Talk:Grandfather paradox

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High traffic

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Um... C-Class???? This is one of the best (most well-written & encyclopedic) articles I've read on Wikipedia...                     ~Rayvn  17:02, 14 February 2010 (UTC)

Miscellaneous commentary[edit]

Isn't it supposed to be "Traveler"? Hard to take an article seriously when a word is spelled incorrectly over and over and over. Oh well, at least he/she is consistent, right?  :) (talk) 17:49, 1 April 2008 (UTC)

The article is obviously written in British English, where traveller is correct, rather than American English where one would use traveler. It has taken years to teach my spell checker to spell words properly in British English 21stCenturyGreenstuff (talk) 23:45, 12 May 2008 (UTC)

What about Azimov who "proved" in his essays and stories that time travel is only possible FORWARD because of a light speed restriction??? NO scientist at this time (2007) has offered a counterpoint to Azimov.

Glass house spell criticism should learn it's spelled "Asimov". Isaac Asimov is well known for arguing both sides of an issue - like "why the moon was necessary for life" and "how life would have been created without the moon". He wrote a prodicuous amount, so I'd be surprised if he didn't prove the exact opposite somewhere. I should also mention that having an opinion does not make it true - no matter how great the man.

PcGnome (talk) 18:13, 2 August 2012 (UTC)

Parallel timeline, Ripple effect concept: What if, (refering to the grandfather paradox), you were succesfull in killing your grandfather. The Paradox theory states that it is not thoerically possible (my interpation) due to bloodline problems. My remany to this problem is the merging of Parallel timelines and ripple effect. To spare a long techinal disscussion, the concept works like this;

1)there are parallel timelines/universe (I believe these words can be interchangable saftey). These timelines can merge and spilt, being dyanimic in time-space. If muiltpile timelines are very close to each other (chacteristics based), then they merge. When actions that can affect the future are made, a slipt occurs.

For Example: The 9/11 attacks. What if it didn't happen. The US would probably not be in Iraq, so on and so forth. But what if, Instead the attack occured 10 years later. Would it create a mirrior image of the Current US status and thus rendering the current timeline and the parrallel timeline satuts quo?

2)Getting back to killing the grandfather thing. The Universe Probably has a protection feature to prevent this, but if there isn't, Could killing a person before the fact cause you in enter a time bubble in which only you exist until a remany. Possible ways to render you back into the regualr timeline:

A)You cease to exist via reaction (you kill grandfather, something kills you)

B)If you were able to go back that point in memory (my interepation of the past is the distance between memories), there is no problem going a tad bit futher past, to prevent yourself from commiting the crime. If a collsion occurrs (ie Both versions of you die) then this off spurt of time ceases to exist, meaning there is no known memory of it and life continues on as if nothing ever happen.

Hopefully I did not confuse or bore anybody with my 2 cents worth. KB1KOI 02:14, 4 October 2006 (UTC)

Concerning the paragraph:

In the 2001 film Donnie Darko, a rift in spacetime is created when a jet engine lands on the title character's house approximately 28 days before the plane carrying it flies over. This creates an unstable parallel (or tangent) universe which will cease to exist at the end of those 28 days if the engine is not returned to the primary universe. The laws of nature in the parallel universe are roughly the same, except characters and events close to the time portal are "manipulated" to return the engine to the primary universe before the parallel universe collapses on itself and becomes a blackhole of spacetime. If the portal were still open when this happened, it would destroy the primary universe and all of spacetime. How this works is never explained, but implies the idea of some universal defense mechanism.

This is not one of the many popular interpretations of the film. Even if it were, it should be labeled as an interpretation, not as the single possible narrative presented. I suggest it be removed completely unless the author wishes to dilute it with a whole lot of, "one interpretation," and, "it could be said..." -- 08:55, 22 June 2006 (UTC)

Orson Scott Card dealt with this in his book Pastwatch: The Redemption of Christopher Columbus. I'm not sure if his explanation is worth repeating in the article since the book isn't widely-known, but I will explain it somewhat here.

The moment you travel to a previous point in time, all time past that point ceases to exist. You (and anyone traveling with you) continue to exist physically, but you are not "tied" to the future in any way.

After looking at what I've typed I realize it's close to the parallel universe theorem, but Card's method was logical and well-written. Goatasaur

Nice summary and notes on fiction authors 'dealing' with it. Would be nice to note the origin of the term. Carl Sagan said it was science fiction, others seem to claim Einstein made it up. Tempshill 05:57, 1 Dec 2003 (UTC)

Removed text:

The grandfather paradox is rather overused though. For those people rather bored with killing their grandfather, there is an alternative which we'll dub "The Oedipus paradox". The essential physics is the same, but the story is different. In the Oedipus paradox the time traveller returns in time and 'loves his mother' (to quote Tom Lehrer). The time traveller then has the potential of never himself being conceived (as his mother is already pregnant at the time of his conception). To avoid the getout of the time traveller being his own father, which would be possible genetically, though statistically unlikely, this would have to take place several months prior to his own conception.
One could argue though, that Novikov could prevent this paradox from occurring - as many time travellers would not be able to follow the lead of Oedipus.

We aren't supposed to dub it anything at all. If this scenario happened in some science fiction story or other, a reference to that story could be made, but this just looks like a contributor's own ideas. As an encyclopaedia we are only supposed to report ideas that have already been made known elsewhere. -- Oliver P. 08:02, 1 Dec 2003 (UTC)

Removed text:

This particular resolution works well because some consider Parallel universes to be a neccesity in order to travel in time. Consider a line. How do you move backwards in the line? Someone - either yourself or others in line must move to the side before you can move backwards.
Therefore for time travel to exist there must be a "side" space-time for you to enter and travel in. This "side" space-time must have physical laws that allow life to exist in it. Therefore if time travel is possible there must be a place where an alternate universe could develop. If there is space for one alternate universe why not an infinite number of them? If an infinite number of universes exist than there would be an infinite number of parallel universes.

Who believes this? Certainly not scientists. If science fiction authors then which ones?

I've read a story like this but it was back in the 80s. Cant tell you where or who, wikipolice will just have to start going to LIBRARIES and get off the damned computer.

I'm curious about a proposed solution presented by Douglas Adams which was phrased (IIRC) "It all works out in the wash". In that you can travel back and kill your grandfather, which might prevent you from going back and killing your grandfather, but the other changes would make the "second take" of the intervening period of time slightly different. After enough "takes" of that particular period of time (which might be a very large number), one would work out that was consistent and stable and time would continue on from there. My questions are 1) did that make sense, and 2) is there a name for this idea? Matt 19:03, 23 Dec 2004 (UTC)

If I understand it correctly, it sounds like a variation on the Novikov self-consistency principle, i.e. the universe prevents paradoxes by making sure that no paradoxical action can succeed, only in Adams's scenario the universe is self-correcting; reactive rather than preventive. In practice, however, the two may be indistinguishable.
Consider - you go back in time and kill your grandfather. According to the NSCP, you either won't be able to do that, or if you succeed, it will turn out that he really wasn't your grandfather. In a self-correcting universe, if you go back in time and kill your own grandfather, history will alter itself so that you will discover he is no longer, and never was, your grandfather. Either way, the result is the same. -khaosworks 19:15, 23 Dec 2004 (UTC)
Or, you kill him, so you were never born, didn't go back in time, and grandpa reappears. However, time proceeds from this point slightly differently (quantum randomness, perhaps augmented by the butterfly effect), and in the new version of the timeline, a different sperm fertilizes grandma's egg (another possibility is that grandma gets a headache that night), another boy (or even a girl) is born instead of your father. If it's a boy, he may well even have the same name, but he wouldn't be the same person, having only, on average, ¾ of the same genes as your father in the original timeline (the same ovum was fertilized, so mother's contribution is 100% identical, however, father's contribution is a different sperm, with, on average, half the same genes, thus 75% genetic similarity), since dad was never born, you were never born, and you couldn't've gone back in time. Paradox solved. Nik42 21:37, 12 May 2007 (UTC)

question about this proposition: so then, what happens if you kill the entire human race?

Same principle. You were never born, thus you couldn't've gone back in time, humanity continues to exist, but the new timeline is slightly different, at least different enough to prevent your going back in time, or at least, your being successful in your attempted genocide Nik42 21:37, 12 May 2007 (UTC)

2 words: Paradox machine.

If you killed your grandfather then you would cease to exist thus negating ANY change to the time line. Just because something is random doesn't mean that it won't happen the same way under the same circumstances. Thus if you cease to exist you everything will happen the exact same way and the paradox will contine foreverSkeletor 0 (talk) 17:39, 21 February 2008 (UTC)

i have two theories to resolve the grandfather paradox: 1. perhaps this happens all the time, people from the future coming back into the past and ending their own existence however the second they end their own existence everything even slightly related to the person is instantly ended at once, but because they cease to exist their grandfather does not die so the are once again born so here is my final resolution, that instead of this being a paradox its a circle in which instead of moving forward in time some ones existence is "trapped" in a circle at a particular point in time. my second and more plausible theory is that for instance if i went back in time and shot my father, the man i shot was undoubtedly my father at the point i shot him but the universe edited all of time to create someone to replace the man i knew as my father. so if i went back in time and shot my dad the universe would instantly create another man that would impregnate my mom and create me and as all of time would have been effected by this i would instantly forget all notions of killing my father and just have a memory of going back in time and assassinating a man. —Preceding unsigned comment added by (talk) 01:50, 27 April 2009 (UTC)

I can't remember the author mentioned (Niven? Adams?) but I remember hearing once about an idea of a rash of cases of scientists traveling forward in time and killing their grandchildren in self-defense. Anybody got a reference? Dougal (talk) 19:40, 31 July 2009 (UTC)

Terence Mckenna's solution[edit]

I don't know if this is significant enough to warrent inclusion, but Terence Mckenna offered an interesting solution to the grandfather paradox. He postulated that the realization of time travel would be either the catalyst for or the result of a sort of temporal singularity that he called Timewave Zero (see the article on Novelty Theory) and that the grandfather paradox would be negated by the fact that all events in time would then exist simultaneously. Or something like that, I don't have the source material on hand. If someone can supply citations for this it may be worth including either here or perhaps in the article on Novelty Theory.

If you ever watch Futurama, you'll know that Fry went back in time and killed his grandfather, but then he impregnated his grandmother, who was now his age.-- (talk) 08:18, 12 April 2008 (UTC)

Pogo Paradox?[edit]

OK, I consider myself a Star Trek fan and I have never heard of this. Can someone explain this? --Feitclub 03:08, Apr 20, 2005 (UTC)

My only theory is that it was mentioned in the Voyager episode where Braxton is teaching Seven about the rules of time travel. Ether that or it was something that Gene Roddenberry just mentioned once. Can anyone confirm how this Pogo thing relates to Star Trek? Arctic.gnome 17:45, 23 Apr 2005 (UTC)

Read Bearing an Hourglass by Piers Anthony he explains a "3 person rule" where a person can only exist in the same time thrice. Similar concept.

It was mentioned in the Voyager episode as per Arctic.gnome —UTSRelativity 18:13, 23 Apr 2005 (UTC)

Restricted action resolution[edit]

About the "Restricted action resolution" - I'm not sure I understand the "free will" part, so I would like to make sure I got it currectly: does it simply mean that, if time travel is possible and this solution is correct - then every action in the past is consistent with every time travel in the future (and everything which lead to it), and therefore everything is deterministic and the future is already "set"?

Yes, that's pretty much it. It's the whole of history that's also set, since even if you go back in time and tell the inhabitants of the past what the future holds, there is no way for them to avert it. --khaosworks 13:07, Jun 8, 2005 (UTC)

"One potential snag to this, however, is that if one were to travel far enough back in time, the time traveller's mere existence, however brief, would still cause changes that would branch out, which would inevitably change the future enough so that the time travel never occurred (see Butterfly Effect)."

How is that a snag? That's not any different than any other situation. - Omegatron July 6, 2005 21:11 (UTC)
I guess the person who wrote this thought that determinism was dependant on other people being around. My view in relation to this theory is that if you mere presence would create change, either these change were already done (the "I created life on earth by leaving my bacterias behind" theory) or you would find it impossible to travel to that point (your time machine broke down on the way there).--Marc pasquin 17:04, 13 August 2005 (UTC)

Paradox, how come?[edit]

How is it that this is listed as a paradox? It’s a self-solving case, nothing to do with a paradox?

If I go back and kill my dad (or grandfather, or grand-grand-father), I will not be born, right? Now if I’m not born, I cannot go back in time at a later date cause I don’t exist, right? And since I don’t exist I cannot go back and kill my dad - and thus I will be born! It’s a loop you can run infinity if you like, but the outcome is always the same, you can’t change it.

Trying to change the loop alters the very existent of the change you try to make, thus the changes no longer exist, and thus the loop is not changed!

What would actually happen I think, speculation of course, is that you simple find yourself infinity pulling the trigger. The second you pull the trigger; you erase the very event (pulling the trigger) you are doing right now and you are back to zero – pulling the trigger :D. You could do this infinite, not realizing that you have already done it infinity times, cause every time you pull the trigger, you erase all knowledge of any previous attempts. Infinite times will blast by in a split second. The loop will continue till one of the small greys says, at the 60.000 gazillion run of the loop “naaar I don’t want to kill my dad” – and bammmm you are out of the loop. You will never know that you just spend an infinite in a loop, cause no time has passed and to you it still seems like the first run.

This is not a paradox, but an easy self-solving loop. Twthmoses 14:55, 10 July 2005 (UTC)

What you are describing is essentially what happens in the Restricted action resolution of the paradox. The reason this is a paradox is because ultimately, it cannot take place - we know we cannot go back in time and kill our grandfather because then we won't exist to do it. The problem is that there is nothing logically preventing us from doing so, so we have to come up with theories as why this cannot happen. What you have laid out is simply one possible solution to the problem as formulated. --khaosworks 15:47, July 10, 2005 (UTC)
I’m not disagreeing with that there are many solutions to this case; I’m disagreeing to the very fact that this is perceived as a paradox. It is not a paradox.
It has well defined parameters, it has a beginning and an end, and there is nothing illogical over it. It is a simple case. Why should this is any way be a paradox?
1) You are born. Without birth there is no case. This whole case rests on this very beginning.
2) You go back and try to erase your birth.
3) You succeed in doing this. However consequently in succeeding in this, you also erase the very action that made you succeed.
4) You are never born
5) You never travel back
6) You never kill yourself.
7) see 1)
What is illogical or paradoxical in this? It’s a loop that has no strange mechanism requirement to sustain itself, to start or even end. Of course you need to be able to time-travel. At any given moment can you choose to start it or end it anywhere in the sequence and it will leave no door open for exploits. I see nothing paradoxical in this?? Twthmoses 16:41, 10 July 2005 (UTC)
How are you able to choose to enter and exit if by this formulation you are not even aware of the loop in the first place? --khaosworks 16:48, July 10, 2005 (UTC)

That’s easy. Just choose too: D
What makes you decide on a warm summer day to go and get a coca-cola and not a Pepsi (or any other for that matter). Or better what makes you take this bottle and not the one right next to it? Its that little spark in the brain. How exactly it works, I can’t tell you, but it makes you make a decision about a specified subject at a specified movement, every second - all life long.
That little spark is (presumably) available in ever loop of the grandfather case, regardless if you have knowledge of the loop or not. And by sheer statistic in one of the loops, you will choose to not pull the trigger in last sec. For you it will simple seem like you just chose to abandon your original plan, and not pull the trigger – not a big deal.
In fact now that I think of it. Our very existents could be a series of loops all life long and we would not know anything about it, and the very decisions we make daily, makes or breaks these loops. Heheh.. ok, I got a little philosophically carried away there :D Twthmoses 17:20, 10 July 2005 (UTC)

The reason why it is presented as a paradox is that it is assume that having lived you would have made the same decision: you lived, you killed your grandfather. The paradox comes from the fact that no matter what you did, you encounter an impossibility: You killed your grandpa, you don't exist, you can't have killed your grandpa or you didn't killed your grandpa, you lived so you do go and killed your grandpa (which obviously can't have happened). Of course, this is based on the theory that there is but one timeline (the other theory described here wouldn't all find it to be impossible).

A loop on the other hand you be something self-fulfiling: you receive a time machine from some stranger, you spend your entire life trying to figure out how it work. moments before you die you figure out how to use it, go back in time and give it to yourself. Not going back would be the thing that would create a paradox.--Marc pasquin 17:04, 13 August 2005 (UTC)

^^Not to mention an ontological paradox. Where did the time machine come from to begin with?

Technically, it is an antinomy, not a paradox. However, there are several similar ideas that commonly are also called "paradoxes", such as one attributed to Bertrand Russell concerning a barber who shaves everyone in the village who does not shave himself. Notice that it is not necessary to involve time travel or causality, but merely some form of self-contradiction. The only point of real interest in these things is that the description seems to meaningfully denote something, although through logical analysis we can see that it cannot actually be denoting any real existent. Russell tried to solve this through his "theory of types", but that just sweeps the problem under the rug, much like the alternate universes theory. The relatively recent development of fuzzy logic provides another resolution by allowing the truth value of a proposition to be an intermediate value between "definitely true" and "definitely false"; in fact it would assign the precise value 0.5 to the Grandfather being killed, assuming the validity of backward time travel. My personal view is that the truth value needs to be 0 or 1 in this case, so 0.5 is unacceptable and thus the assumption (validity of backward time travel) must be false. — DAGwyn (talk) 01:25, 11 December 2007 (UTC)

Basically, all these theories are could be incorrect in the logic that you cannot go back into time any further that your own lifetime in the first place. How can you exist before you are?

Another theory is that if you were able to go back into time, all you would be able to do is observe and not be able to interact with it, as the past is nothing but a shadow of the present.

Further theorizing, on the assumption that true time travel is available to the subject, the grandfather paradox could only have a single outcome. When the subject goes back in time, time to the subject is still marching forward, never backward. Therefore, if a 50 year old man goes back in time to see (or kill, as the argument is going here) his grandfather, he would still be 50 years old. All the subjects memories and experiences would be there, right along with his body's age. Suppose the subject spends a year looking for the grandfather, meets him and then returns to their own time at the exact time they left, and guess what...he's a year older. Time for the subject has not stopped. The subject did not disappear when they killed their grandfather, and the subjects history has not changed. This implies that there IS another timeline where the subject did kill their grandfather, in which case the subject never existed in the first place to go back and kill him. This creates a dillema for the subject contemplating going back in time. Just the subject's existence in a previous time would create a new timeline, because in the subject's own history, they were not there in the first place. (talk) 04:36, 31 October 2008 (UTC)Joseph Nam'lonaem71.176.55.23 (talk) 04:36, 31 October 2008 (UTC)

"Thrice Upon a Time" in wrong subsection?[edit]

The page lists Thrice Upon a Time under "Parallel universes resolution", but I just reread the book a few months ago and it explicitly assumes a single timeline -- there's even a diagram. Whenever a message is sent into the past, the timeline gets "reset". Because of the arrival of the message in the past, subsequent events are altered, often to the point that nobody even sends the message into the past. The message, however, remains.

I suspect the confusion is caused by Hogan's decision to call moments in time "universes". In other words, right now is a universe, one second ago is another universe, and one second from now is yet another universe, and each of these universes is visualized as sliding along the timeline from the past to the future. In Hogan's usage, sending a message to a prior universe modifies that universe and triggers a cascade which alters all subsequent universes.

I believe that this book should be listed under the "Relative timelines resolution" subsection, but I thought I would seek input since I have never modified a Wikipedia page before.

TuklaRatte 04:17, 7 December 2005 (UTC)

List removed from Time travel in fiction[edit]

Back to the Future trilogy Bill and Ted's Bogus Journey The Butterfly Effect Donnie Darko Harry Potter and the Prisoner of Azkaban The Flipside of Dominick Hide The Terminator series The Time Machine Timecop Timerider Twelve Monkeys

TV Futurama episode "Roswell That Ends Well" In this episode, the grandfather paradox is turned upside down. Red Dwarf episode "Ouroborous"

Just in case anyone thinks it's not useless cruft...Yobmod (talk) 12:25, 14 May 2008 (UTC)

Space-Time Continum[edit]

In theory, would this not cause a hole in the space-time continum, destroying the entire universe(and if we're lucky, only this universe)?

And anyways, who would be stupid enough to do this?!?!?!?

Yugiohguy1 (talk) 03:05, 15 May 2008 (UTC)

I think the point of this article is to explain the different theories of what would happen, although it seems more geared to philosophy than to actual physics. I'm no physicist, but I would guess that there isn't a single accepted theory that says what would happen, let alone whether it would create a hole in space-time and destroy the universe. I would like to see more explanations from physics in this article (the discussion above about the universe not even existing at that point in time would be great, if there were some research to back it up).
I won't speculate on the second question. (talk) 22:07, 15 May 2008 (UTC)
I don't know how stupid you'd have to be... but it would certainly be tempting wouldn't it? I mean... it's like a big red shiny history eraser button that you're not allowed to press. I mean, let's kill Grandpa just to see what happens. The real problem, I think wouldn't be the obvious changes (killing Grandpa) but the minor changes, scaring Grandpa and causing him to miss the bus and thus never meeting your grandmother... it's more illustrative that an actual plan Duggy 1138 (talk) 04:39, 16 May 2008 (UTC)

to specialized[edit]

I thought this artical concentrated to much on the particular problem of the grand father paradox. this particular paradox falls under a much broader catagory known as the effect preventing the cause. can this artical be rewritten under that title and include the grandfather paradox as the primary example. i think that would be alot more helpful. —Preceding unsigned comment added by (talk) 23:22, 24 June 2008 (UTC)

If I went back in time and forced you to actually use a spellchecker on that atrocious thing, I wouldn't have a reason to leave this reply. Therefore I wouldn't go back in time to force you to use a spellchecker, so you wouldn't. Which means I'd need to leave this comment because, again, your grasp of the language you are using is tenuous at best.

Quite the paradox. (talk) 01:18, 8 March 2011 (UTC)


The Futurama episode, Roswell That Ends Well has a similiar theory exept Fry becomes his own grandfather by killing his grandfather and making love to his own grandmother. This could maybe be added to this article? —Preceding unsigned comment added by (talk) 16:02, 7 July 2008 (UTC)

Hundreds (thousands?) of earlier and more in depth fictional examples could be found. In The Man Who Folded Himself, the main character goes back in time and becomes his own father, mother, son and daughter. The futurama example doesn't give the reader any more information on the paradox.Yobmod (talk) 16:06, 7 July 2008 (UTC)
Regarding the text that did make it into the article, isn't "autoinfanticide" the wrong choice of word, since Fry killed his (supposed) grandfather and not himself? zzyss (talk) 04:52, 23 November 2008 (UTC)
I think the Futurama episode is better suited as an example of predestination paradox, where it currently resides, rather than here. It is far more suitable for that scenario.

You could not become your own grandfather, because the genes and chromosomes that you are made up of are a product of your mother and father's, your grandmother's and grandfather's. If you went back in time and screwed your grandma, your father would come out looking different, and then you would come out different. It seems crazy, but it's very sensible. You+Your Mom=Not you because You=Your dad+Your mom —Preceding unsigned comment added by (talk) 03:57, 11 August 2010 (UTC)

Unless you are your own father, in which case you would be the product of you + your mother's genes already. Your statement is assuming that you start off as the product of your mother and father at some point, when in a universe where time travel is possible you travel back in time, impregnate your mother, which produces you. It's a closed loop. Your statement is based on the idea that you + your mother would produce nothing. (talk) 01:26, 8 March 2011 (UTC)


I think "time paradox" should redirect to "temporal paradox," rather than Grandfather paradox. Time paradox is just a synonym for temporal paradox, and Grandfather paradox is just a type of temporal paradox.Wikieditor1988 (talk) 04:24, 1 January 2009 (UTC)

Merge with Temporal Paradox[edit]

Take a look at the temporal_paradox page. should we consider merging these two? 1215drew (talk) 03:31, 13 October 2010 (UTC)

"Primer" reference / uncited 'theory'[edit]

Totally removed the reference to the Primer film, sorry. I really don't think it's following WP standards using the synopsis of a film on IMDB as the basis of a 'theory' on time travel paradoxes. Frankly, I couldn't even find the cited reference on the page, so it's gone. It's all well and good to discuss various authors' views on the paradox and time travel in general, but citing them as 'theories' (lending them some fairly undue credence) is a little over the line in my book.

From that logic, there is a 'theory' going around that if you wish upon a star, you're little wooden puppets will magically come to life. :-/ —Preceding unsigned comment added by (talk) 18:56, 28 October 2010 (UTC)

Novikov self-consistency principle and free will[edit]

I think that the free will argument needs a little expansion. This is conjecture, but outside of our universe, the universe would appear as an infinitesimal point, since time and space do not (presumably) exist outside of our universe. From that point of view, everything in this universe and every time in this universe would coexist at the same point. The flow of time within our universe was set up in the beginning, as it is a property of the universe. It is true that we experience the passage of time in only one direction, but that doesn't mean that, in the larger picture, that causality depends upon a past to future flow of time.

To put it another way... if you wanted to throw an omnipotent deity into the mix, a deity could be aware of our future actions not because that deity could see into the future, but because he is able to view all possible times in the universe simultaneously. He would see our future actions simultaneously with all actions we take. That's different from seeing the future, because to the deity there would be no past or future, only eternity. I always have difficulty expressing this in words, so if there's anyone who gets what I am saying please help me out here. Thanks. Primium mobile (talk) 21:15, 24 May 2011 (UTC)

Parallel Universe != Alternate Timelines?[edit]

Is it just me or was "Alternate Timelines" added by someone who didn't understand the "Parallel Universe" idea? To my understanding it is the exact same idea. The fact that both examples come from popular culture (and not particularly sophisticated works) in my eyes confirms that the author/s didn't give much thought to this. I'm going to remove the "parallel timelines" from the article. If anyone comes up with a good answer why it is not the same as the "parallel universe" idea he may feel free to re-add it. -- (talk) 08:39, 25 November 2011 (UTC)

IMO, parallel universe is an umbrella term, it means any self consistence bubbles of spacetime that are separated temporary, spacially or even probability (i.e. the alternated versions). Parallel universe also include bubbles of spacetime with completely different laws of physics. Alternate timelines are just a "worm of spacetime" separated by probability, it is a subclass of parallel universe ~Secret ultraviolet — Preceding unsigned comment added by (talk) 12:02, 17 January 2012 (UTC)