Sept 26

We mostly talked about scales of the Universe, and reviewed SCIENTIFIC
NOTATION and SCALING. While we used the scaling "if xxx were the size of a 
compact disk" in class, we used a different scaling, "if xxx were the size
of a grain of sand," in the homework. 

So look at the homework 1 solution set for a review of much of what we talked
about.

But please keep in your head (ie, memorize) that if the diameter of the Sun
is the size of a CD, the Earth is a grain of sand 40 feet away. Pluto
would be 1/3 of a mile away, the nearest star would be 2000 miles away
(Washington DC from Tucson).