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