THE SUNS HEAT. It Will Last 10,000,000 Years as it is Now.

Te Aroha News, Volume IV, Issue 196, 26 March 1887, Page 8

THE SUNS HEAT. It Will Last 10,000,000 Years as it is Now.

A brilliant audience filled tho theatre of the Royal Institution last night (January 2lst) while Prof. Sir William Thomson expounded the latest dynamical thoorits regarding the "probable origin, total amount, and possible duration of the sun's heat " During the short 3 000 years or more of which man possesses historic records theie was, the learned physicist showed, no trace of variation in solar eneigy ; and there was no distinct evidence of it" even, though the earth as a whole, from being nearer the aun, received in January G-\ per cent, more heat than in July, But in the millions of years which geology carried ue back, it might safely be j t«aid there must have baen great changes. How had tho solar fires been maintained during those ages ? The scientific answer to this question was the theory of Helmholtz that the sun was a vast globe gradually coolj ing, but as it cooled gradually shrinking, and that the shrinkage- which was tho effect of gravity upon its rna^a— kept up its tempera I ture. The total of the sun's heat was equal to that "which would bo required to keep up 476,000 millions of noillione of millions of horee-power, or about 78,000 horsa power for every square metre - a little more than a square yard— and yet the modern dynamical theory of heat shows that the sun's mass would require only to fall in or contract thirty -fivo'metres per annum to kaepup that tremendous energy. At this rate the solar radius in 2,000 years' time would be about 100 per cent, less than at present. A time would come when the temperature would fall, and it waa thua inconceivable that the sun would continue to em?t beat sufficient to sustain existing life on the globe for more than 10,000,000 yeara. Applying the same principles retrospectively, they could not suppose that the sun had existed for more than 20,000,000 yeara — no matter what might have been its origin — whether ib came into existence from the clash of worlds pre-existing, or of diffused nebulous matter. There was a great clinging by geologists and biologists to vastly longer periods, but the physicist, treating it as a dynamic question with calculable elements, could come to no other conclupion materially different from what he had stated, Sir William Thomson declined to discuss any chemical source of heat, .which, whatever its effect when primeval elements first came into contact, was absolutely insignificant compared with the effects of gravity after globes like the sun and the earth had been formed. In all these speculations they were in the end driven to the ultimate elements of matter— to the question—when they thought what beoame of all 'the sun's heat—what is the lunainiferouß '-ether that fills space, and to that most wonderful of forces upon which Faraday spent so much of the thought of hia later yeara, gravity.— " London Telegraph,"