It is basically traveling in 4D.
Several Ways To Do That
WARNING: THESE WAYS ARE MIND-BENDING
Free travel through past or future
This is the standard de facto approach, a la Back to the Future. You can travel back to any point in time at all, or the future for that matter. It doesn’t matter if your younger self is there or not (although travelling back within your own timeline highlights some questions that I address tomorrow). In general I would quite like to travel in this way. It’s perhaps the main way that people normally consider time travel to be. It would let you be the adult person that you are just now but go back and experience the world in the past. You could even look up your own family and see what they were like and (as long as you didn’t look too much like them) you might even interact with them in some way. And it would also allow you to go back to any time in the distant past and learn about the culture and history of that point in time. Movie reference: Back to the Future
One approach which involves going back through your own timeline is regressing back through your own life. This means that you don’t become a duplicate. You actually go back and occupy the body of your younger self. You’re obviously limited to your own lifespan here. This would be quite cool in some ways, particularly if you went back to when you were a teenager or young adult and you were perhaps at your fittest and healthiest and doing lots of sport or partying every night etc. It might be good to relive some of those experiences from your partying years, but to be honest it might also be a bit strange interacting with younger people all the time when you are in the pretence of being one of their peers. But on the other hand if you’re cool with that it would be great to relive what often people refer to as the prime of your life but with the experience and confidence of your adult self in your younger self’s body. Also think about what it would be like going back to your 10 year old self for example. You could relive the moment of unwrapping your favourite Christmas present, or seeing an amazing movie for the first time in a full cinema. But in reality it might almost be quite creepy if you stayed for too long as you would be walking around with the mind of an adult in the body of a child. Bit weird if you had to live like that for too long perhaps. Just depends what age you regress to. Movie reference: Hot Tub Time Machine, Peggy Sue Got Married. It is also hinted at in the film About Time. Normally his past ‘regression’ into his own body is negligible due to the small distances he travels in time, but at one point he is seen running along the beach as a young boy.
This variation of the above one is perhaps less creepy, particularly when going back to your early youth days. In this version you wouldn’t be in control of anything. In essence you’re just reliving memories. You’re seeing exactly what happened in your own life through your own eyes, with all the smells and sounds etc but you’re just along for the ride. It’s like wearing a virtual reality 4D headset of your past life. This has all the opportunities to relive your warm and fuzzy memories from your youth but without the awkwardness of having to actually interact as an adult in a child’s body. This approach is probably purely for nostalgia. You wouldn’t be able to learn anything much about history from the past (although you may pick up things you didn’t pick up first time round) because you can’t actually control what you do or go and explore. One bonus perhaps though is that there wouldn’t be any danger of inadvertently changing the future.
This approach is similar to the last one, but is more like the Scrooge approach, where he gets to look on past situations from a distance. Just observing them as a third party and not being able to interact at all. Again a nice way to relive happy memories from your past life, although you might keep cringing at how your younger self is acting, or how bad their/your hair and fashion is. Movie reference: A Christmas Carol – Ebeneezer Scrooge
Same as the last one but not restricted to your own life. You could go and watch Julias Ceasar get killed but not have to worry about getting knocked down in the crowd in the aftermath. You’d just be almost watching a documentary of the past without any of the dangers of being able to interact with it.
Gone Missing To The Future
This one is when you travel to the future somehow but you don’t meet a duplicate of yourself because you haven’t lived all those years yet because you went missing somehow. You might have been travelling near the speed of light, or cryogenically frozen, or just kidnapped and sent to the future. You’re certainly the fish out of water and most people that you look up will be dead or have moved on as they assumed you were dead. It’s a pretty harsh way to do it. I’ll always remember the scene from Flight of the Navigator which I still find pretty chilling after David has gone to his parents’ house but finds other people living there, and then is taken to his parents’ new house only to have his dad walk out of the doorway into the light to reveal how old he is. Movie reference: Flight of the Navigator, Captain America, Forever Young
Leaping into the body of somebody else
You could obviously call this one the Quantum Leap approach. In the past I used to think this would be a cool way to do it. You could leap into the body of someone cool from the past and live their interesting lives for a bit. But the more I think about Quantum Leap, and I’ve watched several episodes recently, I find this method a bit of a violation in terms of accosting someone’s body without their consent and potentially screwing up their lives or, in Sam Beckett’s case, being some ‘perfect’ middle-aged, white man who can fix any problem that that person had even if they were female or black. If you could turn back time again and ‘undo’ your leap though this would be a very interesting way to bounce around time, and would also get round the scientific argument of not being able to add new particles to the universe by duplicating yourself (see tomorrow’s post). You could do things like leap into the body of one of Elvis Presley’s friends and live in the shadow of the King for a while, just living the good life in Vegas with him. It would certainly give you access to things you couldn’t usually get as a ‘normal’ time traveller. TV reference: Quantum Leap
When I say linearly I mean you don’t just suddenly appear in a past or future time, but you have to travel linearly and, for example, see the dials on your time machine roll forward or backward until you reach your desired time. This approach was evident in the movie The Time Machine based on the H.G. Wells novel. Both the version in the 1960s and the recent version with Guy Pearce. The protagonist in these films sat in his machine in his conservatory and slowly moved the dial forwards to go forward into the future. But he saw everything age around him. He saw flowers die in his conservatory because he hadn’t been feeding them. He saw windows crack because they hadn’t been repaired. He eventually saw the whole house get overgrown with weeds because it hadn’t been cared for. And then he put his feet on the gas and went forward a few millennia. But it raises the question of what did people that he knew think had happened to him? When he’s sitting there in his time machine smiling, marvelling at flowers dying, supposedly his housemaid and his friends are wondering where he’s disappeared too and they’re mourning him and letting his house get all run down. So he is actually creating a future where he doesn’t exist for ages. In terms of his time travel it was a bit like just being cryogenically frozen, but with the luxury of being able to travel back again. The first The Time Machine movie really did blow my mind a bit with its method of travel. I felt it got a bit weird. I think I prefer when people just hop to a certain date in the future and hop back again. Basically every time the scientist from The Time Machine was pushing forward or pulling back on his lever he was essentially creating a new parallel universe in my opinion. He wasn’t going to a future where he himself existed. He was actually just pressing fast forward on time and from his perspective just sitting in one place for years. So what would people see if they saw him in his time machine during that time. Surely in all those hundreds of years people would have gone into his conservatory and seen him there? And also if he is scrubbing back and forth through time itself then what happens if multiple people have similar time machines and are doing the same thing? Must be parallel universes. I told you it was a mind-f***. Movie reference: The Time Machine (both versions)
This is a really interesting one. It’s not really time travel that you can proactively choose to do, and it normally happens to you in the present day, but once you find yourself in a time loop you can use some of the benefits of time travel and really make the most of it. You live the same day over and over and you can learn so much about the minutiae of the day that you can become an expert on everything in it. Plus you have the time to learn whatever skills you need to learn in order to get yourself out of the loop. It’s not about travelling to the past or the future to learn anything but it’s about using your control of time to your advantage, and knowing what is about to happen, which is pretty cool. Movie reference: Groundhog Day, Edge of Tomorrow, Source Code (to some extent)
This is barely a category of its own and there’s not a huge amount of examples of it. It is a temporary and focussed event or situation from the past or future which crosses over with the present. Almost like a ghost. A ripple in the fabric of space time. One ‘real life’ example is Mr and Mrs Gisby who were driving through France on their holiday in 1979. They claimed to have stayed overnight at a curiously old-fashioned hotel and decided to stay there on the way back but couldn’t find it. Photographs they took when they stayed there were missing, even from the negative strips, when they got the pictures developed. Bit of a strange one that, but intriguing nonetheless. You could possibly say that Woody Allen’s Midnight in Paris is a variation on this theme. Movie reference: Midnight in Paris
Travel through time and place anywhere
Most time travel stories assume you can just jump to ‘anywhere’ as well as ‘anywhen’. That’s more of a transporter mixed with a time machine. This method is probably most famously demonstrated by the Tardis or Bill & Ted’s phone booth. It’s probably the ultimate method to time travel with as you can go absolutely anywhere. You can go to see the pyramids being built and then pop off to see Napoleon fight, before rounding it off with a trip to throw rocks at some dinosaurs. But if you don’t have this ‘location functionality’ in your time machine then you have to be very careful where you are when you time travel. A fixed location for a time machine is perhaps a dangerous thing, and you would have to research your spot well so that you don’t travel back into what used to be a pile of molten lava. Or alternatively make your time machine mobile like a DeLorean so that you can move it to a place you know is safe each time. Good thinking Doc! But a time machine that travels through space as well as time is probably the best kind to have. Movie reference: Bill & Ted’s Excellent Adventure
So ‘time travel’ is by no means a fixed, standard way of thinking. There are many interpretations. Obviously these are very much science-fiction with the emphasis on the fiction but it’s still something that is a great deal of fun to daydream about.