Explorations: Introduction to Astronomy (Arny), 6th Edition

Chapter 7: The Moon

Problems

1
A laser pulse takes 2.56 seconds to travel from Earth to the Moon and return. Given that the speed of light is 300,000 kilometers per second, how far away is the Moon? How might this time delay affect conversations between an astronaut on the Moon and someone back on Earth?
2
A lunar crater has an angular diameter of 1 minute of arc. What is its diameter in kilometers?
3
A spacecraft orbits the Moon 100 kilometers above its surface and with an orbital period of 114 minutes. What is the Moon's mass?
4
The Moon's orbital period is 27.2122 days. Its synodic period, the period of the phases, is 29.5306 days. Show that 242 orbital periods very nearly equals 223 synodic periods. How long is this in years? What does this suggest about eclipses and why? (This match of cycles is called the saros and was used by ancient astronomers to predict eclipses.)
5
Calculate the Moon's density (see end of section 12.1 in the Earth chapter for how to calculate density). The Moon's mass is about 7.3 x 1025 gm, and its radius is about 1.7 x 108 cm. On the basis of your value for the density, what can you say about the amount of iron in the Moon? (See table 12.1 for iron's density.)
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