Alan McDougall Posted August 3, 2012 Share Posted August 3, 2012 (edited) Hi, Some astronomers and psycisists theorise around the possibilty of time travel, one example is the concept of a block universe (which I do not agree with!), where all events that have ever happened or will happen continue to exist in an infinity of identical universes. As far as we know there have never been any evidence of time travellers coming to our present from the past or the future. However,maybe an civilisation a billion years in advance of our own might have solved the problem? What is your position on the matter? Edited August 3, 2012 by Alan McDougall Link to comment Share on other sites More sharing options...
alpha2cen Posted August 3, 2012 Share Posted August 3, 2012 What is your position on the matter? Going to the future is possible. But backing to the past is not possible. That is a cause of time problem. Time is a order of the event. We can change future order, but we can not change past order. V=(X2 - X1) / (t2 - t1) is one of the moving event. So this phenomena is Event 2 (t2) and Event 1 (t1) exist. Why event? Event 1 is consists of mass, volume, apace, energy, etc.. Link to comment Share on other sites More sharing options...
Alan McDougall Posted August 3, 2012 Author Share Posted August 3, 2012 Going to the future is possible. But backing to the past is not possible. That is a cause of time problem. Time is a order of the event. We can change future order, but we can not change past order. V=(X2 - X1) / (t2 - t1) is one of the moving event. So this phenomena is Event 2 (t2) and Event 1 (t1) exist. Why event? Event 1 is consists of mass, volume, apace, energy, etc.. I agree! In a way we are all time travellers because we move with the arrow of time from the present moment into the future. You are right we can time travel into the future in one direction only, as far as we know, by speed/energy/mass/gravity, even at the relatively slow speed of a Jet Fighter, time dilation kicks in , albelit minutely. Thus, the movement of the Jet slows time around it, relative to the faster moving time on the ground. Both Richard Feynman and Alan Guth have speculated about time travel but lets go into that in more detail late! Link to comment Share on other sites More sharing options...
LaurieAG Posted August 28, 2012 Share Posted August 28, 2012 What is your position on the matter? Time travel will only exist in those universes where you can put a dead cat in Schrodingers box, run the experiment backwards, and get a live one out. Link to comment Share on other sites More sharing options...
swansont Posted August 28, 2012 Share Posted August 28, 2012 Physics has restricted the possibilities quite a bit. If you could build a time machine, you can't time travel to a time before the time machine is built. Link to comment Share on other sites More sharing options...
Alan McDougall Posted August 29, 2012 Author Share Posted August 29, 2012 Physics has restricted the possibilities quite a bit. If you could build a time machine, you can't time travel to a time before the time machine is built. Why not? Link to comment Share on other sites More sharing options...
swansont Posted August 29, 2012 Share Posted August 29, 2012 Why not? Because the only possibility that physics affords us is a closed timelike curve. http://blogs.discovermagazine.com/cosmicvariance/2009/05/14/rules-for-time-travelers/ 2 Link to comment Share on other sites More sharing options...
Tres Juicy Posted August 29, 2012 Share Posted August 29, 2012 (edited) Because the only possibility that physics affords us is a closed timelike curve. http://blogs.discove...time-travelers/ In other words - you cannot travel back in time to before the point in time when time travel became possible. http://en.wikipedia.org/wiki/Closed_timelike_curve http://en.wikipedia.org/wiki/Minkowski_space Edited August 29, 2012 by Tres Juicy 1 Link to comment Share on other sites More sharing options...
Alan McDougall Posted August 30, 2012 Author Share Posted August 30, 2012 In other words - you cannot travel back in time to before the point in time when time travel became possible. http://en.wikipedia...._timelike_curve http://en.wikipedia....Minkowski_space From your link above, You can’t travel back to before the time machine was built. Right now, at the particular place you are sitting, at the time when you are sitting there, one of two things is true: either there is a closed timelike curve passing through that point in spacetime, or there is not. And that situation will never change — no matter what clever engineers may do in the future, if they create closed timelike curves they cannot pass through events in spacetime through which closed timelike curves did not pass (corollary of Rule 6). Or in plain English: if you build a time machine where there wasn’t one before, it may be possible for future travelers to come back to that time, but nothing can help you go back to times before the machine was built. What if a person born say 200 years after the creation of the time machine goes back a 150 years and kills his grandfather, this leads to the Grandfather Paradox" or maybe the universe would prevent the GP by simply making it impossible to interact in any physical way with events that have already happened from the time travellers time frame? Link to comment Share on other sites More sharing options...
Ronald Hyde Posted August 30, 2012 Share Posted August 30, 2012 You've gotten some really good replies on this question, the 'fundamental' constants have little to do with it, but simple logic and the realization that amongst other things, time is the order of events, has everything to do with it. I'm very leery of using the word 'fundamental' to describe anything in Physics. After all, the job of the theorist is to derive as much as possible from as little as possible, so he should seek to treat as few things as possible as being fundamental. Link to comment Share on other sites More sharing options...
O'Nero Samuel Posted August 30, 2012 Share Posted August 30, 2012 Time travel will only exist in those universes where you can put a dead cat in Schrodingers box, run the experiment backwards, and get a live one out. That, I believe is not the ides. If something like that actually works and you put the cat in an S-box, the cat wouldn't be in the box after the experiment, and neither would you be by your S-box. Both of you would be transported back to a time when the cat was not dead and you weren't even with it. This is to say that if backwards time travel was possible, then it can not be isolated. Has anyone watched a movie TERA NOVA? I believe they made this flaw, ie if I was correct in the first place. Physics has restricted the possibilities quite a bit. If you could build a time machine, you can't time travel to a time before the time machine is built. The machine would somehow map out the limit to its back time travel? Physics has restricted the possibilities quite a bit. If you could build a time machine, you can't time travel to a time before the time machine is built. The machine would somehow map out the limit to its back time travel? Physics has restricted the possibilities quite a bit. If you could build a time machine, you can't time travel to a time before the time machine is built. Physics has restricted the possibilities quite a bit. If you could build a time machine, you can't time travel to a time before the time machine is built. Link to comment Share on other sites More sharing options...
O'Nero Samuel Posted August 30, 2012 Share Posted August 30, 2012 From your link above, You can’t travel back to before the time machine was built. Right now, at the particular place you are sitting, at the time when you are sitting there, one of two things is true: either there is a closed timelike curve passing through that point in spacetime, or there is not. And that situation will never change — no matter what clever engineers may do in the future, if they create closed timelike curves they cannot pass through events in spacetime through which closed timelike curves did not pass (corollary of Rule 6). Or in plain English: if you build a time machine where there wasn’t one before, it may be possible for future travelers to come back to that time, but nothing can help you go back to times before the machine was built. What if a person born say 200 years after the creation of the time machine goes back a 150 years and kills his grandfather, this leads to the Grandfather Paradox" or maybe the universe would prevent the GP by simply making it impossible to interact in any physical way with events that have already happened from the time travellers time frame? Does that mean that one can travel back in time with present memories? Link to comment Share on other sites More sharing options...
Alan McDougall Posted August 30, 2012 Author Share Posted August 30, 2012 You've gotten some really good replies on this question, the 'fundamental' constants have little to do with it, but simple logic and the realization that amongst other things, time is the order of events, has everything to do with it. I'm very leery of using the word 'fundamental' to describe anything in Physics. After all, the job of the theorist is to derive as much as possible from as little as possible, so he should seek to treat as few things as possible as being fundamental. How can we exclude fundamental constants , they are how the universe works? Tell me how a theorist could derive anything by exculding FC from his research? Link to comment Share on other sites More sharing options...
Ronald Hyde Posted August 30, 2012 Share Posted August 30, 2012 How can we exclude fundamental constants , they are how the universe works? Tell me how a theorist could derive anything by excluding FC from his research? And how exactly do we know which 'constants' are fundamental, and which are derivative? And are they all really constant. We may find that some change slowly with time, others not at all. And we can't change what happened in the past, regardless of what value the constants have, now or then. So one part of your question isn't really connectable to the other part. When you say 'Tell me how a theorist could derive anything by excluding FC from his research?', you're introducing even more vagueness and confusion. What is his research, building a Time Machine? If so, what would the FC's as you call them, have to do with the construction of it? Link to comment Share on other sites More sharing options...
JohnStu Posted September 18, 2012 Share Posted September 18, 2012 Define time travel. Do u mean others around thou go back in time or just urself go back in time or youself plus the surrounding go back in time? Link to comment Share on other sites More sharing options...
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