Who first measured the speed of light?
Who discovered the speed of light? When was it discovered? How was it calculated or derived?
Scientists have been trying to study the speed of light since the ancient Greeks. Greek astronomers believed, amongst other things, that the speed of light was effectively infinite. They had no way to test this educated guess, however. Nevertheless, it was generally taken for granted that light-speed was infinite until the astronomer Galileo in 1600. One of Galileo's more unsuccessful experiments was his attempt to quantify the speed of light, by using distant lanterns with shutters, which an assistant opened at specified times. Galileo would try to record how long it took light to get to him from across the field on which the experiment was done. His only conclusion was that light-speed was "fast."
The first true measurement of light-speed came in 1676 by a fellow named Olaf Roemer. He noted that the time elapsed between eclipses of Jupiter with its moons became shorter as the Earth moved closer to Jupiter and became longer as the Earth and Jupiter drew farther apart. This anomalous behavior could be accounted for by a finite speed of light. He calculated that the speed of light was something like 2.14 x 108 meters per second. This measurement, considering its antiquity, method of measurement, and 17th century uncertainty in exactly how far Jupiter was from the Earth, is surprisingly close to the modern value of 2.99792458 x 108 meters per second. These modern values are obtained using devices called laser interferometers, which can very precicely pin down speeds and distances.
Get More 'Curious?' with Our New PODCAST:
- Podcast? Subscribe? Tell me about the Ask an Astronomer Podcast
- Subscribe to our Podcast | Listen to our current Episode
- Cool! But I can't now. Send me a quick reminder now for later.
- Why is looking out into space the same as looking back in time?
- How do scientists slow light down?
- What is the speed of gravity?
- Is the speed of light constant?
How to ask a question:
If you have a follow-up question concerning the above subject, submit it here. If you have a question about another area of astronomy, find the topic you're interested in from the archive on our site menu, or go here for help.Table 'curious.Referrers' doesn't existTable 'curious.Referrers' doesn't exist
This page has been accessed 93999 times since September 29, 2002.
Last modified: December 8, 2004 10:03:04 PM
Ask an Astronomer is hosted by the Astronomy Department at Cornell University and is produced with PHP and MySQL.
Warning: Your browser is misbehaving! This page might look ugly. (Details)