Time Travel

[muguly]

If it were possible to travel through time, would it be possible to change the future?

I say maybe. If time travel became a reality and people did go back to change things, who's to say that the reason the future is the way it is due to that person going back in time and changing something? The same would happen if they didn't go back in time:the future(or present)would remain the same.

The only way I could think to change to future is monetarily.

Any thoughts?

[Monte314]

Can't I change the future right now without time travel?

[SirJac]

Reverse causality experiment (To view links or images in this forum your post count must be 2 or greater. You currently have 0 posts.)

[blueback]

I've always enjoyed the idea that all of the close scrapes in history are the result of a person traveling back in time and changing things for the better. Things like the Allies winning WWII and the North winning the American Revolution just seem too unlikely.

[Jakalwarrior]

Multiverse theory :( My guess is you would create a new dimension at that point. Otherwise once you changed the action you wouldn't know to be there to be changing anything unless you left yourself a note for your future self as you were doing the action.

[Homini Lupus]

Multiverse theory always looked the one that made more sense to me. Or a form of determinism in wich both past and future are determined. Those are the possible solution I can understand to the problem of going back in time and exterminate your family.

[Antares]

Well, coming from intuition, the theory that makes most sense to me is that a separate timeline gets created. If my mother were to go back in time right now and kill her past self (because there's no reason that her past self should somehow vanish as a result of the same person of different age being in the same time), then I'd never have been born. But if she returns to this timeline, I'd still be around and history would be unchanged, that is, IF she can return to this timeline. If she's somehow stuck in the timeline that she diverted and travelled to the same time that she'd left this time but in the other timeline (suppose she left on 2008. She went to the 'other' 2008 where she has changed time), then she would have no history (because she'd died by killing her past self and left a huge gap in time that she skipped where she simply did not exist). From our universe, if she leaves in 2008 and cannot return to this future, then she would simply cease to exist in this timeline. She would have been born in 1964, been around until 2008 and disappear without a trace, never to be seen again.

Similarly, if time cannot be diverted, then the moment she kills her past self both her present self and me would simply disappear (time is forever changed, and if she killed her past self then her present self and myself cannot exist, so even if she remains in that time she'd still disappear. You can see how that makes no sense to me); but since that violates my common sense and I haven't got much to build on except my intuitive nonsense (I'm not knowledgeable in this field, and I don't plan to be until I go to college. Until then, my imagination is everything). Another possibility is that there is a fixed and unbreakable timeline. That any changes she makes would not affect my existence or her present self's existence. But that would create a paradox, of course, We all know I exist in 2008. But she killed her past self. So how would I exist when her past self's time reaches 2008? Would it be that my fifteen year-old self pops into existence? So let's move out of the 'killing past self' territory. If time is fixed, then you would not be able to change anything at all (so you cannot kill your past self). Any attempts you make would ultimately contribute to triggering whatever you're trying to prevent. If you want to prevent your friend from being born, all you'd do is to trigger it. It goes a full cycle and there's nothing you can do. That's the predestination paradox. < I find this sort of depressing.

[TheLastMohican]

I've always enjoyed the idea that all of the close scrapes in history are the result of a person traveling back in time and changing things for the better. Things like the Allies winning WWII and the North winning the American Revolution just seem too unlikely.

That would either be the North winning the American Civil War or the Americans winning the American Revolution. I assume you meant the latter.
An interesting idea. But then there were also many improbable events that turned out for the worse (as far as we can tell). Hitler, for example, could have been shot during WWI by a British soldier, but the Brit held his fire because he thought it would be unchivalrous to kill a wounded soldier like that. That was a close call, and it gave us an infamous dictator. It seems to me that the overall probabilities are as they should be, and we tend to notice the ones that turned out well.
(On a side note, my mother suggested that history has turned out better than probability dictates it should have, and this can be attributed to God. She thinks that without God, humanity's average fortune would be much worse. Blueback, you apparently think the same except with the possibility of a time-traveling do-gooder instead of God. Both are viable ideas, I suppose, but it just seems to me that the probability is fine the way it is.)

[Beery Swine]

Time travel (of a sort) is absolutely possible e.g. time dilation from high velocities or traveling through curved space-time ("gravity well" might be a good metaphor). It's going backwards in time that seems impossible with our current understanding of physics. Plus there's always the old "grandfather paradox" which imho has only ever been satisfactorily explained with the "multiverse" hypothesis, which itself seems radically unlikely.





Beery Swine added to this post, 8 minutes and 57 seconds later...

Hitler, for example, could have been shot during WWI by a British soldier, but the Brit held his fire because he thought it would be unchivalrous to kill a wounded soldier like that. That was a close call, and it gave us an infamous dictator. It seems to me that the overall probabilities are as they should be, and we tend to notice the ones that turned out well.

Or the real dictator was killed in WWI by the time traveller and we got the lesser evil. Think about that for awhile.

[Antares]

Can't I change the future right now without time travel?

No you can't. Because what you do now IS the future; you're not changing anything, just weaving the future. Unless you know the future, you can't change it; you would not have the knowledge to know what to change.

to transform or convert (usually fol. by into): The witch changed the prince into a toad

So all this fuss is to illustrate one point (I'm being rather redundant): You can't change the future without time travel.

[thod]

Of course the big assumption is that if you went back in time there would be a universe there. If you went back a day in time you would explode in space because the earth has moved around the sun. The same applies in general to time travel, the material universe is now here, at this point in time, and the point you went back to would be empty.

[Beery Swine]

Of course the big assumption is that if you went back in time there would be a universe there. If you went back a day in time you would explode in space because the earth has moved around the sun. The same applies in general to time travel, the material universe is now here, at this point in time, and the point you went back to would be empty.

Okay, what you said I don't think makes any sense (unless I've misunderstood, which is somewhat likely), but you made me think of something. Go back in time and the Earth will be in the place it was at that particular time. When you embark on your journey with your magic De Lorean, Earth is in position ABC, in time D. Your destination, however, is time Z, and at time Z Earth was in position WXY. Never mind space-time expansion for now: I'm no physics expert, or really even layman, but wouldn't you be occupying space where earth will be at time D when you travel instantaneously from time D back to time Z? Maybe this was the point you were trying to make, I don't know.

[thod]

Consider time as the x axis and the universe as a line, the y axis. The universe is traversing the x axis at the speed of time. Thus if you were to move to another point on that x axis there would be no universe there.

The problem with back to the future type movies is that don't take into account the movement or rotation of the Earth or the movement of the Sun spinning around the galactic core etc. In just 12 hours your momentum is one direction, then the other, as the earth rotates. So even if you changed position with your time travel you would still be traveling at thousands of mph relative to the Earth. You need to change a lot of physical variables to be just standing still on the surface.

[Homini Lupus]

That's the problem of hypotetical instant travel. Maybe this means that we would be limited to leaps in time and space of years (1, 2 ,3 years but not 1 year and three days)? Or that time travel would be limited to open space? I would say the latter since it's quite unlikely to cathch a point of the earth with the same composition of forces in future, but It's not my field.

[Neuro]

Trying to reason with unknowable abstract concepts angers up the blood. Time travel is particularly convoluted and I have become quite upset in the past when the subject has come up (typically in movies). Comedies excluded of course as absurdity is quite welcome there.

[PHS Philip]

Doesn't time travel also require either the creation of matter or that the atoms in your body exist simultaneously where they did at that time and in your body? So that time travel would only work based off really low probability quantum weirdness?

[SirJac]

^^^ I wouldn't think so, since hypothetically you would just be moving a person's position in space-time. Your not creating or destroying matter, simply changing space-time location.

Either way, I think that the best we can expect to see in our life times is space/time dilation at the subatomic level, which would still be an incredible feat that could be used in so many different applications that it would fundamentally change our world much like computers, internet or flight.

[PHS Philip]

^^^ I wouldn't think so, since hypothetically you would just be moving a person's position in space-time. Your not creating or destroying matter, simply changing space-time location.

Either way, I think that the best we can expect to see in our life times is space/time dilation at the subatomic level, which would still be an incredible feat that could be used in so many different applications that it would fundamentally change our world much like computers, internet or flight.

But their body has to exist there, right? Consciousness isn't just some abstract quality, it's the functions of your brain, so moving the consciousness implies moving the brain (and thus the body). And your atoms were in something else farther back in time? Putting two of the same atom in a certain point in time would be like putting two atoms in exactly the same point in 3 dimensional space, I'd think.

[SirJac]

That's why it's important to distinguish it as space-time and veiw it as a 4 dimentional model. It's true that the the same atom could not appear twice in the same location in space time, but going back in time does not do that. The same atom might exist twice at the same time, but time is still only one of 4 dimentions of space-time. So it would have to exist in two different locations in the other 3 dimentions. Nor is the atom being created either since it is simply a movement along the time axis, as opposed to moving along the 3 dimentions we are familiar with. Freely moving along the time axis is no different then moving along any of the other axes and would not involve changing vessels for your consciousness anymore then walking forward.

[PHS Philip]

Time doesn't work exactly the same as a spacial dimension, from what I remember. Cause and effect hold up because time, unlike space, is one directional. They're part of the same fabric, but they behave differently.

[SirJac]

They behave differently because you cannot move freely along it. The essence of time travel is moving freely along time, and so the normal limitations of time must be assumed to not be absolute for the sake of even having a discussion about time travel.

[Bandit]

I've always enjoyed the idea that all of the close scrapes in history are the result of a person traveling back in time and changing things for the better. Things like the Allies winning WWII and the North winning the American Revolution just seem too unlikely.

The North winning was a good thing?

[bricklayer]

It's possible to go into the future but not the past. But yes you can impact the future without necessarily going into it. Although one could argue we're constantly going into the future even though the only thing that ever really exists is the present.

[Beery Swine]

The North winning was a good thing?

Gee, let me think, um...YES!

[muguly]

What if time was kinda like string theory(indulge me for a minute): if the beginning of time was the first pluck of the string then every second, minute, hour, day, etc., has it's own particular frequency. Now, if scientist could somehow find these frequencies and pinpoint which frequency vibrated at a particular time, they could build something to vibrate on that the various frequencies and potentially have an object exist in any. period of time.

Keep in mind that I have given this no in depth thought, it just crossed my mind.

[Beery Swine]

What if time was kinda like string theory(indulge me for a minute): if the beginning of time was the first pluck of the string then every second, minute, hour, day, etc., has it's own particular frequency. Now, if scientist could somehow find these frequencies and pinpoint which frequency vibrated at a particular time, they could build something to vibrate on that the various frequencies and potentially have an object exist in any. period of time.

Keep in mind that I have given this no in depth thought, it just crossed my mind.

I'd love to see a video game based on that. The concept sounds friggin sweet.

[Phalanx]

The philosophical questions are more easily answered after you determine the mechanism for accomplishing time travel. There are several possible ways to travel into the past, each one implying different consequences for the future. What you want to do is engineer a method of time travel that allows you to change the future while avoiding the paradoxes that traditionally come with it. A practical time travelling solution does not have to be "pure" in order to accomplish objectives of human concern. I will assume the goal is to go back into recent human history and change the outcome of a nuclear holocaust.

One method of travelling into the past is to simply reverse the velocities and time arrows of everything in local space, perhaps on a solar system scale, except for what is inside the time machine. This can be accomplished by manipulating universal constants locally by deforming Calabi-Yau space until you exactly reverse the time variance of the decay of the K-meson (since the violation of time invariance by the decay of the K-meson into two pions instead of three is an indicator of the precise direction of the cosmological arrow of time, and from there the thermodynamic and electromagnetic arrows of time). You won't be moving back in time in an absolute sense because the rest of the universe keeps moving "forward"; you are merely rebuilding the solar system as it was at a previous time by modifying the physical component of space that sets time arrows. You cannot reverse the time of the whole universe because there exists nowhere else to absorb the entropy, but you are allowed to reverse small areas because the rest of the universe can absorb that entropy and remain in compliance with the second law of thermodynamics. The fact that Sol jumps behind 20 years in its galactic orbit relative to the rest of the stars will be a matter for the astronomers to ponder while you go back in time and save the world.

From the perspective of the universe, time has continued to move forward. From the perspective of the Earth, an extremely unlikely series of events occur resetting everything to as it was at a previous time: people unbury coffins as the dead regenerate and come back to life, walking backwards through their timelines towards their births; the planets reverse their orbits about the sun; clocks run backwards; the missiles reassemble themselves and fly backwards into their silos as the generals unpress their buttons. The time traveler must not interfere while time is reversed; otherwise, his actions will alter the future of the time-reversed earth, which is to say he will be changing the past (his future). Eventually the time machine will restore the local Calabi-Yau spaces to their original dimensions, flipping the time arrows back to their original directions. You are in the past (with slight differences due to cosmic radiation from space outside the time-reversed area and the resulting butterfly effect.)

One consequence of this method is that since you were inside the time-machine while the Earth was resetting, the atoms that make you up will be absent from history. If you were important, then you will return to a very different past; but if you were fairly insignificant, adverse effects might be minor. Since the universe's time arrow did not change, the "future" you came from is part of the universe's past, so no paradoxes are created. You are free to stop the impending nuclear war. No need for multiverses either.

It isn't elegant, but it allows the sole survivor of a future nuclear holocaust the ability to resurrect humanity, at the cost of him being erased from history and the lives of everyone who knew or loved him, and spend his time posting on internet forums, his story too unbelievable to ever be told, as the world charts itself a new journey, blissfully unaware of just how close it came to destruction.

[Dzepxich]

^^^One of the coolest posts I've read in a long time. Thanks!