Abstract
FROM human history we know that for several thousand years the Sun has been giving heat and light to the earth as at present; possibly with some considerable fluctuations, and possibly with some not very small progressive variation. The records of agriculture, and the natural history of plants and animals within the time of human history, abound with evidence that there has been no exceedingly great change in the intensity of the Sun's heat and light within the last 3000 years; but for all that, there may have been variations of quite as much as 5 or 10 per cent., as we may judge from considering that the intensity of the solar radiation to the earth is 6½ per cent. greater in January than in July; and neither at the equator nor in the northern or southern hemispheres has this difference been discovered by experience or general observation of any kind. But as for the mere age of the Sun, irrespective of the question of uniformity, we have proof of something vastly more than 3000 years in geological history, with its irrefragable evidence of continuity of life on the earth in time past for tens of thousands, and probably for millions of years.
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The Sun's Heat 1 . Nature 35, 297–300 (1887). https://doi.org/10.1038/035297b0
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DOI: https://doi.org/10.1038/035297b0