How Did Physicists Determine the Speed of Light?

[T.O.E Dream]

This isn't on why the speed of light is the cosmic speed limit. I want to know how did physicist determine it? What experiment did they perform? What calculations did they make? They obviously didn't go into outer space and shined a light then see how long it took. Did they use a telescope? Help!

 

[malawi_glenn]

I did some google:
http://www.colorado.edu/physics/2000/waves_particles/lightspeed_evidence.html

One can also measure the speed of light by measuring masses of particles (E = mc^2) etc.

 

[Entropia]

The determination of the speed of light is a fundamental achievement in the field of physics, and it has been a topic of interest for scientists for centuries. The first successful attempt to measure the speed of light was made by the Danish astronomer Ole Rømer in the late 17th century. Rømer observed the eclipses of Jupiter's moons and noticed that the time between eclipses varied depending on the Earth's position in its orbit around the Sun. He hypothesized that this was due to the finite speed of light, and he was able to use this information to estimate the speed of light to be approximately 220,000 kilometers per second.

However, it wasn't until the 19th century that more accurate and precise measurements of the speed of light were made. One of the most famous experiments in this regard was conducted by the French physicist Hippolyte Fizeau in 1849. Fizeau used a rotating toothed wheel and a beam of light to determine the speed of light. He observed that when the wheel rotated at a certain speed, the light beam could pass through one gap and be blocked by the next gap. By measuring the rotational speed of the wheel and the distance between the gaps, Fizeau was able to calculate the speed of light to be 315,000 kilometers per second.

Another important experiment was conducted by the American physicist Albert A. Michelson and the chemist Edward W. Morley in 1887. They used an interferometer, a device that splits a beam of light into two perpendicular beams and then recombines them, to measure the speed of light. By measuring the interference patterns of the two beams, Michelson and Morley were able to determine the speed of light to be 299,796 kilometers per second, which is very close to the currently accepted value of 299,792.458 kilometers per second.

In modern times, the most accurate and precise method of measuring the speed of light is through the use of lasers. By measuring the time it takes for a laser beam to travel a known distance and using the equation speed = distance/time, scientists can determine the speed of light with incredible accuracy.

In conclusion, the determination of the speed of light has been a result of centuries of experimentation and refinement. From the first observations of Jupiter's moons to the use of advanced technology like interferometers and lasers, physicists have continuously improved our understanding of the speed of light and its fundamental role in the universe.