New pathways in science / by Sir Arthur Eddington.

  • Eddington, Arthur Stanley, Sir, 1882-1944.
Date:
1935
Catalogue details

Licence: In copyright

Credit: New pathways in science / by Sir Arthur Eddington. Source: Wellcome Collection.

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    with the speed of Hght; 300,000 years’ supply of radiation would be squandered in an instant. The atoms dam back this flood, catcWg and turning away the aether waves as they try to escape, absorbing and re-emitting them in a new direction, so that they go aimlessly round and round the maze. Thus only a shght leakage of radiation dribbles out to illuminate and warm the earth and the other planets. This leads us to the principal aim of investigation of the stellar interior. Having found the internal distribution of temperature in the star and knowing therefore the quantity and quahty of the radiant energy imprisoned there (for this is determined solely by the temperature), knowing also the density of the matter and therefore the number of atoms engaged in holding back the radiant energy, we ought to be able to calculate how much escapes. It is hke calculating the flow of water through a pipe, when we know the head of water causing the flow and the resistance obstructing the flow. Here the increasing concentration of the X rays as the temperature increases inwards supphes the pressure gradient, and the opacity of the matter obstructing the transmission of X rays supplies the resistance. Our aim then is to calculate from the known laws of absorption of X rays how much radiation will get through, and so ascertain theoretically the amount of the energy flow which is slowly leaking outwards through the star. If our calculation is right, it will agree with the amount which emerges at the surface and constitutes the hght and heat of the star. The calculation therefore gives us the brighmess of tlie star, or more strictly the “heat-bright¬ ness” which measures the total radiant energy emitted irre¬ spective of its luminous efficiency. The heat coming to us from many of the stars has been measured directly; but in any case the heat-magnitude of a star can easily be computed from its hght-magnimde by applying a well-known correc¬ tion depending on the colour or spectral type. Effectively therefore by the method here outlined we