Jimma University College of Natural Sciences
Department of Physics
Assignment I
For Course General Astronomy (Phys3302)
Total Mark: 10%
Write the correct answer for the following questions. You can expand your answers depending on the
depth of the questions.
1. How is modern science rooted in ancient astronomical observations?
2. Explain, according to both geocentric and heliocentric cosmologies, why we see the retrograde
motion of the planets.
3. In what ways did the work of Copernicus and Galileo differ from the views of the ancient Greeks
and their contemporaries?
4. The Sun was once thought to be a planet. Explain why? Does the sun rotate on its axis? How
many degrees does the Sun move per day relative to the fixed stars? How many days does it take
for the Sun to return to its original location relative to the fixed stars?
5. What is Constellations? What is asterism? What is the difference between them? Explain how
the zodiacal constellations are different from the other constellations.
6. Is the ecliptic the same thing as the celestial equator? Explain.
7. Why did Ptolemy have to introduce multiple circles of motion for the planets instead of a single,
simple circle to represent the planet’s motion around the Earth?
8. Consider three cosmological perspectives—the geocentric perspective, the heliocentric
perspective, and the modern perspective in which the Sun is a minor star on the outskirts of one
galaxy among billions. Discuss some of the cultural and philosophical implications of each point
of view.
9. What are Kepler’s three laws of planetary motion? discuss them in detail.
10. How many kilometers are there in a light-year?
11. The angular diameter of Jupiter is 360. If the distance of Jupiter from the Earth is 825 million
kilometers, find the diameter of Jupiter.
12. A tennis ball is 2.5 inches in diameter. At what distance would it have to be so that it would have
the same angular size as the Moon (about 30 minutes of arc)? (Note: Your answer must be in
feet)
