### ASTR 220 - Collisions in Space

#### Homework 1 (12 points) Due Thursday September 16 at the beginning of class

Postscript Version

Homework is due at 11AM on the lecture date indicated on the syllabus. Homework handed in after 11AM on the due date will be considered late (a 2 point deduction). Homework turned in after the due date will lose additional points, but partial credit is better than none at all. Late homeworks will NOT be accepted after graded homeworks have been returned.

If you make use of references other than the textbooks or class handouts, include the reference information (book title & author; WWW URLs) at the end of your assignment. The University's honor code will be enforced. See page 35 of the Schedule of Classes.

#### Homework 1 Questions:

1. Volcanism vs. Impacts:
Describe the historical debate over the volcanic versus impact theories for the origin of craters on the Earth and Moon.
2. Catastrophism and Uniformitarianism:
Give an example of a catastrophic theory. Give an example of a uniformitarian theory. Compare catastrophism and uniformitarianism.
3. Observed Crater Densities:
Satellites (moons) and planets with solid surfaces show great variation in the number of craters that are visible. Describe the processes which can modify a surface which started out with many craters when the solar system was young (4 billion years ago).
4. Make use of the WWW tool Astronomical Distances to answer the following questions:
• a) How long would it take you to reach the Moon if you traveled in a spaceship as fast as a car? As fast as a commercial airliner? Choose typical values for these speeds. If you are unsure of typical speeds, ask someone!
• b) How many times further away is Pluto than our Moon? How many times further away is Proxima Centauri than Pluto? How many times further away is the center of the Milky Way than Proxima Centauri? (HINT: how is the ratio of travel times related to the desired ratios of distances?)
• c) A club popular with all space faring species in the galaxy is Joe's Canteen and Deuterium Depot, conveniently located at the center of the Milky Way. Joe's is particularly noted for its delectable FAF (Flaming Arcturian Flamingo). Alas, the Arcturian Flamingo has been placed on the Galactic Endangered Species List. This news will reach Joe's in 25,000 years, where there will no doubt be one last great multi-species interstellar feast. If you leave Earth now and make the best possible speed, can you make it in time to eat FAF at Joe's?
Why or why not?