10
The Scale of the Cosmos
Zoom outward in steps of
100
•It has taken twelve steps
of 100 to go from human scale to the scale of the cosmos
•How do we quantify
this?
•Appropriate units
•In ordinary life we use
inches for small things, miles for large
•Astronomers use meters for
small things, “AU” for planets, light-years for stars
•Use scientific
notation: 10 = 101 100 = 102 1000 = 103 0.1 = 10-1
0.01 =
10-2
•It makes it possible to
easily express large and small numbers
•It also makes dividing and
multiplying them easier.
17,000 ly
1,700,000 ly
170,000,000 ly