Who discovered the speed of light ?

[bikeinn]

  Who discovered   the speed of Light and How?

[Thunderchild]

can't help you as to who but it has been known for like 200 yrs and the speed 300'000 KM per second

[IndieSinger]

Part One:

According to this site:

The first recorded discussion of the speed of light (I think) is in Aristotle, where he quotes Empedocles as saying the light from the sun must take some time to reach the earth, but Aristotle himself apparently disagrees, and even Descartes thought that light traveled instantaneously.

[Galileo] then goes on to suggest a possible way to measure the speed of light. The idea is to have two people far away from each other, with covered lanterns. One uncovers his lantern, then the other immediately uncovers his on seeing the light from the first. This routine is to be practised with the two close together, so they will get used to the reaction times involved, then they are to do it two or three miles apart, or even further using telescopes, to see if the time interval is perceptibly lengthened. Galileo claims he actually tried the experiment at distances less than a mile, and couldn't detect a time lag.

[IndieSinger]

Part Two:

The first real measurement of the speed of light came about half a century later, in 1676, by a Danish astronomer, Ole R�mer, working at the Paris Observatory. He had made a systematic study of Io, one of the moons of Jupiter, which was eclipsed by Jupiter at regular intervals, as Io went around Jupiter in a circular orbit at a steady rate.

Wikipedia also has a good article on the speed of light with a section on its history.

And finally: Click here to find out how to measure the speed of light using a bar of chocolate and a microwave.

[rojash]

IndieSinger, none of the links in your Part 2 seem to work. Perhaps you could just type the address in clear?

Thanks

[IndieSinger]

You're right, they don't. I know why, it's ok. Here they are again:

Wikipedia article, Wikipedia's history and measuring the speed of sound with a bar of chocolate and a microwave.

Apologies for any confusion.

[rojash]

Ta

[Calvesy]

There was an experiment done in America early last century where a bright light was shone onto a rotating octagonal mirror powered by compressed air. The beam was reflected back from a remote hilltop whose distance was accurately known, back onto the mirror and into an eyepiece. If the beam could be seen it meant that the mirror had turned 1/8 th of a revolution in the time it took the beam to make the round trip.

[jake-the-peg]

The experiment Calvesy is referring to is the famous Michelson-Morley experiment this verified that the speed of light was a constant and that the speed of the earth does not affect it.

This was the spur from which special relativity was formulated.

If you look up Michelson-Morley you'll find a ton of stuff about it.