Ch. 21,  p. 608, #1-4, 6, 8

1.  Why did the ancients believe that celestial objects had some control over their lives?

The close association of the positions of the celestial objects with recurring events on Earth, such as the seasons, led the ancients to believe that all Earthly activity was controlled by the celestial objects.

2.  Describe what produces the retrograde motion of Mars.  What geometric arrangements did Ptolemy use to explain this motion?

In actuality, when Earth overtakes Mars in its orbit, Mars appears to be moving backward against the background stars.  Ptolemy, in assuming that all the planets orbit around Earth, proposed that Mars (and other planets) made a small backward loop in its orbit, called an epicycle.

3.  What major change did Copernicus make in the Ptolemaic system?  Why was this change philosphically significant?

Copernicus proposed that the planets orbit around the Sun, instead of the Sun and planets orbiting around Earth.

4.  What was Tycho Brahe's contribution to science?

6.  Use Kepler's third law to determine the period of a planet whose solar distance is

a) 10 AU

A.  31.6 years


b)  1 AU

A. 1 year

c)  0.2 AU

A.  0.89 year

7.  Use Kepler's third law to determine the distance from the Sun of a planet whose period is.

a) 5 years

A.  2.9 AUs

b)  10 years

4.6 AUs


c) 10 days

0.01 AUs

8.  Did Galileo invent the telescope?

No, Galileo did not invent the telescope.  However, he was the first to use it astronomically.

12.  Of what value are constellations to modern-day astronomers?

Constellations provide astronomers with a means of dividing the sky into identifiable regions.


Last update 6/15/2005

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