Traditional thinking tells us: it must be super-light. Even elementary school students know the answer, which is a simple superimposed arithmetic problem.
But if it really exceeds the speed of light, it means that Einstein's theory of relativity will be overturned. And if even elementary school students know the answers, how could Einstein not know?
So, the final answer is definitely: it has not exceeded the speed of light. So what's going on?
Simply put, once the problem of sub-light speed flight is involved, we cannot think about the problem with traditional thinking. The relative speed superposition formula we learned in school is actually the Galileo transformation , which is based on the absolute view of time and space in Newton .
But the theory of relativity tells us that space-time is not absolute, space-time is elastic. In a state of high-speed movement, time and space will change significantly.
and the speed is equal to distance (that is, space) divided by time. When time and space change significantly, of course, we cannot simply use speed superposition to solve the relative speed problem.
That is to say, in the sub-light speed field, speed superposition is not desirable, the Galileo transformation is no longer applicable, and the formula V=V1+V2 is no longer applicable.
To put it bluntly, the Galileo transformation is only applicable to the low-speed world. In the low-speed world, we can approximately believe that time and space are absolute. In our daily lives, your second is no different from the second I feel, because we all live in a low-speed world and cannot feel the impact of speed on the passage of time.
But once you come to the sub-light speed world, it is very different. The Galileo transformation error is relatively large. If you no longer use it, you must use the more accurate Lorentz transformation , because the sub-light speed world will have obvious time expansion and ruler shrinkage effects. The faster the speed, the slower the time and the shorter the distance.
Lorentz transformation is expressed in formulas, w=(u+v)/(1+u·v/c^2).
From the formula, it can be seen that the Galilean transformation is actually a special case of the Lorentz transformation and is an approximation of the low-speed world. Because when both u and v are very small, the denominator in the formula approaches infinitely 1, and the formula is simplified to: w=u+v, that is, Galileo transformation.
But when u and v are close to the speed of light, the influence of the denominator cannot be ignored. In a special case, that is, both u and v are equal to the speed of light, what is the final result? Still the speed of light, not twice the speed of light!
So, even if the speed of both objects reaches the speed of light, their relative speed still cannot exceed the speed of light, but is still the speed of light. If the speed of any of the objects does not reach the speed of light, the relative speed of the two will be smaller than the speed of light.
and Special Relativity tells us that the speed of an object cannot reach the speed of light, so, no matter what, the relative speed of both objects will be smaller than the speed of light. Even if both objects fly in the opposite direction at 99% speed, their relative speed still cannot reach the speed of light!
