Joseph Alphonse Adhemar (1797 - 1862) was a French mathematician. He was the first to suggest that ice ages were controlled by astronomical forces in his 1842 book "Revolutions of the Sea". The earth's orbit is elliptical, with the sun at one focus; lines drawn through the summer and winter solstice; and the spring and autumn equinox; intersect with the sun at right angles. Wikipedia
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