The Book Of THoTH

Ok Penthar, before you get all upset I have some serious reservations about this too, such as the Energy Requirements, but it is an interesting article!

Professor Predicts Human Time Travel This Century
http://www.physorg.com/news63371210.html
April 11, 2006
Ronald Mallett, Professor at the University of Connecticut, has used Einstein’s equations to design a time machine with circulating laser beams. While his team is still looking for funding, he hopes to build and test the device in the next 10 years.
With a brilliant idea and equations based on Einstein’s relativity theories, Ronald Mallett from the University of Connecticut has devised an experiment to observe a time traveling neutron in a circulating light beam. While his team still needs funding for the project, Mallett calculates that the possibility of time travel using this method could be verified within a decade.
Black holes, wormholes, and cosmic strings – each of these phenomena has been proposed as a method for time travel, but none seem feasible, for (at least) one major reason. Although theoretically they could distort space-time, they all require an unthinkably gigantic amount of mass.

Mallett, a U Conn Physics Professor for 30 years, considered an alternative to these time travel methods based on Einstein’s famous relativity equation: E=mc2.

“Einstein showed that mass and energy are the same thing,â€

I must admit that even though my technical knowledge of the math involved for such an accomplishment is of quite a low level, my understanding of the interaction between the energies is quite precise. I hope this does turn out to work AND for the best of all Earth.

I'm sure there's a larger underground scientific community working on this as we speak, and that this whole community will expose itself when nothing more can be hidden, which should be quite soon.

Thanks for the article Carlisleboy, keep 'em coming!!

Sure there are benefinits for Time Travel (like going back through history and
photographing hi-res photos of the past and releasing them on the Internet or recovering lost texts from ancient libraries that were distroyed throughout history) but if a Government organization is building one, it's most likely their going to use it for their own twisted purposes.....

But I is haxors and with my l33t power I will bring the goverment down!


Plus, so far we're quite informed about the manufacturing of this time machine, and 10 years from now we can expect a larger release of sensitive information.

For all that it's mentioned and suggested,one of these days I'd seriously like to hear an even semi-plausible explanation of how genuine time travel is possible in any way shape or form. Considering the minds that have contemplated it I'd have to assume there is one,but I've certainly never seen it.

Well, there is a myriad of ways that this could be explained... Of course there is the mathematical equations which, if you understood the level of math (which I sure as hell don't! ), would probably prove most advantageous for you.

I can explain this though, and it's a theory based on observations and my knowledge of fields such as quantum and philosophy. I am not an expert on math and do not know the mathematical basis for time travel, but I do know the theoretical explanation of why space-time fabric can be corrupted.

Imagine the idea that everything you do is inter-connected. Past, present, and future are just a different ripple from the same splash. You're the splash. As you should notice, you already have this infinitesimal presence due to the fact that you are the source of all the ripples, which are the events caused by you and which eventually will get back at you.
So let's say that you can mentalize a moment from yesterday when you were doing something or, let's say, were feeling rather uncomfortable. Then, you pick up that time-frame today at some point and begin to mentalize positive energies in the accurate direction of your reality at that moment the day before. You can effectively interact with that moment and your own thoughts back then and even change the way you felt things. Energy is not eliminated, it is transferrable and therefore there is an overwhelming presence of the bonds between the past and the present.
This means that we only need to prescisely understand the foundations of energy and the reasons of its behavior to effectively device a machine that can acquaint to the energies and produce results within them that can be measured with lab equipment or the naked human eye.
A reason why the future may be different to interpret is just because of how fragile our lives and thoughts are, and how intelligent our brains will always be, regardless of our intent. By this I mean that when it comes to reading the future or affecting it, it is harder to know what the consequences will be, and therefore we inhertly refrain ourselves from doing anything stupid, in the orthodox sense.

I hope this helps a bit Sub (can I call you Sub? ) and anyone else who might stumble upon the same issues.


nibx

edit: btw, I really like your avatar Sub (?), it reminds me of Billy Meyer's mind enhancing device and of course proves to enlighten my thoughts just by looking at it.

I understand what you are saying there Nibiru. I've delved in most of the sciences including physics. I did physics in high school in grades 11 & 12. I also have 14 credits in math. Combining the 2 can come up with some amazing stuff. Time is used often in different formulas. We get many different negatives & positives.
There's been ongoing research trying to match or pass the speed of light. We've already beat the speed of sound. We easily know what the the velocity of these properties are. Why not time? I dare say there are many theories out there, so who's to say it hasn't already happened?
We are able to see into the past. There's still a lot that we haven't discovered yet.
We'll just have to wait & see, unless ourselves in the future come back in time & show us the future so we don't have to wait. That would be cool.

I've seen mathematical equations based on the Special Theory of Relativity used to theorize "time travel". But it's only time "travel" in the relative sense, not a literal movement back in time itself as you'll often see it confused it with. Now I've seen it theorized that time may be a substance, but I've never heard the reasoning behind it.


The thing with time is that I don't think it lends itself to raw data as it's not a tangible item or location.





OK, using this analogy, if you're the splash and the past is a ripple(meaning you created it by entering the water) then how can you be before the ripple that is the past? And what does the water that you're splashing into represent? And if time is ripples,what was elapsing as you fell into the water in the first place?





Energy can't be eliminated but time can since it's not energy. In other words, you can't connect with a lightning bolt from 5 minutes ago because while the energy still exists, that time doesn't. It's passed. To go back to it would require a complete reconstruction of reality itself(and the destruction of the current reality as well) so far as I can figure.







Well, since everyone else does...





Thanks. Glad to see the design works. I've never heard of the device you mentioned though.

Well, those are standard questions. I hope you understand when I take with them a rhetoric sense given the reality of our knowledge of the universe as a group.

I am at the time not able to correctly answer all your doubts and questions on the issue given that as of yet I have still to conclude whether all we do everyday even matters!

I really do mean it, even though my body tingles with a humoresque sensation at the thought of it.

One way to explain the idea of one being before the time "ripple" (not abusing the word ripple, only using it in context for reference) is imagining ourselves as we think of a blackhole. Inter-connected to one another or not, they seem to have an infinite precedence once they are formed.
In this example we have the "ripples" reciprocating quite strongly as the electromagnetic field of the hole causes items from about to collapse into the hole. So, this could prove to settle down the issue of precedence of the mind before existence in time and the issue of mental and physical time travel (same thing?).

To clarify, it could be the case that our mind or thought is the black hole, and the matter coming in is the result of our actions; the electromagnetism.

Sorry to blabber, just thought the observations made by Sub were interesting enough to ramble on for a while about



Well, you should check out this link for info and pics and more; http://www.semjase.net/index_en.html

Also, check out video.google for more a video about Billy Meyer, VERY cool; http://video.google.com/videoplay?docid=3412948702721106318&q=billy+meyer



nibx[/quote]

It's very late and I'm very lazy. So instead of saying something new I'm throwing in something I said in another thread a while back (I'm literally copying and pasting what I wrote with a few minor revisions):


The schemes for time travel from established science tend to fall into a few categories:

Special Relativity

Special relativity is the theory with all that jazz about traveling near the speed of light. Changes in masses, lengths, and most importantly here, time. This is the one you mentioned, Sub, and what you might call a one way ticket to the future; traveling near the speed of light slows time down for you relative to somebody not along for the trip. It's the Planet of the Apes scenario (made a bit more clear in the Boulle book than in the Heston movie but eh). Backwards travel doesn't seem to come up, unless you get into the speculative world of tachyons, which would travel faster than light (and we have a few threads around here dedicated to them). But those aren't thought to really exist and even if they did, it doesn't seem they'd let us travel back through time.

General relativity

This is essentially a more thorough version of special relativity, that actually amounts to a theory of gravitation. This is the one that talks about mass/energy curving spacetime. Much more info on that is available in Thread 1, Thread 2, and particularly Thread 3.

Since arrangements of mass/energy shape both space and time in this theory, it becomes possible to manipulate spacetime in such a way that you get what're called closed timelike curves. To take something I said a while back in another thread:



General relativity also allows another kind of "one-way ticket to the future" time dilation that doesn't involve zipping around at near-light speeds. This variety is called gravitational time dilation and relies on the fact that clocks tick more slowly in gravitational wells--clocks at the base of a very tall tower tick ever so slightly more slowly than clocks in the top-floor penthouse. The stronger the gravitational field, the more pronounced the effect. If you take a bunch of mass and construct a kind of shell around yourself or take a little trip down near the (very hazardous) surface of a neutron star, you could wait a while then climb out to find time outside your gravitational well was going faster and you're "in the future."

There are other senarios, like this one (from an old paper on this subject called Constructing Time Machines):


Unfortunately, after analyzing what happens if two such shock waves head straight for each other, the author concludes that answer to that one is "no." But even though that one doesn't look like it works out for would-be time travelers, the fact that there are such possibilities at all should be encouraging.

Other oddities of spacetime geometry that general relativity might allow to exist could also function as time machines. Wormholes would be links between different spots in space and, conceivably, time. A Caltech physicist named Kip Thorne and a couple grad students wrote a paper a number of years ago analyzing how a wormhole could conceivably be not only constructed but turned into a time machine. So there's that.

Quantum Mechanics

This is another area of physics time-travel enthusiasts sometimes look to; this is the way things operate on the very smallest of scales.

In (I believe) the second installment of our short-lived This Week in Science threads in the science forum, the first story was a New Scientist article concerning work that seemed to indicate that (while allowing travel backwards through time) quantum mechanics doesn't allow paradoxes. Convenient. :



In fact, in my thread Just one of those mysteries... I slipped into discussing a theory cooked up six decades ago by the physicists John Wheeler and Richard Feynman that used waves going back through time to explain why electrons feel a force when they try to accelerate:

[quote]Wheeler and Feynman used the fact that the equations of electromagnetism are symmetric in time, working backwards as well as forwards. They allow not only the so-called retarded waves of radiation that we're used to (that arrive somewhere after they left) but also “advancedâ€

Oof, long one. Gonna have to read this one when I wake up, again!

Good night and

Penthar,


That's a man-sized chunk of reading there but at a glance it looks like alot of this speaks to what I was referring to earlier about relative time dilation as opposed to actual movement through time. And how the theories that do propose genuine time travel seem to always be based on cold calculations that, so far as I can see, real world factors would render entirely irrelevant.

Without having really dug into your links yet, are you personally of the belief that genuine time travel is possible, or...? By "genuine time travel" I mean actually travelling back or forward in time. For example, travelling back from today to the year 2000.

There are a few things to note here. Physics isn't done yet. There currently exist two very powerful theories (general relativity and quantum mechanics) that cover different domains and facets of the physical universe. Unifying them into one theory would yield a new one which would have to itself be probed to see what time travel schemes it does or doesn't allow. But until such a unified theory exists, you can only look at the current (very good, by the way) individual theories that exist now to see what they allow. And one thing general relativity unquestionably allows is "travel to the future" via time dilation. However unsatisfying a mode of time travel that is to you it is the only one that's been observed experimentally and indeed is a central component of the theory. Further, taking a step into the slightly more speculative, Sergei Krasnikov has played around and come up with a theoretical kind of "tube" a relativistic spacecraft could unfurl behind it as it travels that would allow the ship to return home shortly after it left, regardless of how far it went or how long it was gone. Not quite time travel as you're considering it but interesting anyway.

With that in mind you should realize that until this kind of thing (aside from time dilation) can be demonstrated experimentally every scheme for time travel will necessarily be "cold calculations"--that is the nature of theoretical work. I'm not sure what you mean by saying real world factors would make, say, closed timelike curves irrelevent. I imagine you either mean (1) they can't actually occur in the real world, in the spirit of the Chronology Protection Conjecture mentioned above or (2) it would be very hard to ever create them. If it's the latter I hate to break it to you but time travel (if it ever becomes technically feasible) won't be easy. You may indeed need to do something ridiculous like getting two rotating black holes together or whatnot. If that's the kind of thing you mean by real world limitation then you should brace yourself because it doesn't seem like time travel (regardless of what the original articles says) is going to be possible for a long while.

My post above was just to give a very brief overview of what is allowed theoretically today. If you want to know how time travel could work with real (known) physics, that's it. The stuff in my post above (along with a few variations on the themes) are pretty much all that exists. Note that the UConn professor from the original post in this thread is talking about generating a closed timelike curve. His original paper on this stuff 3 years ago was about how solutions to the Einstein field equations containing closed timelike curves can be found when considering the gravitational field of a cylinder of light.

As for whether I believe time travel is possible, I would lean toward yes. Hell, I don't think it's implausible that you generate a little bit of time travel every time you lift up a heavy textbook (though that goes into something a little different than Time Machine-style time travel).

Hey Penthar, that's a great article, can I use it for the front page ? Lot of work gone in to that, thanks

Calculations are, sure. But by "cold" I mean calculations that are written up without benefit of simple organic thought. Similar to the teaching method(to help teach students not to cold calculate) where one is asked to convincingly prove something on paper that is known to be incorrect in reality. Such as using principles and equations to prove that boulders can float, etc.




Both really.






OK. I may want to bounce some questions off you then when I finish reading. There's a few things that have always immediately jumped out at me as to why time travel is impossible that I've long wanted some opinions on. And I've never really seen them addressed in any equation.

Sure, Thoth, no problem.



Absolutely, that's what I'm here for.

Alright. Again only dealing with actual time travel here and not relativistic time dilation...



If time travel is possible then how would chronal paradoxes not occur and either prevent any attempts at time travel, or destroy reality if time travel is achieved? One of the articles you posted deals with paradoxes but it does so under the context that you could travel back in time but you wouldn't be allowed to "commit" a paradox like meeting your younger self. But that misses the actuality that any venture into the past would create a paradox simply by having been done. You wouldn't have to meet anyone or do anything in particular to create one. Your very presence would be a paradox in and unto itself. The butterfly effect also compounds the matter perhaps infinitely. As any physical interaction with the past reality(such as say, with the air that will suddenly be displaced when you appear in it) irregardless of how insignificant starts a chain reaction.

My view on how to get around time paradoxes is simple: all that ever has happened or will happen is already written in the big history book of the cosmos. If you're going to travel back in time to 2000 someday then it will happen because in a sense it already has happened. There is no question of whether that will or won't take place--some future version of you was either there in 2000 or he wasn't.

Your presence in another time is not a paradox but in a sense a fulfilment of destiny (though I'm not a particularly big fan of this wording, it gets the point across). As in the article above that you mentioned there is no possibility of changing the past; it already happened. Time travel gets a lot of treatment in sci-fi films but the only one I can think of off the top of my head that sticks to this philosophy is 12 Monkeys (and I think one of the Harry Potter movies might've, as well). I recommend seeing it but if you haven't I'm going to have to spoil the ending for the purposes of this thread.

Bruce Willis' character is a time traveler sent back to 1996 from 30 years in the future to get a "pure" sample of a man-made virus that decimated the world's population after an act of bioterrorism so that some sort of cure can be concocted in the future (curiously, no effort is ever made to stop the virus from being released in the first place; in fact Bruce Willis explicitly tells someone in 1990 that "I can't save you, nobody can; this already happened.") Throughout the movie Willis is haunted by dreams of an event he witnessed when he was a child (c. 1996)--a man being shot to death in an airport. Long story short, the movie ends with Willis being shot in 1996 in that airport in front of his younger self, a clear case of a traveler fulfulling future history.

No possibility of a paradox ever really existed there because there was in reality never any question of whether that character would die in that airport on that day (though, of course, you don't realize that until the movie's over). He had known it unconsciously for 30 years. It hadn't happened yet (from one point of view) but still it was done.

Anyway, that's the short version of my philosophy (which I'm sure will raise further questions).

I've seen 12 Monkeys. I'm not proud of it, but I have.




But there's a huge obstacle in that theory. In order for you to have gone back in time there must first be an original timeline in which your going back in time has not happened. For example, if you're 40 years old(today) and you go back to 1986, then that means in the original elapse of time between the years of 1986-2006 you had not gone back in time. That being the case, when you go back in time on your 40th birthday you are indeed creating a paradox because originally you hadn't been there. To go back in time at age 40 would mean the destruction of the previous timeline of 1986-2006.

Or to put it more simply, time has to actually elapse first before you reach the day a time machine is even invented. Therefore any use of that time machine automatically creates a paradox should you travel to any time before it was invented.

Well, no. That's the point. There is no "original timeline." There is one block universe in which everything (past and future) has already happened. Regardless of where in this universe you find yourself (in space or in time) the events remain the same--you can't be at one particular set of coordinates and suddenly your trip through time somewhere else along your worldline is erased from the universe.

Let me say it again: suppose in 2021 you're going to take a trip through time to the year 1250. That means right now (May 6, 2006) you can find artifacts of your presence in that year. If you carve your initials somewhere on that future trip then you'll be able to go see that carving right now. If you made the front page of Serfs Weekly in 1250 you can go to the library today and look that up. There is no sense in which your trip hasn't happened yet simply because right now it's 2006. Your 2021 trip is already in the history books. There is one history.



From one point of view yes. From age 20 to 40 (which of course you lived in the years 1986-2006) you certainly never travelled through time. But if you decide to travel through time on your 40th birthday to 1986 and live out your life that way there's no problem. You live out age 40-60 in the same years where a younger version of yourself is living out ages 20-40 (that is, there are two of you in that span of time). That younger you has no inkling of what he'll do in the future (i.e. travel through time) unless you tell him but nevertheless he will follow the path you've laid out. His future is your past. They are one and the same; one timeline.

It is one history, yes. But it's a different one from the original. What you're saying is that you retroactively have already done it. Which is true in that scenario. But what I'm saying is that scenario is impossible to begin with. There still has to be an original elapse of time before you make your trip. That is, you cannot make this trip until a time machine is invented. You cannot leave your initials or make the cover of Serfs Weekly until you travel back in time originally. Yes, if hypothetically you travelled to the past you will retroactively have already done it. And yes, in this retroactive scenario everything will be destined to happen as it technically already had. But this hypothetical couldn't happen in the first place because it skips over the critical impasse that can't be skipped over:which is that in order to travel back in time a timeline in which you had not done so must first originally exist and extend to the year of your trip before you can make it.





But this hits the same problem every time. Which is that time must originally elapse up to the point of your 40th birthday first before you do any of this retroactive stuff that makes it so you've already done it. This is what you're proposing as I understand it.--You want to travel back in time. But you can't because your future self did not exist in the time you want to travel back to(paradox). So your future self travels back to that time he can't travel back to in order to create his existence(the lack of which being why he couldn't travel there to begin with) there/then. From there, everything happens paradox-free because retroactively there is no paradox. But that in itself is a paradox.

That's essentially like saying you want to buy an iPod but you don't have any money. So you buy a couple of iPods and sell them to get the money to buy an iPod. That doesn't work because that money(future self) you bought the iPods with doesn't/didn't exist.






Correct. But that one timeline your future and past self share would have to be a different timeline from the original. Because in the original your future self did not exist then. Which effectively prevents the trip from ever happening.

To be honest, I'm not clear on exactly what you objection is. It sounds like (and correct me if I'm wrong) you're saying that the problem is that in order for you to have been in 1250 you must first reach 2021. Until that time you've never been back to that year (the "original timeline") but once you get to 2021 and make your trip then everything magically rewrites itself so that you were "always" there.

But that's not correct. I suppose I should make a few things clear about the scenario I've been talking about.

• First, the distinction between past and future is gone. Or rather, the apparent significance of such a distinction is gone. It becomes no more fundamental than a distinction between left and right--a distinction that obviously depends entirely on your vantage point and really means nothing. You seem to be relying on the notion that the future hasn't happened yet and thus we must wait for it; in this, it has indeed happened.
• Another way of looking at or stating that previous point is that, in a sense, all things happen at once. Or as Richard Feynman once wrote: "It may prove useful in physics to consider events in all of time at once and to imagine that we at each instant are only aware of those that lie behind us."
• Backwards causality doesn't defy logic.
• The timeline is extremely rigid. There is no flexibility at all; what that means for free will, etc is a separate matter.

Point (1) does not occur. Anywhere your future self will travel to, he exists in. Right now. I'm not sure what you're saying in point (2). There is no "creating of his existence" in the past just as there is no "original" timeline.

Let me try to get at this a slightly different way. Perhaps I get my hands on a time machine at the age of 40 and decide to head back and tell myself at age 20 about it. That means at age 20 I meet my older self and find out I'll be getting a time machine at age 40, a memory I'll have for the intervening two decades. There is no original history and no sense in which 40-year-old Penthar didn't travel back in time. I'll remember the encounter that resulted from that trip throughout my 20s and 30s. Further, there is no way in which I can fail to get my hands on that machine and no way in which I can fail to make that rendezvous with my younger self. It has already happened.

The iPod analogy isn't particularly apt because there's no backwards causality at any point there. Since the money always goes one way through time (into the future) of course there's no looping around to meet you at an earlier time (i.e. before you bought the iPod). The idea is to introduce a closed timelike curve such that the money from the sale of the iPods flows back to a time earlier than their purchase in the first place. This is a very real possibility, however offensive to common sense it may be.

This is what Igor Novikov called jinn. It's something with a closed worldline (i.e. one that loops back on itself)--essentially, the creation of something from nothing. There are distinct periods in which the object in question doesn't exist at all. Here the money doesn't exist before some point prior to the iPod purchase. Once you sell your iPod the money follows a curve back through time at which point it comes into your possession just when you need it to buy the iPod in the first place. Of course this requires a precise chain of events that (due to the rigidity of the timeline) can't ever be changed. You don't have the option of getting the money from nowhere, buying the iPod and keeping it. You must send the money back to be received by your slightly younger self.

While not logically impossible in the right kind of universe, I don't really see jinn being a big problem, as I doubt such loops would really occur. The real point, though, is that a time traveler is not jinn. He can create jinn, perhaps by giving Mozart a particular quartet that the traveler himself only had access to because Mozart had popularized it centuries before the traveler's birth (though, as I said, while this is possible, I can't really see this being common). A time traveler follows a world line that perhaps does loop back in time and may even overlap with itself (as in when the 40 year old and the 20 year old coexist in the same slice of time) but is not closed.

I'm not sure if this answers your concerns (of if I even read them correctly) but I'll stress again that there are no other timelines. There is no "first time" that things went differently that time travel could change. If your actions in 2021 and 1250 are causally linked that will be and will have always been the case. If you aren't already there then you never will be.

Yes.



If not then I'm a little confused as to what you're saying.



You seem to be making the very important distinction between things only seeming to happen at once and things actually happening at once. But your scenario does not make this distinction. Your scenario suggests past and future literally occur at the same time. Which would not be true since time progresses linearly and progresses forward. May 1st comes before May 2nd and May 2nd doesn't exist yet on May 1st. There is a metaphysical belief that time is circular but I assume that's not what you're referring to.

So for clarification since this is the point the rest hinges on, you acknowledge that retroactivity does not negate the fact that time does initially progress from the past to the future, correct?

Ah, I see now where the confusion lies.



This is why you're having difficulty with what I'm suggesting. The above is a seemingly reasonable assumption that is consistent with human perception. But I'm throwing it out.

The question of the arrow of time is a very big question, to be sure. But at a fundamental level the laws of physics are symmetric in time, meaning they work just as well backwards as they do forwards (in fact, in was only a few years ago that any inkling of a real arrow was seen in the decay of neutral pions). What I'm saying here, in the words of Albert Einstein, is that "The distinction between the past, present and future is only a stubbornly persistent illusion." That, coupled with the Feynman quote I provided above, is the essence of everything I've said so far (the qualifiers about seeming and actually being what's going on were because Feynman was suggesting this might well just be a utilitarian move to make physics easier--I'm suggesting that's how the universe really is, for the purposes of this notion)

The point I was trying to get across is that (in what I'm suggesting) May 2 very much does exist on May 1. Past and future do literally take place "at the same time."

Let me put it together with a physical example mentioned in my original post above. It's a curious fact of nature that a charged particle resists changes in its state of motion more than a neutral particle with the same inertial mass. The obvious reason would seem to be that having an electric field somehow makes it a little harder for a particle to accelerate--that is, this has something to do with a particle interacting with its own field. But the closer you get to a charge the stronger the field gets, quickly going to infinity as you near the point where it sits. So if we believe a particle interacts with its own electric field then we might wonder if it's ok to have a model in which every particle is sitting at a spot where the electric field has an infinite value. Gets weird fast.

The alternative in considering the source of this so-called radiation reaction force is to throw out the assumption that charged particles interact with their own fields and instead look elsewhere (i.e. find an external cause for this reaction force). Sixty years ago John Wheeler and Richard Feynman developed a theory based on an observation Paul Dirac had made a few years earlier: advanced wave solutions to Maxwell's equations could get a clever calculator just the right force to account for the radiation reaction. Maxwell's equations are the four equations that govern all of electromagnetism and, like most of the rest of physics, they are symmetric in time. That is, while they allow the regular emissions of radiation we're familiar with (retarded waves)--the ones that arrive at an absorber after being emitted--another solution is also allowed. These are the backwards-through-time solutions called advanced waves; they arrive at an absorber before they are emitted.

Wheeler-Feynman absorber theory suggested that every time a charged particle wiggles and sends out radiation it actually sends out half retarded waves and half advanced waves. So suppose we try to accelerate a charged particle. It will send some radiation out backward through time but half of it will go forward through time. These retarded waves will arrive at an absorber some time in the future (doesn't matter how long it takes--the light could go on for light years) causing it to wiggle and send out its own waves. The advanced waves this absorbed emits will travel back through time, following the same route the retarded waves took forward through time to get to it (some thought will show you that these retarded and advanced waves will coincide at every step along that path). The retarded waves arrive back at the original emitter at the exact moment we made it wiggle to start this process and they provide a back force--the radiation reaction force.

Hopefully that'll help you see what I'm talking about. If that theory were correct then every time you accelerate a charged particle you're in fact communicating with the future, in a sense. If the absorber is a light-day away out in space and you wiggle the original emitter on May 1, then indeed the instantaneous reaction force you experience is coming from May 2. The retarded wave will be received (the sort of destiny fulfilment stuff I mentioned above) because in a sense it already was--you have confirmation of that in the reaction force back on the charge.

Does that help?

Ah. ...OK.




Well that changes alot. If that's your belief then the question of "How is time travel possible?" doesn't really apply. This is more a fundamental disagreement of what time is then, rather than a matter of schematics for travelling through it.

That's one way to look at it, I suppose. I should add that I don't know of any other satisfactory way to both allow time travel within a universe and keep everything paradox free. Further, if time travel is possible I don't see how you could escape the conclusion that the future already exists. This view doesn't necessarily suggest how to travel through time (again, the suggestions from established physics are above) but it does help visualize what exactly that would mean.

Did you have a different take?

Hence why I don't think time travel is possible.




I see only two possibilities should time be violated. If someone somehow, someway, travelled through time even if just a thousandth of a milisecond, by laws of nature one of two things absolutely must happen as a result.

1)Time folds in on itself and the universe is destroyed--which I believe the most likely result. If this is the case, then by virtue of backwards causality we retroactively don't exist right now. But since we're currently having this conversation, then according to the above, that means at no point does anyone ever accomplish time travel anywhere in our future. Because if they did it would be like none of this ever happened.



2)A divergent universe is instantly created by the time traveller's interchronal existence. This new universe would be exactly identical to his own up until whatever moment he time travelled to. At which point it diverges from there. But I believe #2 is less likely due to the Law of Conservation so I lean more to time travel meaning the end of reality instead of creating a new one.


So I lean toward #1 being the case. But poetically(though confusingly perhaps), the nature of time retroactively prevents any time travel to begin with so neither of these can occur. Or ever will occur.

I'm not sure I know exactly what you mean by saying time is "violated." It seems you have a view of time as having an inherent flow or direction, past to future; we know as a matter of fact, of course, that this flow is not an absolute and can be altered in relativistic ways so I assume you're talking about dropping out of this stream and going back the other way. There are some things that could be said about that view with regard to admittedly speculative theoretical toys like the Krasnikov tube mentioned above and, indeed, anything said above about arranging the metric just right.

But there's something more interesting to suggest. You said that in your view if anything travelled through time by just a thousandth of a millisecond it could be catastrophic. You've probably heard of antimatter--particles just like the regular ones we're familiar with but with opposite charge and spin. It is in fact a perfectly reasonable and acceptable (which is not to say widely accepted) interpretation of antimatter to suggest that antimatter is in reality a negative energy state that propogates backwards through time (this is sometimes called the Feynman-Stuckelberg interpretation).

If you're not familiar with Feynman diagrams, they're a very easy way to depict interactions between particles. Look at this one:



This shows, in a nutshell, how electromagnetism works. We see two electrons travelling through space, gradually getting closer to each other but then they exchange what's called a virtual photon (the squiggly line) and begin to get further apart in space (i.e. they've repelled each other). It's pretty easy to understand what's going on if you imagine floating alongside (but gradually toward) somebody out in space and then you throw a heavy ball to him and he catches it. When you throw it you're knocked the other way a bit (recoiled) and so is he when he catches it. You guys float on getting further apart, having "repelled" one another.

The interesting thing is that if you flip the space and time axes in that diagram and thus make the scattering that causes the recoil across time instead of space you'll end up with a real and well-known process--matter-antimatter annihilation. An electron and positron, being oppositely charged, will attract each other until they meet and annihilate, leaving behind only photons. We usually think of this as two separate particles but it's completely equivalent to think of that process as one particle that scatters off a photon and ends up heading backwards through time with negative energy. Thus when we see an electron and positron heading toward the same spot in space, we're actually seing a kind of "before and after," with the positron coming from that spot (i.e. that spot lies in its past) while the electron heads toward it (since that spot lies in its future). Then there's no collision and annihilation but rather one particle making a U-turn in time at that spot. It just looks like there's two particles because at any given slice of time (prior to the scattering or annihilation event) the same particle exists twice--its "younger" self going forwards through time and its "older" self going backwards. Here it is in diagram form:



Now how much "mathematically equivalent" translates into "this is what actually happens physically" is anyone's guess. But there's certainly nothing that makes this interpretation physically impossible. And the universe hasn't imploded yet.

//editted to insert second diagram

And therein lies the fundamental disagreement. Time cannot be altered in relativistic ways. What can be altered is the speed at which processes occur in/on a body and thusly the effect of time on it. Those are two very different things. Which is why time travel is almost exclusively spoken of in relative terms instead of genuine time travel. Despite the name, "time dilation" doesn't do anything to time itself. It's a referrence to how (completely unaffected)time is percieved by a body. 20 years is still 20 years irregardless of the relativistic scenario. What's relative is the speed of changes over those 20 years, not the 20 years themselves.

I've never heard it put quite that way but I think you'd be hard-pressed to determine how exactly those two statements are very different things. All measures of time (biological clocks, mechanical clocks, light clocks) slow at the same derivable rate. A muon created at the top of the atmosphere in a high energy collision has a lifetime measured in microseconds, too short to make it to a detector on the ground. Yet they do arrive at the ground. Saying that the rate of decay relative to an observer on the ground slowed and saying the rate at which time passed for the muon relative to an observer on the ground slowed is equivalent. A spaceship hovering over a neutron star for a few minutes might return to a distant starbase or whatnot and find several hours have passed. Again, saying that every single process on board the spacecraft (from the biological to the nuclear to the mechanical and so on) slowed in the vicinity of the neutron star (relative to outside observers, of course) is equivalent to saying time ticked at a different rate for those in the spacecraft than it did for those further away from the neutron star.

Really, the easiest way to see this (and I'm talking specifically about the gravitational form of time dilation here) is to actually stick a clock deeper in a gravitational well (say, on the earth's surface) and compare it with one, say, on a Scout rocket 10,000 km above the surface of the earth. This was done 30 years ago and the clocks do indeed tick at different rates. Time passes at different rates in different frames. Different kinds of experiments have also independently verified this.



I would encourage you to follow the link in my original post in this thread to the old intro to special relativity thread. One of the fundamental points of special relativity is that time is not an absolute and is not simply a matter of perception. Time in fact does literally stretch while space contracts. "20 years" means nothing in an absolute sense. 20 years on your clock and 20 years on mine need not measure the same thing and yet neither of us is wrong. I can live 20 years in the same interval you experience 10. What's 20 years? Twice what you experience in that interval or exactly what I experience in that interval? Both. The answer is relative.

Now when it comes to time travel obviously this isn't particularly helpful for travelling backward through time (unless something like a tachyon actually were to exist which seems unlikely); this is simply a recipe for altering the amount of time and space you travel through in going from point A to B. Time dilation would only be useful if you were interested in seeing a point in the distant future that you would otherwise never live to experience.

edit// I guess to sum this up in a nutshell: there is no fundamental disagreement. This is 101 years of extremely well-established physics.