ASTR 1110H – Homework #1

Fall 2009 – Dr. Magnani

1. Explain why we see certain constellations only in summer and others only in winter? Feel free to use diagrams.

2. What is precession? What does it do to the positions of stars on the celestial sphere?

3. Explain how Eratosthenes estimated the size of the Earth.

4. What is retrograde motion? How is this phenomenon explained in a geocentric model of the Solar System? How in a heliocentric model?

5. Explain the basics of the Ptolemaic model. How did it explain the motion of Mercury and Venus (you might begin by explaining the behavior of Mercury and Venus).

6. Why do we need leap years? What is the difference between the Gregorian calendar and the Julian calendar?

7. What is the difference between solar time and sidereal time?

8. What is Aristarchus’ contribution to astronomy?

9. What was Aristotle’s argument for rejecting the heliocentric model?

10. What was Eudoxus’ contribution to astronomy?