I’ve been obsessed with time travel since I watched “Back to the Future” and possibly before that. To a curious mind, not being able to go back to, say, the time of the dinosaurs and actually see them is incredibly frustrating. Despite my fascination and probably everyone else’s, time travel wasn’t seriously entertained as a possibility until the early twentieth century, when our new theories about space-time seemed to allow a new batch of crazy possibilities.
The whole “serious science” talk about time travel got started with General Relativity. To be more precise, with Special Relativity it already became demonstrably true that time travel is possible, though only to the future: if you travel at close to the speed of light, you will age less than the people around you and thus will be able to see the future. Unfortunately, you may not be able to go back, which makes the whole thing a lot less attractive.
The idea of backwards time travel, however, turned out to be lot more problematic. In this case and despite what Doc Brown said in Back to the Future, it’s not enough to travel at 88 mph on a Delorean to disappear into the past. However, General Relativity does provide us a way to go back: since space-time is curved, one can imagine different regions of space-time located at different being connected by “bridges,” which are normally referred to as wormholes.
So yes, General Relativity allows for time travel, apparently. But combining Relativity with Quantum Mechanics does not. In 1993, Matt Visser proved that the only method for keeping the two mouths of a wormhole open (feeding it exotic matter) will either collapse the wormhole or make the mouths repel. So there went most people’s hopes for time travel, including mine.
Of course, there were already some of very powerful arguments already against the possibility of time travel, of which I will mention a couple. The first is by Stephen Hawking, who uses a modified version of the Fermi Paradox: he argues that the fact that we’re not seeing any travellers from the future means time travel is not possible: otherwise, the place would be packed with people from other epochs! The second is the classic grandfather paradox: if you could go back to the past you could kill your grandfather and thus never be born, which is impossible since you have been born.
You will be amazed, then, to hear that my recipe for time travel solves all of these technical hurdles and skilfully avoids all the paradoxes. It just requires a huge amount of one single thing: luck.
Here’s the idea. There is a non-zero probability that, for example, a pink elephant materializes in the middle of your room. The chances are slim, admittedly, but they are there. Not only that: if you believe in the Many-Worlds Interpretation, then in fact one such elephant has materialized in your room in some parallel universe you’ll never get to see, since you’d need a humongous amount of luck.
Now, that elephant could also have materialized at the time of Julius Caesar’s assassination, for example. In fact, the MWI tells us that one of them did, though sadly we are not in that branch of time, so we don’t get to hear about how Caesar got flattened by a huge pachyderm. And where I say “elephant” I could also say “you:” there is a non-zero chance of you having materialized during Caesar’s murder. This means that you have actually materialized, but you will never get to experience that because it would require a huge amount of on thing: yes, luck.
The main idea is that nothing (except for overwhelming odds) prevents you from disappearing here and magically appearing in the past, thus feeling the continuity a time traveller would feel. Hence, no wormhole is required and therefore we just don’t care what happens to wormholes. So there, Matt Visser.
How does this theory avoid both the grandfather and Hawking’s pseudo-Fermi paradoxes? Well, here’s the thing: in this scenario, it doesn’t matter if you kill your grandpa. In fact, you can kill all of your family for all I care. All this means is there will be a bunch of universes where you will never be born. In fact, there has really been no change: the possibility of your magically appearing and killing a lot of people was there from the start. You haven’t affected the universe in any way.
So why isn’t our planet full of visitors from the future? Simple: since there are a myriad of presents, the odds of a visitor from the future landing in ours are astronomically small. In fact, they become astronomically small because of the fact that the probability of someone appearing out of nowhere is very, very close to zero. Remember, it’s the same as for the pink elephant.
- Time travel is possible.
- You will never experience it unless you’re very, very lucky.
- There is actually no travelling involved, since it is already hard-wired into the make-up of our universe.