(16 a M) 16 × 2,280,000,000
———————————————— = —————————————————— = 3,400.
14,000 × 772 × M 14,000 × 772
Hence we see that
The energy liberated in the contraction of the sun from infinity to its present dimensions, is as great as could be produced by the combustion of 3,400 globes of coal, each as heavy as the sun.
We may speak of 3,400 in this case as the coal equivalent.
§ 5. On the Further Contraction of the Sun and the Heat that may thus be Given Out.
Let us suppose the sun contracts to the radius r, and then, as already proved, [§ 3], the energy it gives out is
⅗ (ε M2)/r,
but we have
ε M/a2 = 27,
whence on contraction to the radius r the total energy given out from the commencement is