Hey, there 🙂 As I told you in my last post about Time Loop, today I will offer you a few time travel paradox examples and we will try to understand them together.
Which are time travel paradoxes?
First, we will start with asking – what exactly is a paradox? A time travel paradox is a logical contradiction or apparent contradiction which is associated with time travel generally. They are classified into two categories: Consistency Paradoxes and Closed Causal Loop Paradoxes. A Consistency Paradox is also more well-known as a Grandfather Paradox and other variants such as the Hitler Paradox.
A Closed Causal Loop Paradox is the Predestination Paradox and the Bootstrap Paradox. Here we have to deal with a self-existing loop. In this case, cause and effect create a circle.
What is the grandfather paradox?
So, let’s see first what the Grandfather Paradox is, and I think even from the movie (Paradox), most of you know about it. What about if you found out that your grandfather did something very bad, he was a criminal or he killed your mom later…or anything like this?
You would go back in time to kill him before he has the chance to hurt people wouldn’t you?. But what happens in this case? So, if you kill your grandfather before he met your grandmother, you will never have been born and of course, you will not be around at this time to travel into the past. If you don’t travel into the past, nobody will kill your grandfather so….he will still do the crime he did. If he is not dead you will be born so…you will be able to go back in time to kill him, and so on:). It never ends:). Did you understand the idea?
This idea of going back in time and killing your grandfather, parents or any other ancestor before you are born presents a real problem for time travelers. When you go back in time and you try to kill your grandfather, we have two possibilities.
First, we have the Timeline Protection Hypothesis. In this situation, you try to kill him and every time something stops you, and you fail: Or your gun blocks or something in your way or…anything else but YOU JUST CAN’ T KILL HIM. The universe protects him and you at the same time, keeping safe the timeline you are in.
And again we have the situation when you succeed. You kill him and you just go back to your time. What happens there? You never existed, also your family and everything related to your life you knew until now would not exist. You would create a new timeline.
Scientists tried to find the answers to this problem and a new theory suggests that quantum teleportation can help to avoid the grandfather paradox; this theory was proposed by physicists at MIT. First, this is why they say it is important the post selection. Scientists claim that what a traveler can do and what he cannot do has to be post selected and such an action as killing your ancestors should be strictly forbidden during a travel into the past.
Other alternatives of grandfather paradox
Talking about changing history and timelines, the Grandfather Paradox is only on a personal level. But what about if you want to go back in time to kill Hitler (Killing Hitler paradox).
Of course, the whole world can change. The effect will not be only for you but you will create a totally different world. Even the history books are different 🙂
But, again in this situation, if you would succeed and kill Hitler, then the world would be different and you wouldn’t have any reason to kill him. It is a circle.
Another theory was proposed by the American physicist Joseph Polchinski. He showed a time paradox similar to grandfather paradox, with a billiard ball entering a wormhole and going out on the other end just in time to hit his younger self. What happens? The collision stopped the younger billiard ball to go into the wormhole.
This idea was accepted by scientists because it was based upon the laws of motion. Polchinski claims that while time travel is possible, paradoxes are forbidden. This is the solution he gave and it was called ‘timeline protection hypothesis’. It states that something will occur to stop you killing your grandfather, in order to avoid the paradox.
Seth Lloyd and other scientists have a new theory. They combine quantum teleportation with post-selection. So, in this case, they had a theory of post selected closed timelike curves (CTC). CTC is a path of the space-time which returns to the point where it started.
Talking about quantum teleportation, quantum states can be transmitted one to the other in different locations and with the post selection applied, scientists have the possibility to accept only certain results and only a certain type of state can be teleported. The states which are post selected to be self-consistent are the ones that will be teleported and only then, after being selected they can travel in the past. In this way, paradoxes will be avoided.
What do you think about this? Is it mind blowing?
Lloyd says that in order to avoid the grandfather paradox, ‘some little quantum fluctuations would whisk the bullet away at the last moment’ when trying to kill your grandfather for example.
The post selected closed timelike curves theory has an important advantage. It doesn’t require the distortion of space-time to travel in the past as in other theories. The distortion of space-time can be found only in black holes and other extreme environments which make time travel in the past impossible to realize as we can see in those theories.
Post selected closed timelike curve is still a theory but scientists hope that soon will be proved and they say that it will maybe allow time travel in the past without general relativistic closed timelike curves and if nature provides the nonlinear dynamics than particles and humans can tunnel from the future into the past.
What can we do? Just let the time and the great minds to do research and give us more details? Can we travel in the past without creating a mess in the present? What do you think?
I will show you here a short video, helping you to understand everything easily. Thanks for visiting my site and today and I would really like to know your opinion 🙂 Feel free to leave your comments below.
So if you are still here and read the post until the end I suppose you may like the posts below too :). Have a nice day.