Astronomy 201
Summer 1996
Sullivan / Beck-Winchatz

Quiz #1 (07/03/96)

    1. Suppose that it were found that the nearby Andromeda galaxy was larger than any other known spiral galaxy. Why would this fact be worrisome?

    2. One way to reconcile the above problem would be to adjust the distances to all the galaxies (except Andromeda) to much larger values. If one did this, how would the Hubble time be affected?

  2. You are traveling at a constant velocity on a highway and are measuring the velocities of 3 cars which are in front of you. Car #1 is 10 miles ahead of you and is going 23 mph faster than you. Car #2 is 25 miles ahead of you and going 48 mph faster than you. Car #3 is 50 miles ahead of you and going 103 mph faster than you are (you are on a German autobahn which does not have a speed limit).

    1. What is the Hubble constant of this "Highway Universe"?
    2. When did the "Big Bang" occur in this Universe (assume that all involved cars have been travelling at a constant rate since the "Big Bang")?

    For your answer, use the graph below. Plot all three data points and draw a straight line through your data to represent your "Highway Hubble Relation". Make sure that the Hubble Constant as well as the age you derive have the correct units.

  3. The following are images of two distant galaxies from the Palomar Obsevatory Sky Survey. You can assume that the linear size of both galaxies (in kiloparsecs) is the same. The angular size of galaxy #1 (left) is 1.2 mrad, that of galaxy #2 (right) is 0.6 mrad. Both, the Ca H and K lines of galaxy #1 are red-shifted by 6 Angstroms.

    1. You measure the distance of galaxy #1 to be 20 Mpc. What is the distance to galaxy #2?
    2. Galaxy #1 has a recession velocity due to the expansion of the Universe of 1200 km/s. What is the recession velocity you would expect for galaxy #2?
    3. What red-shift (in Angstroms) do you expect for the Ca H and K lines of galaxy #2?
    4. What is the Hubble constant you derive for galaxy #1?

  4. Suppose one finds that the volume of spheres around the Earth is closely proportional to the cube of their radii even for very large radii (just like you would expect in Euclidean geometry). (The way one measures volumes is to assume that galaxies are evenly distributed in space and then count the number of galaxies up to a certain distance).

    1. What does this tell us about the curvature of space? (Hint: Think about the analogy of 2-dimensional persons studying how circles of varying radii behave.)
    2. With this observed amount of curvature, what can be said (qualitatively) about the amount of matter in space? Explain!

  5. True or False?

    1. A scientific model of the Universe makes predictions, so it can be disproven.

    2. A scientific model of the Universe must obey the Cosmological and Copernican principles.

    3. An "ad hoc" model of the Universe makes predictions, so it can be disproven.

    4. An "ad hoc" model of the Universe explains general concepts rather than specific events.

    5. An "ad hoc" model of the Universe always puts the Earth in a special place.

  6. For a lab on a rocket ship passing the Earth at a constant velocity close to the speed of light, you observe that time is passing more slowly and a yard-stick is shorter than one yard. What does the person in the moving lab observe in your lab on Earth?

    Astronomy 201 Homepage
    Astronomy Mac Lab Homepage

    bbeck@astro.washington.edu