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Old May 1st 2018, 01:46 PM   #1
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Roemer's measurement of the velocity of light

Roemer's calculation of the velocity of light is based on an observer on the surface of the earth propagating from L to K on the left side of figure 2 and an observed, on the surface of the earth, that propagates from F to G on the right side of figure 2 where Io forms eclipses at positions L, K, F and G. The path distances of LK and FG correspond with the 40 rotations or 1.831 x 1011 m. The earth is propagating away from Jupiter when the observer is propagating on the path of LK and the observer is propagating toward Jupiter on the path FG; consequently, the light from Io would propagate a shorter distance on the path of LK compared to the path FG. Roemer observed a 10 minute time delay of Io's eclipse, at G, that he attributed to the light propagating the extra distance KL when the observer is moving away from Io; consequently, Roemer uses the path length of FG and the 10 minute (600 s) time delay to calculate the velocity of light but Roemer does not indicate the dates of the eclipses of Io that form at L and K that is required in justifying Roemer's method in the calculation of the velocity of light.
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Old May 1st 2018, 07:33 PM   #2
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Originally Posted by lovebunny View Post
Roemer's calculation of the velocity of light is based on an observer on the surface of the earth propagating from L to K on the left side of figure 2 and an observed, on the surface of the earth, that propagates from F to G on the right side of figure 2 where Io forms eclipses at positions L, K, F and G. The path distances of LK and FG correspond with the 40 rotations or 1.831 x 1011 m. The earth is propagating away from Jupiter when the observer is propagating on the path of LK and the observer is propagating toward Jupiter on the path FG; consequently, the light from Io would propagate a shorter distance on the path of LK compared to the path FG. Roemer observed a 10 minute time delay of Io's eclipse, at G, that he attributed to the light propagating the extra distance KL when the observer is moving away from Io; consequently, Roemer uses the path length of FG and the 10 minute (600 s) time delay to calculate the velocity of light but Roemer does not indicate the dates of the eclipses of Io that form at L and K that is required in justifying Roemer's method in the calculation of the velocity of light.
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