General Astronomy -
Spring 2011
Homework #8 - due March 25
1. (4 pt) You are
in a rocket and move at a speed of 0.99c past a stationary
person. Do you see the person's clock as going faster,
slower, or the same as yours? By what factor?
2. (4 pt) A person in a train car arranged things so that two
lights, one at the front of the car and one at the back, flash
simultaneously in his frame of reference. You are watching
the car move past at a speed of 0.5c. In your frame of
reference, do the two lights flash simultaneously? If not,
which one goes off first. Explain.
3. (6 pt) Muons are unstable, sub-atomic particles with a life
time of 2.2 microseconds. Many muons are produced by
interactions of cosmic rays in Earth's upper atmosphere. Can
a muon produced at an altitude of 10 km reach the ground before
decaying? Explain and calculate the velocity required.
4. (4 pt)
Calculate the fractional gravitational redshift for light emitted
from the surface of a star with a mass of 10 solar masses and a
radius of one Earth radius.