Is the invariance of the speed of light redundant in special relativity?

If a velocity greater than c is taken, the value of the Lorentz transform equation becomes an imaginary value. If infinity is substituted for the speed of light c, the Lorentz transform equation becomes the Galilean transform equation. So the speed of light has a "limit" meaning here.

The invariance of the speed of light is definitely not superfluous in special relativity. If the principle that the speed of light does not change is redundant, then the whole edifice of relativity will collapse. If this theorem is not satisfied, the value of the speed of light will change with the reference object to the point that it will be completely meaningless, and it will become impossible to measure the speed of light.

For details, please refer to "A Brief Introduction to Special and General Relativity".

You can't always have zero bounty points for such a question, right? Hehe.

The speed of light does not change, and the principle of variable time is the basis of the theory of relativity.

If the speed of light was variable, the theory of relativity would not hold.

If you understand this, would you still think that the principle of the invariance of the speed of light is redundant in special relativity?!!?

First of all, there was the McMoe experiment, and then there was Maxwell's equation. The principle of relativity cannot explain the McMoe experiment, because what the McMoe experiment wants to prove is not the equivalence of the inertial frame, but the impracticality of the superposition of velocities to the speed of light.

For example, if you are on Earth, you see a light (the light source is on Earth) shooting to the right with a velocity of c, and at the same time, a train on the right is coming to the left with a velocity of v. In this way, according to the principle of velocity superposition, you can conclude that the relative velocity of the train and the photon is c+v. However, the experimental results show that the speed of light seen on the train is still c, and the speed of light is constant for any reference frame, which is called the theory of invariance of the speed of light.

It is also the basis of the theory of relativity.

Not allowed, I don't know if you have read the "Encyclopedia of China" or "Encyclopedia of Chinese Children", all of them have answered this question, the answer is no, One of the explanations is: Scientists once studied the possibility of exceeding the speed of light, and fantasized about one day being able to build rockets moving faster than the speed of light. In this way, people can catch up with the light signals emitted on the earth by simply riding this rocket and thus see what happened on the earth in the past.

This means that at the speed of light, time will be reversed, and people will pass tomorrow, today, and then yesterday. In other words, a person becomes an old man first, then a young man, a teenager, and then a baby. This phenomenon is unimaginable for people living in our physical world.

As you know, if a missile is launched at the speed of a jet fighter flying at the speed of sound, and its speed relative to the aircraft is also comparable to the speed of light, then, in the eyes of people on the ground, the missile will fly forward at twice the speed of sound. This is a conclusion based on the synthetic formula of the velocity of classical physics. But if a beam of light is fired at a rocket traveling at the speed of light, will that light travel forward twice the speed of light for an observer on Earth?

This question was a headache for scientists at one time. It was not until the end of the last century, when American scientists Michael Sun and Morey collaborated on a famous experiment that gave a largely clear answer to this question. They confirmed such an important conclusion:

The speed of light in a vacuum never changes, regardless of the observation system in which it is measured, and whether or not the light source emitting the speed of light is in motion. This shows that the speed of light is the "absolute champion" of nature as we know it today, and it is the limit of movement. Therefore, time is never turned back.

In fact, sometimes the explanation is very simple, in space physics, space and time are closely related. I'll give you an example, and you'll probably understand why. Take sunlight as an example, because it takes 8 minutes and 23 seconds for sunlight to reach the Earth, in other words, the sun you see is always the same as the sun 8 minutes and 23 seconds ago.

Light travels at the speed of light, so in space physics, distance is sometimes expressed in terms of time, such as light years that you are familiar with. A light-year is a distance of light that has one year. There is both time and space in it.

All that's left is to solve the problem of exceeding the speed of light. You should draw a timeline, you are standing at this point, the sun is 8 minutes and 23 seconds ago, if it exceeds the speed of light, then you are not seeing the sun 8 minutes and 23 seconds ago? So if you exceed the speed of light, time will go backwards.

In general relativity, it is not allowed to exceed the speed of light. Thank you、It's not easy、Everyone。

Isn't the speed of light constant?

After bending, the resistance is increased, so it changes.

Is special relativity or general relativity right? It can't all be right, right?

This point alone is true in a broad sense.

What about in the narrow sense? Constant, huh?

Teacher: Why don't you speak?

This is the principle of relativity, to put it bluntly, when studying motion, you need to choose an inertial frame of reference first, and in contrast to other references, special relativity holds that the speed of light is constant.

Isn't general relativity an inertial frame?

Inertial and non-inertial frames are not defined by general relativity.