• Question: Here's a big question...Is time travel possible? If so, how would it happen?

    Asked by jakeronson to Antonia, Douglas, Hugh, Matt, Tom on 23 Jun 2010 in Categories: .
    • Photo: Matthew Hurley

      Matthew Hurley answered on 15 Jun 2010:

      There are lots of people that think it is possible, but I think it’s probably a better story to read in books – I don’t think it would ever happen, otherwise wouldn’t people have come back from the future to tell us?

    • Photo: Hugh Roderick

      Hugh Roderick answered on 15 Jun 2010:

      I don’t know if it is possible. I read an article about photons of light being able to travel backwards in time, but that it wouldn’t be possible for whole objects. How it would be possible I don’t know – and I didn’t understand the explanation in the article!

    • Photo: Tom Hardy

      Tom Hardy answered on 15 Jun 2010:

      I think everything is possible, we just need to work out how. I don’t pretend to know or understand how time travel could work and I can’t suggest how we find out, but I’m confident one day we will understand enough to make it happen! Sorry if that isn’t much help.

    • Photo: Antonia Hamilton

      Antonia Hamilton answered on 16 Jun 2010:

      It probably isn’t possible because it throws up too many weird paradoxes.

    • Photo: Douglas Blane

      Douglas Blane answered on 23 Jun 2010:

      Until recently time travel was just science fiction. Then a few physicists realised that general relativity, which is the physics theory for space, time and gravity didn’t rule out time travel completely.

      It might be possible. But if it was it would be very difficult to do and take enormous amounts of energy.

      It’s a big subject so I’ll just touch on it and point you to more reading you can do if you want..

      First it’s easier to travel to the future than the past. All you need to do is set off in a space ship and either go very fast, close to the speed of light, or skim the edge of a black hole.

      When you come back to Earth, after a year or two of your time, all the people you knew will be long dead and thousands of years will have passed.

      That’s travel to the future and science tells us it’s perfectly possible. Here’s a video about it: http://www.youtube.com/watch?v=TuNNurWCzCc

      Travel to the past might be possible or might not.

      There is for a start the grandfather paradox – what if you go back in time and stop your grandfather meeting your grandmother?

      Then you would never have been born. But then you couldn’t have gone back in time. So you would have been born. But then you would have gone back in time …. And so on. A real mind-bender.

      Some physicists believe, though, that the universe is made in such a way that these time travel paradoxes don’t happen, and travel to the past is possible.

      So how might it be done?

      Well one way is to do some heavy engineering on wormholes. Two problems with that are we don’t know if wormholes exist. These are shortcuts through space, like going straight from one piece of a folded paper through to the other without going the long way round. (Here’s a diagram:)

      Second problem is engineering a wormhole is much harder than building a bridge, and would take a big chunk of the energy in a whole galaxy. So we’re a long way from being able to do it.

      But we’re talking about what’s possible here, not what we can do tomorrow.

      A guy called Carl Sagan, who’s a really good science explainer and writer asked a bunch of top physicists to think of time-travel ideas that could work for a book he wrote called Contact. (You can still buy it and they made a film of it with Jodie Foster.)

      Anyway these physicists took a closer look at time travel and came up with quite a few ideas. Take a look at this vid of a famous physicist called Paul Davies talking about this. (He was my tutor when I studied black holes at King’s College and, like Carl Sagan, is good at explaining hard physics). http://vega.org.uk/video/programme/61

      Final puzzle for the moment: If time-machines are possible why are there no people from the future coming to visit us, like Dr Who?

      Answer to that is that if – and it’s a big if – time travel to the past is possible, you can’t go back further than the time the machine was first built. So there are no travellers from the future because the first time machine hasn’t been built. Yet.

      Sagan’s book is a good place to go if you’re still interested and want to find out more about time-travel and making contact with aliens. http://www.amazon.co.uk/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=contact+sagan&x=0&y=0

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