Introduction to Astronomy

HW0801022

due in one week

1. Find out what the Alexandrian Library was. Around 200 BC, its librarian and director Eratosthenes devised a way to measure the circumference of the earth, to an admirable accuracy. Describe his method.

2. Use the U. S. Naval Observatory website to find the times of sunset and sunrise on (a) your birthday and (b) the date this assignment is due. Are the times the same for the two dates? Explain why or why not.

3. How many more sidereal months than synodic months are there in a year? Explain the reason.

4. Which planet would you expect to exhibit the greatest variation in apparent brightness as seen from Earth? Which planet would you expect to exhibit the greatest variation in angular diameter? Explain your reasoning.

5. A satellite is said to be in a “geosynchronous” orbit if it appears always to remain over the exact same spot on the rotating Earth. (a) What is the period of this orbit? (b) At what distance from the center of the Earth must such a satellite be placed into orbit? (c) Explain why the orbit must be in the plane of the Earth equator.