1. Røomer measures the orbital period of Io
The date was April 29, 1676. The place was the Royal Observatory in Paris. The Danish astronomer Ole Rømer was observing Io, one of the moons of Jupiter. He had been measuring the orbital period of Io since at least March 7. This can be done quite accurate to the nearest second, by noticing the exact moment at which Io enters or leaves the shadow of Jupiter. In other words, for half of each orbit, Io is eclipsed by Jupiter; one second you see it, the next second it enters Jupiter’s shadow and you don’t see it. Or, one second it is invisible, and the next second you see it, as it emerges from Jupiter’s shadow. These two events are called eclipses and emergences.
To download the article click on the link below:
http://www.michaelbeeson.com/interests/GreatMoments/SpeedOfLight.pdf
The date was April 29, 1676. The place was the Royal Observatory in Paris. The Danish astronomer Ole Rømer was observing Io, one of the moons of Jupiter. He had been measuring the orbital period of Io since at least March 7. This can be done quite accurate to the nearest second, by noticing the exact moment at which Io enters or leaves the shadow of Jupiter. In other words, for half of each orbit, Io is eclipsed by Jupiter; one second you see it, the next second it enters Jupiter’s shadow and you don’t see it. Or, one second it is invisible, and the next second you see it, as it emerges from Jupiter’s shadow. These two events are called eclipses and emergences.
To download the article click on the link below:
http://www.michaelbeeson.com/interests/GreatMoments/SpeedOfLight.pdf
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