The question philosophers are interested in when it comes to time travel stories is whether or not time travel is possible. There are two sides to this question: the scientific and the logical. The scientific side is about whether the technology will one day allow for time travel, in the same way that technology has allowed for human flight, for instance. The logical side – and the side that philosophers are interested in – is whether time travel makes logical sense or not. It could be argued that if time travel makes no logical sense then it would follow that it would be impossible for the technology to one day achieve time travel. So, for instance, someone might argue like this:
- It is impossible for any one thing to be in two places at the same time.
- If you were to travel back into your own past time then you would be in two places at the same time.
- But this is impossible so time travel must be false.
Some will feel that it is paradoxical and some will see a time-loop in which the time traveller is trapped. It might boil down to whether we think of the two time travellers in the story as the same person or not. This has implications for personal identity and refers us back to the theme of personal identity, which informs many of these sessions.
You are an inventor working on a time machine. You have been working on it for years now and you feel that the breakthrough you need to achieve your dream is just around the corner. One day you have been working for 24 hours non-stop, the excitement of completing your task the only thing that keeps you going. However, you are desperately tired and are beginning to make silly mistakes. As a result of an accident there is an explosion that knocks you unconscious as the fire burns around you... A little while later you awaken to find yourself inside your time machine. You are shocked to find yourself in your own time machine when you know that you haven't even finished it yet, but not at shocked as you are when you turn to face your companion who is working furiously at the time machine's control panel: it's another you!
"Who are you?" You shout
"I'm you. Can't you see?" Your companion says impatiently without looking up from the controls.
"C'mon, haven't you worked it out yet?" Then your companion mutters, "Maybe I'm not as clever as I think I am."
You stop and think for a moment. "Are you a future version of me?" You ask.
"Finally, I've – I mean –' you've' worked it out. It took long enough."
"So," you say (to yourself), "I've saved myself from certain death and now I am free to continue with my work and so will finish the time machine."
"Yeah, that's it. But it's not the same time machine I'm afraid; the other one was destroyed so you have to begin all over again, but it does mean that you make a better one. All you've got to do now is remember to go back when you finish it so that you can save yourself."
Still reeling with the shock of it all you simply look up and say, "Is that all? Okay, I'll do that." Then you ask, "When can I get out of here? There's not a lot of room. I should have made it bigger."
Your double replies: "That's exactly what I was thinking: you should have made it bigger! Especially as this time machine is the same size on the inside as it is on the outside. But, anyway, stop moaning: it travels through time doesn't it!"
"It's your fault as much as mine!" You protest. But then you remember that you should be grateful to yourself for saving your life.
Task Question 1:
Does this story make sense? Is it possible?
Before setting the Task Question make sure you give some Comprehension Time: get the class to go through the story. Facilitate this with a diagram.
Do you think time travel will one day be possible?
What is time travel?
We travel through time from one moment to the next; what would a time machine need to do that we don't already do?
What is time?
Further time and time-travel thought-experiments:
If a scientist created a time machine that took 1 hour to travel 1 hour into the future or 1 week to travel 1 week into the future, would that be a time machine? Are we time travellers and are our bodies time-machines travelling through time at one-minute-per-minute?
If you take a bowl of water and put it in the freezer and then take it out again and leave it in the living room has the water travelled back in time when it returns to the state of being water again?
Explain to the children how the light from the sun and stars takes time to reach us and that we actually see the sun (though remind them that they should not look directly at the sun) how it was 8 minutes ago and not how it actually is now. (There's a wow-factor to this when they get their heads around it). TQ: does this mean that when we look at the stars we are looking into the past?
Imagine a machine that could stop time universally for any amount of time you wished. Would you want to have a go?
When we move the clocks forward and back are we travelling through time? If we stopped all the clocks in the world at the same moment would time stop?
What would happen if someone travelled back in time and changed something about their own past such as stopping their parents from getting together?
If somebody took Shakespeare's plays back in time for Shakespeare to copy, then who wrote Shakespeare's plays?
What would happen if you went into the distant past and accidentally stepped on a butterfly? Do you think it would change the future (your present)? If so, in what way?
In the film Superman (starring Christopher Reeve and directed by Richard Donner) there is a scene where Superman flies around the Earth faster than the speed of light resulting in the Earth changing its direction of spin. In the film, this results in time reversing so that he can save Louis Lane from a fatal accident. Many of the children will have seen the film - but if not it is easy enough to explain. TQ: would changing the direction of the Earth's spin really make time go backwards?