Wikipedia defines Time Travel as the concept of movement between certain points in time, analogous to movement between different points in space by an object or a person. Now time travel is a renowned genre in fiction and philosophy. It's ability to allow a person undo his past mistakes which might end up giving people a better present makes it a widely popular concept. Come on, don't you guys ever whine about your mistakes in an exam and how had you had a time machine you would have gone back to correct the incorrect. Time travel is hypothesis and so are it's rules and paradoxes, everything on a piece of paper. So in this blog, instead of writing if time travel is practically possible, we will deal with it's limitations and overcoming those limitations. Buckle up because it is gonna be a ride beyond the space-time continuum!
The grandfather Paradox
Most of us would have watched Back to the future where Marty travels back in time using an eccentric scientist's time machine. Well the grandfather paradox disproves Marty travelling back. The grandfather paradox is a paradox of time travel in which inconsistencies emerge through changing the past. It describes a person who travels to the past and kills his or her own grandfather before the conception of his or her father or mother, which prevents the time traveller's existence. Now before fella grandfathers leave the chat, the paradox doesn't exclusively insist on the contradiction of killing someone's grandpa. It indicates that even a slightest change in the past may result in a catastrophic present.
Limitations of the grandfather paradox and The Bootstrap Paradox
The limitations of grandfather paradox include the existence of multiverses. But before jumping straight into multiverses, let us look into another possibility, which we call destiny.
What if the grandfather the guy who goes back in time is not biological grandfather, but just an average Joe who works as a mechanic in a garage. The guy goes back in time, kills his grandfather, realises that he is still alive because his real grandfather abandoned his father at birth who was adopted by the guy he just killed. The guy then meets his real grandfather and they share a family moment, and that's how you make a freaking good ending! This grandfather thing is all made up, but what if a person travelling to the past was always meant to happen? Like in Harry Potter and the Prisoner of Azkaben, where Harry and Hermione travel back in time to save Sirius' soul being sucked.
Let us hear the story of a guy who receives a book "How to build a time Machine" from a random guy who knocks his door. He spends years building a time machine. After 20 years of unsuccessful attempts, he finally builds a fully functional time machine. He writes all his work in a book, travels to the past, knocks his door and gives his younger self the book he has written, so that he doesn't read the wrong book and doesn't spend twenty years building a fully functional time machine. The younger self receives the book and because of lack of technology, he spends 20 years trying to build a time machine and then again he makes one, travels back in time, gives himself the book. So what we see is a loop, called casual loop. And it doesn't violate the grandfather paradox. It is as if the person was destined to receive the book from his future self so that he builds a time machine.
But what if we ask that who gave the man the book for the first time? We cannot answer that. Because this is similar to who came first, the egg or hen! This is the Bootstrap Paradox.
But then if we introspect then this question is as good as what is the numerical value of the left extremum on number line. So dropping this question won't harm anyone.
The Grandson Paradox
The above paradoxes exclaim that going to the future is theoretically possible, because going to the future won't change the past, so the present won't change. But but suppose, a person goes 50 years in the future and his grandson kills him in the future before he procreates his son in present. The person's son is thus never born and the grandson never existed. But the grandson just killed him, didn't he! Now the future won't change within a fraction of a second. This is the grandson paradox.
So where are we getting it wrong. Now with past travel already Debatable and future travel pretty much hanging in the middle of uncertainty, where do we stand in travelling from one point in time to another.
Back from the future
So the thing is if someday we build a time machine and go to the year 2030,then yeah, it's fine. Nothing bad happens as long as we don't get ourselves killed. But the thing is if we go to the future, then the future becomes our present and the present becomes our past. And bootstrap doesn't work in the future, because unlike the present which is destined, the future is more of a subjective kind of stuff and may differ based on differences in our present actions. So even if we go to the year 2050,there is no turning back from there! A time traveller from the past will be stuck in the future till eternity or death, whosoever comes first!
So we cannot consider time travel in our universe. But what if there exist other universes. Stay tuned to my blog as this time we travel beyond our observable universe.
New blog on multiverses on 22nd May.
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