AST 324: HOMEWORK 2
Imagine that you throw a baseball straight up in the air; make a plot of
the ball's height above the ground versus time. The details are not
important, so just sketch how it would look in such a plot. Now suppose you
were such an incredible pitcher than you could throw the ball faster than
11.2 km per second (or 7 miles per second), the escape velocity for the
Earth. In this case, the ball will escape the gravity of the Earth and
coast into space, gradually slowing down, but never coming to a stop.
Sketch the path of this ball in the same plot. Which kind of Universe is
each of these paths similar to? What would happen if you threw the ball at
a velocity exactly equal to the escape velocity of the Earth? What kind of
Universe would this path correspond to?
You are piloting the Millenium Falcon toward Alderaan, the planetary
base of the rebel forces, when you begin to notice a large field of
asteroids expanding from a point where the planet should be. Using your
ship's Doppler radar, you establish that the asteroids farthest from the
center are moving fastest. You quickly establish that the "Rubble Law"
applies and find that the value of the "Rubble Constant" is 3 x 103 km s-1
per light hour. (A light-hour is the distance traveled by light in one
hour.) How long ago was the planet destroyed? How is this problem similar
to the determination of the age of the Universe from the Hubble constant?
How is it different?
Zarkon, famous astronomer of the first galactic empire, while working
for the Galactic Ma Bell Laboratories, discovered a uniform radio
background with a blackbody spectrum. The temperature characterizing this
background radiation was 6 K. How much bigger (in the sense of the scale
size a) is the Universe now than it was in Zarkon's time? Zarkon then
moved on to measuring redshifts of distant galaxies. He soon announced
that their velocities were proportional to their distances -- Zarkon's Law.
What was the constant of proportionality (Zarkon's Constant?)? From this
information can you date the first galactic empire? (In this problem,
assume the cosmic background temperature at present to be 3 K.)
Evans's 324 |