Practice Questions for
Chapters 1 and 2
1. The Sun is on average 150 million
kilometers from the Earth. If a comet is 20 A.U.'s from the
Sun, how many km away is it?
2. A star is 100 trillion miles from Earth. Express
that number as a power of ten.
3. If we represent the Earth as a golf ball 4 cm across, how
should we model Jupiter - a baseball, a marble, beach ball, hot air
balloon? (To find their actual diameters, see the
chart on p. A-2 in back of The Cosmos.)
4. Let's make Solar System one light-year across (that includes
the most distant comets). If we represent the Solar System as a 1-cm
dime, what object should we use to model the Milky Way Galaxy,
which is 100,000 ly across? (round table, CD, round swimming
pool, domed stadium). Explain your answer!
1. What evidence do we have (before the
Space Age) that the Earth rotates once every 24 hours?
2. How do the stars tell us that we have completed one revolution
around the Sun.
3. Why did Copernicus choose to devise the Heliocentric Model
(Sun-Centered)? What does retrograde motion of planets have to do with
4. How do you draw an ellipse? How does this model the orbit of a
planet? Where do you put the sun? (NOT the center!)
5. Galileo discovered the phases of Venus and the moons of Jupiter. Why
did this lead him to accept the Copernican model of the universe?
6. According to Kepler, the distance of a planet to the sun cubed is equal to the period of
revolution squared (P2 = A3). If the semi-major axis of a
comet is 400 AU, then what is its period of revolution?
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