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Unformatted text preview: and sometimes they took a little less time. Io’s period seemed to fluctuate: first Io would be behind schedule; then it would be ahead of schedule. This pattern repeated itself every year, which hinted to Roemer that the fluctuation had to do with Earth’s motion around the sun. Historical Background (cont.) Because Jupiter is farther from the sun, it moves much slower around the sun (recall Kepler’s third law). During the sixmonth period depicted above, Earth is moving away from Jupiter. Therefore, the light carrying the information of the eclipse took a little longer to reach Earth, since Earth was “running away” from that light. At the end of the six months, the light from Io had to travel an extra distance about equal to the diameter of Earth’s orbit. Roemer’s observed that Io eclipses were about 8 minutes behind schedule after six months. Knowing approximately Earth’s orbital diameter, Roemer calculated the speed of light at around 125,000 miles per second! Roemer’s speed,...
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This note was uploaded on 11/17/2011 for the course PHYS 121 taught by Professor Burgeson during the Fall '11 term at BYU.
- Fall '11