Talk:Time travel/Archive 9

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Parallel universe time travel and break of symmetry

I wrote that the parallel universe version necessarly breaks symmetry between universes. To me it was kind of obvious when I wrote it.

But now that I'm thinking about it, I'm not so sure. Does it make any sense to consider an operation that would switch between two alternate universes ?? I doubt it would, unless you consider some kind of a meta-universe that includes all alternate universes. Which is kind of weird.

Therefore, if someone removes all remarks concerning the breaking of symetry in the article, I would understand.

--Grondilu (talk) 16:37, 27 October 2010 (UTC)

Another way of interpreting the parallel universe theory is to say that you travel across to a universe where it's present or 'now' .is. 5 seconds ago. That is to say their universe is identical to ours as it was in the past.

It's not the most popular of the theories among many because it questions whether or not we can really call this time travel.

“The time traveler who journeys to 1001 is not traveling back to 1001 at all, as the traditional conception of time travel would seem to require; rather, it is more precise to think of his traveling across to 1001” Abbruzzese 2001

By getting rid of reverse cause and effect, haven't we basically got rid of time travel? Well, no. We may well travel ‘across’ time not 'backwards' but this other universe (which up until our arrival is the same in .every. respect to our own) could in fact be thought of as a ‘present’ version of the past. So rather than questioning the existence of other universes, this argument means we may well need to redefine what time travel exactly .is.

STEVEN ROBERT GILL — Preceding unsigned comment added by 82.30.25.224 (talk) 15:31, 19 August 2011 (UTC)

Thinking about this further, you could in theory add a fifth animation on the main page representing this alternate interpretation of time travel. Someone will have to do it on my behalf since I haven't got the first clue as to how you go about doing it. — Preceding unsigned comment added by 82.30.25.224 (talk) 16:14, 28 August 2011 (UTC)

No Causality Problem

If time travel is possible, and you do travel to the past, then you already have been in the past and it's a part of the present already. For whatever reason, if you travel to the past to change something that contributed to the present as you know it, you can't, because it didn't get changed. From the perspective of the present, events in the past are immutable, and the most a time traveler could accomplish is to create the future that he knows already exists. Nothing else can happen because it didn't happen. No paradox, no causality issues.

Personally, I think time travel is impossible due to the conservation of mass/energy. Something sent into the past would look like destruction of mass/energy in the present and creation of mass/energy in the past.Jlodman (talk) 05:29, 29 October 2010 (UTC)

Well, your first paragraph suggests you believe only in the self-consistent time travel version (see article). Conservation of mass/energy is not an issue in the continuous time travel version. Anyway, let me remind you that this place is not a forum about the article's subject. Do you have anything to say concerning the article itself, and not just about time travel ? --Grondilu (talk) 00:50, 2 November 2010 (UTC)

Time travel into the future

From the lead section:

"...one-way travel into the future is arguably possible..."

Why arguably? I thought this effect had been experimentally confirmed (albeit, given current technology, by only minute amounts). 86.179.118.226 (talk) 21:58, 13 February 2011 (UTC)

Please show your sources for the experiments done and results thereof. HumphreyW (talk) 04:47, 14 February 2011 (UTC)

I thought this was common knowledge. See e.g. Time_dilation#Experimental_confirmation. I think I also remember reading that the GPS system has to be adjusted to compensate for the different speed that the clocks run at while whizzing round Earth. Are we talking about the same thing here? 86.160.222.121 (talk) 12:33, 14 February 2011 (UTC) Edit: Sorry, the GPS thing is mentioned at the link given...

I suppose it's "arguably" because there are some people who don't consider differential aging via relativistic time dilation to qualify as "travel into the future"--perhaps they think that travel into the future would have to match the science fiction convention of just disappearing from the present and reappearing in the future, having skipped over the intervening years completely. And there are also others who don't think one-way travel into the future can ever be called "time travel", see Talk:Time_travel#sleeping_is_.2Anot.2A_time_travel. Still, this isn't the point of view of any authority I know of (a physicist, a science fiction critic, etc.) so I wouldn't object to removing the "arguably". Hypnosifl (talk) 17:07, 15 February 2011 (UTC)

I think you may be right about why "arguably" was used. However, I read it as implying that the existence of relativistic time dilation effects is debated (rather than, as I understand it, being an established scientific fact). How about we change "arguably" to "theoretically"? If I could go arbitrarily fast, then 100 world-years could be swallowed up in a couple of seconds of my time -- is that right? If so, then I think most people would accept that as being "one way travel into the future". 86.181.174.241 (talk) 18:37, 15 February 2011 (UTC)

Only problem with "theoretically" is that it might suggest it's purely theoretical, when in fact it's been verified with atomic clocks that space shuttles and the like do age slightly less than clocks on the ground. Maybe something like "and a form of one-way time travel into the future is possible given..." ('a form' would suggest that other forms which appear in sci-fi, like jumping forward in time and skipping the intervening years, may not be possible). Hypnosifl (talk) 00:11, 19 February 2011 (UTC)

Yes, I see what you mean about "theoretically". However, regarding your wording, I'm not sure exactly what other "forms" you are thinking of that are not possible. Why is "jumping forward in time and skipping the intervening years" not possible (in principle)? In principle, can I not, for example, condense 500 world-years into what seems to me like 1/10 second? That sure seems like skipping the intervening years to me. I thought the only thing I couldn't do was condense those years into exactly zero seconds. However, that seems an unusual and severe requirement. I think most putative time-travellers would be pretty happy with a "journey time" of a second or a few seconds. How about "and one-way time travel into the future is in principle possible given..."? 86.181.174.240 (talk) 18:46, 23 February 2011 (UTC)

I meant "skipping" as in actually not being physically present in the intervening years, like in "Back to the Future" where the DeLorean just vanishes from one time and place and appears in another, a pretty common convention in sci-fi time travel. In relativity even if you traveled 500 years into the future in Earth's frame in only 1/10 of a second of your own time, in the Earth's frame your ship would still be present at every moment in those 500 years, it's just that all processes aboard your ship would be running incredibly slow in that frame. Anyway, "in principle" would be OK with me, though I'd suggest "possible in principle" rather than "in principle possible", I think it's the more common phrase (and the two p's in a row sounds a little awkward). Hypnosifl (talk) 00:01, 24 February 2011 (UTC)

Very true. I know this place is not a forum about time travel, but I can't help noticing that, since the ship's internal clock is running extremely slow from Earth's perspective, it can not move at any substantial speed, because such a speed would be ridiculously high in the ship's reference. Thus, the ship has to resist any external force applied to it, which shows how mass and time dilatation are closely related. --Grondilu (talk) 18:19, 24 February 2011 (UTC)

Actually, despite the time dilation, speed is completely symmetric--if the ship measures the Earth to be moving away at 0.6c (60% the speed of light) relative to itself, then the Earth also measures the ship to be moving at 0.6c relative to the Earth. And as long as both are moving inertially (not accelerating), time dilation itself is symmetric, in this example the ship's clock will be running slow by a factor of 0.8 in the Earth's frame, but the Earth's frame will be running slow by a factor of 0.8 in the ship's frame. It all has to do with the fact that each one is using their own set of rulers and clocks to measure the other one, and each one thinks the other guy's rulers are shrunk due to length contraction and the other guy's clocks are slowed-down due to time dilation and out-of-sync due to the relativity of simultaneity. Here is a thread on physicsforums.com where I illustrated how it would look in both frames if you had two ruler/clock systems moving at relativistic speed next to each other, you might find that helpful in understanding how it can all work out. Hypnosifl (talk) 18:34, 24 February 2011 (UTC)

reducing article size - move fiction stuff to merge with "Time Travel in Fiction"?

To reduce the length of this article, perhaps the section of ideas from fiction should be merged into the related article Time travel in fiction. That article has taken a science fiction history approach to the subject, which perhaps could be nicely complemented by the approach taken in THIS article. ChrisBaker (talk) 17:31, 6 March 2011 (UTC)

The problem is that most of the "ideas from fiction" is about the theory of how time travel would work, just using fiction to illustrate these ideas, and so it fits in naturally with the earlier stuff concerning ideas about how to resolve paradoxes from physics (Novikov self-consistency principle, parallel universes, etc.) and from philosophy. So I think that stuff fits better in this article than in "Time travel in fiction". The section on "Origins of the concept" might make more sense in that article, though. Hypnosifl (talk) 03:58, 8 March 2011 (UTC)

reducing the size of the article

The article is currently tagged as too long, and indeed I think it is.

In order to shorten the article, I think we shoud discuss which parts should stay in it, and which part should be put in a separate article.

Time travel is still a very imaginary experiment. Actually science fiction is by far the most common place for time travel to occur. Therefore, I think the ideas from fiction should be the most part of the article, and it should be one of the first sections. Rigourus science hypothesis should be regarded as digressions, and should be put at the end of the article, or in a separate article.

--Grondilu (talk) 16:47, 28 February 2011 (UTC)

I don't think it's that bad, currently the readable text (as opposed to references and the like) is about 73 KB, and Wikipedia:Article_size only offers loose guidelines...judging from that I would say pages only slightly larger than 50 KB could go either way, they only say an article "almost certainly should be divided" if it exceeds 100 KB, and elsewhere they say "Articles of about 200 KB (~30 pages) are not uncommon given that many topics require depth and detail, but it's typical that articles of such size get split into two or more sub-articles." There may be certain sections that could be merged into other articles, but completely splitting apart the physics content and the fiction content would seem a little excessive to me. Hypnosifl (talk) 04:08, 8 March 2011 (UTC)

I don't think this article is that long either. We have articles much longer than this. It also seems fairly easy to navigate through. Thus, I am removing the "too long" tag, per my and Hypnosifl's comments. Flyer22 (talk) 06:48, 14 April 2011 (UTC)

time traveling train?

i have heard somewhere that if a train travels at the speed of 7 rounds of earth in a sec it would go 100 years forward in just 1 week.is it possible in future?can a train can travel at that much speed on earthronitd 09:28, 25 March 2011 (UTC) — Preceding unsigned comment added by Ronitd (talk • contribs)

I highly doubt a train can sustain such a speed without overheating. Even if a train could be that fast it would not go forward in time. A train ride with that speed would be like arriving at your destination the time you went aboard the train. . . . I guess? Matthew Goldsmith 22:11, 27 March 2011 (UTC) — Preceding unsigned comment added by Lightylight (talk • contribs)

This is just a theoretical illustration of relativistic time dilation due to velocity--not practical of course, but theoretically you could make the time experienced by the passengers arbitrarily small compared to the time experienced by those at rest relative to the surface, by making the train's velocity sufficiently close to the speed of light. In theory, if you traveled around the Earth at about 0.99999998161 the speed of light (which would mean you would travel around the Earth about 7.5 times a second), in 100 years as experienced by those on the surface you would experience only 100 * sqrt(1 - 0.99999998161^2) years, or 0.019178 years, which is equal to almost exactly 1 week. Hypnosifl (talk) 03:22, 3 April 2011 (UTC)

Such a speed would be far greater than the escape velocity so I doubt there is any way we could maintain this train on Earth surface. Just wondering: is there any terrestrial or maybe solar orbital trajectory that provides signifcative speed at periapsis, compared to speed of light ? -- Grondilu (talk) 12:55, 4 April 2011 (UTC)

Yes, again it's not intended to be remotely practical, there's also the issue that the centrifugal force from traveling in an Earth-sized circle at that speed would create unbelievably huge G-forces on board the train. And to answer your question, no free-fall orbit (i.e. one that didn't require constantly firing rockets or applying some other non-gravitational force) around the Earth or the Sun could have a speed that was a significant fraction of light speed, for a free-fall orbit to approach light speed you need something approaching the density of a black hole. At 1.5 times the radius of the event horizon, the speed needed to orbit a black hole would be exactly the speed of light, this is known as the photon sphere...so just outside the photon sphere, orbits would have speeds close to light speed. Hypnosifl (talk) 07:45, 5 April 2011 (UTC)

Fatalism And The Grandfather Paradox

According the the grandfather paradox if I were to travel to the past to kill my grandfather and succeed I would have never existed in the first place. Killing my grandfather would result in my parents never being born and without any parents to give birth to me I wouldn't exist. According to fatalism what has already happened cannot be changed because it was fated to happen. Since my grandfather had married, raised my parent, and my parent raised me, I cannot kill my grandfather. He was fated to live so he will live regardless of any murder attempt. Matthew Goldsmith 22:33, 27 March 2011 (UTC) — Preceding unsigned comment added by Lightylight (talk • contribs)

I agree. If time travelling is possible it means the travelling subject/object would have to be immune to causing events that cause his/its non-existence in the future.

Tourism in Time -- Proposed Further Material

The Tourism in Time section contains various suggested reasons why time travelers, if they exist, might not be visible to us. However the text does not mention a very compelling reason why we would not see time travelers, even if time travel in the future is very common. This is the fact that travelers, in selecting the time that they wish to travel back to, would have to choose the very time in history which we occupy, to a tollerance of better than +/- 5.3 x 10 -44 second, the time taken by light to traverse the Planck Length. This is the "thickness of the present" on the historical time-line. It is the amount by which an object in front of you would have to move ahead or behind you in time, in order to fade from view. So if the travelers are further in the past or the future than this, we will not see them. Consequently there could be many trillions of time travelers on Earth, not one of which would we have any realistic chance of ever seeing. It is not sufficient for time machine operators to just select the year, month and day as in popular fiction. They have to "get it right" to the nearest 53 nano-pico-pico-picoseconds. Enough time travelers to pack-fill the entire solar system, all conveniently heading for the very second we occupy, and shooting with an accuracy of +/- half a second, -- would not have a single success. Yet the Article has no mention of this very major explanation for their absence. (204.112.72.203 (talk) 20:07, 8 April 2011 (UTC))

Huh? That doesn't make any sense, "we" don't occupy a single Planck time of history, we occupy many different ones, for example I was around throughout 2010, 2009, 2008, 2007 etc. If a time traveler had appeared on any of those dates and announced their presence to the world, I'd remember it today. In any case, see wikipedia's policy on original research, the articles should only discuss arguments that have appeared in some "reliable source". Hypnosifl (talk) 23:30, 8 April 2011 (UTC)

Starting at a point in 2007, you move forwards, occupying one infinitessimally small point in time at once, until, as the universe expands at the rate of 1 second per second, you get to 2011. But a time traveller who didn't match your position in time, to within a single Planck-time, moves on ahead of you or behind you, remaining the same distance ahead or behind, as he goes forwards too at 1 sec/sec. You never see him! And he cannot leave any thing or any information behind, as that too moves forward at 1 sec/sec, and stays ahead of you or behind you. Its like driving along a "highway of time" and theres a car in front. Any announcement he makes, on a piece of paper, which he throws out the window, just bounces along the road at 1 sec/sec and remains alongside him and ahead of you. But the car never came through you, did it? And it would have to stand still in time and wait for you, if you want to hear any announcement he makes. In short, he is in a parallel universe, located a tiny distance ahead in time. He missed yours by a whisker. What I was discussing above was the remoteness of his chances of first appearing exactly alongside you (considering the length of the road and the accuracy required), so that you can see him and communicate with him. (204.112.72.203 (talk) 00:57, 9 April 2011 (UTC))

You appear to be imagining some sort of "meta-time" dimension that allows me to "move" along the time axis, so at one point in meta-time I am at a single Planck-slice in 2010 but not at any other date, then later in meta-time I am at a single Planck-slice in 2011 but now the Planck-slice in 2010 is "empty". That's not how physicists think of spacetime! Rather the idea is that spacetime is like a frozen 4D record of all moments in my life, so the cross-section of my 4D world line in 2010 shows what I looked like at some instant in 2010, and the cross-section of the same world line in 2011 shows what I looked like at some instant in 2011, both cross-sections (and every other possible cross-section of my world line) exist "frozen" in spacetime like different points along strings frozen in a block of ice. See Eternalism (philosophy of time) for more on this way of thinking. Hypnosifl (talk) 06:36, 9 April 2011 (UTC)

Yes, on the one hand it is possible to conceive of a 4D hyperparticle which moves through time so that it no longer occupies where it was, and that our 3D particles are merely cross-sections of this hyperparticle; on the other hand yes it is possible that all the 3D cross-sections are connected ie the hyperparticle is actually a string which stretches thru time. In other words, the "car in front" is connected to your car and the driver in front is you. This is my other model of the cosmos.... imagine a central hypershpere, which has a "north" pole and a "south pole". Then (back to school!), imagine the "lines of force" coming out the north, bending around the sphere, and going into the south. At the north pole, a ring of material has been ejected, (looks a bit like the aurora ring as seen from space) and this wraps around the cluster of "lines of force" coming out the pole. The ring moves outwards, expands, moves down over the "equator", at which point it girdles the hypershpere (making the whole thing look a bit like the planet Saturn but with a much less broad ring), and then it begins to shrink as it moves over the southern hemisphere, before it crashes into the south pole. The line of the ring ie its circfumference, represents our 3D spacial cosmos. Time is the direction along a line of force, from north to south, and is therefore at 90 degrees to the ring ie at right angles to 3D space. Notice that as the ring leaves the north pole, it expands at an accelerating rate, due to the trumpeting out of the lines of force. Then, as the ring progresses, its expansion halts (as it passes over the equator), before it then shrinks again as it passes over the southern hemisphere and approaches the south pole. Notice also, that, expanding or contracting, the ring always moves the same way thru time. Now... at the other pole (opposite polarity) another ring was ejected at the same time as ours. This is the 3D antimatter cosmos which "partners" ours, and it moves the "wrong" way thru time, ie from south to north. This will appear briefly in our 3D cosmos as the 2 rings meet over the equator. At this time, particles may be left in our cosmos which did not originate here. Now suppose that the "strings" we spoke of, are the lines of force themselves! Its possible to make predictions from this model.

1.. The model explains the question that, until now, any 6 year old kid could always have used to shoot down other models: "If the cosmos is infinite, then what is it expanding out into?" Answer: the hypersphere isnt expanding; the whole shooting match stays the same size. 2.. Prediction: Expect the rate of expansion of the 3D cosmos to be increasing. However this will not last. 3.. The 3D expansion has nothing to do with gravity! It takes place at 90 degrees to that! All that gravity will do, is pull material around the circumferance of the ring, to create a "diamond ring" concentration at one place on the ring. The actual expansion is driven by the central hyperelectrostatic force which generates the field! 4.. All the talk of the cosmos expanding til the lights go out, is misconceived. It also fails to answer the 6-year-old kid. The lights will come back on again as the ring passes over the equator and eventually shrinks towards the south pole. 5.. The 3D cosmos Bangs (ejected from north pole) and Crunches (falls into south pole ) endlessly. However the 4D hypershpere has always existed. Next time round, we are all antimatter, coming the other way! 6.. There is probably no Freewill. This is because the lines of force (=strings) are pretty stationary (although they might move a bit). This means that a time traveler who manages to bend back his lines of force so he can visit the Past, would not be able to change much. Moreover he would not get the inclination to do so, as the particles in his brain are also strings (lines of force)connecting the past to the future. If however he did manage to make changes, things would work their way back to how it was, as the strings settle into their usual positions again. This explains every time-travel paradox. It should have occured to physicists that, as there is only 1 reality, these paradoxes were arising out of Misconception. 7.. Parallel 3D universes are concentric rings one following behind the other as the pole repeatedly ejects them. They are therefore seperated in time, but they each have pretty much the same history. 8... From time to time our 3D space fills with antimatter galaxies which leave a few strange particles here. This is just an antimatter ring passing thru. The galaxies will vanish again.

As you can see, I'm an independent thinker. I've had this model on the internet for some years, although its down at the moment. Now...is there anything this model doesn't explain? Over to you! I'm also Valhalan; I'll sign myself properly this time :-) (Valhalan (talk) 19:39, 9 April 2011 (UTC))

Physics is about mathematical models that make precise quantitative predictions, not conceptual pictures that are used to make qualitative predictions (and when it comes to merely conceptual pictures, showing that a "prediction" actually follows from the picture is going to be fairly subjective). General relativity has a lot of very precise quantitative predictions that have been verified observationally, no model that doesn't replicate all these same verifiable predictions can be treated as a serious competitor. And your question from the 6-year old isn't really the showstopper you imagine, GR gives a mathematically well-defined model of what it means for space to "expand" even if there is nothing it's expanding into, using intrinsic definitions of the geometry of spacetime. And it's actually not that hard to visualize if you think in terms of an analogy where the number of spatial dimensions is reduced from three to two, a la Flatland; for a finite universe with positive curvature you can just picture the expanding surface of a sphere (the balloon analogy...note that although we picture the sphere expanding in 3D space, this is not part of the "space" defined by the surface itself and such an "embedding space" is unnecessary if we are defining geometry in intrinsic terms), and for an infinite universe you can picture something like an infinite chessboard where all the squares are growing simultaneously at the same rate while the pieces at the center of each square remain the same size.

In any case, please take note of the line in the box at the top of this talk page: "This is not a forum for general discussion of the article's subject." The discussion here should be about improvements to the article based on verifiable sources, not about personal speculations. Hypnosifl (talk) 23:20, 9 April 2011 (UTC)

Read Freud. Is it likely that an incorrect model which is so simple, explains so much? Abstracting into the complex, where a simpler model has shown this unneccessary, is almost always the localised contortion of good after bad, trying to make the ends fit where they don't seem to want to. Regarding verifiability, the theory must come first, then experiments should be designed from that to test the theory. Yes there needs to be a General Discussion page attached to these Articles, making three pages in all. I am campaigning for this.(Valhalan (talk) 23:43, 9 April 2011 (UTC))

Is This an Appropriate External Link?

I'd like to offer for consideration by those maintaining this page the following external link to an essay titled 'On the Impossibility of Time Travel':

http://www.fqxi.org/data/essay-contest-files/Smith_IOTT6.cwk.pdf

Thank you. JCNSmith (talk) 16:16, 16 April 2011 (UTC)

No, I would say your article is expressing a fringe argument (and in any case doesn't meet wikipedia's criteria for reliable sources), you basically write from a presentist perspective that assumes only the present configuration of particles "exists", but you seem unaware of the alternative eternalist philosophy of time, and also seem unaware of the relativity of simultaneity which poses serious problems for the presentist philosophy. In any case general relativity does include the possibility of closed timelike curves, so unless you think philosophical arguments can discredit relativity, even a presentist would have to allow for such a possibility. Of course a presentist might interpret the situation somewhat differently, saying that the time traveler's appearance in the dinosaur age objectively happened before the traveler's departure from the future and that the traveler's "memories" of the future just reflect a predetermined truth about what will happen later in history (see the second paragraph in the section Time travel#Presentism vs. eternalism for some links to presentist arguments of this sort). Hypnosifl (talk) 23:34, 16 April 2011 (UTC)

Okay. Sort of expected this reply, but wanted to run it up the flagpole. Thank you for taking the time to look it over and provide this constructive reply. I'm personally convinced that we're overdue for a change of paradigm in our thinking about the nature of time, but this isn't the place for that debate. Thanks again. JCNSmith (talk) 02:57, 17 April 2011 (UTC)

The only way time travel can be true is if the age and knowledge of the traveler remain unchanged.

The only way time travel can be true is if the age and knowledge of the traveler remain unchanged. Concerning time travel this is the most important law. Therefore we are NOT traveling forward through time but only experiencing an quantum instant called "now". —Preceding unsigned comment added by Tpculp (talk • contribs) 13:51, 7 May 2011 (UTC)

Redoc's addition of External link

Redoc continues to add an External link ( http://lighttrap.codeplex.com/ ) to the See also section, which is for internal wiki links. Also, he has made NO case for inclusion of the link, merely pointing on user talk pages to somebody's general musings about time (at http://code.msdn.microsoft.com/lighttrap ). I am removing it again at least until until he explicates HERE at least ONE reason for inclusion. Being able to locate an image in space and time does not make it an example of time travel, not does its continued existence over time. --JimWae (talk) 17:25, 24 July 2011 (UTC)

Pretty obviously falls under WP:ELNO, and only tangentially related at best anyway. –CWenger (^ • @) 17:37, 24 July 2011 (UTC)

Experiments carried out

In this section, should there be a concern of undue weight WP:UNDUE being given to claims of violating any laws of physics. I mean if it is one researcher is making such claims versus the mainstream view, then does it deserve an entire paragraph? ---- Steve Quinn (talk) 01:35, 27 July 2011 (UTC)

As noted in the talk message box, the subject of this article is controversial, so this is the appropriate article for non-mainstream views, but such views would not be appropriate for an article like time. Obankston (talk) 16:16, 7 August 2011 (UTC)

Definition of timeline

The article should include a definition of "timeline" as used in the article, since that word is used frequently in the article and has a specialized meaning.

• Sequence of events and timeline are talking about a human description of some select recorded events, so these definitions do not apply.
• "Timeline" in this article refers to all physical events in history, recorded or unrecorded by humans. This is comparable to the set of all world lines of general relativity.

Obankston (talk) 00:31, 8 August 2011 (UTC)

Yes, I think your definition looks good and it would be helpful to add it to the beginning of the "ideas from fiction" section, which is currently the first section of the article where the term is used. Hypnosifl (talk) 17:35, 8 August 2011 (UTC)

A Google search of "timeline worldline" suggests that in fiction the word "worldline" is used more frequently than the word "timeline" to represent this concept. So perhaps this article needs to use the word "worldline" rather than "timeline", or at least mention that these are synonyms. Obankston (talk) 03:39, 11 August 2011 (UTC)

I think if you look at the details of those pages, most use world line in the sense that scientists use it, as a description of the entire 4D history of a single object, not all objects throughout space. The concept of using "worldline" to mean something more like an entire history of the universe is something I can't remember ever seeing in published science fiction, in fact the first place I remember seeing it was in the John Titor hoax, as "John" liked to insert poorly-understood science terms into his writings to make them sound more technical. Hypnosifl (talk) 06:44, 11 August 2011 (UTC)

Proposed changes to the "ideas from fiction" section to add the definition of timeline: "...they are placed under. As used in this section, timeline refers to all physical events in history, whether recorded or not recorded by humans. This contrasts to worldline, which usually refers to the history of a single item. This meaning of worldline is similar to a world line of general relativity, and may be expressed as a sequence of events, a history as recorded by humans. Note: These classifications..." Obankston (talk) 20:46, 14 August 2011 (UTC)

Looks basically good, but why say the meaning of worldline is similar to that used in relativity, as opposed to just giving the relativistic definition itself? The only place "wordline" is used in the remainder of the section is at the end of the "immutable timelines" section, where the context is a discussion of physics, not fiction:

"In addition, the second law of thermodynamics only states that entropy should increase in systems which are isolated from interactions with the external world, so Igor Novikov (creator of the Novikov self-consistency principle) has argued that in the case of macroscopic objects like the watch whose worldlines form closed loops, the outside world can expend energy to repair wear/entropy that the object acquires over the course of its history, so that it will be back in its original condition when it closes the loop."

Also, is sequence of events really a common enough term that it needs to be specifically referred to, giving people the idea that it's some kind of accepted technical term? It doesn't merit its own wikipedia page, and the only references for using "sequence of events" as a quasi-technical term are to some elementary school teaching files about learning basic ways to organize information. I don't think it's really worth mentioning here, I would propose the added sentence instead read something like: "As used in this section, timeline refers to all physical events in history, so that in time travel stories where events can be changed, the time traveler creates a new or altered timeline. This concept is distinct from that of a world line, a term from Einstein's theory of relativity which refers to the entire history of a single object (usually idealized as a point particle) that forms a distinct path through through 4-dimensional spacetime." Hypnosifl (talk) 23:16, 22 August 2011 (UTC)

I see that timeline also has its own wikipedia page, so perhaps it should be something more like: "As used in this section, timeline refers to all physical events in history, so that in time travel stories where events can be changed, the time traveler creates a new or altered timeline. This usage of "timeline" is fairly common in time travel fiction, and is distinct from the usage of "timeline" to refer to a type of chart created by humans to illustrate a particular series of events (see Timeline). This concept is also distinct from the concept of a world line, a term from Einstein's theory of relativity which refers to the entire history of a single object (usually idealized as a point particle) that forms a distinct path through through 4-dimensional spacetime." Hypnosifl (talk) 23:29, 22 August 2011 (UTC)

Sequence of events is a common enough term that it needs to be specifically referred to, because a Google search gets 6.7 million hits on that specific phrase, and Wikipedia itself gets over 1000 hits. I added additional references to the paragraphs for sequence of events. Obankston (talk) 15:21, 11 September 2011 (UTC)

I have removed these four unreliable sources as references in the Time article per wp:RS. DVdm (talk) 15:29, 11 September 2011 (UTC)

I don't think the mere number of google hits proves that it is a quasi-technical term as opposed to just a phrase a lot of people happen to hit on when talking about a collection of events arranged in time. (how many other ways are there to express this in a compact way?) Notice that "series of events" gets even more hits (19 million) than "sequence of events" (6.78 million), and "set of events" gets about a fourth as many (2.6 million). Meanwhile if we were to talk about music, "series of notes" gets 1.7 million google hits, would that phrase therefore deserve its own wikilink too? Hypnosifl (talk) 23:34, 14 September 2011 (UTC)

A NASA JPL article uses the technical term Sequence of Events (SOE). A technical device for recording a series of events is called a sequence of events recorder. It is normal for informal and colloquial phrases to be more commonly used than the corresponding technical term. Editorial discretion decides whether to use the technical term "sequence of events" or the commonly used phrase "series of events" in the article time travel. Obankston (talk) 06:42, 16 September 2011 (UTC)

In that case it does look like a technical term, but one with a restricted use--the "sequence of events" there refers specifically to a sequence of signals which are recorded and assigned a time by a particular type of electronic device like the "sequence of events recorder", not to arbitrary historical "events" like a person's birth and death dates, or arbitrary physical events like the decay of a radioactive isotope. The wikipedia article is talking about arbitrary events in a timeline, so you'd need to find some sources that show that it is more technically correct to call an ordered collection of such events a "sequence of events" rather than a "series of events" (if you search google scholar for the phrase "series of events" you do find many scientific papers which use that phrase rather than "sequence of events"). Hypnosifl (talk) 22:32, 16 September 2011 (UTC)

Time travel to the past via faster than light travel not possible

Scientists have proved than photons cannot go faster than light and so this method is impossible. http://news.discovery.com/space/time-travel-impossible-photon-110724.html 175.142.167.192 (talk) 13:54, 15 September 2011 (UTC)

Seems rather tautological. So they claim "Photons can't travel faster than light", but photons ARE light, meaning that 'Light can't travel faster than light'.

Also, what has the speed of a photon got to do with time travel? It seems that light can't travel faster than itself but this says nothing of the velocity of matter. HumphreyW (talk) 14:15, 15 September 2011 (UTC)

The reason it's not tautological is because they are informally using "speed of light" as a synonym for the constant c, which can be measured in ways that don't involve light (for example the constant appears in the time dilation equation, so measuring time dilation allows for a type of measure of the value of c). Relativity also says that it would take infinite energy to accelerate slower-than-light particles to faster-than-light, but neither relativity nor this new finding rules out the possibility of tachyon particles which always travel faster than light, although there are other reasons why physicists are pretty confident they don't exist. Hypnosifl (talk) 23:55, 15 September 2011 (UTC)

Entropy on closed timelike curves

Sorry, I think "On the other hand, the second law of thermodynamics is understood by modern physicists to be a statistical law rather than an absolute one, so spontaneous reversals of entropy or failure to increase in entropy are not impossible, just improbable (see for example the fluctuation theorem)." is improper to describe the abrasion of a watch, because in "real world" no law will predict different results from classical ones. Ltysdd (talk) 07:54, 29 September 2011 (UTC)

But spontaneous decreases in entropy have been observed, something which is predicted by statistical mechanics but not by classical (non-statistical) thermodynamics--see the fluctuation theorem, which is derived from statistical assumptions and which predicts the relative likelihood that entropy will increase or decrease in a given time, and which has been tested experimentally as discussed in the second-to-last paragraph of the section Fluctuation theorem#Statement of the fluctuation theorem. Hypnosifl (talk) 06:25, 30 September 2011 (UTC)

Not done for now: I am closing this edit request pending a response to Hypnosifl and a consensus to proceed. Monty₈₄₅ 19:02, 1 October 2011 (UTC)

additions to oldest time travel stories list .

18:09, 15 October 2011 (UTC) the Talmud relates that Among the Tannaim, the generations of rabbinic teachers whose work is recorded in the Mishnah, Rabbi Akiba is generally considered the towering personality. Approximately one hundred years after his death, a legend is reported by R. Judah bar Ezekiel (219-299 C.E.), in the name of his teacher and sometime traveling companion, Ray: - Rav Judah said in the name of Rav, - God translated Moses in time so that Moses himself attended a lecture given by Rabbi Akiva. story is told of Rabbi Akiva that when Moses ascended Mount Sinai, he saw that God was putting little taggim (the small 'crowns' on the top of the letters in the Torah scroll) on top of the Torah that was to be presented to the Jews at Mount Sinai. Moses asked God to explain the meaning of these taggim. God explained that in the future a man by the name of Akiva ben Joseph will reveal what these signs mean. - - Moses asked God to reveal to him this man and so God replied to Moses to turn around. When Moses turned around he saw a sage surrounded by many rows of students listening eagerly to this man's teaching. The greater students sat in front and the lesser in the rear. Moses, being a very humble man, took a seat in the eighth row and began listening. Rabbi Akiba taught a certain law and the students asked him what is the source, he replied that it came down to us from our great master Moses. At this lecture, Rabbi Akiva stated that all that he was teaching originated with Moses - yet Moses himself heard these matters for the first time! - Moses came back and questioned God, if there is such a great man like that why give the Torah through me? God answered, "Be silent, this is my will." (Menachoth 29b) - - One can then understand this in this way : Rabbi Akiva indeed originated the material, and then this fact allowed the material to become known to Moses via God prior to Rabbi Akiva's birth, at Mt. Sinai, creating again a non-causal loop.IF so this is the first time paradox story. - - The means by which at Sinai Moses was made aware of all the halachot which would eventually be developed is generally taken to be via direct transmission from God, as was the case with the rest of the Torah. However the means by which Moses is made aware of those matters discovered by Rabbi Akiva may have been by the bringing of Moses forward in time to participate in Rabbi Akiva's lectures. - ( see Rabbi Akiba's Crowns: Postmodern Discourse and the Cost of Rabbinic Reading - by Laurence L. Edwards http://findarticles.com/p/articles/mi_m0411/is_4_49/ai_68738707/) - eli eshed The earliest time travell to the past known is FAUST THE SECOND PART " by Johann Wolfgang von Goethe. Part of it was already published in 1827 and completly in 1832 . And in it there is what seems to Be a time travel of Faust to Ancient Greece. It is possible though that it is a journey to a parallel world of ancient Greece in which Greece gods still exist.The point in not very clear probably since the comcept of time travell to the past was not very clear to Goethe himself, he was just the inventor of it.... Time travell to te future on the other hand is ancient concept which exist from antiquity. eli eshed — Preceding unsigned comment added by 87.69.168.53 (talk)

Hans Christian Andersen Journey on Foot from Holmen's Canal to the East Point of Amager". a journey to the future of 2129.

MAY 1838 Hans Christian Andersen The Goloshes of Fortune - http://hca.gilead.org.il/goloshes.html - which is among other things about time travel to the past to Denemark of medieval times.After that the hero make a space journey. 1845 Hans Christian Andersen Lykkens Blomst (The flower of happiness). Magic comedy in two acts,C.A. Reitzel Publishers, 1845. this is a time travel play in which a 19 century dane is taken by magick to inhabite the bodies of a ,medival prince and a 18 century poet and eventuall returned to his time and place. eli eshed . — Preceding unsigned comment added by 87.69.168.53 (talk) 01:15, 16 October 2011 (UTC)

The story of Moses and the rabbi (spelled Akiva on most pages) could simply be a vision of the future, since Moses doesn't interact with anyone. And the time loop theory seems dubious, since according to this page Moses didn't understand any of the exposition in the lecture, and furthermore the page says that:

You see, when Moses heard Rabbi Akiva teaching, he was concerned. How could he know for certain that this was the Torah as he had received it? But once he heard that this man was not one to take credit for himself, but rather to quote in Moses’ name, he understood that Rabbi Akiva’s teachings were pure, unadulterated Torah, the same Torah Moses was to receive, only unfolded and unpacked.

So, Moses was just getting in advance a preview of the Torah that he was to receive as a revelation from God, it would only be a time loop if that vision was the only place he got the idea for these teachings (but since he didn't understand what he was hearing in the story, that doesn't particularly make sense).

The ones by Goethe and Hans Christian Andersen would be good to discuss, though. From the description here it sounds like Faust is taken to ancient Sparta to meet Helen of Troy by a homonculus that his assistant Wagner has created, and The Galoshes of Fortune definitely seems to involve magical transport to medieval times (someone has already added these to the list of stories but there could be a few sentences about them in the writeup). Hypnosifl (talk)

Also, I don't know if we really need to include Hans Christian Andersen's "Journey on Foot from Holmen's Canal to the East Point of Amager" since there had already been stories of magical travel to the future written before that, as detailed in that section. Did the main character return to his own time in that story? Hypnosifl (talk) 23:37, 16 October 2011 (UTC)

Light travels in time, per definition

This article is a bit ridiculous. Rather than focusing on the hypothetical, why not focus on the physical realities we know about first?! Nowhere in the article do I see it mentioned that light actually travels in time. Per definition, light travels in time. For the light, no time passes, and only the surrounds seems to speed up, which is in fact what I understand to be time travel. Albeit, only in one direction: forward. And with a speed limit. Doesn't anybody else think this relevant to mention in the first or second paragraph even?! — Preceding unsigned comment added by 196.215.115.224 (talk) 09:11, 28 November 2011 (UTC)

Moved this comment to the bottom, per wp:TPG.

Please sign your talk page messages with four tildes (~~~~)? Thanks.

I have removed the phrase you added ("much the same way that light travels"), as it is not sourced, and it isn't clear to which part of the sentence "much the same way" refers. The expression "much the same" is also quite vague — see, sort of, wp:WEASEL. - DVdm (talk) 09:22, 28 November 2011 (UTC)

There isn't really a meaningful sense that one can say "for the light, no time passes" since light does not have its own reference frame in relativity, nor can we construct any sort of physical clock that travels at precisely the speed of light. If you made a trip away from the Earth and back at a large fraction of the speed of light, hundreds/thousands/millions/etc. of years might have passed on Earth while the time experienced by you (as measured by a clock you carried, for example) could be arbitrarily small, but this is already discussed in the article, it's what's known as "time dilation". Hypnosifl (talk) 04:15, 7 December 2011 (UTC)

The ICARUS result just reproduced OPERA's results on the energy front

They found nothing new. If Cohen/Glashow is right, then the OPERA results are inconsistent; the ICARUS replication, despite the media hoopla a month after the paper came out, means nothing. Check the one line on ICARUS in the OPERA neutrino anomaly.

How is this relevant to the line you want to cut from the article? It didn't even mention the ICARUS argument, it was just talking about the analysis by Cohen/Glashow, which shows that if you consider the mainstream ideas about how the Standard Model could be extended to allow Lorentz-violation (as mentioned in this post and this one written by physicists, for example) you would get a prediction about Cerenkov radiation that was not observed. You could be correct that the results at OPERA are already demonstrably inconsistent with this prediction without the need for the additional ICARUS experiment (although I'd like to see a source for that, since the "one line on ICARUS in the OPERA neutrino anomaly" doesn't make clear whether the inconsistency with the Cohen/Glashow prediction was equally clear in the data from both experiments), but that doesn't mean that the Cohen/Glashow argument is "not credible" on a theoretical level, and that theoretical level is what the line you cut from the article was talking about. Hypnosifl (talk) 01:23, 20 December 2011 (UTC)

The line I cut mentions "and another group of experimenters argue that the lack of Cherenkov radiation indicates the neutrinos cannot have really been traveling faster than light, and the OPERA group must have just made a mistake in timekeeping." The "another group of experimenters" is the ICARUS experiment (I assume you are not debating that?) The line says nothing of Cohen-Glashow (the link to Cherenkov radiation does not mention C-G emissions, since, well, they are hypothetical). As to your other question, check ref 2 in the article: "Indeed, Dario Autiero, a physicist at the Institute of Nuclear Physics in Lyons, France, and OPERA's physics coordinator, says that measurements of the neutrino energies by OPERA, reported in a February 2011 paper, already failed to show signs of the effect later predicted by Cohen and Glashow. 'It is very well known, and it has been presented in tens of OPERA talks at conferences,' he says, 'it is not something that we learn today because of ICARUS.' Blogs are not reliable secondary sources, see WP:SPS. Nature News is. Ajoykt (talk) 03:33, 20 December 2011 (UTC)

The line says nothing of Cohen-Glashow (the link to Cherenkov radiation does not mention C-G emissions, since, well, they are hypothetical)

True, the line you cut doesn't go into details about how the prediction of Cherenkov radiation was derived, it's not necessary to go into those sorts of details in a short statement which contains a reference to an article. The reference itself does mention that the ICARUS analysis was based on Cohen-Glashow:

"Immediately after OPERA first announced its result two months ago, physicists Andrew Cohen and Sheldon Glashow at Boston University argued that radiation analogous to Cherenkov radiation, but tailored to the case of neutrinos rather than charged particles, ought to have been emanating from the neutrino beam studied at LNGS. As the neutrinos emitted this radiation, they ought to have been losing a commensurate amount of energy."

"David Cline, a physicist at the University of California, Los Angeles, and a member of the ICARUS team, said Cherenkov-like radiation in the form of photons and electron-positron pairs would have spewed from what physicists call "virtual particles" hovering around the neutrinos."

As to your other question, check ref 2 in the article

Yes, I only said that the OPERA neutrino anomaly article itself doesn't make clear whether the OPERA data was sufficient, but that reference does clear it up. The fact remains that this is not a good reason to call the article "not credible", since the article doesn't claim that the ICARUS data was necessary to the argument, it just discusses the analysis by the ICARUS group, which did use their own data but presumably could have just as easily used the OPERA data.

Blogs are not reliable secondary sources

No blogs were cited in the section you cut, I just cited some blogs by professional physicists for the purposes of discussion on this talk page. Do you debate the point they make that the argument of Cohen-Glashow and the ICARUS group was based on mainstream ideas about how one might incorporate Lorentz-violation into the Standard Model? I'm sure some more academic sources could be tracked down for this point, but it isn't even discussed in the section you cut so I don't see how it's necessary.

Meanwhile, I don't see that you've cited any secondary sources for the claim that the analysis by the ICARUS group is not viewed as "credible" by mainstream physicists. Just pointing to sources that say the assumptions they make could perhaps be wrong is not the same thing as saying their analysis is not credible--it is only intended to be a credible demonstration that the most straightforward way of incorporating FTL into known physics would yield to predictions inconsistent with the OPERA/ICARUS results, no claim is being made that it would be absolutely impossible to imagine new laws of physics that would allow FTL without Cherenkov radiation. Hypnosifl (talk) 03:55, 20 December 2011 (UTC)

The analysis by ICARUS is correct. The question is whether it is relevant and notable. In other words, whether your line there is an accurate and unbiased summary of the two paragraphs in the OPERA neutrino anomaly on the Cohen-Glashow effect. It is not - the issue is debated, and you have presented just one side. You should either leave the whole thing out, or present both sides succinctly. Since the whole issue is peripheral to the article, I think the first approach is right.Ajoykt (talk) 04:19, 20 December 2011 (UTC)

It's not intended to be a summary of the OPERA neutrino anomaly article, but to be a quick summary of what's said in the article given as a reference. While there may be no factual errors in the OPERA article, I think the amount of weight it gives to arguments supporting the possibility that the effect is real vs. arguments that it's probably not is actually pretty far from what the majority of particle physicists would see as the relative likelihood of those two possibilities. Virtually all the physicists I have seen interviewed on the subject (or discussing it in blogs) who were not directly involved with the experiment have expressed strong skepticism that the results will hold up, and the Cohen-Glashow analysis is often cited as one of the reasons to be skeptical. But in any case, the section you wanted to remove makes no claims about how strong the argument is, it simply mentions the analysis of a "group of experiments" and gives a reference to a reliable source, which is a sufficient justification under wikipedia's policies for putting a sentence like that in an article. If your reason for removing it is that you think it is "not credible", then you should find a reliable source that says words to that effect; but the sources in the OPERA neutrino anomaly article don't go that far, they just say that the assumptions might be wrong since they are based on current mainstream ideas in physics, and current physics itself might turn out to be badly wrong (if you want to add a sentence to that effect to the article, citing one of those sources, that'd be fine with me). Hypnosifl (talk) 04:53, 20 December 2011 (UTC)

Time Machines

• Time Machines via Google Scholar

Thom5738 (talk) 06:07, 26 February 2012 (UTC)

Additions to the "Forward Time Travel Section"

Perhaps the best example of forward time travel (at a rate faster than normal of course) is the Ender's Game series by Orson Scott Card. Throughout the series, the concept of Time Dilation at Relativistic Speeds (Speeds very near, but certainly not at, the speed of light) is taken into account. Many of the plots in the series feature this manner of time travel; examples include the Earth fleet in the Third Bugger War in Ender's Game, Ender's travels from planet to planet that allowed him to experience 3000 years of Human History in about 20, the Lusitania Fleet and more. It should be noted that this sort of time travel is scientifically sound. — Preceding unsigned comment added by Belac Athanasius (talk • contribs) 01:25, 29 June 2012 (UTC)

Time travel and free will

I was glad to hear in this Sean Carroll's conference a nice part about the compatibility between the concepts of free will and determinism. Here's a quote:

A lot of people are disturbed by the idea of determinism: the idea that if we have the system of the universe perfectly right now we could predict the future. I'm here to tell you: "don't be disturbed".

The idea of determinism is not like an ancient, wise man who says: "This is what will happen in the future and there is nothing you can do about it." It is not like that.

The idea of determinism is an annoying little kid who says "I know what you're going to do next". And you say "well, what am I going to do?" and he says "I can't tell you that'. And then you do and the kid says "I knew you were going to do that".

People often think determinism is in conflict with free will so they might think it is not pertinent to talk about free will in this article about time travel. I believe this is wrong: there is a problem between time travel and free will, but not between free will and determinism. Therefore, a dedicated section about time travel and free will would be pertinent I think, and could use a link to this conference as a starting source reference. --Grondilu (talk) 16:09, 17 July 2012 (UTC)

May I add The Bible Book of Genesis to Literature_timeline?

May I add The Bible Book of Genesis to Literature_timeline? In Genesis, God created the universe in 7 days despite it being billions of years old and God created things out of order. The movie Time Bandits puts forth that he used time travel. I'm not going to add it without discussion, but I think it seriously merrits adding. Think so too? Are you ready for IPv6? (talk) 23:13, 17 July 2012 (UTC)

Please don't. To me it seems quite a drastic interpretation of what the authors of the bible thought when they wrote that God created the universe in 7 days. They almost certainly meant seven days in the pure litteral sense of the expression.--Grondilu (talk) 06:10, 18 July 2012 (UTC)

Lacking A Rigorous Definition of Time Travel

Given that all matter does move through time constantly and moves through time at different rates, the introductory statement that time travel is simply moving from point A to point B on the timeline then questioning whether or not it is possible to do so is mistaken.

The bulk of the article seems to focus around the question of "if we could travel back in time, would we be able to experience historical events?" Physics has already shown that that is not possible. This was firmly established as soon as Einstein demonstrated space-time. Because physical laws are time symmetrical, there is no difference between moving backwards on a time-line or forwards on a time-line; the physcical results are the same. We do not have the ability to tell the difference between objects moving in opposite directions along the time-line, only if they are moving at different speeds. Our GPS satellite system proves Einstein's theory on time dilation and disproves any fictional concepts or hypothesis about time working any other way. — Preceding unsigned comment added by 74.213.51.98 (talk) 23:40, 6 December 2012 (UTC)

Absolute Zero

I was very surprised to see no mention of the most likely first form of time travel, which would involve super cooling. A partical with enough energy taken away from it will infact by moving in space time at a slower rate. Hence time travel — Preceding unsigned comment added by 24.207.129.95 (talk) 15:31, 22 January 2013 (UTC)

Misleading Article

The "science" of this article leans more toward speculation bordering on science fiction, yet presents it in such a way that it is hard to distinguish speculation from proven science. Forward time travel has been proven experimentally (any modern physics textbook will recount the details for you), while time travel into the passed is purely speculative and indeed runs contrary to conservation of energy. This article should be cleaned up to differentiate speculation (even that done by respected theorists) from mainstream science.129.63.129.196 (talk) 19:35, 31 January 2013 (UTC)

a few seconds into the past graphic

With that graphic, wouldn't it also mean that once his double steps out of the doorway that if someone tried to restrain him from going through, there is no way they can succeed in doing so? 66.189.38.183 (talk) 01:32, 27 July 2013 (UTC)

Freezing Time

The Time Travel page should also include insights on stopping time in one place. — Preceding unsigned comment added by 72.231.27.203 (talk) 20:51, 27 January 2013 (UTC)

Freezing time very important to be mentioned in the article. — Preceding unsigned comment added by Rhalawan (talk • contribs) 11:05, 18 June 2013 (UTC)

Quantum Entanglement Suggests Time Travel is Possible

Is there a way to work this article in here? It looks like relatively new information (2011) with fairly wide press coverage.

http://gajitz.com/quantum-entanglement-suggests-time-travel-is-possible/

http://www.wired.com/wiredscience/2011/01/timelike-entanglement/ Damonthesis (talk) 02:29, 1 May 2013 (UTC)

Uncited material - source it or lose it

I remove one section about uncited references to time travel in fiction and one in a subtly different form pops up. the section, 'Ideas from fiction' and the subsection 'Rules of time travel' both are largely uncited and contain more than a little Synthesis. We need to start seeing less editorial extemporizing and more references where reliable sources have made these connections/drawn these conclusions.
Without it, some significant parts of these sections are going to be removed as per our guidelines. - Jack Sebastian (talk) 03:03, 30 June 2013 (UTC)

A fun experiment you can do yourself

Want to know if time-travel is possible within your lifetime? Easy. Just plan on meeting yourself at Noon tomorrow at your home, for example. If you show up and you meet yourself, then woohoo, you just proved that time travel will exist, and you will have access to it. Of course, if you don't meet yourself, this could mean that you died before sending yourself back. B) the cost is too much, and you wont be able to do it. C) you change your mind about meeting yourself and telling yourself to masturbate less frequently.— Preceding unsigned comment added by 72.70.202.28 (talk) 18:31, 9 May 2013 (UTC)

Please sign your talk page messages with four tildes (~~~~). Thanks.

Good question for the wp:Reference desk/Science. Here we discuss the article content and format. See wp:TPG. Good luck! - DVdm (talk) 19:29, 9 May 2013 (UTC)

"Today I Died Again" is the title of an early Simple Minds track. They must have been toying with similar ideas. — Preceding unsigned comment added by 83.254.151.33 (talk) 03:20, 12 August 2013 (UTC)

Possible

Can we write in the article about if it's possible?--78.156.109.166 (talk) 15:46, 25 January 2014 (UTC)

Category:Time travelers

Would this be a defining aspect of a character worthy of categorizing? CensoredScribe (talk) 04:12, 10 February 2014 (UTC)

No.—Ryūlóng (琉竜) 16:16, 10 February 2014 (UTC)

Need examples in literature of this?

In the paradoxes section, there is this statement: "On the other hand, Stephen Hawking has argued that even if the MWI is correct, we should expect each time traveler to experience a single self-consistent history, so that time travelers remain within their own world rather than traveling to a different one." But then in the discussion of the theories as played out in literature, in the Type 3 universe, this type of scenario isn't talked about. 108.84.252.8 (talk) 13:38, 29 September 2014 (UTC)

What to call this

Frequently seen in fiction: Stacey puts Jim into a trance and sends him back 20 years. For Jim, 5 minutes later, while walking down the street, Jim stubs his toe. We see that Stacey has been monitoring Jim for that 5 minute interval without incident, then future Jim moans with the pain that his past self experiences from stubbing his toe - as if future and past are two different places which are "synchronized" so that the 5 minutes after Jim's arrival in the past some how correlates in a causative way with Jim's existence in the future. Or Ed goes into the past and 4 days later destroys the MacGuffin Box, then we see those who remained in the future waiting and then voila 4 days after Ed's departure to the past, the MacGuffin Box disappears. Does this dopey plot device have an official name? "Dopey Synchrony" ? MistySpock (talk) 02:31, 30 June 2014 (UTC)

Unless this discussion is going to result in an improvement to the Time travel article here on Wikipedia, please review WP:NOTFORUM and limit your contributions to article Talk pages to the discussion of such improvements. Thanks. Dwpaul ^Talk 03:13, 30 June 2014 (UTC)

   Point 4 of the cited policy-page subsection actually does say "talk pages exist for the purpose of discussing how to improve articles", and IMO leading with "Unless this discussion is going to result in an improvement ..." in responding neglects WP:AGF, which IMO includes having enough imagination to realize that (while "Dopey Synchrony" is unlikely to be an accepted term) suggesting (however obliquely) directions like treating a sub-topic Temporal paradox#Displaced synchrony (or some other section title that hasn't occurred to me, for this approach to resolving paradoxes) is part of improving articles.
   (BTW, some of our editors and talk readers may not be aware of our article MacGuffin.)
--Jerzy•t 03:23, 3 February 2015 (UTC)

The Mahabharata

The story in mahabharatha specifically say about the speed difference of time in different dimensions. Which can be compared easily with time dilation in modern physics. Thus the topic is inappropriate in the context. Please review and take necessary measures.Vishnujithts (talk) 14:06, 1 April 2015 (UTC)

It's unclear to me what you mean by "the topic is inappropriate in the context" and what change(s) you are proposing to the article. Perhaps it will be more clear to another editor, but you may want to explain in more detail what it is you are suggesting and why, in case not. Dwpaul ^Talk 14:21, 1 April 2015 (UTC)

WP:LEAD need improving

Given the length and level of detail of this article, the lead is woefully inadequate. The lead should be a summary of the article that should be able to stand alone as a concise overview of the article by establishing context, explaining why the topic is notable, and summarizing the most important points, as stated in WP:LEAD. That's not what it's doing now. Requesting assistance and feedback for improvements to lead. BlackHades (talk) 20:08, 3 November 2013 (UTC)

Agreed. I've added tag which might get the attention of some more editors. In the absence of any assistance I will have a go myself, but not right now, as I'm a bit tied up time-wise (pun intended). Jodon | Talk 13:58, 14 February 2014 (UTC)

I've started expanding it. It still does need more expansion though. But any thoughts or suggestions are welcome in the meantime. Jodon | Talk 20:48, 14 February 2014 (UTC)

I'm inclined to suggest, nay, propose, that the article be split into two or more articles as the casual reader must needs be daunted by the breadth of the article as it stands. It strikes me that Time travel in literature is really a very different category than the scientific concept, which has dimensions in physics, mathematics and logic. ZarhanFastfire (talk) 06:55, 2 August 2014 (UTC)

I agree with this proposal. This article is trying to cover two distinct topics: time travel in literature and time travel as a hypothetical phenomenon in the real world. -Jason A. Quest (talk) 22:04, 27 June 2015 (UTC)

External links modified

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Thinking about adding to the article about time travel

I think that this article needs a history section (If not) And the improvement is similar to Albert Einstein's Theory of Relativity with Time Travel would be perfect because it starts with that. DatNuttyWikipedian (talk) 07:55, 15 March 2016 (UTC)

May 2016

This was copied from User talk:BruceGrubb

Hello, I'm DVdm. I noticed that you made a change to an article, Time travel, but you didn't provide a source. I’ve removed it for now, but if you’d like to include a citation to a reliable source and re-add it, please do so! If you think I made a mistake, or if you have any questions, you can leave me a message on my talk page. Thanks. DVdm (talk) 19:10, 14 May 2016 (UTC) Note: I have undone the following of your recent edits per wp:unsourced and wp:nor ([1], [2], [3], [4]). Please read these aspects of Wikipedia policies. - DVdm (talk) 19:18, 14 May 2016 (UTC)

Please note some of the references are in the text and that we are talking about Time travel in fiction; the examples are the novel and works cited. The references on the other pages was also in the text. Also don't clutter people's talk page with material that should be here.--BruceGrubb (talk) 00:18, 15 May 2016 (UTC)

^(Off-topic)As you can see in Wikipedia:Talk page guidelines#User talk pages: "While the purpose of article talk pages is to discuss the content of articles, the purpose of user talk pages is to draw the attention or discuss the edits of a user." That is why I used the template {{uw-unsourced}}, which is meant to be left on user talk pages, not on article talk pages. Also, please do not copy talk page comments to article talk pages as you did here. Doing so can create the impression that someone abused the article talk page. I have collapsed the copied text to make clear that I did not made that comment here. If you want to refer to user talk page messages, you can refer to comments with wp:wikilinks and wp:diffs, as I did in the title of the collapse part.

As for the on-topic part, OK, I will leave the judgement of possible wp:original research and/or wp:SYNTH in your edits to other contributors here. - DVdm (talk) 08:43, 15 May 2016 (UTC)

Inconsistency

The article says in the lead: "traveling to an arbitrary point in time has a very limited support in theoretical physics", while in the following text it says: "one-way time travel into the future via time dilation is a proven phenomenon in relativistic physics". So which one is it? Time travelling into future is fully supported by theoretical physics. The article claims something that is wrong and then it contradicts itself by claiming that the future time travel is a proven phenomena. 141.138.44.114 (talk) 21:03, 5 June 2016 (UTC)

Time travel to an arbitrary point in time has very limited support in theoretical physics. Time travel into the future via time dilation is a well-established phenomenon in relativity. There is no contradiction. BrightRoundCircle (talk) 21:27, 5 June 2016 (UTC)

Ok, thanks.141.138.27.198 (talk) 08:46, 27 June 2016 (UTC)

Removed bibliography section

I've removed the bibliography section since the article uses inline citations now, and has been that way for a long time. Below are all the sources from that section. Bright☀ 22:09, 25 April 2017 (UTC)

• Curley, Mallory (2005). Beatle Pete, Time Traveller. Randy Press.
• Davies, Paul (1996). About Time. Pocket Books. ISBN 0-684-81822-1.
• Davies, Paul (2002). How to Build a Time Machine. Penguin Books Ltd. ISBN 0-14-100534-3.
• Gale, Richard M (1968). The Philosophy of Time. Palgrave Macmillan. ISBN 0-333-00042-0.
• Gale, Richard M (1968). The Philosophy of Time. Palgrave Macmillan. ISBN 0-333-00042-0.
• Gleick, James (2016). Time Travel: A History. New York: Pantheon Books. ISBN 0-307-90879-8.
• Gribbin, John (1985). In Search of Schrödinger's Cat. Corgi Adult. ISBN 0-552-12555-5.
• Miller, Kristie (2005). "Time travel and the open future". Disputatio. 1 (19): 223–232.
• Nahin, Paul J. (2001). Time Machines: Time Travel in Physics, Metaphysics, and Science Fiction. Springer-Verlag New York Inc. ISBN 0-387-98571-9.
• Nahin, Paul J. (1997). Time Travel: A writer's guide to the real science of plausible time travel. Writer's Digest Books. Cincinnati, Ohio. ISBN 0-89879-748-9
• Nikolic, H (2006). "Causal paradoxes: a conflict between relativity and the arrow of time". Foundations of Physics Letters. 19 (3): 259. arXiv:gr-qc/0403121. Bibcode:2006FoPhL..19..259N. doi:10.1007/s10702-006-0516-5.
• Pagels, Heinz (1985). Perfect Symmetry, the Search for the Beginning of Time. Simon & Schuster. ISBN 0-671-46548-1.
• Pickover, Clifford (1999). Time: A Traveler's Guide. Oxford University Press Inc, USA. ISBN 0-19-513096-0.
• Randles, Jenny (2005). Breaking the Time Barrier. Simon & Schuster Ltd. ISBN 0-7434-9259-5.
• Shore, Graham M (2003). "Constructing Time Machines". Int. J. Mod. Phys. A, Theoretical. 18 (23): 4169. arXiv:gr-qc/0210048. Bibcode:2003IJMPA..18.4169S. doi:10.1142/S0217751X03015118.
• Toomey, David (2007). The New Time Travelers: A Journey to the Frontiers of Physics. W.W. Norton & Company. ISBN 978-0-393-06013-3.
• Wittenberg, David (2013). Time Travel: The Popular Philosophy of Narrative. Fordham University Press. ISBN 978-0-823-24997-8.

Sleep, but not cryonics, in history section

Modern medical advances in cryonics have little to nothing to do with the history of the concept of time travel. Bright☀ 17:04, 8 June 2017 (UTC)

Based on your edit comments, I assumed you were removing my edit because it referenced forward time travel at ordinary rates via unconsciousness rather than via some extraordinary means (such as wormholes), which seemed like a legitimate point of contention, which is why I removed the other reference to unconscious time travel. Are you saying that only historical references to time travel should be in that section or are you saying that only fictional references should be there? If the former, how old does something have to be for it to be considered history? There is a reference later in the section dated 1951. The content I added was dated 1962 and 1967. Should the section be renamed? Sparkie82 (t•c) 02:31, 10 June 2017 (UTC)

The references explain why the historical references are significant (they're early, they have many parallels in myths, they are regarded in fiction as time travel). Modern advances like suspended animation and cryonics are a little more removed from time travel proper, and while they serve the same purpose in modern fiction as prolonged sleep did in ancient myths, most of the references treat them like a medical procedure, not necessarily a means of time travel. There was a medical section in the article but it was left unreferenced for so long that I removed it. Bright☀ 12:55, 10 June 2017 (UTC)

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Bond paradox

Some persistent IP address editor is trying to re-title the grandfather paradox as the "Bond paradox". This name is taken from a piece of fanfiction on the internet. It is not suitable for inclusion in Wikipedia since a self-published piece of fan fiction is not a reliable source, and even if it were, mentioning information that exists only in a single piece of fan fiction is undue weight. Editor, if you're reading this, please stop trying to insert what is presumably your fan fiction into Wikipedia. Bright☀ 10:46, 15 February 2018 (UTC)

Not feasible with current technology

Regarding this edit, the issue is not whether Hawking is generally reliable, but whether the source is reliable for the particular statement it's supporting. I don't agree that it is, because it doesn't appear to support the statement (or perhaps it just needs clarification?), and because it presents one perspective as absolute fact (compare for example this source). Nikkimaria (talk) 16:08, 29 September 2018 (UTC)

I think the article is indeed a bit too hazy on details to be used. Bright☀ 12:29, 25 January 2019 (UTC)

Extended-confirmed-protected edit request on 26 April 2019

Add 'time travel theories' Theory 1: If one is to travel back in time, it is impossible for their actions to affect the future in any way, as the future/present is already set. This means that their actions have no consequences in the past. They could go back in time to kill their grandparent, but they are prevented from doing so in some way.

Theory 2: If one is to travel back in time, their actions create an alternate timeline, where the events can be drastically different, or have unnoticeable details changed(for example, an alternate timeline could be created by flicking a switch on, or more noticeably, murdering someone).

Theory 3: Similar to theory 1, the present is set and unchangeable, so your past self can be killed and you would remain alive, as you are the one in the present.

Theory 4: The actions of one who has travelled to the past create a new reality, the one everyone experiences in the present. Only the people who travelled back in time to change the future would know of the old past. Everyone else would have different memories of a changed past. This theory is similar to the movie X-Men: Days of Future Past. Roganliv (talk) 02:32, 26 April 2019 (UTC)

• Please present specific edits with reference to reliable sources; please don't place forum posts here with some chatter about a movie. Drmies (talk) 02:33, 26 April 2019 (UTC)

Semi-protected edit request on 12 December 2018

At the end the first paragraph of "Absence time travelers from the future" where it talks about "a region of spacetime that is warped...", add this sentence: "Kurt Vonnegut explored this idea in his novel "The End of Eternity." 2601:1C0:8100:B4E3:F51E:5AA:C039:5EAF (talk) 20:13, 12 December 2018 (UTC)

I'm sure that most of the concepts in this article have been addressed in science fiction at one time or another. Sci-fi is covered briefly in this article but in far more detail at Time travel in fiction. Is there a reason this story is the exception that is noteworthy for a mention here? ‑‑ElHef (Meep?) 21:24, 12 December 2018 (UTC)

Yes, I think it's better to put it there. That article was specially created for the purpose. - DVdm (talk) 22:02, 12 December 2018 (UTC)

Kurt Vonnegut was not the author of "The End of Eternity". Issac Asimov is. — Preceding unsigned comment added by 104.0.216.102 (talk) 21:48, 12 February 2020 (UTC)

We are all time travellers really!

Hi, I think we are all time travellers. We are all from the 'past' right? as soon as you think, the time has passed. We are also moving forward in time, no one stop! The only thing is, some people may travel a little faster than others such as the people work on the airplane or outer space.

I have now a question if anyone can answer me. Please email me on sendittomequick@hotmail.com: I am not a physicist, if I swing my arm with speed which is attached to my body, should my arm be present in a different time as my body does? — Preceding unsigned comment added by Sendittomequick (talk • contribs) 21:17, 24 August 2018 (UTC)

I can't talk to your time travel question, but you should be able to just get messages through Wikipedia. It's usually a bad idea to put your email on Wikipedia, but it is not (to the best of my knowledge) against the rules. Nonetheless, I would suggest removing it from your comment.

Second, this space is really to talk about the article Time Travel, not to ask subject matter questions. You would probably be better off finding another forum to ask your question if you really need a response.

Finally, my apologies for deleting this comment originally - I made an error and thought it was the main article (where it would be inappropriate).

--KNHaw ^(talk) 21:25, 24 August 2018 (UTC)

This is discussed in the article, in the lead, "Forward time travel, outside the usual sense of the perception of time, is an extensively-observed phenomenon and well-understood within the framework of special relativity and general relativity", and more in-depth in the appropriate sections. Bright☀ 10:24, 25 August 2018 (UTC)

What people are calling "forward time travel" is really no such thing. If I get on a spaceship and travel near light speed for a century, I will return to the earth hardly aged at all but everyone on earth will be 100 years gone or older... did I travel forward in time? no. I did not cease to exist in the present moment at any point in my journey... but I was not changing at the normal rate of earthbound changes is all. it may SEEM like I traveled to the future but I just aged slower, not that different from traveling in cryogenic suspension.Jiohdi (talk) 01:55, 25 January 2019 (UTC)

Off-topic here per wp:Talk page guidelines: "Talk pages are for improving the encyclopedia, not for expressing personal opinions on a subject or an editor." - DVdm (talk) 08:55, 25 January 2019 (UTC)

Jiohdi correction of forward time travel does improve the article. It improves it by correcting it. — Preceding unsigned comment added by 104.0.216.102 (talk) 21:53, 12 February 2020 (UTC)

Not sure if "time travel" is possible but time machine(s) do exist apparently

Those who have them want me to think that particle accelerators are actually time machines. There is even a documentary called "The World's First Time Machine" (https://www.imdb.com/title/tt0867212/) which suggests that they are only able to receive messages from the future using their time machines. I posted about it on the reddit "conspiracy" sub (https://www.reddit.com/r/conspiracy) and now believe that everyone but me already know about the existence of time machine(s). Might want to update the article with information about real life time machine(s) or mention something like "if they exist, they are classified...". Otherwise even articles labeled "good" like this one - https://en.wikipedia.org/wiki/Deep_biosphere - shouldn't be believed. By the way, I noticed that the article about particle accelerators is not labeled "good" (https://en.wikipedia.org/wiki/Particle_accelerator). ¯\_(ツ)_/¯ — Preceding unsigned comment added by 103.57.84.115 (talk) 05:52, 21 March 2020 (UTC)