science · 23 September 1710 · 314 years ago
death
Died 23 Sep 1710 at age 65 (born 25 Sep 1644).
Danish astronomer who demonstrated conclusively that light travels at a finite speed. He measured the speed by precisely measuring the length of time between eclipses of Jupiter by one of its moons. This observation produces different results depending on the position of the earth in its orbit around the sun. He reasoned that meant light took longer to travel the greater distance when earth was travelling in its orbit away from Jupiter.
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