the orbital ellipse.
The mass of a planet is determined primarily by what method?
observation of its gravitational influence on an orbiting moon
In order of increasing density,the Jovian planets are
Saturn, Uranus, Jupiter, Neptune.
The planet with the highest mean density is
Earth.
The smallest terrestrial planet is
Mercury.
The largest of the terrestrial planets is
Earth.
The average number of natural satellites(moons)per planet for the terrestrial planets is
less than one.
We have discovered moons around
all the planets except those nearer to the Sun than Earth is.
The discovery of nitrogen gas(N2)in the atmosphere of Titan was made by
ultraviolet spectroscopy from Earth.
A laboratory on the surface of the Earth makes a spectrum of radiation that originates at the Sun and reflects off a celestial body with an atmosphere such as Saturn's large satellite Titan. Which one of the following statements about the resulting spectr
The atmosphere of the body can contribute sharp absorption lines to the spectrum.
An oxygen(O2) molecule has twice the mass of a methane(CH4)molecule.In a planet's
atmosphere at some particular temperature, the average kinetic energy of an oxygen molecule is
the same as that of a methane molecule(i.e.,all molecules have the same average kinetic
energy).
A typical asteroid is made of
rock and metal.
The asteroid belt is made up of
rocky bodies from a few meters to tens of kilometers in diameter.
What is the basic difference between comets and asteroids?
Comets are mostly composed of ices,while asteroids are mainly composed of rocks.
Based on its mean density, Pluto appears to be composed of
a mixture of rock and ice.
Planets and satellites with a large amount of surface cratering generally havein significant atmospheres. Why are these two conditions correlated?
A large amount of cratering implies a small size,and this,in turn,implies a low escape
speed.
The craters on the Moon are all nearly circular. Why is this?
Theobjectsthatproducedtheimpactcraterscameinatavarietyofangles,butthe
craters were actually made by the shock waves generated by impact�and this results in
circular craters.
In general,large bodies in the solar system show less evidence of cratering than do small bodies. Why should we expect this correlation?
Largebodiescoolmoreslowlyandaremorelikelytoretaininternalheatandbe
geologically active, capable of resurfacing the planet and obliterating craters.
A general summary of the planets in the solar system is that
the planets are remarkably different in size,magnetic field strength,and magnetic field generation method.