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Physics 109n Pledged Homework #1
Due Thursday, October 10, 1996
ANNOUNCEMENT: Tonight, October 1, PBS is running
a two hour special about Einstein on NOVA. You should watch
it, or tape it to view later.
READING ASSIGNMENT: Read Sidereus Nuncius.
NOTE: Clarity of presentation, in both words and diagrams,
should be your aim here. Answers don't have to be very long, just
cover the essential points. Figures should be easy to interpret.
- Show on a diagram the relative positions of earth and sun
when it is winter here, and when it is summer here. Make clear
how this relates to the earth's position.
- Wood floats in water. How was this explained by (a) Aristotle,
(b) Archimedes (and Galileo)?
- Explain with a diagram in the Copernican scheme why Mars sometimes
seems to be going backwards in its journey through the Zodiac.
- Bruno was burned at the stake in 1600 for suggesting there
were infinite numbers of inhabited worlds. Why was this idea more
plausible after Copernicus than before?
- Suppose an astronaut is walking around on the moon in the
middle of a vast flat plane. How far away is the horizon?
- Galileo states in Two New Sciences:
"A small dog could probably carry on his back two
or three dogs of his own size; but I believe a horse could not
carry even one of his own size."
Explain the point Galileo is making here in terms of scaling.
- Sorry about the eclipse! Here was the announcement from the
Washington Post. What is wrong with their diagram of the
earth's shadow creeping over the moon?
- If you had been able to see the eclipse, you would
have noticed a bright star very close to the moon - actually,
the planet Saturn. Can you figure out from that whether the earth
is closer to Saturn than its average distance, or further away?
(Hint: draw a Copernicus-like diagram showing the orbits
of earth, moon and Saturn, and put the moon in the right place
for an eclipse.)
- Why was Galileo particularly anxious to give an explanation
of the tides?
- Considering how high he claimed the mountains were on the
moon, how did Galileo account for the fact that the moon looks
so round? Why isn't it jagged? Were his explanations correct?