The Earth's Beginning

by Robert S. Ball

16 M (a²/r)

The average density of the sun at present is 1.4. Let us suppose it condenses until it has a density ρ.

r³ ÷ a³ = 1.4 ÷ ρ,

whence the energy becomes

14 a M · ∛ρ;

but the coal equivalent of 16 a M has been found in [§ 4] to be 3,400, and hence the coal equivalent in this case is

3,000 ∛ρ.

If we take ρ to be the density of platinum (21.5), we get a coal equivalent 8,300. This, therefore, seems to represent a major limit to the quantity of heat which can be obtained from the condensation of the nebula from infinity into a sun of the utmost density.

§ 6. On the Present Emission of Sun Heat.

According to Scheiner, “Strahlung und Temperatur der Sonne, Leipzig, 1899,” the value of the solar constant, i.e. the number of cubic centimetres of water which would be raised 1° Centigrade by the quantity of sun heat which, if there were no atmospheric absorption, would fall perpendicularly on a square centimetre, at the earth’s mean distance from the sun, is between 3.5 and 4.0. If we take the mean value, we have (translated into British units), the following statement:—