On This Day In Space: Nov. 21, 1676: Astronomer accidentally discovers speed of light (Image Credit: Space.com)
On Nov. 20, 1998, the first piece of the International Space Station launched into orbit.
The 42,000-pound module is called Zarya, and it’s about the size of a tour bus. Zarya launched on board a Russian Proton rocket. Two weeks later, the STS-88 shuttle mission brought the Unity module into space.
The STS-88 astronauts connected the two modules in orbit. Zarya was built by the Russians, but it was paid for by the United States. NASA contracted a Russian company to build it for half the price of what the American company Lockheed Martin would have charged.
To his surprise, the timing of the eclipses was not consistent. When Earth was closest to Jupiter, the eclipses happened 11 minutes early. Likewise, when the two planets were farthest away, the eclipses were 11 minutes behind schedule.
Rømer figured out the pattern and made an accurate prediction for Io’s eclipse on Nov. 9, 1676. Then on Nov. 21, he took his findings to the Royal Academy of Sciences and explained that a finite speed of light must be responsible.
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