If a person travels back n years ago, can't what he did change what happened in the future? For example, if you kill a person, and that person is your ancestor, then you shouldn't exist? Why are you still alive?

Let's start with a well-known "grandmother's paradox". It is to the effect that if we go back in time through the time tunnel and meet our grandmother, and we unfortunately kill her, then since my grandmother died when she was young, where will I come from? If I didn't have me, how could I go back in time and kill my grandmother? This creates a paradox.

This paradox is based on Einstein's general theory of relativity. General relativity holds that our universe is parallel and interconnected, and can go back in time through holes. As conceived, if a return to the past is true, the paradox described above will inevitably arise. In Einstein's special theory of relativity, we are again told that time and space are interconnected, and since the speed of light is constant, all motion, even time itself, must correspond to it, and thus time is also relative. Therefore, in order to explain the above paradox, people put forward the concept of "parallel universe", which is Hawking's "parallel space theory".

Is there an identical you somewhere in the universe reading an article that looks exactly like this one? That guy isn't you, but lives on a planet called "Earth" with mist-shrouded mountains, endless fields, noisy cities, and 7 other planets revolving around a star? His or her life experience is the same as yours every second. However, maybe she's about to put down the article at the moment, and you're going to read it.

The idea of this "doppelganger" sounds strange and implausible, but it seems that we have to accept it because it has been supported by the results of various astronomical observations. Today's most popular and simplest model of the universe states that there is a galaxy about 10^(10^28) meters away that is identical to our Milky Way, and there is an identical you in it. Although this distance is beyond people's imagination, it does not affect the reality of your "doppelganger" existence. The idea originated from a simple "natural possibility" rather than the assumption of modern physics: that the universe is infinitely large (or at least large enough) and, as astronomical observations point out, evenly distributed with matter. That being the case, according to the laws of statistics, it can be concluded that all events (no matter how similar or identical) will happen countless times: there will be countless planets that give birth to humans, and among them there will be people who are exactly like you—the same looks, names, memories, and even the same actions and choices as you—and there will be more than one, to be exact, an infinite number of them.

Recent cosmological observations show that the concept of parallel universes is not a metaphor. Space seems infinite. If that were the case, everything that could have happened would have happened, no matter how ridiculous it might have been. Far beyond our astronomical capabilities, there is a universe that is exactly like ours. Astronomers have even calculated their average distance from Earth.

You may never see your shadows, but science tells us they exist. The farthest distance you can observe is the farthest light traveled since the Big Bang: about 14 billion light-years, or 4 x 10^26 meters – that defines the size of our observable horizon, or simply the size of the universe, also known as the Hubble volume. In the same way, the other universe you are in is a sphere of the same size. The above is the most intuitive explanation of "parallel universes". Each universe is a small part of the larger "multiverse".

Speaking of which, another concept is introduced - space-time tunnel

Let's start with the concept of time

Time, people know. One point, two points, three points, one minute, two minutes, three minutes, and the time system is composed of seconds, minutes, hours, days, weeks, months, years, and centuries. In fact, there are those that are less than the second, and there are those that are greater than the century. Like an object, such as a stone, a block of stone, a molecule of stone, an atom, a proton, a quantum, etc. Time is the same. The difference is that stone can be seen and molded, while time is colorless, tasteless, and formless. But they live in every corner around us. The location where it exists is also part of the constituent system. The time system develops with events and matter, and events and matter are also constrained by the time system, and no event or matter can leave this time system. In the invisible system of time, any matter, event is unconditional, automatically follows the law, it is not a treaty, it is not a law. If time is a system, then it is the most perfect system. There are no so-called loopholes, upgrades. This time system has no head and no tail, and even if all human beings are wiped out and all living things disappear, time still exists in every corner.

Here's an experiment to illustrate:

This is a hypothesis: there is a person and a beam of light (matter); On a straight road, surrounded by pitch darkness, the five fingers of the hand are not visible (condition); Conduct a race (event); Note: The human eye here does not act as a guide, only as an input graphics device.

Okay, you've got it all. Let's get started:

1. Under normal circumstances, people are slower than light, so light will first transmit the end of the situation to people's eyes. This is normal.

2. Let's assume that man is faster than light, and at this time, I reach the end before the light, but he sees nothing.

In this way, in two cases, the conclusion is: beyond the speed of light, you can't see anything, nothing, but this is still calculated by time, and we still live in a time system. That is to say, no matter how we run, the capital city will not be able to get out of this circle (time system).

Then some people will say that in reality, there is light everywhere, and it is not everywhere, so where do we still have things to see?

Yes, in reality, there is light everywhere, but have you ever had such an experience: sitting on the train, looking at the scenery outside the window, the car is driving so fast, what do you see? What you see is a picture distorted by time, and what is light to time? It's just a guy who wants to lose the race against it.

My point of view is that one of the systems of existence in this universe is the system of time.

Space-time turbulence is the chaos of time and space, in a certain period of time, a small black hole appears in space, sucking people (things) into it, then this person (thing) travels through time and space, to other times and places. Occasionally, this kind of small black hole appears in space-time, and it is a small error of it, and the chance of its occurrence is only a few hundred million. Time and space are just like people, when they do something, there will be a little difference from reality. And this black hole is a little difference in time and space, this black hole can only be said to be abstract, it can also be abstracted into a gap, a gap, in short, a flaw. This flaw is big and small, temporal, spatial, and spatial: temporal, as small as an hour ago, or an hour later; As big as traveling to the time before the birth of the earth, when the sun goes out.

In terms of space, it is as small as shuttling to about 100 meters; As big as traveling beyond the galaxy!

Time and space are all traveling, or from Beijing in the 21st century to New York in the 17th century, or from Xianyang today to Xi'an tomorrow.

Personally, I think it's pseudoscience, and humans always classify those unsolved mysteries as "traveling through time" or "being captured by aliens". But if I think about it differently, this is not necessarily impossible, in short, there is no conclusive evidence for human beings to prove the turbulence of time and space.

so

Can you turn back time?

In fact, human wisdom is not enough to stop the flight of time; Theoretically, it's not impossible to go back in time and back to the past. According to Einstein's theory, time and space can change at the speed of light. So, if an object is traveling at the speed of light at 300,000 km/s, space can be shortened and time can be slowed down.

American physicists Ford and Roman argue that Einstein's theory of relativity does not strictly rule out travel faster than the speed of light or time travel. There are two major conditions that must be met for time travel, namely "wormholes" and "negative energy". Different times and spaces in the universe can be communicated through "wormholes". "Negative energy" can defy gravity and be used to open "wormholes" and stabilize "time tunnels". Johnson, a professor of theoretical physics at the University of Oxford, also believes that one day mankind will be able to travel the universe through the ages. Professor Ford of Tufoz University said that "going back to the past" is logically problematic: in the movie, back to a time when grandparents never met, the grandson "blocked" them from meeting, and there would be no parents, and of course the grandson "protagonist" would not be born. However, the "Possibility" argues that people who come to the "past" cannot obstruct or intervene in what has happened in the past like the grandson in the movie, and that the "time travelers" can only watch and cannot change the past, so there is no logical problem. (To be continued.) )