Question: You mentioned that there was such thing as travelling in time, how does it work and are people regularly using these machines? And why would people want to prevent teleportation? What dangers or risks are there? :)

James Vokes answered on 20 Mar 2012:

***Time Travel***

OK here’s the time travel explanation, remember what I’m saying is absolutely true. I’ll put evidence at the bottom.

If you’ve ever been nerdy enough to watch Star Trek you may have heard of the “Space-time continuum”. One of the best things about Science Fiction is that sometimes they describe real theories based on real science! Space and time really are a “continuum” and what that means is that you can’t separate them. You can’t talk about just one on its own. You can travel through space (by moving around) and you can travel through time. You’re doing it right now; you’re travelling into the future by one second every second. At around 1910, Einstein realised that time and space were inseparable and he also theorised that when you travel through space you travel slightly less through time and the *faster* you move through space the *slower* you move through time.

Let’s stop for a second, this is incredible already. If he’s right it means that time is different for different people depending on how fast they’re moving. It means time is relative (Hence Theory of Relativity, you may have heard of it). Let’s get back to what this means…

Unfortunately you can’t go backwards in time because time only goes forward (Why is this the case?) but you can travel into the future. By travelling really fast, what feels like only a month or so for you will mean hundreds of months will pass for everyone else (who isn’t going fast) meaning you’ll be in the future.

This is not Science Fiction. Einstein came up with the theory and we have tested it countless times since then and proven it correct. In fact (to bring it back to Engineering) the GPS satellites that travel around the Earth move fast enough that we have to include corrections to how they count time because they count a second to be slightly less then what we say.

So, if you were curious, you can make a time machine. I car is a time machine, a plane is a time machine. How good a time machine? It depends on how fast they can go…

This is advanced stuff, I’ve tried to simplify it but if you have any questions then put them in the comments.

***Teleportation***

This next bit is quite advanced physics and I don’t have the same sort of examples as the Time Travel one so you’re going to have to trust me when I say: things that are really small act in really weird ways. You may have heard of this strange world where we talk about tiny bits of matter that are smaller than atoms – the Quantum world. Now, one of the unbreakable rules that you must know when you’re dealing with particles this small is: Heisenberg’s Uncertainty Principle. what the rule states is that “You *cannot* know a particle’s *exact* position and its *exact* speed at the same time”. You may be able to see already why this would be a problem for teleportation. You are probably not surprised to hear that human beings are made up of billion upon billion of these tiny particles. If you want to teleport someone you have to know the exact position of all those particles and put them back in the exact same positions. Think what would happen if a few molecules in the brain got mixed up and put in the wrong place. So teleportation is pretty much off of the table.

Again, any additional questions in the comments and I’ll be happy to answer.