According to Einstein's theory of relativity speculation, if the realization of FTL, humans can travel through?

If humans achieve superluminal speed, then by then we cannot achieve time rewind, can travel back to the past?

This is a topic that we often mention, but also a topic of relative interest.

Let's continue to explore it today.

Einstein's theory of relativity tells us that time in the universe will change with the speed of the object's movement, the faster an object moves, then the time around it will slow down.

If the object is moving at the speed of light, then the time around it will be at a standstill.

Time varies with speed, and this has been confirmed by scientists so far.

In the previous topic we have also mentioned, for example, using the people on the plane and the people on the earth at rest to do a comparison, the people on top of the plane, their time will pass slower than us.

People who often fly in the sky will also be younger than our people on the ground, but because this speed gap is not particularly large, so the stationary people on the ground and the people on the plane will not give us much visual difference.

Thus, according to Einstein's theory, we assume that if at some point in the future, we humans can achieve FTL, then we can go back in time.

Think about it. The faster the speed, the slower the time, when the speed is equal to the speed of light, time stands still, so if the speed of light is exceeded, will not time flow backward to the past?

Then that time does not also mean that we humans can change the trajectory of history.

To solve this question, we must first understand what is light.

Light is an important medium for us to see all objects in nature, the reason why we can see everything around us, that is, we can see the flowers and trees, the most fundamental reason is because of the existence of light.

Scientists through the astronomical telescope observe dozens or hundreds of light years away from the universe galaxy, but also because of the existence of light can be observed before you can take a picture.

Light propagates in a homogeneous medium and travels at a steady speed along a straight line.

The speed of propagation in a vacuum is about 300,000 km per second, so everything we all see in front of us now is delayed.

As a simple example, the moon and our earth are about 380,000km apart, and the speed of light is 300,000km per second.

So a beam of light wants to pass from the moon to the earth, then it takes about 1.2 seconds to experience the time.

So when you look up at the sky at night, the moon is the moon you see at this moment, not the moon now, but the moon 1.2 seconds ago.

The sun that you see when you look up now is also the sun of eight minutes ago.

On July 12, the United States published a full-color map of the universe 4.6 billion light years away.

Let us not consider the effect of the expansion of the universe, we see this scene at this moment on July 12, is also this piece of the universe 4.6 billion years ago.

Because the distance is too far, the light to our Earth telescope, the human eye inside the time, also takes a long time.

And what they are like now, we do not know.

Some of the planets may have been destroyed, or possibly by the effect of cosmic expansion, they are far away from each other.

According to such a hypothetical theory, if we humans achieve FTL and catch up with the light emitted by the Earth 2,000 years ago at FTL speed, then we could be in the Universe.

Does that mean that we humans can change history at this time?

Rigorously and rationally speaking, of course, we cannot change history.

When human beings want to stop to change history, the scene in front of us will disappear immediately.

Because as the speed decreases, all the things that can be seen in front of us will disappear.

So we can also understand it this way.

Even if mankind achieves FTL flight, advances to a corner of the universe, and waits for the light emitted from the earth two thousand years ago, then what is seen in front of us is just like a movie.

Also in terms of the law of cause and effect, anywhere in the universe, as long as something happens is something that there is no way to change.