One cubic foot of the sun averages 87 pounds, so that
M = 4⁄3 π a3 × 87
16 M dr = 464 × 4 π a3 dr.
We have to equate this to the expression in the last article, and we get
dr = 700,000,000,000/(464 a) = .65.
This is the shrinkage of the sun’s radius expressed in feet. Hence the daily reduction of the sun’s diameter is 16 inches.
One coal equivalent possesses energy represented by M × 14,000 × 772. Hence we can calculate that one coal equivalent would supply the solar radiation at its present rate for about 2,800 years.
II.—THE CONSERVATION OF MOMENT OF MOMENTUM.
We give here an elementary investigation of the fundamental dynamical principle which has been of such importance throughout this volume.