The precise speed of light is not three times ten to the eighth power?It was only finally determined in 1983!

If you were to ask what is the fastest speed in nature? Everyone should know that it is the speed of light. But what is the speed of light? Most people's answer must be 3 times 10 to the eighth power in meters per second. And I don't know how the speed of light is calculated. Let's talk about the speed of light today. (My summary of the article's highlights is at the end of the article. If you're in a hurry, you can skip straight to the end to read the summary.)

Let's start with the definition of the speed of light, which is the speed at which light or electromagnetic waves travel in a vacuum or medium. Note that light does not travel at the same speed in a vacuum and a medium. Even if light can pass through a medium, the speed of light propagation will slow down or even decrease. So the fastest speed in nature would be the speed at which light travels in a vacuum. 3 times 8 times 10 is not the most accurate value of the speed of light. The most accurate value of the speed of light is 299792458m/s. Of course, we don't normally need such an accurate value, but if we were to calculate it precisely, this difference could lead to many deviations.

So how did the speed of light come about? The ancients believed that the speed of light was infinite. After all, light gives the impression of being instantaneous. Who would have thought that light had a speed limit? Of course, ideas were not as advanced and technology was not as developed as it is now. Some people might have thought about it, but wouldn't have calculated it.

The first person to try to measure the speed of light failed. This was Galileo. He sent men to two hills about a kilometer apart. Two men held lanterns in their hands. One lifted the cloth covering the lantern and the other lifted the cloth covering the lantern as soon as he saw the light coming from it. This time interval is calculated to obtain the speed of light. But Galileo did not take into account human reaction time, the speed of light was too high and the interval of one kilometer was too short.

This dilemma was not broken until 1676 when the Danish astronomer O.C. Romer proved that light travels at a finite speed using the time variation of eclipses of Jupiter's moons (the satellite eclipse method). He observed that Jupiter has satellite eclipses at regular intervals. This cycle time is longer when the Earth is far from Jupiter than when the Earth is close to Jupiter. Such observations can only be made when the speed of light is limited. To obtain reliable results, Romer made observations for a whole year and eventually arrived at the speed of light by observing the time variation of satellite eclipses and the diameter of the Earth's orbit.

However, the calculated speed of light was only 214,300km/s. Although inaccurate, this was the first time in human history that the speed of light was measured. The reason for the inaccuracy was not the wrong method, but the radius of the Earth's orbit used in the calculation. The exact value was not known at the time. So this inaccuracy led to the inaccuracy of the speed of light. Later, when the exact value of the Earth's orbit was known, a relatively accurate speed of light was obtained (299,840 60 km/s).

In 1727, the British astronomer j. Bradley used stellar aberrations to estimate the speed of light as 303,000 km/s. Aberration is the deviation of the direction of light observed by a moving observer from the direction of light observed by a stationary observer at the same time and in the same place. Bradley spent a year observing the stars and finally calculated the speed of light, but the data is not the most accurate because the Earth is rotating.

Both of these methods calculate the speed of light by observing celestial bodies. Both methods are always less accurate. The experiment to directly measure and calculate the speed of light was proposed by the French physicist Fissot in 1849, the spinning gear method. This is a method in which light is allowed to pass through a rotating gear that regularly blocks the light and hits the rear view mirror. However, the results calculated with this method are not as accurate as the first two methods.

In 1851, the French physicist Foucault changed the rotating gear method to the rotating mirror method by replacing the gear with a high-speed uniform reflector. This change led to the speed of light eventually being measured at 298,000 ± 500km/s. Later, the Polish-American physicist Michelson combined the two previous methods to create the rotating prism method. In 1926, the most accurate speed of light of the time appeared, 299,798 4km/s.

Later, with the development of electronics, more methods of measuring the speed of light were created, such as Kerr boxes, resonant cavities, and photoelectric distance meters. , an order of magnitude higher than direct optical methods. The laser device was invented at a time when the uncertainty in the measurement of the speed of light was greatly reduced. Eventually, at the 17th International Congress of Metrology in 1983, the speed of light in a vacuum was determined to a precise value of 299792458m/s.

By this time, the fastest speed in nature had been determined. The speed of light plays a very important role in the development of science. One of the things that most people should pay attention to is what Einstein said. When we can exceed the speed of light, we will be able to travel through time and space. But so far it has not been possible to exceed the speed of light. As the speed increases, the dynamic mass increases with the speed. So only a photon without mass can reach the speed of light. Other objects with mass, even if they are small, become heavy as they approach the speed of light.

Perhaps one day there will be a technology that will allow us to break the speed of light, but that will never wait for our lifetimes. Maybe there is a technology that will avoid the whole FTL thing and allow us to travel through time and space, but it's also out of reach. Let's not worry about things that are too far away. Let's live in the present!

I think it is a summary of the main points :

1. the speed of light is the speed at which light or electromagnetic waves travel in a vacuum or medium.

2. Light does not travel at the same speed in a vacuum and a medium. Even if light can pass through a medium, the speed of light propagation will be slowed down or even cut. So the fastest speed in nature would be the speed at which light travels in a vacuum.

3. The most accurate value of the speed of light is 299792458m/s.

4. In 1676, Danish astronomer O.C. Romer first calculated the speed of light using the eclipse times of Jupiter's moons.

5. In 1727, the English astronomer j. Bradley estimated the speed of light to be 303,000 km/s using stellar aberrations. The Polish-American physicist Michelson combined the previous methods of rotating gears and rotating mirrors to create the rotating prism method. In 1926, the most accurate speed of light at that time appeared, 299798 4km/s.

6. With the development of electronics, more methods of measuring the speed of light were created, such as Kerr boxes, resonant cavities, and photoelectric distance meters. , an order of magnitude higher than direct optical methods. The laser device was invented at a time when the uncertainty in the measurement of the speed of light was greatly reduced. Eventually, at the 17th International Congress of Metrology in 1983, the speed of light in a vacuum was determined to a precise value of 299792458m/s.