Astronomy 102, Fall 2004
Homework Assignment #2
This homework set is due at the beginning of class on Friday, September 3. It must be turned in by 9:10AM that day. Late homework will not be accepted. This is includes your being late to class!
Staple. If you have more than one page, staple them together; do not just fold the corner. If you have multiple pages and do not staple, I will deduct one point from your score..
The first three problems are required. The remaining problems are optional, and will not be graded; they are here as additional review problems for you. After the homework has been graded, solutions will be posted to all problems.
Please write out the problem statement at the top of your solution. (This is for two reasons; it is so I can know which problems you answered, and that you answered the right problem from the bit. It also will make your graded homework more useful as a study aid later.)
You may consult with other students (as well as with the TAs and professor) on this homework set. However, your final answer should be your own. Do not write down an answer you don't understand, and do not "dictate" an answer to somebody else.
There are a range of laitudes where, on at least one day of the year, the Sun will pass directly overhead (i.e. at the Zenith). Which latitudes of the Earth meet this condition? Does this happen in Nashville?
(a) Suppose you are standing on the moon, looking at the Earth. Would you see the Earth go through phases the way an Earthbound observer sees the moon go through phases? How long would it take for you to observe one cycle of Earth phases?
(b) When an Earthbound observer sees a full moon, what Earth phase would you observe?
(c) Describe how you would see the Earth move across the Moon's sky over the course of a day, and over the course of a month.
(a) The Earth is 1 AU from the Sun, and Pluto is on average 39.5 AU from the Sun. Would there be any advantage in measuring the distance to stars using parallax from Pluto? If so, why would it be easier to measure parallax from Pluto?
(b) Ignoring the expense and trouble of getting to Pluto in the first place, and of surviving in such a hostile environment, would there be any disadvantage in measuring stellar distances using parallax from Pluto? If so, suggest a way to get around this disadvantage.
The problems below are optional; they need not be turned in, and they will not be graded.
In the northern hemisphere, June 21 is the longest day of the year and December 21 is the shortest day of the year. How long is the day (in hours) at the equator on June 21? Can you identify the shortest day in the year on the equator?
Chapter 4, Question 17 in Pasachoff & Filippenko (p. 75).
The moon and all of the planets appear to go through phases, meaning that most of the time we see only a part of their surface illuminated. The Sun never goes through such phases. Explain why the Sun is different from the Moon and the planets