Time travel is not possible, and will never be discovered

[AAFitz]

If there's any reason to discount time travel, it would be that if there was time travel, we would have already seen time travellers...though perhaps they would have visited a time more interesting....not to say we would know that for sure, but my guess is, time travel would have been discovered, like all inventions, before intelligent fail-safe controls were in place...so they'd have messed something up by now for sure.

Time as you mentioned is not a constant however, and slowing time is possible and already done, so going into the future is a reality already. The entire fabric of time is literally curved by gravity of large massess. Its really only a matter of attainable speed to skip earth time, and end up in the future...The only limit is the speed of light and the amount of time for which one can travel at it, which for all intensive purposes is time travel...ie, going into the future...however inconvenient a method.

But going back in time is different, and while I agree it seems impossible...im educated enough to know im not educated enough to discuss it on a practical level.

[ManBungalow]

If you could travel faster than the speed of light then you would go backwards in time. Imagine racing towards a light source faster than the light could reach you. You'd quite simply see the light produced by the source in the past which has long since passed. My apologies if you don't quite understand what I'm trying to say, but it's not exactly an easily understood concept. Of course, the speed of light is supposed to be the fastest thing in the universe. Even if you did manage to travel at 3x10^8 m/s you'd be ripped right apart by the billions of particles hitting you almost simultaneously.
As with Timminz, I'll be back later to try and explain this a little better and mention black holes where light itself goes 'backwards' under the influence of gravity.

[lgoasklucyl]

If you could travel faster than the speed of light then you would go backwards in time. Imagine racing towards a light source faster than the light could reach you. You'd quite simply see the light produced by the source in the past which has long since passed. My apologies if you don't quite understand what I'm trying to say, but it's not exactly an easily understood concept. Of course, the speed of light is supposed to be the fastest thing in the universe. Even if you did manage to travel at 3x10^8 m/s you'd be ripped right apart by the billions of particles hitting you almost simultaneously.

I actually understand what you're saying, as I was lucky enough to witness a device that simulated said theory.

I was the only press allowed in with a meeting between Ron Mallett and a certain big name writer/director who is considering making a movie on Mallett's life/research

The machine was pretty interesting, however, and made all of the scientific jargon actually make sense.

[StephenB]

If you could travel faster than the speed of light then you would go backwards in time. Imagine racing towards a light source faster than the light could reach you. You'd quite simply see the light produced by the source in the past which has long since passed.

You wouldn't be in the past, you would just see it. Not the same thing.

[Lord and Master]

If you could travel faster than the speed of light then you would go backwards in time. Imagine racing towards a light source faster than the light could reach you. You'd quite simply see the light produced by the source in the past which has long since passed. My apologies if you don't quite understand what I'm trying to say, but it's not exactly an easily understood concept. Of course, the speed of light is supposed to be the fastest thing in the universe. Even if you did manage to travel at 3x10^8 m/s you'd be ripped right apart by the billions of particles hitting you almost simultaneously.
As with Timminz, I'll be back later to try and explain this a little better and mention black holes where light itself goes 'backwards' under the influence of gravity.

A photon, a particle of light, has zero rest mass, because when things are accelerated to an appreciable fraction of the speed of light, their mass increases until there can be no more increase in velocity, as the now enormous mass precludes any further increase.
Everything has mass, except a photon at rest. This doesn't prove that you can't have time travel but it does prove that you can't travel faster than light. Unless we now start on about Einstein-Rosen Bridges, or warp-holes, but anyway they're just short-cuts through space-time.
So unless we can find Tachyons (t-particles) and somehow contrive to build a Star-Trek-esque Tachyon-drive, time travel is indeed impossible.
But then the earth was flat once.

[Timminz]

I'm really having trouble trying to put what I'm thinking into words, but here goes.

As a few others have mentioned, it would be almost inconceivable that, were proper time travel ever to be discovered*, we would not have found out about it. Once knowledge of the travel itself was available, knowledge of other things would follow. Eventually, the knowledge of all inventions, discoveries, and events would be available throughout all time, thus rendering our concept of time useless. The "when" of things would hold no more significance.

*- this is, of course, assuming that if discovered, it would be used. I think it's a safe assumption, since how would anyone know they'd discovered time travel, if they never used it.



Anyway, to address a few other points brought up.

Its really only a matter of attainable speed to skip earth time, and end up in the future...The only limit is the speed of light and the amount of time for which one can travel at it, which for all intensive purposes is time travel...ie, going into the future...however inconvenient a method.

There is no "skipping" of earth time in that scenario. Simply passing through time at a different rate than someone on earth would.

If you could travel faster than the speed of light then you would go backwards in time. Imagine racing towards a light source faster than the light could reach you. You'd quite simply see the light produced by the source in the past which has long since passed.

You wouldn't be in the past, you would just see it. Not the same thing.

Exactly. This is similar to simply seeing stars that are very, very far away. What we see is light that was emitted a long time ago. Some, billions of years ago. That star could, very well, have long since ceased to exist. However, us seeing it does not constitute time travel.

As with Timminz, I'll be back later to try and explain this a little better and mention black holes where light itself goes 'backwards' under the influence of gravity.

While I do have more than a passing knowledge of black holes, I wouldn't call myself an expert. I'm interested to find out how light may go 'backwards' in time (although, your use of quotations doesn't have my hopes up), even though it wouldn't do anything to counter the points I've made, as everything I'm basing my argument on supposes that "time travel" would involve matter making the trip, while remaining intact.

[Lord and Master]

I suspect he means the event horizon, so his saying light goes backwards is referring to the inability of anything, light included, to escape from a black hole once the event horizon has been crossed. I think that's what he meant anyway...

On that note though, you know how the popular concept of black holes is that nothing can get out? So how come there's usually twin plumes of plasma/energy (situated above and below the plane of the black holes disc) throwing energy out at simply phenomenal rates? For example the common wisdom has it that there must be a supermassive black hole at the centre of our galaxy because of the enormous radio source. Surely this means that everything is in fact ejected from the black hole after it's been sucked in, processed, and for want of a better expression, cosmically farted out again?

[Timminz]

On that note though, you know how the popular concept of black holes is that nothing can get out? So how come there's usually twin plumes of plasma/energy (situated above and below the plane of the black holes disc) throwing energy out at simply phenomenal rates?

This is news to me. I understand Hawking radiation, but never this plasma energy thing. Do you know of any decent websites to read more about this phenomenon?

[Lord and Master]

Lazily, I just google-imaged black holes and got this

From www.gwu.edu and while I'm not sure what it is, the edu bit gives us hope it's a bona fide scientific thingy!
Off the top of my head, no I don't know any sites but shouldn't be too tricky to find...

[Lord and Master]

Also tried googling "black hole radio sources" and seems a wealth of stuff there.
I just thought it odd that astronomers accept that sufficiently powerful radio sources are ok to use as evidence of black holes when the public at large consider black holes to be ubiquitous vacuum-cleaners, ie how can they emit at all? Seems they do after all!

[Timminz]

First look: Black hole ejects plasma jet

Definitely neat, but I'm not too sure how it would relate to the possibility of true time travel.

[a.sub]

k so i didnt read this thread but im gonna post anyway, so if what i am saying has already been said, my apologies

The issues "non belivers"1 have is that they perceive time as a linear progression over which a 3 dimensional space changes.
first lets imagine the 3 dimensional space we exist in as a single point, so the change in the 3d world over time would be a "normal" graph that you could put on graph paper. now lets say this graph (which in real life is 4 dimensions) is changing too, then the graph would be a 3d graph on paper, and a 5d system in real life. its the change of the 4d system we exist in over time, which i will call absolute time to prevent confusion with time which acts as the 4d. this means that we are no longer traveling in a strait line called time, but changing in two directions, absolute time (the rate at which the 4 dimensions are changing) and local time (the rate at which the 3 dimensions are changing). this means that if i wanted to see myself when i was 5 years old in local time, then i just have to go backwards in local time while still moving forward in absolute time. so the 5 year old me in absolute time local time coordinates (5yrs,5yrs) (using my birth2 as the origin) is still the same so i would still exist, but i could potentially kill the 5year old me at the absolute,local coordinates (17,5) meaning that im killing the 5 year old 17 absolute years since my birth2, if that makes any sense to anybody.


1 im simply using this as a term to separate those who are pro time travel as a possibility and those who are con.
2 my birth is the coordinates when my consciousness was born. you have to realize there are infinite "consciousnesses" of me that exist and are being born.

hope that made sense

[Lord and Master]

First look: Black hole ejects plasma jet

Definitely neat, but I'm not too sure how it would relate to the possibility of true time travel.

Ah well, it doesn't really... I was just going off on a tangent I'm afraid, sorry!

k so i didnt read this thread but im gonna post anyway, so if what i am saying has already been said, my apologies

The issues "non belivers"1 have is that they perceive time as a linear progression over which a 3 dimensional space changes.
first lets imagine the 3 dimensional space we exist in as a single point, so the change in the 3d world over time would be a "normal" graph that you could put on graph paper. now lets say this graph (which in real life is 4 dimensions) is changing too, then the graph would be a 3d graph on paper, and a 5d system in real life. its the change of the 4d system we exist in over time, which i will call absolute time to prevent confusion with time which acts as the 4d. this means that we are no longer traveling in a strait line called time, but changing in two directions, absolute time (the rate at which the 4 dimensions are changing) and local time (the rate at which the 3 dimensions are changing). this means that if i wanted to see myself when i was 5 years old in local time, then i just have to go backwards in local time while still moving forward in absolute time. so the 5 year old me in absolute time local time coordinates (5yrs,5yrs) (using my birth2 as the origin) is still the same so i would still exist, but i could potentially kill the 5year old me at the absolute,local coordinates (17,5) meaning that im killing the 5 year old 17 absolute years since my birth2, if that makes any sense to anybody.


1 im simply using this as a term to separate those who are pro time travel as a possibility and those who are con.
2 my birth is the coordinates when my consciousness was born. you have to realize there are infinite "consciousnesses" of me that exist and are being born.

hope that made sense

Ok, it makes sense iff (that's the "if and only if" double-f spelling) it were possible to move around in "local" time as easily as you suggest. Which, as far as anybody knows, it isn't! In fact all you've done is re-state the problem in a slightly more enigmatic way. So while I liked your attempt to tell anyone who doesn't believe in time travel the error of their ways I'm afraid I'm gonna have to say nope to your eloquent theory!
Also, let's say you did go to your absolute,local coordinates (17,5) and killed yourself at age 5, you've just re-opened the grandfather paradox and we have no satisfactory resolution to that, other than the ultra-pragmatic view of you can't have got into that situation in the first place cos time travel's impossible for that precise reason! (ie to stop buggers like you destroying the very fabric of the multiverse)

*EDIT* You've got me thinking now Timminz (damn you!) and I've been trawling through sites looking for cool stuff thats relevant and found this Relativity, FTL and causality which very scientifically, and confusingly, confounds the possibility of time travel (or at least of faster than light travel) all the comments and arguments at the end of the article are prob the best for aiding understanding!

[Timminz]

Relativity, FTL and causality which very scientifically, and confusingly, confounds the possibility of time travel (or at least of faster than light travel) all the comments and arguments at the end of the article are prob the best for aiding understanding!

A brief note to my recent visitors: If you’ve arrived here from sites with highly misleading blurbs and expect to find a discussion of how faster-than-light travel is possible, I’m afraid you will be disappointed. This article outlines an argument commonly accepted by physicists which demonstrates that in special relativity faster-than-light travel is not possible.

The comments section is huge. Is there a particular part, or link i should be looking for?

[sgom]

heres one for you then, is cause and effect faster than light?
light travels at about 180300 miles a second. imagine a tube 1000000 miles long full of ball bearings. you push another ball bearing in one end and instantly the one at the other end would fall out, whereas light would take almost 6 seconds to travel the 1000000 miles. noy very scientific i know but just a thought that was rattling around up there.

[Lord and Master]

I just kinda read through most of Rich's comments, as he's the host/author/resident expert! I think particularly comments that deal with how you can only pick 2 from the set of {special relativity, FTL, causality} as otherwise you get nonsense results.
I only ended up there in the first place 'cos I got to thinking about the ansible, which I came across in the Ender saga of science-fiction books, and thought was a cool idea!

[Lord and Master]

heres one for you then, is cause and effect faster than light?
light travels at about 180300 miles a second. imagine a tube 1000000 miles long full of ball bearings. you push another ball bearing in one end and instantly the one at the other end would fall out, whereas light would take almost 6 seconds to travel the 1000000 miles. noy very scientific i know but just a thought that was rattling around up there.

Well no, all of the ball-bearings have moved along by one haven't they, so no fancy warp-speed effects were needed!
Sod this, I'm off to bed!

[ser stiefel]

heres one for you then, is cause and effect faster than light?
light travels at about 180300 miles a second. imagine a tube 1000000 miles long full of ball bearings. you push another ball bearing in one end and instantly the one at the other end would fall out, whereas light would take almost 6 seconds to travel the 1000000 miles. noy very scientific i know but just a thought that was rattling around up there.

Well no, all of the ball-bearings have moved along by one haven't they, so no fancy warp-speed effects were needed!
Sod this, I'm off to bed!

I have heard this type of thing described to provide faster than light communications. imagine a "really long" pencil. You could start writing by holding the pencil at this end, but the point is 1 light year (or some other very large distance) away, and begins to scribe your message instantly, much faster than light could travel the same distance.

There are some obvious difficulties in creating such a large pencil, but the concept is interesting. I believe there are other arguments against this sort of thing working, but it has been a long time since I first heard of this example, and can't remember them anymore. old age.

[AAFitz]

I'm really having trouble trying to put what I'm thinking into words, but here goes.

As a few others have mentioned, it would be almost inconceivable that, were proper time travel ever to be discovered*, we would not have found out about it. Once knowledge of the travel itself was available, knowledge of other things would follow. Eventually, the knowledge of all inventions, discoveries, and events would be available throughout all time, thus rendering our concept of time useless. The "when" of things would hold no more significance.

*- this is, of course, assuming that if discovered, it would be used. I think it's a safe assumption, since how would anyone know they'd discovered time travel, if they never used it.



Anyway, to address a few other points brought up.

Its really only a matter of attainable speed to skip earth time, and end up in the future...The only limit is the speed of light and the amount of time for which one can travel at it, which for all intensive purposes is time travel...ie, going into the future...however inconvenient a method.

There is no "skipping" of earth time in that scenario. Simply passing through time at a different rate than someone on earth would.

That is the same thing as skipping. If youre body doesnt age, and you arrive back on earth and more years have gone past than you have lived, than you have gone into the future. Not technically, which is what you are saying, but for all intensive purposes, its the same effect. Its a time machine, just not an instant one. But if you are 40 and your identical twin back on earth is 80, you have jumped 40 years into the future, simply because while he is at the end of his life cycle, you still have 40 more years of life on earth to reach his age. You are in the future. The fact that it took some time to do it is irrelevant. Earths history moved forward, and you were unaffected by it. You get to see a future that you would never have otherwise been able to see, or live in...or at least with your body at the age it returned at. Granted, I think stopping the aging of the body will come far before traveling fast enough to have any impact on this. But even then, if you can spend two years in a ship, and come back to say 40 years of progress, thats going into the future... its a relative future, but relativity is all that matters in this case.

Youre only arguing semantics on going forward in time. Obviously you really arent going forward, but by delaying the effects of time as compared to those on earth, you end up in the future, even if you never technically go to the future. Its no more time travel than say being frozen and revived in 40 years, but the effect is the same. Its irrelevant to the person if the time went by when he was an ice cube, or while he was speeding away. One day it was 40 years earlier, and the next 40 years had gone by. From his point of view, he certainly went into the future.

[Timminz]

I'm really having trouble trying to put what I'm thinking into words, but here goes.

As a few others have mentioned, it would be almost inconceivable that, were proper time travel ever to be discovered*, we would not have found out about it. Once knowledge of the travel itself was available, knowledge of other things would follow. Eventually, the knowledge of all inventions, discoveries, and events would be available throughout all time, thus rendering our concept of time useless. The "when" of things would hold no more significance.

*- this is, of course, assuming that if discovered, it would be used. I think it's a safe assumption, since how would anyone know they'd discovered time travel, if they never used it.



Anyway, to address a few other points brought up.

Its really only a matter of attainable speed to skip earth time, and end up in the future...The only limit is the speed of light and the amount of time for which one can travel at it, which for all intensive purposes is time travel...ie, going into the future...however inconvenient a method.

There is no "skipping" of earth time in that scenario. Simply passing through time at a different rate than someone on earth would.

That is the same thing as skipping. If youre body doesnt age, and you arrive back on earth and more years have gone past than you have lived, than you have gone into the future. Not technically, which is what you are saying, but for all intensive purposes, its the same effect. Its a time machine, just not an instant one. But if you are 40 and your identical twin back on earth is 80, you have jumped 40 years into the future, simply because while he is at the end of his life cycle, you still have 40 more years of life on earth to reach his age. You are in the future. The fact that it took some time to do it is irrelevant. Earths history moved forward, and you were unaffected by it. You get to see a future that you would never have otherwise been able to see, or live in...or at least with your body at the age it returned at. Granted, I think stopping the aging of the body will come far before traveling fast enough to have any impact on this. But even then, if you can spend two years in a ship, and come back to say 40 years of progress, thats going into the future... its a relative future, but relativity is all that matters in this case.

Youre only arguing semantics on going forward in time. Obviously you really arent going forward, but by delaying the effects of time as compared to those on earth, you end up in the future, even if you never technically go to the future. Its no more time travel than say being frozen and revived in 40 years, but the effect is the same. Its irrelevant to the person if the time went by when he was an ice cube, or while he was speeding away. One day it was 40 years earlier, and the next 40 years had gone by. From his point of view, he certainly went into the future.

Take, for example, one person in Chicago, and one person on a space ship traveling at nearly the speed of light around the galaxy. For each time, and place that each of those people occupy, there is exactly one time, and place that the other exists. There is no time where one exists, and the other does not; nor is there a time when either of them exist more than once; nor do either of them ever exist at any point outside of their natural existence. It is not time travel, in the sense that this discussion is about. The "skips" that do not exist in this example, are precisely what I am saying are impossible.

[john9blue]

Who's watched "Imagining the Tenth Dimension"? That video seems to indicate that we could go through time using higher dimensions (if that's possible at all).

Atomic Robo explains time travel and its problems quite well.

Click image to enlarge.

I thought of something while reading this. Going through time could make travel faster than the speed of light, at least relative to a certain spot in the universe (maybe the center, or where the Big Bang occurred, I dunno).

[mpjh]

Timmiz is correct. The last time I went far into the future, they had not invented time travel.

[Timminz]

where the Big Bang occurred

That's everywhere.

[notyou2]

Time travel may or may not be possible, but what about crossing between parallel universes?

[Timminz]

Time travel may or may not be possible, but what about crossing between parallel universes?

I used to love Sliders.