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What If You Die During Time Travel? | Unveiled

VOICE OVER: Noah Baum
We'd all like to travel in time... but what if the worst happens? In this video, Unveiled discovers what would happen if you traveled backwards (or forwards) in time but died in the alternate timeline... What if you caused your own death? Or you were responsible for your own birth never happening? There are plenty of paradoxes at play in this one!
Transcript

What If You Die During Time Travel?


In theory, time travel would provide us with endless possibilities… but what happens when you rearrange spacetime and it goes wrong? Really wrong.

This is Unveiled, and today we’re answering the extraordinary question: What if you die during time travel?

There have been various representations of time travel in the media, and various ideas put forward by academics about how we might one day achieve it in the real world… but at its core, the concept of time travel is quite an easy one to follow. It’s the ability to move through time; to jump to and from any two points on any given timeline. Where now we can all travel to, say, the train station, and then the movie theatre, and then back home… with time travel we could journey to 1820s Europe, and then 1920s America, and then 2120s Mars. The past and the future are ours to visit as we please. But that apparent freedom is actually riddled with problems and paradoxes.

Probably the most famous time travel conundrum is the grandfather paradox, which asks what would happen if you travelled back in time and caused the death of your own grandfather, before they parent either your mother or father? If time travel to the past were ever possible, then this would naturally be a possibility… but if your grandfather dies before one of your parents is born, then you’re never born either, which means you’d never be alive to travel back in time to cause your grandfather’s death in the first place. There are variations on the paradox, too, where you might want to travel back in time to kill any individual (one that you’re not directly related to), only to find that the gun, inexplicably, doesn’t shoot. The general idea is that if you were motivated to go back in time to kill someone, then you’d never actually be able to do it, because if you did then you’d never have that motivation to spur you on. The same applies to any action to change the past, too… it doesn’t always have to be killing. In theory, time travel is simple; in practice, it’s really not.

But what about you as an individual? In regular, every day, non-time travel life, there are countless ways you could die. And, seeing as you’d still be inside that same, organic, perilously kill-able body even if you were to travel backwards or forwards in time “x number” of years… you’d still be just as vulnerable to fatal accidents in the past and future as you are in the present. This isn’t about cutting down your family tree, anymore. Your grandfather lives, your parents live, and you live, up until the moment that you time travel someplace else and, well, you don’t live. Say you zapped to just a regular day in nineteenth century London, crossed the street without looking and got trampled by a horse and carriage? Or you popped up inside a moon base in the year 2296, took a wrong turn down the wrong corridor and got ejected out into space? Both times you die, despite the fact that you weren’t meant to be there.

But, is that really true? Would you really be “not meant to be there”? One of the more straightforward ways to contemplate travelling through time is just to accept it as a part of life. As far as we know, it isn’t a part of life right now… but one day, it might be. And, if we do reach that stage, any place or time we travel to only actually accounts for one moment on the overall timeline of our own individual existences. So, from this point of view, any time travel destination we happen to die at is simply the last location in a long series of locations we’ve visited, much like how it is for any death… Despite the fact that their timeline would move all over the place, a time traveller would simply look back at this list of locations as having been “their life”. They can’t possibly have been (or died) anywhere they weren’t meant to be, because their route through that life had simply led them to that point.

The repercussions get a little foggier, however, were a time traveller to meet their past or future selves. If they met their past selves and somehow caused them to die (maybe their past-self doubletakes at the sudden appearance of their apparent doppelgänger, and because of that gets hit by a passing car), well, we’re back into grandfather paradox-type territory - where present-day-you-in-the-past causes present-day-you-in-the-present not to exist. If a traveller met their future self and somehow caused them to die, however… it’s probably an even bleaker prospect. Now, more than ever, time travel theories become wrapped up in ideas on fate, determinism and retrocausality.

Retrocausality is the idea of an effect preceding its cause; that something only happens because something else happens after it. It’s linked to something called Newcomb’s Paradox, too, where one person’s ability to see into the future affects the actions of someone else in the present. In the case of meeting your future self and causing them to die, then, retrocausality relates to the time in between that moment as seen by your younger self (the one causing the death) and that moment as seen by your older self (the one dying).

Say you travel six months into the future, knock a piano down some stairs and that piano kills “older you” at the bottom. For the rest of that six months on Earth, whatever happens, you’d know with certainty what was about to unfold; one day, you’ll find yourself at the bottom of a staircase when a piano pushed by “younger you” ends your life. In the meantime, in a world where time travel is obviously possible, you might jet here, there and everywhere in a bid to extend the time you’re alive between now and then - “Doctor Who” fans will recall Clara Oswald taking the long way round to her death.

But the moment of your death would still be inevitable. No matter how strongly you resolved never to go to that particular staircase to be crushed by that particular piano, it would be predetermined and inescapable. It’s why many debates about time travel argue that if time travel exists, then free will can’t. Just think of all the things that have to happen just to get the piano to the top of the stairs… the lives of manufacturers, music teachers, budding pianists and removals companies all have to align and interweave to ensure the object that you know will kill you is at just the right place, at just the right time. There’d be nothing you or anyone else could do about it. In this version of reality, it might seem like we make choices… but we really don’t.

So, time travel death essentially raises three main possibilities; you either die as you were always meant to, just not in traditional, chronological order… or you erase yourself from existing in the first place (even if that is problematic)… or you set an inescapable future moment at which you definitely will die, but you at least get to live a predetermined life before then. Of course, the other possibility is that you die during the time travel process itself. Not in the past or the future, but whilst you’re travelling to the past or future.

One aspect of time travel that’s often overlooked is the apparent re-materialisation of a traveller at their destination. Clearly, we don’t yet know how time travel would actually physically work (or if it ever could), but there’s some argument that - even if we had viable time machines - simply arriving in the right place would be an impossible feat in itself. The Earth rotates while orbiting the sun, which orbits a black hole at the centre of a galaxy, which is one of billions of galaxies in the universe. Fast forward or rewind just one year, then, and it would take some incredible mathematics to land in exactly the right spot, rather than getting cast off into the oblivion of space. Like drops of rain in the ocean, time travellers could find themselves lost and absorbed into the void. And, even if there was no chance of a spatial error like this, it’s a sure bet that any hypothetical means of time travel would place the human body under incredible strain.

Until we have working time machines, it’s really impossible to predict how they might immediately affect time travellers. But we do know that just the idea of time travel opens up a wealth of philosophical thought experiments and temporal puzzles to solve. If anyone could ever be in the past, present and future, then that person’s death could truly occur at any time... but does that mean it could be avoided? Probably not. Because that’s what would happen if you died during time travel.
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