Question

How come we haven't measured the speed of light yet?

Answer 1

Hi,

-The reason why we haven't measured the speed of light is because it has already been accurately measured. In fact, the speed of light is a fundamental constant in physics and is known to be approximately 299,792,458 meters per second in a vacuum.

The first successful measurement of the speed of light was done in the 17th century by Ole Rømer. He observed the moons of Jupiter and noticed that the time it took for the moons to appear and disappear varied as Earth moved closer to or farther away from Jupiter in its orbit. Rømer realized that this variation was due to the finite speed of light, and he estimated its value to be about 225,000 kilometers per second.

Since then, various methods have been developed to measure the speed of light more accurately. One commonly used method involves using a laser and a rotating mirror to measure the time it takes for light to travel a known distance. This method, known as the "time-of-flight" method, allows scientists to measure the speed of light with high precision.

Another method involves using interferometers, which are devices that split light into two beams and then recombine them. By carefully analyzing the interference pattern created by the recombined beams, scientists can determine the speed of light.

In addition to these experimental methods, the speed of light can also be derived from fundamental constants of nature, such as the permittivity and permeability of free space, which are related to the electric and magnetic properties of light.

So, to summarize, the speed of light has been measured using various experimental methods and can also be derived from fundamental constants of nature.

Let me know if my answer is wrong or not what you were looking for because I would like to help all I can.

If you have any questions let me know and I may be able to help.

I hope that my answer helped you out. :)

Answer 2

The speed of light is an assumption, not a certainty. It’s an assumption in that we have never experimentally measured the one-way speed of light. The best we have been able to do, even with our most sophisticated modern technology, is measure the roundtrip speed of light and assume that the speed is the same in both directions. This is what’s known as being isotropic — a value is uniform no matter the direction. To be anisotropic, then, means that a value varies depending on the direction. Einstein’s theory of special relativity assumes that the one-way speed of light is constant and isotropic. So what happens if the one-way speed of light is anisotropic? What does it mean for our universe if one of our most successful theories of physics is based on an assumption that turns out to be false?

let’s ignore the fact that our measurement units are currently related to the supposedly constant speed of light. This wasn’t always the case and as was already pointed out we did try to measure the speed of light many, many times.

However, we can only effectively measure this if you measure the two-way travel of the light from point A to point B and back to point A. We can never measure the speed of light one way, from A to B.

In order to measure speed you calculate the time it takes for something to reach from point A to B and then divide this time by the distance, right? The problems is that in order to do that for light for one way trip, you need two clocks and they must be perfectly synchronized. The theory of relativity makes this virtually impossible, there is no way for us to synchronize our clocks through distance and time.

So we end up with the only possible measurement here, from A to B and back to A. This makes it perfectly possible for light to have different speed from A to B than from B to A. Yes, it may seem highly unlikely, but it is possible. We have no way to test it, no way to prove it and nothing will be different for us either way.

I hope this helped!

~~~Harsha~~~