We all wanted to go back in time. Everyone had something that could be done correctly, a mistake that could have been prevented, lives that could be saved, or a nightmare that I would like to unsee. It would seem that you come back in time, and all the world at once would have stood in its place. First love would be successful. Bitcoin would be purchased in time. We don’t know how to go back in time, and could go to what is not impossible.
And the fundamental reason for this is very simple. Right when Doc brown from Back to the future? He believed that the time paradox may break the continuum of space-time and destroy the universe. How is this even close to reality?
Well, it was a fantastic assumption, but temporal paradoxes — a serious thing. Let’s face it.
Back to the future
If you think about the scale of the modern Universe, it may seem that her appearance is something impossible. For 13.8 billion years only the visible part of her saw face and scatter many particles in its possession is of the order of 1090 particles.
In the process of these interactions formed the stars and galaxies on the largest scales, there are heavy elements, organic molecules and planets (Earth for example) that gave rise to life.
The path of our planet to produce each of us, were full of extremely improbable events because of the huge number of possibilities that could choose or not choose universe. A small change, which was negligible ten years ago, like a buzzing fly in your ear that could affect notice you your future love or not. You stumble on a Hiking path in one of the excursions, and you could be bitten by a poisonous snake, when you were still at a tender age, unable to endure the horror. The flow of water molecules along the shore of the ocean could mean the difference between the current day and the day when the ridge was tragically drowned child.
Physicists call this phenomenon “chaos”. A small difference in initial conditions of the system may eventually lead to completely different results. If we somehow could track the history of every particle in the Universe, we would find that there were specific ways and interact each of them, their unique course of events. This path has not been carved in stone; if you wanted to play a simulation of the Universe a second time, you wouldn’t have had the same result.
Many of the processes in our Universe are random, including processes at the fundamental, quantum mechanical level. Their results are inherently uncertain and almost unpredictable. In quantum physics, all we can calculate is the probability of a result but not the result itself.
All this once again highlights how amazing is our universe where dizzying a large number of quantum decisions that have occurred throughout the history of the Universe, there is a picture in which you are reading this article now. The chance that the same thing will happen, even given similar circumstances and similar laws is almost zero.
So if you are going to go back in time and change the past, you will definitely find yourself in a completely different universe. All around will inevitably be different, however, there may be dire consequences.
What, for example, if you makhloevs would go back in time and meddled in important to your own existence situation? What if you prevented your parents to meet and fall in love with each other? Of course, you wouldn’t have happened. Nevertheless, you obviously exist, so can go back in time and do something that your parents didn’t conceive.
Such experiments have led people to think that traveling in past is impossible. There are so-called “grandfather paradox”, according to which the universe should not allow you to go back in time to kill your own grandfather and prevent your own birth.
But whether it will break the space-time continuum? Destroy the whole Universe?
Most likely, no. Paradoxes tell us that our usual way of thinking about this subject will at best be incomplete. But this does not mean that the consequences will be so gloomy that break the space-time or destroy the Universe. Perhaps, in the Universe there will be something else, what we do not know.
And any physicist will tell you that the most likely result of this thought experiment will not be a catastrophic paradox. Based on our understanding of the laws of physics, it is possible to outline two potential solutions.
The first is to say that the past can not be rewritten and it is carved in stone. But this assumption does not negate the possibility of travelling back in time. Imagine that you learned that with your friend something terrible would happen and you need to go back in time to warn him. You get in your time machine, go back, warn the friend and jump back to the future.
This looks like a good plan, right?
Well, in that scenario, what was meant to be has already happened. Your friend would remember that he had received your warning in the past, and would be ready for the inevitable. You have returned, did what he wanted, and jumped in future. All of this has happened before, you understand, because the events that are happening now, already happened in the past of the Universe.
In accordance with this first scenario, it turns out, out of the paradox is to realize that all you want to do and all that you do, returning back in time has already happened. The fact that the universe reached its present state, is due, in particular, actions which you undertook on each step of its existence, including your move in time.
So you essentially give up the ability to change the Universe by their actions. You are well aware that the actions that you take are of great importance for future results. If you go to work, hit your boss or go by car to the sea, the consequences will be huge. But if you go back in time and do everything there, the consequences of those actions have already been predetermined. And it’s uncomfortable and disturbing thought.
The second way is to assume that the past is not carved in stone, and your every action counts. The universe that exists today will not be tied to its current state, if you go back to the past. In this case, any action that you take will create a new, alternative history of the Universe. You can kill your grandfather before your parents are conceived; may prevent parents to meet; to kill Hitler before the Second world war or to kill Brutus before the fall of Caesar.
In short, you can change history.
In this case, the only thing you have to give up, it’s the fact that the universe in which you live will be the same once you break past and decide to return to it. Your actions can change the future, but at what price: all what will happen after your antics in the past, will be recorded in the new, alternative history. The universe, which you know has not been written or recorded in the form of the Universe that you no longer occupy.
And that’s where you were, the whole future will unfold differently. And in this new future you may never have been born. You just appeared in that moment, when arrived from his trip to the past. You’re literally from another Universe.
We don’t yet understand the true nature of our reality in full. We don’t know if our observable universe, with its rules of quantum mechanics, one of a kind or there are many other parallel universes. A lot of theories. We don’t know whether our universe is deterministic or not; although quantum physics confidently said that there may be loopholes. We don’t know whether the past is carved in stone, or water wears away the stone.
Travel back in time is definitely possible mathematically. But is it possible physically? Nobody knows.
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