The velocity of light, denoted by the symbol "c," can be measured through various experimental techniques. However, it's important to note that the speed of light is not directly measured by tracking the velocity of an electron in a circuit. Instead, the speed of light is a fundamental constant of nature that is determined through a combination of different experimental methods and theoretical considerations.
One of the earliest and most famous experiments to measure the speed of light was performed by Danish astronomer Ole Rømer in the 17th century. Rømer observed the motion of Jupiter's moon, Io, and noted that the time between its eclipses by Jupiter varied depending on the Earth's position in its orbit. By analyzing these observations, Rømer was able to estimate the speed of light, although his measurement was not very precise.
Over time, many other methods and experiments have been developed to measure the speed of light more accurately. These include:
Fizeau's Rotating Toothed Wheel: In 1849, French physicist Armand Fizeau used a rapidly rotating toothed wheel and a beam of light to measure the speed of light. By comparing the speed of light in the laboratory with the rotation speed of the wheel, he obtained an experimental value for the speed of light.
Michelson's Interferometer: In the late 19th century, American physicist Albert A. Michelson used an interferometer, a device that splits a light beam and recombines it, to measure the speed of light. By comparing the time it takes for light to travel different paths in the interferometer, he determined the speed of light.
Time-of-Flight Techniques: Modern techniques involve measuring the time it takes for light to travel a known distance. This can be done using highly accurate clocks and sophisticated instruments. For example, lasers and optical fibers are employed to measure the time it takes for light to propagate over specific distances.
It's worth noting that the speed of light is now defined as a fixed value in the SI (International System of Units). It is defined to be exactly 299,792,458 meters per second, making it a fundamental constant of nature.
To summarize, while the maximum velocity of an electron in a circuit is limited to speeds on the order of magnitude you mentioned, the measurement of the speed of light involves specialized experimental techniques that are not based on tracking electrons in circuits. Instead, these techniques are designed to directly measure the propagation of light itself and have been refined over centuries to determine the precise value of the speed of light.