Definition of the speed of light: c = 299792458m/s = 299792.458km/s.
Calculated value of the speed of light: c= the speed of light (299792.500.10) km/s) Function: When the moving speed of one object relative to another is close to the speed of light, the time of one object relative to another slows down, and the time change conforms to the Lorentz transformation. (In 1970s, it was confirmed by the difference of the same time and position of solar eclipse observed by satellite and ground observatory. The speed of light is the maximum speed known at present, and when an object reaches the speed of light, the kinetic energy is infinite, so it is impossible to reach the speed of light according to the current human cognition, so the problems of the speed of light and superluminal are beyond the scope of physics discussion.
Since the beginning of the 20th century, our theory has been subject to the speed limit verified by Einstein, namely186,282 miles per second (about 300,000 kilometers per second). Even if we accelerate the spacecraft to this speed, it will take nearly ten years to reach our nearest star system-Alpha Centauri (about 4.3 light years away) and return. In addition, the spacecraft itself has to consider energy constraints. Therefore, to achieve these goals, we must break through the speed limit. Scientists have carried out many related experiments, such as the experiment conducted by Wang Lijun of Princeton University in 2000 and the experiment conducted by German scientists in 2007, and all of them have made some progress. At first, scientists firmly believed that no matter or information can break through the speed of light, but light pulses can. In a vacuum state, light pulses measured at different positions seem to travel at incredible speed. However, this speed still can't provide much help for our space travel. The experiment in 2007 is still controversial.