Why Time Travel Is (Probably) Impossible! (Part 2)

( for part 1 see here).

OK – so part 1 seems to contradict it’s title… by travelling at or very near the speed of light our time slows down relative to a ‘stationary’ observer so that we seem to be able to travel forwards in time relative to them! (But not so relative to us).

So how about going backwards in time? Can we go ‘back’ once we have gone ‘forwards’? Sadly, not by the same method. We can skip ahead by travelling at high speed but we can’t skip back. This is because Time slows down for us relative to a stationary observer. The slowest speed we can travel at is always a positive number or else it is zero – which means we are not moving at all relative to them and our timelines are identical, while we travel at the same speed as them. Travelling in the ‘reverse’ direction is possible in space (forward v backwards, up v down, etc.) but it is always a positive speed relative to a stationary observer; we cannot travel in reverse ‘speed’.

Although Einstein showed it to be impossible for anything with mass to travel faster than the speed of light -because, as you approach that speed, time seems to slow to zero – some have hypothesised that if you could go any faster time would start to travel in the ‘reverse’ direction – As Star Trek and a few other Sci Fi movies like to have us believe could be possible. But we can’t and so it isn’t (probably!) 😉

1701

Physicists hold out a hope for those who want to travel back in time however. To understand why it is necessary to rethink how we view both Time, and Space.

To most of us Time is different to space: we know we can move in any combination of 3 directions called ‘dimensions’  (up/down, left/right, into screen/out of screen) whereas time for us is only in one direction and we cannot move in it in any way other than by seconds that can’t be stopped (but see time and speed in part 1).

Einstein though, developed an entirely new concept – Space-Time, where instead of our 3 dimensional space universe the Universe is actually a four dimensional structure (here is where most minds start to really ‘boggle’ – we know we can simulate a 3d image on a 2d screen, that’s how old televisions and pictures work. These days the effect is improved with the use of glasses or special screens on our TV or cinemas. To simulate a 4d ‘image’ though would need a minimum of three dimensions and some pretty fancy special effects. You can’t do it any justice with a 2d picture – so i won’t even try.

What is important about it though is this… it treats time just like any of the other dimensions. it has a forwards/backwards, up/down thing going on with Time. In space-time every point in time AND space can be uniquely defined, anything in the ‘now’ our past, or our future EXISTS as a possible ‘point’ in space time.

As for the ‘backwards’ part in Time Travel? Physics proposes that things called ‘wormholes’ are possible in space-time, things similar to the ‘bubbles’ in a block of Swiss cheese. If we could enter one of these and live they could (emphasis on  the 2nd ‘could’) be a ‘shortcut’ through space-time to another point. They could connect two points massively far apart in space- or in time, or both!

Travelling through the wormhole would take far less time to travel between those points than it would if we used conventional methods – like walking or ‘fast’ spaceships. (Note: walking is NOT recommended for travel in actual space). Theoretically we could go ‘back’ in time. ONE of the main difficulties though would be the ability to determine where the wormhole ‘came out’.

Our conscious perspective of time is that the time dimension just ‘goes’ one way, one speed… but that is JUST our perspective. Different ‘observers’ in different places and possibly moving at different speeds to us will have different perspectives of our ‘reality’.

This means that different people see the same things happening at different times and in different places.

Weirdly, something that we see as happening in the ‘past’ someone else might see as happening in our ‘now’.

Even weirder, something we think of as ‘will happen’ in our future ( say a solar eclipse) someone else could see as happening in our ‘now’. Their perspective has the exact equal validity as does ours.

This means that the past, future and present may all exist simultaneously, for all of us! Altering our ability to perceive a thing may mean we can see the future, or see the past as though it is happening ‘now’ and what we perceive of as a one way stream of time is just an illusion created by our consciousness and our speed as we travel through space-time. (Remember time effectively slows down to zero, there IS NO ‘time’ at light speed, relative to a stationary observer).

But i digress… the post is supposed to be why Time Travel is (probably) impossible…

I’ll show you, in part 3! 😉

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3 Comments

  1. to me time travel is impossible for two reasons, one when you go the speed of light you just get from point a to point b alot faster, and secondly the future of people hasn’thappened yet, babies have not been born yet or raise up yet so how can you meet them simply because you went faster forward, and if in reverse the people who died would still be dead, so how can you meet them again? time is just a way to measure forward back or present, a person who in a coma time stops until they wake up, to them it has only been a minute while eveyrone else’s concept of time has moved forward, and they have grown older (and so did the coma guy) but he is unaware of it. he still grew older. so the concept of time travel is just a fun thing to play around with and makes for interesting movies, but in reality time is only a concept not a tangible thing anyway.

    Reply
  2. Welcome Roberta and thank you for your thoughts.

    On the face of it, and to any casual observer, time can seem like only a concept, something man measures passing by a clock and uses to distinguish between something that has happened (past) is happening (present) or will happen (future).

    In those tenses time is ‘fixed’ and nothing can change it – to us mere mortals.

    But thanks to the efforts of some quite clever men (and women – possibly?) 🙂 Science has shown us there is far more to time than just that.

    Time may not be tangible to everyday mankind, but it is far more integral to our daily lives than being a mere ‘concept’. It is woven into the very fabric of the Universe in a very precise and now understood manner. It is indivisible from the vast dimensions of space we know exist in near infinite directions all about us and in the microscopic worlds of the Quantum. This is not ‘guesswork’ – it has been proven by experimentation, experimentation only made possible by modern man’s technology.

    Albert Einstein (who believed in God, although admittedly not in the same way you or i might) was instrumental in conceiving of the idea and his theories and the predictions he made concerning them and things that had to wait for almost a century to be proven to be true, have virtually all been verified in recent times.

    Time does slow down the faster you go – it is not a ‘constant’ thing under all conditions.
    Matter does distort space-time so that light (and time) can be ‘bent’ simply by passing by a large enough mass. Singularitys do exist.

    In the case you mention of a man in a coma waking up, it was his loss of conscious awareness that left a time gap that made it seem to him like he had ‘travelled’ through time, but as you say, his body aged while he was unconscious.

    By travelling near the speed of light and making a ‘fast’ round trip back to earth, while 50 years might have passed on Earth, anyone in the spaceship would still be close to the same age mentally and physically as if they had been away for only a few months!

    Doesn’t ‘sound’ logical, yet that is what happens. It was a prediction of Einstein based upon mathematically established theory and the limited experiments we can currently do fit his mathematical predictions precisely.

    ‘Reality’ is far more complex than we humans can begin to imagine. A lot of what we think ‘is’ is simply something our minds make up to ‘deal’ with that complexity in a way our all too human brains can handle.

    Just because we can ‘handle’ it and live a ‘life’ from it does not mean that it is necessarily accurate (true) or that it applies the same way ‘everywhere’, or in all circumstances.

    Reply
  1. Why Time Travel Is (Probably) Impossible! (Part 3) | The World Is My Soapbox

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