. Classics of modern science (Copernicus to Pasteur). Science; Science -- History. CHRISTIAN HUYGHENS 57. Let S be the sun, B C D E the yearly orbit of the earth, J Jupiter and G H the orbit of his nearest satelHte, for this one because of its short period is better suited to this investigation than any one of the other three. Suppose G to be the point where the satelHte enters, and H where it leaves, Jupiter's shadow. Suppose that when the earth is at B, the satellite is seen to emerge [at G], at some time before the last quarter. Were the earth to re- main stationary there, 421^ hours would
. Classics of modern science (Copernicus to Pasteur). Science; Science -- History. CHRISTIAN HUYGHENS 57. Let S be the sun, B C D E the yearly orbit of the earth, J Jupiter and G H the orbit of his nearest satelHte, for this one because of its short period is better suited to this investigation than any one of the other three. Suppose G to be the point where the satelHte enters, and H where it leaves, Jupiter's shadow. Suppose that when the earth is at B, the satellite is seen to emerge [at G], at some time before the last quarter. Were the earth to re- main stationary there, 421^ hours would elapse before the next emergence would take place, for this much time is taken by the satellite in making one revolution in its orbit and returning to opposition to the sun. For example, if the earth remained at B during 30 revolutions, then after 30 times 42I/2 hours, the satellite would again be seen to emerge. If in the meantime the earth has moved to C, farther from Jupiter, it is clear that if light requires time for its passage, the emergence of the satellite will be seen later when the earth is at C than when at B. For we must add to the 30 times 42I/2 hours, the time occupied by light in passing over the difference between the distances [of the earth from Jupiter] G B and G C, i. e., M C. So in the other quarter, when the earth travels from D to E, approaching Jupiter, the eclipses will occur earlier when the earth is at E than when at D. Now by many observations of these eclipses throughout ten years, it is shown that these inequalities are actually of some moment, amounting to as much as ten minutes or more: whence it is argued that in traversing the whole diameter of the earth's orbit, K L, double the distance from the earth to the sun, light takes about 22 minutes. < LjIlibrary. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfe
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