Answer 1. The Sun & You


My `diameter' (height), mass (weight), and age are:

DY = (6 ft) × (0.3048 meters/ft) = (6 × 0.3048) meters = 1.83 meters
MY = (165 lb) × (0.454 kg/lb) = (165 × 0.454) kg = 75 kg
AY = 43 years

Dividing the Sun's diameter, mass, and age by my diameter, mass, and age, I obtain:

DS ÷ DY = (1.4 × 109 meters) ÷ (1.82 meters) = 7.7 × 108
MS ÷ MY = (2 × 1030 kg) ÷ (75 kg) = 2.7 × 1028
AS ÷ AY = (4.5 × 109 years) ÷ (43 years) = 1.05 × 108

Note that the units cancel out, so the final numbers have no units attached. These quantities are `pure' numbers, independent of the system of units. I would have got the same final numbers with any choice of units, as long as I use the same units for myself and the Sun.

1. In which way am I least like the Sun?

2. In which way are you most like the Sun?

3. Are you surprised by your answers to the two questions above? Why or why not?


Joshua E. Barnes (barnes@ifa.hawaii.edu)
Last modified: September 2, 1999
http://www.ifa.hawaii.edu/~barnes/ast110_99/homework/ans1.html