Time Travel Paradoxes

[IBelieveWhatIWant]

Not sure if this is the correct place for this discussion but it was the closest I could find, anyway.

I was trying to sleep last night when I was thinking about time travel and the possibility of going back in time even though it has been stated that if you were to go back in any form other than observation then it could create paradoxes, that being said.

Why would it create a paradox, for a paradox to exist must mean that we are on a set timeline of sorts where everything has already been determined for us because if we weren't then the timeline could be changed there fore avoiding any paradoxes created by time travel.

So I figure that it is either 1 of 2 answers that time travel into the past IS possible but any changes just changes the time line and our future is left up to us and it isn't predetermined or that time travel into the past ISN'T possible but that would mean that our timeline has already been set and everything from the beginning of the universe to the end is already set in stone.

I find this to be very interesting subject I would very much like to hear other opinions on this because I could have a very basic on how this stuff could work seeing as I have very little experience in this field and would like to hear from others with more experience who could shed some light on the possibility of this.

[Frank Merton]

Well paradoxes arise when you go into the past and carry out acts that would prevent you from going into the past, such as preventing your being born.

In such a case you can prevent the act if and only if you cannot prevent the act. This is I think kinda the essence of a paradox, and to me only servers to offer a logical proof that simple travel into the past just simply ain't gonna be possible.

[IBelieveWhatIWant]

Well paradoxes arise when you go into the past and carry out acts that would prevent you from going into the past, such as preventing your being born.

In such a case you can prevent the act if and only if you cannot prevent the act. This is I think kinda the essence of a paradox, and to me only servers to offer a logical proof that simple travel into the past just simply ain't gonna be possible.

But doesn't that only happen if the universes (there fore all life) time line is fixed and predetermined?

[MissJatti]

you can go into the past, only has an observer, and also to drop your 2014 bottle cap, or perhaps bury your Iphone 5s

[StarMountainKid]

I don't believe in alternate timelines, and I don't believe time travel into the past is possible. This wouldn't necessarily mean that the future is set in stone, though. Our 'time line' could be open-ended, such that the future is not predetermined.

However, I do like the idea that since space and time are not separable, each 'moment' of time requires a configuration of space within that 'moment'. Each 'moment' of space-time exists, like frames of a movie film. The past exists as these separate, static slices of space time.

As each slice is a static moment in time and space, our concept of change is an illusion. This would presume that all future slices of space-time must exist as well.

It is only by the nature of consciousness that we experience change and the passage of time as we do. By this concept, everything has already happened and our experience of the passage of time is an illusion created by the brain/mind.

This is a minority opinion here, as it seems most don't even consider time to exist at all.

[Whisperer]

I think that as soon as you travel to the past, your world as you know it ceases to exist because you have left it and irrevocably changed the past by your very presence and actions.

You would carry back viruses and bacteria mutated beyond the time-lines experience, your understanding would impinge on the collective mindset of the current population base and you would in effect be in a position to to be affected by diseases you have no defences for resulting in a hard time for you or an opportunistic moment to rule the world, so to speak.

What ever the case, you would find it impossible to return...

Its highly probable that you would in fact be killed outright as your lack of local language and customs would identify you as a 'stranger' and illicit immediate hostility, perhaps even being taken as an emissary of the devil.

Nothing is fixed and imutable as the universe is based on changes and therefore so too is destiny...

[IBelieveWhatIWant]

I don't believe in alternate timelines, and I don't believe time travel into the past is possible. This wouldn't necessarily mean that the future is set in stone, though. Our 'time line' could be open-ended, such that the future is not predetermined.

However, I do like the idea that since space and time are not separable, each 'moment' of time requires a configuration of space within that 'moment'. Each 'moment' of space-time exists, like frames of a movie film. The past exists as these separate, static slices of space time.

As each slice is a static moment in time and space, our concept of change is an illusion. This would presume that all future slices of space-time must exist as well.

It is only by the nature of consciousness that we experience change and the passage of time as we do. By this concept, everything has already happened and our experience of the passage of time is an illusion created by the brain/mind.

This is a minority opinion here, as it seems most don't even consider time to exist at all.

I find it interesting that most don't consider time to exist yet they still believe in paradoxes. To me those to beliefs seems to contradict each other.

Where as if it were one or the other time could exist with paradoxes or time doesn't exist with the ability to change the past and no paradoxes.

[Frank Merton]

I find it interesting that most don't consider time to exist yet they still believe in paradoxes. To me those to beliefs seems to contradict each other.

Where as if it were one or the other time could exist with paradoxes or time doesn't exist with the ability to change the past and no paradoxes.

I don't think you quite get the idea. I tend to think time is an illusion and the paradoxes serve to prove it. If the past were a "place" where one could go, then the paradoxes arise. If it isn't -- if it is just memory and other traces of how things were -- then there are no paradoxes of this sort.

The problem is that Lorenz Transformations are real and measurable. This is hard to fit in a picture of there being only the present and change being the cause of the illusion we call time.

[taniwha]

Time travel to the past seems impossible. Even if we walk backwards we are still travelling forwards in time. Perhaps if space started shrinking then we might be able to travel backwards through time. If this happened the past might simply unwind behind us with the same ease as the future unwinds before us. Would we know it if this happened. Probably not. We would unngress from one moment back to the last moment and so forth and so forth. We wouldnt recognise it happening as even our memories are simply erased as if the future hadnt yet existed. Only the now would exist and time would still seem as linear as ever full of choice and potential.

The only thing that seems certain is everything is ageing due to growth due to the expansion of space-time. And we may never know for certain at any one moment if we are travelling into the future or into the past.

[Frank Merton]

On our level of existence, that is the size level we live in and several orders of magnitude either way, time seems to have a specific direction. This is statistical.

If you have two chambers, one filled with gas A and the other filled with gas B, with a small opening between the two, over time because of random motions of the gases, both chambers will come to have a mixture of the two gases. Then no matter how long you wait the odds are overwhelmingly against the gases, with continuing random motion, sorting themselves back into their original chambers.

I'm sure this has been explained to all of us dozens of times. It is these probabilities that serve to give time its apparent motion. It is also I think the thing that gives randomness the appearance of making things seem caused and determined. When any individual molecules crosses the barrier may be random (or, because of chaotic conditions, effectively random), but the net result and the time it will take there are pretty much determined simply by probability.

[sepulchrave]

There are other contexts that one can consider when discussing time travel, in particular how time travel affects conservation ``laws''.

I put the word ``laws'' in quotes, because if time travel were possible then the mass-energy of a closed system (in the conventional sense) need not be conserved.

If you have a time machine inside a locked room and you use it to go back in time by 1 hour, and then 59 minutes after that you and your time-travelled self use it again to go back 1 hour, and then 59 minutes after that the 3 of ``you'' use it again, and so on... is there are hard limit on the identical self-copies of mass-energy that can accumulate at a given time?

When if (after continuous use of this) you achieve enough energy density to make a black hole?

[StarMountainKid]

There's an interesting Wiki page titled 'Temporal Paradox' that lists various hypothetical solutions to time travel paradoxes. It's pretty good.

http://en.wikipedia.org/wiki/Temporal_paradox

[White Crane Feather]

Not sure if this is the correct place for this discussion but it was the closest I could find, anyway.

I was trying to sleep last night when I was thinking about time travel and the possibility of going back in time even though it has been stated that if you were to go back in any form other than observation then it could create paradoxes, that being said.

Why would it create a paradox, for a paradox to exist must mean that we are on a set timeline of sorts where everything has already been determined for us because if we weren't then the timeline could be changed there fore avoiding any paradoxes created by time travel.

So I figure that it is either 1 of 2 answers that time travel into the past IS possible but any changes just changes the time line and our future is left up to us and it isn't predetermined or that time travel into the past ISN'T possible but that would mean that our timeline has already been set and everything from the beginning of the universe to the end is already set in stone.

I find this to be very interesting subject I would very much like to hear other opinions on this because I could have a very basic on how this stuff could work seeing as I have very little experience in this field and would like to hear from others with more experience who could shed some light on the possibility of this.

There are no paradoxes. They exist only in our imagination. Why? It's not only that travel back in time is impossible its that time doesn't really exist as a thing. It's simply the recognition of change. There is no future other than probabilities and there is no past other than records and deduction. To travel back into the past you would have to rearrange the entire universe back to exactly the way it was, including you, so it would no longer be the past anymore it would then be the present. It's cool to speculate, but what perceive as time isn't really a thing, or even a dimension like space as some suggest. It's an illusion of sentience.

[psyche101]

The best minds today on the frontiers of science seem to think it's possible:

LINK - Michio Kaku The Physics of Time Travel Is it real, or is it fable?

LINK - Stephen Hawking Space and Time Warps

We thus have experimental evidence from the bending of light, that space-time is curved, and confirmation from the Casimir effect, that we can warp it in the negative direction. So it might seem possible, that as we advance in science and technology, we might be able to construct a wormhole, or warp space and time in some other way, so as to be able to travel into our past.

LINK - Michio Kaku Big- Is Time TRavel Possible? Big Think

In fact, since then, a series of solutions of Einstein's equations have been discovered which allow for time travel back into the past. Time travel is allowed for:

a) traveling around a spinning universe

traveling around a spinning cylinder which is infinitely long

c) traveling around two colliding cosmic strings

d) traveling through a spinning black hole

e) stretching or compressing space via negative matter

f) traveling through a wormhole.

[StarMountainKid]

I have a kind of involved opinion of time and time travel, but I hesitate to post it as I think it will just be dismissed as the ramblings of an old man. I'll just say I consider time to be a real dimension, the past and the future to exist, and a time-traveler to the past would just become his/her past self, and would not know he/she had traveled back in time.

[psyche101]

I have a kind of involved opinion of time and time travel, but I hesitate to post it as I think it will just be dismissed as the ramblings of an old man. I'll just say I consider time to be a real dimension, the past and the future to exist, and a time-traveler to the past would just become his/her past self, and would not know he/she had traveled back in time.

Me too, I am hesitant to post much as it is a very speculative field. But Hawking's "simple" tie machine concept seems to break no rules. IF one had the ability to create a traversable wormhole that is though.

[White Crane Feather]

Me too, I am hesitant to post much as it is a very speculative field. But Hawking's "simple" tie machine concept seems to break no rules. IF one had the ability to create a traversable wormhole that is though.

Yes it involves stringing the worm whole with something that dosnt exist as of yet... A super string I think is the only possible candidate. Never mind tidal forces that will rip you to your X-rays as you approach an event horizon. How do you possibly use gravity to warp space enough to pull you through time while avoiding tidal forces?. Obviously gravity must be acting on you to get you through time, and if it is, you will be stripped to your atoms.

I have a theory of my own. Our best minds are also dreamers. Many things that fall out of equations don't exist. Some very few do. The ones that keep them on television must be addressed to stay relevant and published.

It's a roamantic pipe dream. All this time travel speculation is based on the quirky world of time dilation which is really just a function of the fixed speed of light. No where, no how does it suggest there is even a past to go back to. It's like that Stephen king movie where the big scary PAC man things chomp up the past, so you better not find yourself there, because there is no there. There is absolute nothing to suggest that a time dilated end of a worm hole is somehow further in time. When it returns to its original frame of reference it will not be further in a time dimention, its system will have simply ticked less. This is assuming its a thing at all.

It's a fun idea so scientists talk about and discuss it like we do, and this is productive. Other things fall out sometimes, buck backward time travel is obsurd.

[Frank Merton]

I have a kind of involved opinion of time and time travel, but I hesitate to post it as I think it will just be dismissed as the ramblings of an old man. I'll just say I consider time to be a real dimension, the past and the future to exist, and a time-traveler to the past would just become his/her past self, and would not know he/she had traveled back in time.

So one can move physical things back in time but not information?

[Frank Merton]

I think if you could move back in time you would not arrive at your own past but at the past of a new time line that you create and that runs on its own from your arrival forward. Thus is you killed your grandfather neither you nor your father would be born in that time line, but you, from a different time line, would still be there watching it all not happen.

In that case too if you did not kill your grandfather, and you lived long enough, you would see yourself be born and raised and have a younger double.

My point is that stuff is information; saying one could move back in time but not move memories back is saying you can't move back.

In the end I come around to the intuitive view that there is only a present, that past and future are constructs of the human mind. Somehow I think this view will eventually be brought into line with time dilation and the various other phenomena that tend now to persuade people time is a dimension.

[psyche101]

Yes it involves stringing the worm whole with something that dosnt exist as of yet... A super string I think is the only possible candidate. Never mind tidal forces that will rip you to your X-rays as you approach an event horizon. How do you possibly use gravity to warp space enough to pull you through time while avoiding tidal forces?. Obviously gravity must be acting on you to get you through time, and if it is, you will be stripped to your atoms.

Not sure where the super string comes into it but I did qualify that IF one had a wormhole, this could be done, so I figure we might look at gravitational forces should we be able to build a stable version yes? Which according to theory can be done, you just need some exotic matter, which we do not seem to have ever seen, but have postulated. But if we could build a wormhole, I am sure X Rays would be the least of our worries.

I have a theory of my own. Our best minds are also dreamers. Many things that fall out of equations don't exist. Some very few do. The ones that keep them on television must be addressed to stay relevant and published.

That is a theory that is unsupported though, the dreamers you qualify have math behind them, something. QM is a rather open field not being observable, but unless you try and integrate it with GR, it explains quite a bit rather sensibly.

It's a roamantic pipe dream. All this time travel speculation is based on the quirky world of time dilation which is really just a function of the fixed speed of light. No where, no how does it suggest there is even a past to go back to. It's like that Stephen king movie where the big scary PAC man things chomp up the past, so you better not find yourself there, because there is no there. There is absolute nothing to suggest that a time dilated end of a worm hole is somehow further in time. When it returns to its original frame of reference it will not be further in a time dimention, its system will have simply ticked less. This is assuming its a thing at all.

The Langoliers. Good song too.

Time travel via time dilation is not quirky, two men have been measured to have travelled in time in this way by atomic clocks. The most is 1/20th of a second I believe, but it's been done and verified.

It's a fun idea so scientists talk about and discuss it like we do, and this is productive. Other things fall out sometimes, buck backward time travel is obsurd.

What physics say it is impossible? It's a more modern concept taken seriously, but more and more people are becoming open to the idea. Yes, it is indeed a fun idea, but no more so than life death, aliens and the Universe in general.

I honestly find it more than perplexing that you have every faith in an afterlife, but find time travel a preposterous concept!

[psyche101]

I think if you could move back in time you would not arrive at your own past but at the past of a new time line that you create and that runs on its own from your arrival forward. Thus is you killed your grandfather neither you nor your father would be born in that time line, but you, from a different time line, would still be there watching it all not happen.

In that case too if you did not kill your grandfather, and you lived long enough, you would see yourself be born and raised and have a younger double.

My point is that stuff is information; saying one could move back in time but not move memories back is saying you can't move back.

In the end I come around to the intuitive view that there is only a present, that past and future are constructs of the human mind. Somehow I think this view will eventually be brought into line with time dilation and the various other phenomena that tend now to persuade people time is a dimension.

Yes, that theory exists, the future is not written, also a theory exists that time is like a roll of film and is already recorded, if you go back and kill your Grandfather, you may not disappear, like Groundhog day, you might find your Grandfather well and alive the next morning, with no memory of having died. Seeming as history is already written. Another says paradoxes will resolve themselves through temporal modification or if you watch Dr WHo - The Bad Wolf Resolution.

Be fascinating to see if any of them at all are correct.

[taniwha]

Einstein realised that somehow natural laws prevent time travel to the past and that is why twin paradoxes arent happening.

He dismissed the concept altogether to engage in his more favoured idea that time travel into the future was theoretically possible because of time dilation.

He soon found that to avoid a time paradox that we would become far too massive and never gain that last 0.1% of light speed, the time paradox being that we would achieve immortality by bringing time to a standstill, which is too ridiculous a conception anyway.

This means nothing in the universe is completely at rest and even if you do go fast enough to distance yourself from the confines of gravity, you will increase in mass an appropriate amount that you will attain a gradual curve away from the edge of space-time.

Therfore the universe can never be breached and time travel into the future cannot happen unless it is in the process of ' happening'

[White Crane Feather]

Not sure where the super string comes into it but I did qualify that IF one had a wormhole, this could be done, so I figure we might look at gravitational forces should we be able to build a stable version yes? Which according to theory can be done, you just need some exotic matter, which we do not seem to have ever seen, but have postulated. But if we could build a wormhole, I am sure X Rays would be the least of our worries.

That is a theory that is unsupported though, the dreamers you qualify have math behind them, something. QM is a rather open field not being observable, but unless you try and integrate it with GR, it explains quite a bit rather sensibly.

The Langoliers. Good song too.

Time travel via time dilation is not quirky, two men have been measured to have travelled in time in this way by atomic clocks. The most is 1/20th of a second I believe, but it's been done and verified.

What physics say it is impossible? It's a more modern concept taken seriously, but more and more people are becoming open to the idea. Yes, it is indeed a fun idea, but no more so than life death, aliens and the Universe in general.

I honestly find it more than perplexing that you have every faith in an afterlife, but find time travel a preposterous concept!

Hahahaha well yes. I can understand that. I do have several hats. My science hat and my tin foil hat. Ironically, and many will disagree, I don't think they are incompatible. But yes, sometimes I will speak purely from a scientific point of view when the thread calls for science. There is much more evidence for the existence of an afterlife than there is for the existence of the past or future, but that's another discussion.

Here is one for you. I don't believe that the past exists, but I do believe certain parts of the past that have not manifested yet can be affected by the present even the future. This is based on experimental evidence. Mull that one over for a while and look up the delayed choice quantum eraser.

For a stable worm whole to exist it must be strung with an "imaginary substance". It's like a rope through the wormhole. ( imagine poltergeist 1). I quoted "imaginary substance" because its not me that calls it that ---- I think it was hawking or suskind---. This substance has to be immune to the approaching infinite forces inside of black holes. The only thing that MIGHT exist that cannot be shredded by gravitational forces is a super string because its a fundamental particle and does not consist of things that can be torn apart.

Its not the X-rays that will hurt you. It's the tidal forces. --You know tides. The moon pulls more on one side of the ocean than it does the other---

Approaching a black hole tidal forces become so immense that matter is ripped to shreds. ( the gravity is so emensly stronger at your feet than it is at your head you are torn apart even your atoms experience this) Only Some X-rays have enough energy to escape close to the event horizon ( though not past it). This is why scientists find black holes by observing X-rays.

Yes "time" dilation is well understood and proven. But think of this example. Due to the nature of space-time, C is fixed. If you are standing still then the electrical signal you send to wiggle your toe travels at C to the toe, then your recognition of it travels back up via nerve cells at C also.

Now get in your car and start moving. Now when the signal leaves your head by the time it gets to your toe, your toe has actually moved before it got there. No matter what you do you cannot make C travel through any more SPACE in the same amount of TIME. The only solution is that the time RELATIVE to your twin standing standing still for you toe to wiggle must be slower, though you will not perceive this to be the case, because everything is slowed by the same amount, you see it as being the same. Though when you compare it to the stationary reference frame your clock will be off. You see it has nothing to do with a time dimension. It's the nature of space-time to limit C. The "time" experienced by anything moving must be slower relative to something that is not.

Apply that to a wormhole. One end of the wormhole in our space ship is "time" dilated. So.... It's connecting two pieces of space... There is no real "time" just relative motion. When you go backward through the worm hole you are not traveling back in time. You are simply going to a different reference frame that is less accelerated at the moment. Even if you return the end of the hole to the original reference frame it now is simply ticking ( if it ticks at all) at the same rate. Time dilation is the result of slower ticking clocks through space, not traveling faster through an imaginary time dimension.

I think the subject is popular... But there is zero evidence that the universe even has a past or future in the context of something you can physically go to except our current march into the future. Those things traveling at relativistic speeds are simply ticking slower. There simply is no reason to think otherwise. Mathematics treats both the "past" and the "future" as if its something that exists, that dosnt mean it does.

Now with my metaphysics hat on, I can see all times existing as one. But that is another discussion as well.

[StarMountainKid]

So one can move physical things back in time but not information?

I don't think traveling into the past is possible, just an opinion, but I think what I said would be compatable with my scenario. As the past is fixed and unchanable, you as a time-traveler would have to be assimilated into that unchangable moment in space-time. The only way this could happen is if you became your past self physically and psychologically.