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Is a time reversal like that in the movie Creed scientifically possible?

Before answering this question, I think it is necessary to state in advance: first of all, the term "time" here refers to the familiar and general understanding of time in daily life. Secondly, what we want to talk about today is the overall time reversal, not simply going back to the past.

Although Einstein said: time and space are one, can not be separated. But in the world we are familiar with, the dimension of time is very special. Unlike all spatial dimensions, the dimension of time is always one-way.

From the perspective of special relativity alone, the "clock slow effect" means that for a mass object, the faster it moves, the slower its time travels relative to the outside world, that is, "time expansion".

"nonsense! is there any proof?"

Yes, and there are many. Without taking the example of today's satellite positioning, in fact, as early as the 1940s, scientists proved the existence of the clock slow effect through cosmic rays.

They experimented with muons produced by cosmic rays colliding with the atmosphere: if the clock slow effect of relativity is not taken into account, the muons coming from high altitude should soon decay into other particles, so the number of muons measured at different elevations should vary widely. But in the experiment, low-altitude detectors also captured a large number of microns. This is because for the muon itself, because it flies to the ground at near the speed of light, the time of the muon itself becomes slower for ground observers, so the number of decaying muons becomes smaller.

I believe the saying that "the faster the speed, the slower the time" is no stranger, and many people should have heard the second half of the sentence: "when the speed exceeds the speed of light, then time will go back." Does this statement make sense?

You might say that the speed of light is the upper limit of the speed of the real world, and it is impossible to move faster than the speed of light in terms of special relativity.

Yes, usually you can say that the second half of the sentence is "nonsense". After all, for any particle with mass (rest mass), it can't be faster than a zero-mass photon. Unless there is an exception: the mass of this particle is an imaginary number! This is a kind of tachyon (tachyon) proposed in the 1960s.

Tachyons are hypothetical particles derived mathematically.

Taking the special theory of relativity as an example, if the energy-momentum equation (

After a simple transformation, you can get the following formula:

Where E is the total energy of the particle and m is the rest mass of the particle.

As you can see, if the velocity v of the particle is forced to exceed the speed of light c, then it becomes negative under the root sign. Squaring a negative number means that the denominator becomes an imaginary number. In order to prevent the total energy from becoming an imaginary number, then the molecule must also be an imaginary number. And because the speed of light c is a constant, what is imaginary can only be the mass of the particle. Therefore, if a particle is to exceed the speed of light, it must have an "imaginary mass" (imaginary mass).

If you say "negative" mass, I can understand it. What on earth is this "virtual" mass?

And it can be seen from the formula that the faster the speed, the greater the energy of normal particles, and the faster the tachyon is, the smaller the energy is. And it is not "can" faster than the speed of light, but "can only" be faster than the speed of light. Even if there is no extra energy, the speed of the tachyon will be infinite. Well, the world of daring tachyons is all teleportation! )

Of course, you can say that these are all mathematical tricks, how can there be such a strange thing in the real world?

But if you, like Dirac, who predicted antiparticle, believe that there must be mathematical existence (even if it is not in our universe), then we can boldly imagine that there may be a "tachyon-universe universe" where matter cannot stand still and they are "running" all the time. Because the slowest speed in this universe is also the speed of light, the word "stillness" here means "moving at the speed of light"!

In the tachyon universe, all particles here are tachyons moving faster than the speed of light. If you want these particles to slow down, you need to apply extra energy to them. For particles to "stop" (that is, down to the speed of light), you will need an infinite amount of energy (just as we want to accelerate matter to the speed of light).

It can be seen that this tachyon universe is the exact opposite of our universe (slow tardyon-universe), including the passage of time here. The saying that the speed exceeds the speed of light will go backwards has become common sense here.

But if time is reversed, doesn't it mean that the law of causality in the universe will be reversed and the law of entropy increase becomes the law of entropy decrease? Is it possible that the inverse space-time in the Creed really exists?

Obviously, the conjecture of "tachyon universe" is so wild that you can't even imagine what the world might look like. But the Creed shows a different kind of time-reversed world, which is not only more "realistic" but also imaginably more "friendly". It is the anti-matter universe (anti-universe) with inverse entropy, also known as "anti-universe".

Before we talked a lot about antimatter in the anti-universe, we should be familiar with it: it has the opposite electric charge, it will annihilate immediately when it meets the positive matter, and so on. However, Feynman has put forward a more "interesting" view of the interpretation of antimatter: a time-inverted particle is actually equivalent to its antiparticle.

How do you understand this sentence?

Remember that Feynman's mentor, Wheeler, said to him one day, "I know why all electrons have the same charge and mass, because they are the same electron!" Anyone will think that this conjecture that there is only one electron in the universe is ridiculous.

But perhaps inspired by the idea, Feynman believes that the antiparticle in the Dirac equation may be an ordinary particle moving in the opposite direction along the timeline. Because he found that if the positive and negative signs of time and charge in the equation are reversed at the same time, the equation still holds. This means that particles in the passage of positive time are positive particles and particles in negative time are antiparticles. In other words, the antimatter we observe can be said to be ordinary matter that goes back to the past.

Not only that, this explanation means that both positrons and antiparticles are essentially the same particle. So the annihilation reaction can be understood as: the time arrow of the particle is suddenly reversed, and the process of time shift is accompanied by the release of energy.

How about Feynman diagram for electron annihilation reaction? is this brain big enough?

This also explains, in a way, the question of "why our universe is full of positive matter" and "where did all the antimatter produced with the Big Bang go". Because the Big Bang is accompanied by two universes, a positive universe with the passage of time and an anti-universe with the reverse passage of time.

The antiuniverse existed before the Big Bang, where there were exactly the same things as our universe: the same galaxies, the same stars, the same planets and even the same Earth. It's just that from the point of view of our universe, this anti-cosmic time flows backwards. Everything we do at this moment is also going on in the antiuniverse, except that they are "upside down" as in the Creed.

All right, to answer the first question: is there a time reversal?

For the world we live in, the inverse space-time does not exist, but it is entirely possible to deduce an inverse world mathematically.

Whether it is a relativistic tachyon universe or an antimatter-based antiuniverse, these space-time reversals are aimed at other universes. For the universe we live in, you can firmly believe:

As long as the speed of light is still the upper limit of the speed of matter, space-time reversal cannot exist; as long as the second law of thermodynamics has not been overturned, the reversal of time will only stay in the imagination.

This article comes from the official account of Wechat: Linvo says ID:linvo001, author: Linvo

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