Popular lectures and addresses / by William Thomson.

  • William Thomson, 1st Baron Kelvin
Date:
1889-
Catalogue details

Licence: Public Domain Mark

Credit: Popular lectures and addresses / by William Thomson. Source: Wellcome Collection.

    403/486 page 385
    branch of solar science to which only allusion can be made at the present time. What concerns us as to the explanation of sun-light and sun-heat may be summarised in two propositions :— (1) Gigantic currents throughout the sun's liquid mass are continually maintained by fluid, slightly cooled by radiation, falling down from the sur- face, and hotter fluid rushing up to take its place. (2) The work done in any time by the mutual gravitation of all the parts of the fluid, as it shrinks in virtue of the lowering of its temperature, is but little less than (so little less than that we may regard it as practically equal to) the dynamical equivalent of the heat that is radiated. from the sun in the same time. The rate of shrinkage corresponding to the present rate of solar radiation has been proved to us, by the consideration of our dynamical .model, to be 35 metres on the radius per year, or one ten-thousandth of its own length on the C C
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