Slashdot Mirror
The Possibility of Paradox-Free Time Travel
relliker writes in with word of a paper up on the ArXiv by Seth Lloyd and co-workers, exploring the possibility that "postselection" effects in non-linear quantum mechanics might allow paradox-free time travel. "Lloyd's time machine gets around [the grandfather paradox] because of the probabilistic nature of quantum mechanics: anything that this time machine allows can also happen with finite probability anyway... Another interesting feature of this machine is that it does not require any of the distortions of spacetime that traditional time machines rely on. In these, the fabric of spacetime has to be ruthlessly twisted in a way that allows the time travel to occur. ... Postselection can only occur if quantum mechanics is nonlinear, something that seems possible in theory but has never been observed in practice. All the evidence so far is that quantum mechanics is linear. In fact some theorists propose that the seemingly impossible things that postselection allows is a kind of proof that quantum mechanics must be linear."
http://timecube.com/ ... obviously.
No, wait, what?
I learned everything about this already from Futurama
One of these quantum universes has to have every quantum event probability = 0%, and one p=100%. Those two together are the paradox of possibility-free time travel. In one, there's no chance of free will. In the other, a time machine is certain.
--
make install -not war
But if I'm going BACK in time, I'm taking some aspirin, toothpaste, deodorant, and toilet paper with me. I hope the machine is big enough.
I piss off bigots.
> However, if nonlinear behaviour is allowed, time travel will be possible wherever it takes place.
This seems obvious, but if you think about it, it starts to make a different, twisted kind of sense...
I can go back and see where the hell I left my keys?
I have neither the capacity nor the will to vet the paper, but it should be noted that ArXiv is not peer reviewed. While experimentalists use it as a place to publish pre-prints of their papers and will typically only put them up after the papers have been accepted, but theorists use the medium as a substitute for publishing and so many wacky and untrue claims get put up there.
Time travel leads to Parallel universes that make paradox not happen in the one you left.
Am I the only person who has noticed the Authors name? Seth Lloyd = Sith Lord I think we should be very cautious of these findings.
If you see it without comments it'll be red.
The problem with all of those approaches is that they assume a "meta-time" (even if not stated as such) that will alter the PRESENT based upon changes in the FUTURE.
That's how a photograph that you have right (taken in the future) now will change based upon events that have not happened yet.
Once you get past that, you understand that there is no "grandfather paradox". If it exists in the current time then it exists in the current time. The future will not reach back and "clean up" the present to make it more acceptable to the future.
Obligatory cartoon linkage:
http://www.smbc-comics.com/
You can dress up pseudoscience with a bunch of equations, but tell me how this is based on any type of actual science. If this is science, then Deepak Chopra must be an actual genius...
I'm not an expert but it does seem like a lot of physicists are just lost in their own little worlds. I realize science is a process, but spending valuable time "researching" time travel, before we can even explain what time or even gravity is, seems like skipping over the hard work to spend time on "fun stuff".
http://www.smbc-comics.com/
Has nobody anything snarky to say?
They are too busy trying to build postselection time machines. Expect to lose your first post status as soon as one of them succeeds.
The Tao of math: The numbers you can count are not the real numbers.
Where are all the time travelers?
There's no red. Probably you've seen a summary from the mysterious future. Post-selected time travel has been used successfully on Slashdot for quite some time now. :-)
The Tao of math: The numbers you can count are not the real numbers.
The movie "Primer" had an interesting take on avoiding paradoxes. http://video.google.com/videoplay?docid=3909854615539675694# (entire movie online)
Insightful and funny are really the same thing, except one has a punch line.
Or, we go with the simple, elegant solution to the problem...it's not possible.
t
Did he prove that paradox-free time travel is possible thanks to possibility that quantum selection is non-linear, or did he prove by contradiction that quantum selection is linear?
A slashdotter who didn't build his own computer is like a Jedi who didn't build his own lightsaber.
Now, if we can just hook in the logic circuits of a Bambleweeny 57 Sub-Meson Brain to an atomic vector plotter suspended in a strong Brownian Motion producer (say a nice hot cup of tea)...
It must have been something you assimilated. . . .
Well you lost me right after 'the grandfather paradox'. I even read the article and I *still* don't understand. Is there a summary for dummies ?
http://www.smbc-comics.com/index.php?db=comics&id=1949
And if you travel outside of your light-cone? (other then math breaking down)
6.8SPC TR of 550, l xwind at 6, drift rt at 26" drops 77". AT has 503 ft-lbs at 1403 fps. FT 0.86
It's all down to the doom field.
Quantum mechanics is a big tease. It seems whenever it's about to give you Jetsons or Stargate technology, there's always a big fucking loophole or caveat. You can go into the past, but you can't come back and/or die; you can travel faster than light, but the universe will end before you reach your destination; you can predict the future, but will change it in the process without knowing what the change is; you can date 3-breasted aliens, but they all have penises, or whatever. (Okay, I made up the last one.)
There must be a God, because nature wouldn't find a way to tease us with so many Almost's and fuck with our minds in so many different ways that QM does.
Or maybe it's the anthropic principle keeping us from destroying the universe with time weapons?
Something odd is going on. Time for a congressional investigation.
Table-ized A.I.
Kinda seems like the Infinite Improbability Drive
As far as I can tell, the article is saying that if you impose a condition in the present, you cause the past to change so that it matches. This process of imposing a condition must affect the quantum mechanical properties of whatever you are checking, similar to a quantum computer.
So basically, if your granddad rigs up a machine that kills him depending on the quantum state of a particle, and then he leaves that particle in an indeterminate quantum state until he has your dad and your dad has you, and then you collapse that particle's waveform into the state that would have killed him, he will have died back then. And somehow paradox is avoided.
Wha?
i'd hit it so hard, if you pulled me out you'd be the king of britain [bash.org]
First post!!
Also, last post. Try to figure that one out!
Qxe4
First post!!
Also, last post. Try to figure that one out!
Simple: Only post.
The Tao of math: The numbers you can count are not the real numbers.
I can accept FTL travel as maybe possible, but time travel seems farfetched to me. It means that every single state that the universe has ever been in is preserved (somewhere) in it's exact state. We're not talking about the awareness of the state being preserved on the speed-of-light boundary away from the location of the state, it's the actual state, in a way that can be modified and changed. Does this even seem reasonable? How could all that be stored?
Not only that, it means that a change in one of those states will instantly change every subsequent state. So when you travel back, everything will be different. This is really hard to believe.
Qxe4
because most of us refuse to 'see' what's going on around us, we continue to 'wait' for the right 'time', or some way to get there. the change is not exactly seamless.
meanwhile (there's always one (while) somewhere); the main distraction to unimpeded 'travel', the corepirate nazi illuminati, is always hunting that patch of red on almost everyones' neck. if they cannot find yours (greed, fear ego etc...) then you can go starve. that's their (slippery/slimy) 'platform' now. see also: http://en.wikipedia.org/wiki/Antisocial_personality_disorder
never a better time to consult with/trust in our creators. the lights are coming up rapidly all over now. see you there?
greed, fear & ego (in any order) are unprecedented evile's primary weapons. those, along with deception & coercion, helps most of us remain (unwittingly?) dependent on its' life0cidal hired goons' agenda. most of our dwindling resources are being squandered on the 'wars', & continuation of the billionerrors stock markup FraUD/pyramid schemes. nobody ever mentions the real long term costs of those debacles in both life & any notion of prosperity for us, or our children. not to mention the abuse of the consciences of those of us who still have one, & the terminal damage to our atmosphere (see also: manufactured 'weather', hot etc...). see you on the other side of it? the lights are coming up all over now. the fairytail is winding down now. let your conscience be your guide. you can be more helpful than you might have imagined. we now have some choices. meanwhile; don't forget to get a little more oxygen on your brain, & look up in the sky from time to time, starting early in the day. there's lots going on up there.
"The current rate of extinction is around 10 to 100 times the usual background level, and has been elevated above the background level since the Pleistocene. The current extinction rate is more rapid than in any other extinction event in earth history, and 50% of species could be extinct by the end of this century. While the role of humans is unclear in the longer-term extinction pattern, it is clear that factors such as deforestation, habitat destruction, hunting, the introduction of non-native species, pollution and climate change have reduced biodiversity profoundly.' (wiki)
"I think the bottom line is, what kind of a world do you want to leave for your children," Andrew Smith, a professor in the Arizona State University School of Life Sciences, said in a telephone interview. "How impoverished we would be if we lost 25 percent of the world's mammals," said Smith, one of more than 100 co-authors of the report. "Within our lifetime hundreds of species could be lost as a result of our own actions, a frightening sign of what is happening to the ecosystems where they live," added Julia Marton-Lefevre, IUCN director general. "We must now set clear targets for the future to reverse this trend to ensure that our enduring legacy is not to wipe out many of our closest relatives."--
"The wealth of the universe is for me. Every thing is explicable and practical for me .... I am defeated all the time; yet to victory I am born." --emerson
no need to confuse 'religion' with being a spiritual being. our soul purpose here is to care for one another. failing that, we're simply passing through (excess baggage) being distracted/consumed by the guaranteed to fail illusionary trappings of man'kind'. & recently (about 10,000 years ago) it was determined that hoarding & excess by a few, resulted in negative consequences for all.
consult with/trust in your creators. providing more than enough of everything for everyone (without any distracting/spiritdead personal gain motives), whilst badtolling unprecedented evile, using an unlimited supply of newclear power, since/until forever. see you there?
"If my people, which are called by my name, shall humble themselves, and pray, and seek my face, and turn from their wicked ways; then will I hear from heaven, and will forgive their sin, and will heal their land." )one does not need to agree whois in charge to grasp the notion that there may be some assistance available to us(
boeing, boeing, gone.
Pretty much, yep. Because you are now existing at a prior point in the chain of causality. So you've already accepted either:
1. circular causality (and a supreme janitor who cleans up the past to keep the future tidy) (and how would you tell the difference) or
2. effect without cause (because you exist prior to your parents giving birth to you).
Expect to lose your first post status as soon as one of them succeeds.
"The Possibility of Paradox-Free Time Travel"
It would be a paradox if someone other than that AC were to get first post. Obviously, the only reason he got first post to begin with is because he already has a postselection time machine. Or at least, he must acquire one at some point in time, and uses it to make FP on this story.
Also, brb, building a TARDIS.
Let q be a radix > 1. I am in ur base-q, killing 10 d00ds.
“The Encyclopedia Galactica has much to say on the theory and practice of time travel, most of which is incomprehensible to anyone who hasn’t spent at least four lifetimes studying advanced hypermathematics, and since it was impossible to do this before time travel was invented, there is a certain amount of confusion as to how the idea was arrived at in the first place. One rationalization of this problem states that time travel was, by its very nature, discovered simultaneously at all periods of history, but this is clearly bunk. The trouble is that a lot of history is now quite clearly bunk as well.”
Well DUH!
For justice, we must go to Don Corleone
The concept of a paradox is entirely a human concept - in other words, it's in the eye of the observer. The universe wouldn't "classify" you going back in time and killing your great-grandparents before you were born as a paradox, simply because the universe is not an observer. It would happen - so what - "It is what it is". That would just be part and parcel of the way the universe works in that particular case.
Attempting to say that this would result in a paradox as far as the universe is concerned is anthropomorphizing the universe to an absolutely unforgivable degree. Sure, it makes for a good time travel story, but the universe won't lose any sleep over it, any more than it does for me writing "The next phrase is false." "The previous phrase is true." "Both the previous phrases are true" "The previous phrase is true" There's no paradox. The universe doesn't suddenly go wonky, and cats mate with dogs, etc.
Clearly no one has watched Quantum Leap. You can only time travel within your own life. Time travel is so far off that we won't see anyone traveling back in time yet.
Yesterdays SMBC had a good point:
You can not have any motivation or objective if you are going to travel otherwise the act of time travel is a paradox. SMBC put it thusly: if you are travelling to change some outcome, and you succeeded, you would not have had the motivation to time travel to make that change.
SMBC's conclusion was that only nitwits have the capacity to time travel and the fact that there seem to be so many confirms that time travel must be going on right now.
But another way to say this is, you can only choose objectives that either already happened in your past or are inevitable no matter what you do.
For example, You could however travel with the objective of sinking the Titanic, but not the objective of preventing the sinking. If you saved the titanic, it would never occur to you to try to save the titanic.
For example, If your objective was to save Abe Lincoln and you succeeded, then it never would have occurred to your pre-travel self that you needed to go back and save abe lincoln.
What all this adds up to I think is that time travel is still forbidden but observational time travel-- gathering information-- is not forbidden.
THere is an interesting proof regarding the computability of any proposition by David Wolpert that shows time travel is forbidden unless the information you gain by doing so is probabilistic or faulty. That is he proves rigorously that it is not possible to answer any arbitrary true/false question about the past with perfect fidelity. Thus time travel that preserves information with fidelity is forbidden. Error prone time travel is however allowed.
Some drink at the fountain of knowledge. Others just gargle.
it does not require any of the distortions of spacetime that traditional time machines rely on.
Wait, did I missed the part where time machines were something traditional or common or anything like that ?
Seriously, time travel became mainstream and nobody told me ?
Segmentation Fault in "Life, Universe and Everything" at line 42. Don't Panic.
I'm completely with the parent.
While I don't think that you can call pseudoscience the exploration of the implications of a theory that are unlikely to be possible in practice, let's assume it's pseudoscience. So what? It was pretty interesting read, at worst it will serve as an inspiration to some science fiction author. It's interesting. You know why? Because it is "fun stuff"! Also, as the parent stated, exploring the theoretical possibilities provides better understanding of the model, allows you to improve the model and might allow you to find the boundaries where the model stops being correct. Also, making advances in the part that don't apply in practise might improve the understanding of the practical part of the model. Infinitesimals don't seem to exist in our universe, but the models that explore their properties closely have been the basis for most of the physics.
Also, I might not understand the article completely, but it, along with another report that was posted to Slashdot less than an year ago, seems to show a method of time "travel" that doesn't allow to send information back in time at all. Seems reasonable, and not against anything that I know about the world I'm living in. It would completely blow out my idea of time -- I'm a firm believer that only the current moment exists, and you can't affect or travel to previous ones, and that other interpretations of time are merely implementation details of the physical models we use -- but these results wouldn't be against any physics I know. Also, even if there is an experiment that confirms that this paper isn't bullshit, and it is empirically proven that this kind of time "travel" is possible, the results won't have a single interpretation. I wouldn't be surprised even if someone builds another model that doesn't involve any time travel that explains the same empirical results.
Yes, someone needs to verify the premises and the conclusions, I don't have good enough knowledge to do that myself on the first read, but I didn't see any mistakes pointed out by the GP, only baseless claims, so I'd rather go with the article and/or the paper. I have a direct question for the GP: We have no idea what time is, OK. Suppose that our current theoretical model allows for time travel (which would seem to be the case unless the article is full of mistakes). Are you denying that testing them would allow us to be closer to understanding what time is?
By the way I forgot to mention that there is a known way to Time travel without violating the grandfather paradox or using post selection. It was the basis for the movie primer, and it actually occurs, mathematically at least, for small particles.
The observation is that when a photon splits into a particle+antiparticle and then later those anihilate you can think of this as a particle going forward in time and another particle going backward in time, whose trajectories intersect at the beginning and the end.
Thus it is possible to travel forward in time as long as the person in the future decides to travel backward in time.
THe movie Primer created a machine that ensured that in a way that you could not avoid this. Thus, as far as I know, it's the only time travel movie that actually is technically possible and devoid of grandfather problems.
By the way if you rent this, plan on watching it twice. Then again a few days later after you google the shit out of all the things that you did not understand. Let me just tell you that EVERYTHING in this movie, no matter how little sense it makes to you, actually makes perfect sense. But the movie does not explain itself.
Some drink at the fountain of knowledge. Others just gargle.
If time travel existed at some point in the future, we would have had evidence of its existence in the past...
Seven puppies were harmed during the making of this post.
Was Seth Lloyd perhaps inspired to design paradox-free time machines by the great Christopher Lloyd?
I am officially gone from
Knowing (not predicting, not hinting, but knowing) our future is, from the future perspective, altering the past. That means that physic proved that we won't be able ever to know for sure our future?
Well, is not so bad, at least we won't go extinct because of blue butterflies.
Yes, but what if with the act of time travel with motivation you also create an alternate reality where the titanic didn't sink or abe lincoln survived? Is there some rule where you must be attached to your original timeline?
You can dress up pseudoscience with a bunch of equations, but tell me how this is based on any type of actual science. If this is science, then Deepak Chopra must be an actual genius...
The part about particles should help. In other words if particles could do what the paper says, then the question should be, what would we observe if true?
Won't be a paradox...Another AC will post it,with the very same words, while the 1st one will die in a very improbable, Final Destination style accident. Thats what the universe have prepared for you if you do first posts as AC in Slashdot.
I would but I'm too busy heading back in time to kill my own grandfather
John Titor
Sig: I stole this sig.
Oh, please... that's just a load of bul{@%_#+`-]$*#":NO CARRIER
I always liked the notion that even if I went back in time and tried to kill my grandfather, I would never succeed, because obviously I didn't kill him.
Of course, there's no great correlation between my liking something and it being physically true. Not yet, anyway.
Citation needed.
If this view or something like it is correct, then "time travel" is a bogus concept. (Negative money, debt, is only a meaningful concept because people agree to pretend that it exists, but it has no objective correlate in the physical world.)
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
Citation needed.
David Deutsch, Quantum mechanics near closed timelike lines, Phys. Rev. D 44, 3197–3217 (1991)
The Tao of math: The numbers you can count are not the real numbers.
The seemingly impossible things that relativity allows is a kind of proof that Newton is right and Einstein is wrong. We'll all laugh at him after light isn't bent around the eclipse.
FTFY
I love these sorts of articles...the ones that allow Slashdot members to pretend they know something about advanced physics, etc. Monday morning quarterback? How about monday morning scientist.
Seriously...half the people offering opinions probably read A Brief History of Time and that's the extent of their knowledge...that won't stop them though from acting like they know something.
"During the week I do desktop support...but in my evenings I comment upon research in advanced theoretical physics. Did I study that at school? Nope...but I stayed at a Holiday Inn once"
That assumes a single linear timeline. There's always the old 'many worlds' interpretation of Quantum mechanics, where every possible measurement of a quantum value results in the universe splitting into several universes, with the measurement having a different result in each. Time travel with a 'paradox' would then involve travelling back in time along one 'branch', then travelling forward back up another branch.
This of course causes some conservation of energy problems.
But another way to say this is, you can only choose objectives that either already happened in your past or are inevitable no matter what you do.
For example, You could however travel with the objective of sinking the Titanic, but not the objective of preventing the sinking. If you saved the titanic, it would never occur to you to try to save the titanic.
For example, If your objective was to save Abe Lincoln and you succeeded, then it never would have occurred to your pre-travel self that you needed to go back and save abe lincoln
What if you just want to go back and change the past event's outcome to the opposite, without regards to what the outcome currently is?
It seems to me that the multiverse itself gets one around the grandfather paradox. Granted, it's as theoretical as time travel itself, but still... Go back in time, poof, a new branch of the universe breaks off. The branch where you went back in time (which, of course, is now spawning an endless number of branches itself). Now everything you do affects the branch you're on and not the branch you left from. Paradox-free time travel.
Unless free will is an illusion - something we only think we have. If we have no free will, and are simply acting out what we were always going to do, then there is no paradox to time travel - we would not be able to change anything by going back in time because whatever we do would be what we always did and were always going to do. If we change something, it could be that whatever we change was what was always going to be changed. It could be that every choice we think we make is simply the "choice" we were always destined to make and is no choice at all, just an acting out of how the universe always plays itself out.
traveling at the speed of light (& beyond), with no moving parts. that could easily be us? we're already moving quite rapidly through space & time. no wonder our casing doesn't last very long? see you there?
it might be less than realistic to be certain (almost nobody really is) that there's absolutely nothing else when we're 'done' here.
Yes, but what if with the act of time travel with motivation you also create an alternate reality where the titanic didn't sink or abe lincoln survived? Is there some rule where you must be attached to your original timeline?
Maybe it works this way: bad shit is happening around me all the time and there is absolutely nothing I can do about it. Bike riders are failing to wear helmets; my employer is buying ClearCase; my wife intends to buy a French car. I know that bad things are going to happen yet I am not a time traveler. Mostly my knowledge of the future has no impact on what actually happens in the real world.
http://michaelsmith.id.au
To Say Nothing of The Dog, by Connie Willis (1998), with its concept of "slippage" to keep time travelers away from critical points in history, and an inability to transport significant objects forward in time.
because that show boating globetrotter algebra can get you into trouble.
lose != loose
I'll tell you this, based on your statement time travel to change anything is impossible, forbidden simply because so many bad things have happened in the past and we know that there are plenty of people who'd like to change that so it wouldn't have happened.
Since all of the murders and wars and accidents and illnesses happened that are in history books it means that nobody changed the flow of history in the past to prevent them and so time travel, at least with the objective of changing something is impossible.
You can't handle the truth.
It's all quantum. When considering a travel back in time, every possible trip with every result exists, but only the consistent options (where past and future do not contradict) are 'permitted'.
There's still plenty of room for free will from the perspective of the time traveler, even though the past and future are effectively written in stone from a 3rd party perspective.
I am with the Time Traveler's Union Local 4096 + i4 and I must say this is not what we do. In order to avoid time paradoxes we invented a device called a time lock so if there is any paradox it ends up in a parallel universe that splits off of the one we want to change and we end up in the future of the universe without the paradox but just the right changes we need. M-Theory aka Super String Theory is flawed, keep looking for that Higgs Boson with a flawed theory. We fixed it in the future by finding particles, waves, and other things smaller than super strings. Then we built software to check for errors in formulas and maths to find the flaws and then fix them.
Our Union Time Travel's rules:
#1 Avoid sex at all costs, to avoid becoming your own grandfather or having your children born in the past and change history.
#2 Avoid killing people esp important people and your grandfather etc to avoid even more paradoxes.
#3 Never admit you are a time traveler or know time travelers, or that killer cyborgs from the future are out to kill you and your son, we call this the Sarah Connor Complex and it is a good way to be put into a mental hospital. If everyone thinks you are insane or crazy or delusional, only then can you admit to being a time traveler or meeting one etc and then nobody will believe you anyway.
#4 Try to blend in, before you go hit some thrift stores to buy clothing that matches what the nation, culture, and society wears at that time period. If not then buy clothes at a costume store that look like that time. But if the method of time travel requires you are naked, scan the area before time traveling to it to fnd a clothes line of clothes in your size and do a Bill Bixby and leave some money after taking the clothes so the people you ripped off can afford to replace them.
#5 Only carry money made during the time period. See if you can find coins and paper bills of that time, if not then work a job with a farner or something and allow extra time to work a job and earn money and then buy what you need. But every trip you make in time that you earn money keep it in the cashomatic device to sort money by time peroid, nation, economy, etc.
#6 Remember sometimes you have to observe events and history without interfering so you can travel back and use the knowledge to be somewhere else and never meet your other self. This is the Marty McFly complex, and you help your past self not get effected by changes you made by being there again.
#7 Make sure any wormhole or hole in space/time is patched up, and every Einstein-Rosen bridge is closed after you use it. If not then the Snow Globe complex can happenin which two parallel universes crash into each other and only one or worse yet none of them survive.
#8 If someone steals your time travel tech and gets a sports almanac or something from the future, make him or her brag about it and then go back o where he/she bragged about meeting him/her self in the past and get that book away from him/her. The Biff Tanner complex.
#9 If you need people from the past because the future had too many people die off, find commercial airplanes that crashed and had no survivors and travel to that plane and take people off it to your future to save the human race. The Millennium complex.
#10 Don't time travel too much, or else too many parallel universes will come into be and then those who are in charge will step in and try to eliminate some of them. The Crisis on Infinite Earths complex.
#11 When giving measurements for something like Stone Henge don't confuse inches for feet. The Spinal Tap complex. :)
Remember, Slashdot does not have a -1 disagree moderation, and no, troll, flamebait, and overrated are not substitutes.
you can time-travel, no problem. you just can't bring any information back.
that said, it shouldn't stop you from assuming NOW what you would do
or say if in the future where you will come back to NOW.
That wouldn't be time travel, that would be inter-universe travel and would be something different.
Persistent Volume manager for Kubernetes - https://github.com/dwimsey/openshift-pvmanager
Mnemosyne says hi and also you're welcome.
Time travel leads to Parallel universes that make paradox not happen in the one you left. ... in the movies.
I love how comfortable people have gotten with throwing around phrases like "parallel universes" as if they are discussing something even remotely meaningful.
sic transit gloria mundi
Circular argument
Fascism trolls keeping me up every night. When I starts a preachin', he HITS ME WITH HIS REICH!
Probability theory suggests that any time traveller attempting a first post on Slashdot will get the familiar "503 Guru Meditation" message.
non-linear recursive circular argument, mobius bitch.
rewriting history since 2109
Also, brb, building a TARDIS.
Don't mind me, I'm just waiting to steal it from you.
rewriting history since 2109
we'll always be
just apes in a tree
rewriting history since 2109
This is probably incredibly silly, but the problem with time travel seems, to me, to be the issue of where you will appear. Relative to the sun (not to mention bigger things), the Earth was in a different position years (or minutes) ago. If you traveled back in time wouldn't you emerge into empty space?
greetings earthlings
I know ArXiv isn't the most formal place for scientific papers, but I can't take anything this guy writes seriously due to the constant grammatical errors. Aren't quantum physicists supposed to be educated people?
He couldn't spend ten minutes proofreading it?
"The question you want answering is which combination of variables makes the expression logically true."
Wrong verb form.
"Before we look at how this idea works, a quick reminder about quantum teleportation. "
Not a complete sentence
"Lloyd and cos idea is to use postselection..."
What?
As this is as good a place for armchair philosophy as any, here's my take on it: I think both will probably be proven possible but not arbitrary - like wormholes of which the ends have to be positioned and opened "manually". For example, you can go FTL via a wormhole but first you need to carry the "other end" of the wormhole in a conventional way to wherever, and the same would work for time-based wormholes - you can time-travel but the "future" end of the wormhole will need to be "carried" to the future. The time-based wormhole would only be a single thing - not two things as would space-based wormholes be. This single opening would be "carried" to the future by simply existing for some duration. The analogy with space-based wormholes dictates that, as you can only travel between the portals to the wormhole and not, e.g. pop up into existence somewhere in between them, that you could only time-travel between "now" and whenever the time-based wormhole was first opened - which probably has something to do with causality. In any case, if at the very moment the wormhole gets opened you don't get a steady stream of grandfather-killing maniacs, you are probably safe forever :)
-- Sig down
Citation needed.
David Deutsch, Quantum mechanics near closed timelike lines, Phys. Rev. D 44, 3197–3217 (1991)
The point is that he nor anyone else 'knows' that, and it's pretentious to pretend like you do. So sure, Deutsch may theorize this.
explain this using a car analogy?
Kind of true, this is what I believe after 10 years of personal experience and experimentation.
Paradoxes are not possible because time, as a whole, isn't linear. That is just how our senses perceive it in 3 dimensional space. Each time line is personal and relative to the observer. "Time as a whole" is more like an infinitely dense tangled web.
I travel forward in a linear manner to kill my father in the past. The "me" that would have been born isn't actually the same me as the traveler, the traveler continues on through time in a linear manner the world forming around them.
Once you start to travel away from your original time line you can never get back. (I should actually say "more generic time line", because you never leave your own personal time line)
It appears to be a many worlds universe but on the larger scale it is not, everything that was or will be... is.
So I took a course in quantum... Can anyone explain what "if quantum mechanics is nonlinear" means? Sounds like gobbledigook to me.
Yes, this is the way I always put it aside in my mind until just now when I tried to write out a response.
The way it comes up to me now is that if that were true and someone killed your grandfather (you or someone else, doesn't matter who did it) then right before he died is a common moment and the moment after that, either he dies, or he doesn't. When you kill him, he doesn't exist anymore and in the others, he survives. Now, before, I always thought that this split made it so it only happened in the universes that you didn't occupy. Unfortunately, there are still a bunch of universes that you were never born in where someone who doesn't exist (you) killed some guy (your grandfather).
Therefore, even thinking that parallel universes fix your paradox, at the split, you still screw things up.
-SaNo
First!
Wait ... oh darn, I set the time coordinates wrong...
No I didn't RTFA, but as a blanket statement, I don't buy time travel (into the past anyway) under any circumstance. Into the future is a matter of semantics, Fry didn't time travel, he was frozen for 1000 years, and neither did the Astronauts from planet of the apes, they essentially just lived along time (I understand and believe what happens when you travel close to the speed of light). In both those cases they never left their timeline. To travel into the past it assumes there is a past to travel to. I exist hear and now, the time when I was six has come and gone and I don't believe I am still six somewhere. Not only would there have to be a past timeline where I was six, but 7 and 8 and 6.24 and 6.0000000000000001 etc.
The other thing I would point out (although not as strong of argument against it) is that if at any time in the future, someone invented time travel, you would know it because people would be coming back to visit us. Now matter how many rules/regs they create in the future to prevent it, there will still be rogue elements that would come back and let there presence be known.
If you could reason with religious people, there would be no religious people
Time is a result of the biological make-up of our brains.
Here's how it works. . .
There is a force, like the wind, which moves through all the dimensions, and somehow our brains are keyed to it. It regulates our conscious awareness and causes us to move focus from one frame of "time" to the next.
That force, as it strikes large objects, like planets, deforms unevenly around them (sort of how wind deforms around an air foil or how solar wind deforms around planets, except this is happening up through higher dimensions).
So then you have areas of where this 'wind' force is pushing unevenly. Objects slide into these areas of uneven force and thus we experience Gravity. Time, as we know, is skewed in a gravity well, (as per Einstein's law of general relativity), but this is only because our brains perceive "time" due to this "gravity wind" pushing forward our perception of reality from one frame to the next. Less wind, less 'speed' of time relative to an outside observer.
If we could stop our brains from riding the gravity wave, we would be able to travel our conscious awareness up and down our existence line within reality according to what we felt like focusing on.
Pretty simple, really.
A working Time Machine need involve only awareness modification, and if you kill your grandfather, you stop existing and grandpa stays dead. So there's no paradox there either.
-FL
Can haz now?
We all just need to go back and "save" any passenger plane that didn't (and therefore won't) crash. ... We'll be heroes.
Just think of all the people that are still here that we could save
You can't take the sky from me
There's a science fiction story that Asimov wrote called The Dead Past ( http://en.wikipedia.org/wiki/The_Dead_Past ) where a form of "time travel" is invented. Instead of a portal/device that sends people back in time, though, it is merely a window on the past. Only the government has them until someone figures out how to make one with "off the shelf" components. The twist is that the government was suppressing the research and for good reason. In a world where anyone can see the past, civilization would collapse. Even 1 second ago is "the past" so all passwords, combinations, etc are rendered useless. No secrets at all can be kept. In addition, people are now tempted to re-watch the best times of their lives or see loved ones who have passed away over and over and over again.
My sci-fi novel, Ghost Thief, is now available from Amazon.com.
Or your attempt to change something fails, or cause the event in question in the first place, and you die in the past. Thus no knowledge of your failure to change the past travels to the future, and thus history repeats itself precisely as it happened. I believe this is closer to the post-selection this story is about.
Higher Logics: where programming meets science.
For example, If your objective was to save Abe Lincoln
Who is Abraham Lincoln? (indeterminate pause) Haha! Had you there for a second.
Then again, are you sure that everybody reading this carries a past that includes Lincoln? Dreadful thoughts of God programming the world with some kind of Lisp, and invoking an infinite number of call/cc functions on all of us, whenever He (^*&^&*^NO CARRIER.
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?
I'm reminded of Robert Aspin's Time Scout series, which basically took time travel as a form of tourism and also used for anthropological study.
"I've spent my whole life figuring out crazy ways to do things. It'll work." -- Montgomery Scott, "Relics"
What all this adds up to I think is that time travel is still forbidden but observational time travel-- gathering information-- is not forbidden.
No. I take from it: compounding entropy is the product of time travel. The ship's going down, and fast! Only terrorists have time travel!
QM may seem "crazy", but it's not like someone just said, "Look, I've got this crazy idea that just might work...". There were lots of experimental results that showed that reality actually is crazy (in the sense of QM) before physicists began to formulate and later accept QM. Also, QM didn't just "pop out of nothing", it coalesced from lots of different ideas that were around at the time. (Not that it isn't a great achievement.)
Crazy ideas are a dime a dozen, so rejecting crazy-sounding ideas is the rational thing to do... unless someone can back it up with the necessary amount of evidence. The necessary amount of evidence scales according the perceived craziness of the idea.
HAND.
I'm not a physicist, but I have read that introducing nonlinear operators into quantum mechanics make it essentially classical theory.
How do you know that they didn't change it from something even worse? Maybe we're stuck with the least bad option.
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
AFAIK all currently accepted physics says that information is preserved by black holes. (As a special case of the preservation of information.)
How does that square with your assertion that black holes only have two variables?
Because having a time machine that allows you to change things is too much of a temptation to keep using it for most people, and those who have agenda to 'fix' stuff would keep doing it. Nobody will invent a working useful time machine that allows changing the past.
You can't handle the truth.
Try The Light of Other Days by Arthur C Clarke and Stephen Baxter for a newer take on that idea.
The post I answered to asked for a citation. And a citation is exactly what I provided. I don't know what you pretend that I pretended.
The Tao of math: The numbers you can count are not the real numbers.
What I want to know is, where are all these time travelers from the future?
It could be that it existed in one timeframe and modify things in that frame, while on the next timeframe it doesn't exist due to modifications made in previous timeframe. What happens in later timeframes is not relevant anymore. See ASCII schematic below:
We assume linear time.
Legend:
| = normal timeframe
- = spacer (to make the scheme more readable, in actuallity, timeframes are imidiately after eachother)
A = Anne (person 'a')
B = Bernard (person 'b')
/ = modified timeframe
()= original time indicator
Awesome ASCII Schematic:
B|-B|-B|-B|-AB/--/--/--/--/-(AB|AB|AB|-B/)--/--/--/--/--
So what happens in this schematic?
Bernard is there from timeframe 1 to timeframe 5. Suddenly Anne pops-up from her timemachine in timeframe 4 and kills Bernard who happend to be her grandfather. Noone knows where Anne came from.
From that point on, neither do exist due to the killing of Bernard. So the question arrises: "Who killed Bernard?". The answer is still that Anne did it. The timespace between the '(' and the ')' shows that they first were both present in those (then yet unmodified) timeframes. But at timeframe 12 Anne gets to her timemachine to kill Bernard which happens at timeframe 13 AND 5. But when Anne got back in time, timeframe 13 and up is not relevant anymore because it never existed. It did exist in reality but the future existed in the (what is now) past. There is no paradox because the past and future are in equilibrium. There are no seperate timelines because that would suggest traveling to the future which isn't theoretically possible at this time. Pun not intended.
The thing that always springs to mind when someone mentions Quantum Mechanics is Schrodinger's Cat and a playing card facing both up and down at the same time. Time travel that has no consequences, thats a bit of a paradox in itself, though if you did go back at least you wouldn't die in the past since it would be recorded and you'd know not to be in that place at that time.
So when you slip into a universe where there are no time paradoxes that's just the way it is. Just like when you slip into one where there are.
Follow me?
"Error prone time travel is however allowed."
Hence, the Tardis is so erratic.
While we are on the topic: http://en.wikipedia.org/wiki/Novikov_self-consistency_principle Of particular interest (read: possible practical application) are time-loop logic processes exploiting this principle.
I don't know about you guys, but this article gave me a raging brainer.
STEPHEN HAWKING: How to build a time machine. The linked article was written by Stephen Hawking.
"All you need is a wormhole, the Large Hadron Collider or a rocket that goes really, really fast."
Hawking has an elegant solution to the grandfather paradox. He hypothesizes that the grandfather paradox is impossible because of feedback. His analogy is with sound amplification, where sound from the speaker is fed back through the microphone intil it shrieks. His answer is a time travel feedback loop would generate enough energy to destroy the time machine itself.
It's an interesting article, here's a snippet:
Free Martian Whores!
First Post!!!!
a.k.a clock, watch, time peace.
Yeah.
Another way of saying it is, "If you shoot yourself, then how can you shoot yourself? It's a paradox!"
Well, actually it's not paradoxical at all. It only seems so because our perceptions wrt time are so limited.
-That, and time travel is misunderstood. There's a big difference between warping space and time with forces in the black hole range, and in picking which time frame to focus attention on.
You existed one year ago, and you exist now. That time frame from one year ago didn't go away. It's still there. We just can't see it anymore from this dimensional perspective. Like Mister 2D in Flat Land riding up an elevator up a 3D building; the floors beneath don't vanish, but from his perspective, they're just, like GONE, man!
-FL
Nothing to do with my post. Try again.
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
http://www.imdb.com/title/tt0390384/
http://en.wikipedia.org/wiki/Primer_(film)
http://en.wikipedia.org/wiki/File:Time_Travel_Method-2.svg
With the first link, the chain is forged.
Plenty to do with your post, there is no way that all of the bad things are the best that could have been. Here is an easy one: had someone gave some money to 'you know who' when he was still a relatively good painter in Austria, so that he could have continued with his schooling, he would have become a painter rather than becoming head of the German government in the thirties and starting the wars.
You can't handle the truth.
Time Travel will NEVER EXIST because all it takes is one person in the future who hates it to travel back in time and prevent it from ever being created.
"I travel forward in a linear manner to kill my father in the past." Killing your grandfather might be acceptable, but killing your father? That's downright nasty.
It's not that easy though: maybe if Hitler didn't become German leader then someone else would have who would have been a more successful war leader, meaning that the war went on longer and more people were killed. Another alternative is that without a German initiated second world war, then there may have been a later war where Russia swept over Europe and ended up killing more people, maybe even through nuclear weapons which since we hadn't seen the effects from Hiroshima would have been launched on dozens of cities at once.
The point is that one can't just imagine what would be better with a change in history, one also has to think about what might happen that's worse. It leaves us with the the original point that perhaps our history is already the least bad one, any further change causing unexpected consequences that make things worse.
Well no, in both cases Stalin and Hitler, the entire countries were swept off their feet with their leaders, they were exceptionally good at manipulating people. In fact a better thing for the world would have been death of Lenin, Stalin, Trotsky, Hitler, Mussolini much before they became known, it would have been easy to set as well, after all, if you are a time traveler you have what it seems like unlimited power. There were multiple points in history where it would have been very easy to change the course of the world. Even nuclear power itself could have been distributed much more evenly in the world, plans could have been provided to most countries at the same time, or the other way around - if enough key people are killed off, the nuclear power could have been prevented from being discovered.
In fact seeing how much imbalance exists in the world, especially related to military it is clear that the time machine does not exist ever in any time, because if it did exist and could have been used to change the past, many people would have changed the past to provide more balance to the world of military power, even if only based on allegiance to any one specific nation.
If you have a French man with a time machine and an Indian with a time machine, why wouldn't they have changed the past to make their countries more powerful by giving them more tools in the past to win in any conflict?
You can't handle the truth.
Also, brb, building a TARDIS.
Well, the Relative Dimension In Space approach is a third, and very elegant, way to do time/space travel, too. It's everywhere and everywhen all at once, simply relocate the projection into spacetime, while the "interior" of that projection sits at the "centre" of the universe, never moving.
"I hope you like Guinness, Sir. I find it a refreshing substitute for, er... food." Col. Jack O'Neil, SG-1
You are assuming that causality works instantly across the distances in space-time, but that, of course, is proven not to be the case around a century ago. Changes made in the past have to propagate toward present and we are each already travelling from our individual pasts toward our individual futures at space-time velocity of c, so there is no catching up.
Agnostics are the last to post
Postselection can only occur if quantum mechanics is nonlinear
"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint, it's more like a big ball of wibbly-wobbly... timey-wimey... stuff."