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    Isn't there some theory that says that time-travel is possible, but that history is fixed and you can only travel back in time to observe and not interact with events that have already happened..?
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    (Original post by Draconis)
    Isn't there some theory that says that time-travel is possible, but that history is fixed and you can only travel back in time to observe and not interact with events that have already happened..?
    Excellent point! I was thinking of exactly the same thing.
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    (Original post by Mike_P)
    How can this be proved?
    A little thing called relativity.

    Einstein disproved the idea that time was a straight line and the same for all observers.
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    (Original post by Robob)
    A little thing called relativity.

    Einstein disproved the idea that time was a straight line and the same for all observers.
    Correct me if I'm wrong - this is because of gravity, and related to how time in space is "slower" than time on Earth? God, I can't believe how little I know about this. And I want to study Physics at uni.
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    In theory, if you could somehow reach a speed of -3x10^8 m/s (note: not velocity) would you travwl forward in time? I can't comprehend being able to travel at a negative speed but yeah... I'm bored.
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    (Original post by joshm)
    In theory, if you could somehow reach a speed of -3x10^8 m/s (note: not velocity) would you travwl forward in time? I can't comprehend being able to travel at a negative speed but yeah... I'm bored.
    go take a break, honey.
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    (Original post by thomaskurian89)
    go take a break, honey.
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    I wrote a 7000 word (philosophical) essay on this :P I think to anyone who knows the relevant science, it's obvious time travel is possible. The only problem comes in with various paradoxes. My conclusion was that time travel _is_ possible, but it's not possible for information to travel through time. Hence, if humans tried it we'd be ripped to shreds by various forces through the black hole's region or whatever, and be reduced to photons in a scrambled order.

    But the important thing is I think for these photons, time travel would be possible:P
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    (Original post by Gesar)
    My conclusion was that time travel _is_ possible, but it's not possible for information to travel through time.
    If it's not possible for information to travel through time, it means that time travel is impossible. Period.
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    (Original post by Draconis)
    Correct me if I'm wrong - this is because of gravity, and related to how time in space is "slower" than time on Earth? God, I can't believe how little I know about this. And I want to study Physics at uni.
    Gravity only comes in in general relativity, which I know little about and I'm a third year physicist...

    Basically, the relative velocity at which you move affects the time you measure between events. Have a look on google, the maths of special relativity can be understood with GCSE maths, it's definitely worth reading up on. It's amazing what the speed of light being constant for all observers leads to.
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    (Original post by Robob)
    Gravity only comes in in general relativity, which I know little about and I'm a third year physicist...

    Basically, the relative velocity at which you move affects the time you measure between events. Have a look on google, the maths of special relativity can be understood with GCSE maths, it's definitely worth reading up on. It's amazing what the speed of light being constant for all observers leads to.
    I looked it up at some sites earlier today, I couldn't find much though. The sites either were too complicated or too basic. It's very interesting though. I remember reading about it in A Briefer History of Time, if I'm not entirely wrong.
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    Isn't time a dimension such as space? If we can figure out how to teleport then we can surely time travel.
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    (Original post by Robob)
    A little thing called relativity.

    Einstein disproved the idea that time was a straight line and the same for all observers.
    Right.
    I'm not trying to be offensive or anything, but how did he do that?
    It's kind of acstrabt stuff, so how can you be so sure?

    Its quite interesting though I barely now nothing about physics.
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    (Original post by thomaskurian89)
    If it's not possible for information to travel through time, it means that time travel is impossible. Period.
    No.

    We want to send a message through time, which needs to go through a wormhole say. The intense gravity scrambles our message as the photons disappear through the wormhole. Then at the other end, the photons are spewed out again in a random order - and yes there is a chance, however remote, that it is exactly the same as our original message. The distinction is any information we send is scrambled along the way, and any information received is purely down to the random ordering of the photons at the other end, after they've travelled through time.
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    (Original post by Mike_P)
    Right.
    I'm not trying to be offensive or anything, but how did he do that?
    It's kind of acstrabt stuff, so how can you be so sure?

    Its quite interesting though I barely now nothing about physics.
    Read about special relativity.

    He started off by saying that all inertial (i.e. non accelerating) frames are equivalent, in that there is no difference between moving at a constant velocity and being stationary, since it's all relative. This then implies that the laws of physics are the same in all inertial frames, and thus that the speed of light is constant in all frames.

    The whole of special relativity follows from those axioms. It turns out that time isn't linear as you might think, but is different for different observers. It really is a physical thing that is part of the universe.
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    (Original post by Gesar)
    No.

    We want to send a message through time, which needs to go through a wormhole say. The intense gravity scrambles our message as the photons disappear through the wormhole. Then at the other end, the photons are spewed out again in a random order - and yes there is a chance, however remote, that it is exactly the same as our original message. The distinction is any information we send is scrambled along the way, and any information received is purely down to the random ordering of the photons at the other end, after they've travelled through time.
    Er...yeah so?
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    (Original post by Gesar)
    No.

    We want to send a message through time, which needs to go through a wormhole say. The intense gravity scrambles our message as the photons disappear through the wormhole. Then at the other end, the photons are spewed out again in a random order - and yes there is a chance, however remote, that it is exactly the same as our original message. The distinction is any information we send is scrambled along the way, and any information received is purely down to the random ordering of the photons at the other end, after they've travelled through time.
    Well then how about if I send one photon, as a 'yes or no' message?

    That way, I have sent information.

    Either you can send information through time, or you can't time travel.
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    Time travel implies sending information through time.
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    Well the theory behind time travel only will allow you to travel as far back as when the time machine was turned on, so untill we invent a time machine we wont see any time travellers.
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    Read about special relativity! the basic theory is that due to energy mass equivilance (e=mc2) it would take an infinite amount of energy to accelerate a particle to the velocity of light, at which point time stops. As something is approaching the speed of light then time dialates for that object. A good way to think of this is that we devote are 'existence' to travelling through the dimension of time, but that when we move through space at a velocity then we are devoting some of our existence to moving through spatial dimensions, and as a consequence are movement through time dialates and becomes slower. To think that something could move faster than light and therefore travel back in time is beyond our current understanding of physics. To travel forward in time we would have to travel slower than sitting still!
 
 
 
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