Children's Science Encyclopedia - (Pocket Library)

Author: Book Writing Group
Publisher:
Publish Date: 2006-08-01
Features: Fizeau made some improvements to the experimental setup. To reduce errors, he replaced the second person in Galileo's experiment with a mirror and used a rotating gear instead of a clock for timing. Fizeau changed the distance between the two mountains, selecting two peaks 7 kilometers apart, and placed the rotating gear and a mirror on each peak. After the experiment began, Fizeau first allowed light to pass through the gap between the two teeth of the gear and shine onto the mirror on the other mountain. After reflecting off the mirror, the light returned through the gap between the other two teeth of the gear. By calculating the speed of the gear's rotation, the time it took for the light to travel back and forth could be determined. Fizeau's experiment yielded a result that the speed of light was 315,000 kilometers per second. To commemorate Fizeau's great contribution, people hailed him as "the man who captured light."
The human pursuit of the speed of light did not stop with Fizeau. In the 19th century, more accurate results were obtained in the exploration of the speed of light. The first American to win the Nobel Prize in Physics was physicist Albert Michelson. He made outstanding contributions in the fields of precision optical instruments and the use of these instruments for metrology and spectroscopy research. Michelson also measured the speed of light, and his measurement result was one of the most precise in history. Michelson graduated from the U.S. Naval Academy in 1873 and was retained by the academy due to his excellent academic performance. Due to practical applications in navigation and theoretical research needs, Michelson was also very interested in measuring the speed of light. In 1879, Michelson received $2,000 in funding from his father-in-law and used this money to improve the rotating gear device. Coincidentally, at the time, the Commissioner of the U.S. Nautical Almanac, Newcomb, was also interested in this work, so the two began to collaborate. Fortunately, the project also received government support. Over the next 50 years, Michelson and Newcomb continuously improved and repeated the experimental results, finally determining the speed of light to be 299,764 ± 4 kilometers per second. Unfortunately, during one of the speed-of-light measurements, Michelson died of a sudden stroke at the age of 79. P25