The Sun & You: Discussion


Most people did pretty well. One error which several people made was to write 101 (= 10) when they should have put 100 (= 1); for example,

  1.75 × 101 m

= 17.5 m

= 57.4 ft
  Alice as a giant in the White Rabbit's house

Another somewhat common error was to mix units, for example:

(4.5 × 109 yr) ÷ (5.7 × 108 sec) = 7.9 (yr/sec) = 7.9 × (3.15 × 107) = 2.5 × 108

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

  Dy = (6 ft) × (0.3048 m/ft) = (6 × 0.3048) m = 1.83 m
  My = (185 lb) × (0.454 kg/lb) = (185 × 0.454) kg = 84 kg
  Ay = 50 years

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

  DSolar symbol ÷ Dy = (1.39 × 109 m) ÷ (1.82 m) = 7.6 × 108
  MSolar symbol ÷ My = (1.99 × 1030 kg) ÷ (84 kg) = 2.4 × 1028
  ASolar symbol ÷ Ay = (4.5 × 109 years) ÷ (50 years) = 9.0 × 107

Note that the units cancel out, so the final numbers don't depend on the units used. 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 are you most like the Sun?

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

3. Are you surprised by your answers to the two questions above?


Joshua E. Barnes (barnes@ifa.hawaii.edu)
Last modified: August 30, 2006
http://www.ifa.hawaii.edu/~barnes/ast110_06/homework/disc01.html
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