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Science

Can Time Flow Backwards? 37

Posted by Roblimo from the latest-way-to-catch-up-on-your-e-mail dept.
PD writes "Exoscience has a story about the possibility that in some regions of space, time can actually flow backwards. Eggs would unbreak, supernovae would unexplode into stars, and living things would grow younger. I wonder if it makes hair grow back."
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Can Time Flow Backwards? More

Can Time Flow Backwards?

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  • Correct, but it is still a problem as to how we perceive the reverse-time.

    If we view time as moving away from boundry conditions, and the other state views them as moving away from their boundry conditions, but towards those defined for our spacetime, then we each perceive time as as moving forward for each other, but backwards with respect to the other.

    The real question is what happens when the Sharks meet the Jets...

  • No, not once you accept that effect does not necessarily follow cause.

    The "motion" of electrons is one example. It is difficult to predict where they are at any one moment, sometimes they can be considered to be in several places at once.

    If you need an easier example, just run a videotape backwards. You can see things "unhappening" in front of you. We won't see any of these things happen in our universe, but if they did, that's what it would look like.

  • Before your head explodes, read the following explanation why the universe has 4 dimensions, not 7 or some other number.

    --LP ;-)
  • Before your head explodes, read the following explanation why the universe has 4 dimensions, not 7 or some other number:

    http://www.hep.upenn.edu/~max/dimensions.html

    --LP ;-)
  • Maybe time is already flowing backwards at the macro level and we just aren't aware of it. The apparent bizareness of quantum physics could be caused by the fact that quantum events and macro events are occuring with different temporal arrows.

  • I know are current universe has 4 dimensions. But before "the Big Bang" there may have been seven dimensions. The inherint instability of 7 dimension caused 3 to collapse and 4 to expand a a terrific rate(big bang). The 3 dimension universe would be smaller then an atom, and probably smaller then the smallest part of an atom.
    Picture a bed with a bed sheet 1 size too small, you can get it to fit around the bed, for a while. but the tension is going to cause one of the corners to pop off in order to stabalize the forces being applied to it.
    Now referring to the link:
    It seems to me that the charts on that link seem to support this theory . look at the nonstable regions of the graph.
  • Why should I expect a highly ordered Big Crunch?
    That I can't answer. What I can say is that Hawking gives arguments for why we should expect an ordered bang and a disordered crunch. Unfortunately his arguments are not themselves time-symmetric invariant but subtly introduduce an asymmmetry (like the way Boltzmann introduces a subtle asymmetry in his H-theorem). (Actually I'm not qualified to read Hawking's paper (not too far off though) - however it is possible to show an argument lacks time-reversal symmetry without understanding all the details and I have to trust Huw Price on this one.) The net result is that we don't really have a good argument for ordered or disordered states at either end except for the obvious "we shouldn't really expect to see order anywhere (why not?) but it looks like the past was highly ordered from observation." This argument is not due to Hawking. BTW While Price's book is excellent at damaging other people's arguments I'm not terribly impressed when he tries to construct his own later in the book. But the earlier part of the book is well worth the effort.

  • Very easy: First, find out what time is. Second, make it go backwards.

    This is something that I just haven't been able to make sense of. How can time go "backwards"? Isn't the whole concept of "backwards" relative to time?

    That is, you'd need some concept of "time" outside of our time by which the flow of our time could be viewed as "backwards". Or would you?

    Am I making any sense here?

  • The article is speaking about thermo-dynamics time-arrow. It basicly says that if one could impose a future boundary condition to a system, as in convincing the air that it should be in the 5 cubic cm in five minutes, the air would act as if it were going back in time in the thermo-dymanic sense.

    Well until now there is no problem, since you're forcing the particles to go back in time (in the thermo dynamic sense). But the amazing thing is that regions where future condition could co-exist with regions with past conditions and exchange information without damaging the time arrows.

    Well matter going from chaos to order is reverse time in the thermo dynamic sense, but as said there are other ways to define time. For instance you can define past everything that you can remember. The passage of time can be defined by memory and you percieve time passing by comparing what you see with your memory of a few seconds ago.

    Even time units are defined by "memory", since they are defined by events that repeat, like for instance the tic-tac of a clock. You can only define this because you have some kind of memory that this event has happen before.

    Now my question for the author of this article would be, if someone would step into erverse time regions, would this unfurtunate person begin to forget past events, as it grows younger? That would be in my definition of time a reversed time arrow. If this is true in both directions, than would this be enougth to prove that the two time arrows are in fact one?

    Please notice that my definition of memory is more abrangent than simply biological, it could mean computer memory or any other way to store information.
    --
    "take the red pill and you stay in wonderland and I'll show you how deep the rabitt hole goes"

  • So if time went "backwards" we wouldn't notice it. And it may be going backards, we just percieve it as "forwards". Or perhapse there is no time Just an "IS" but are Minds can not handle that concept, so we percieve time as a "flow".
    I would like to see some other terms used instead of Forward and backward when we talk about time. Those terms belong to other dimensions, not to time. Of course, I can't think of any, but I'm not a world class physics geek.
    HOW to travel through time:
    jump to the left,
    and Step to the right
    put your hands on your hips,
    tuck your knees in tight
  • paradox would preclude you ever entering. The border'd be like the lint trap of the universe.

    Here's an example:
    You fly towards the zone of reverse time. Upon crossing the border, you go "back" in time, and reverse your newtonian motion back over the line. Once in "forward" zone, you get normal newtonian mechanics pushing you back in, ad nausieum.

    If you wanted to leave in the reverse zone, you'd have to be in it already (good luck!), and you'd have to be reversing along to your entry point. Otherwise, the flow of time would be in defience of itself :-) Since your entry would be reversed once you leave, you'd be trapped again.

    So before you go boldy reversing where no one has reversed before, you have to understand that you're either in it or not, relatively speaking, as your frame of reference would preclude you ever jumping to an alternate time stream/zone. If you were born there, we seem reversed. Vice versa. And there's no way to pass messages or objects, so there'd technically be no way for things to escape. Perhaps black holes are partially pockets of antitime?
    ---
  • There is a theory which states that if anyone ever discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.
  • I wasn't entirely clear how he got around that whole "Second Law of Thermodynamics" problem. From my understanding, entropy increases because all possible microstates of a system are equally likely, and the greatest number of microstates correspond to the most disordered macrostate (basically, that there exist more ways for a collection of air molecules to be scattered around a room than for them to be in a small box...this isn't even physics, it's math/statistics). So how does this become no longer true? Anyone who knows a little more about this theory care to enlighten me?
  • There is another theory which states that this has already happened!

  • Is there really such a thing as Time? (Score:1)

    by Anonymous Coward
    Sure I get the part that Object A will travel distance X, while Object B will travel distance Y.

    If I throw an object it ends up somewhere else.

    But I don't understand the part that you can suddenly get them to move "back". Does the "before" actually exist anymore? Seems rather strange if it does.

    What if the multiverse thing holds true? In one multiverse someone goes backwards in time, but not in the other? Can that work?

    What am I missing? Any pointers to proof that there is a "Before"?

    Link.
  • and wasnt this covered on Red Dwarf ?
  • I see his point that future boundary conditions imply regions of space where the arrow of time appears reversed. But, he's wrong in suggesting that the fact that a future crunch with all of the matter in the universe condensed means a highly ordered state. Hawking states that it is a highly disordered state and differs from the initial conditions of the Universe whice were in a highly ordered state. It's all condense becuase the Universe is smaller. It's not all condensed in a corner of a largely empty Universe just as the initial state wasn't condensed in the corner of an empty universe.

    Also the odds for a future crunch don't look too good with all the observed deviations from a flat univers falling on the side of an open universe.

    In short, Dude needs to drink more. We did better as undergrads in philosophy after a bender.
    Anomalous: inconsistent with or deviating from what is usual, normal, or expected
  • Entropy is a good pointer. It increases as time moves forward. Were time to move backward, the entropy of a system would tend to decrease.
  • Yet another time paradox? I haven't seen this one covered anywhere, but I doubt if I am the first one to think of it. Suppose someone appears out of the "future". Then from our current perspective, the future already exists. So, if the future has already happened, then it must be in the past. (Also, if it has already happened, then we can't change it.)
  • Suppose, somewhere in our universe, an event occurs. (Yes I know the previous sounds remarkably unintelligent, but it leads somewhere.) This event is repeated at exactly the same point in space. With time being non-existant as you have stated, there is no before, and the event has only occurred once. But suppose an independent observer, much to his/her confusion, saw both these events taking place. To him, the event has occurred twice. In his mind, there is a dimension that enables him to distinguish between these two events, which he (or she.. I say only in the hope that this message will not start any completely irrelevant feminist issues) would rationally measure as the interval between the two events. As we are all in a universe similar to this young (or old.. age issues too you see) male (or fe.. forget it), which is bound by the same laws, one of the dimensions with which we interact is 'time'.

    Hence time exists and there is a before and an after to everything between the beginning and the end on the universe, not inclusive. Let us please accept this statement, and not try to bring up any more discrepancies in our basic concepts of the so called 'fourth dimension'.

    Now, Einstein once, speaking of his theory of relativity, said that, "This relativistic analogy can be carried to its logical end." It has already been proved in an experiment concerning synchronised atomic clocks, one in a supersonic jet, and the other positioned at rest (relatively that is.. you have to be very accurate when speaking of relativity) on Earth, that the higher velocity a body attains, the more time appears to slow down for the body. Since time begins to slow down with higher speeds, it can be shown that at the speed of light time stops totally and beyond that begins to run backwards! Of course time flowing backwards would mean a velocity far greater than that of light itself, in sharp contrast to Einstein himself. Or is it? He did say 'logical' end, and it is illogical to travel at speeds greater then that of light. Seems guys like him think ofeverything. ;-)

    Einstein: my nomination for Earth's greatest scientist to date, Time magazine's nomination for man of the century, and the icon for this slashdot's entire science section: a universal figure in the field of science. His equation e=mc2 is probably the only scientific equation recognised on the street (so far). This man was a genius. And he was probably right when he said that the speed of light is the upper limiting velocity in the universe. Similarly, matter having contracted more and more, ultimately vanishes at the speed of light. Beyond that it is hard to imagine negative matter with infinite mass.

    --The answer to the great question of life, the universe and everything: 42!
    --Trinity, in the Matrix: "It's the question that drives us nuts!"
  • Very easy:
    First, find out what time is.
    Second, make it go backwards.
    We can measure time, but thats all we know about time. If you suscribe to the idea that there are 7 dimensions to the universe,and because of there inherant instability, they collaspe into a set of 3 dimension, and a set of 4 dimensions. This means there is an universe without time(the 3 dimensional universe)and a 4 dimensional universe(ours)with HWD and T.Now this means there is an universe WITHOUT time.
    Now get your brain around this: Not only does that universe not have time, It doesn't have Height, Width, or, Depth either.
    Must go now head exploding
  • If you actually read even the articles there summarizing the findings, you'd see that the author addresses your points. To wit:

    1D and 2D basically aren't complex enough to have life and self-aware creatures that could observe the universe (i.e. why "we" couldn't be in 2D universe)

    you can model two or more time dimensions via mathematics. 2 time dimensions makes motion unpredictable, unpredicatable; self-awareness requires some ability to predict from "past" results

    Not bulletproof of course, but thought-provoking.

    --LP

  • Hawking states that it is a highly disordered state and differs from the initial conditions of the Universe whice were in a highly ordered state.
    This looks like an argument by authority to me. Maybe you were already down the pub when they started lecturing to you on these. Leave those kinds of arguments to the social scientists. Hawking's views do not necessarily represent the physics mainstream, they are not necessarily correct, and check out Huw Price's excellent book "Time's Arrow and Archimedes' Point" for a pretty good argument showing how Hawking implicitly assumes what be must prove in this particular case.
  • finally... i thought i was the only one here who reads h2g2 books
  • Future constraints is a "given" which I don't easily accept. Atomic cowboys are going to coral the atoms into a 1m cube in five minutes? Sounds like work to me! Or maybe it's like the pool-table trick where all the balls return to the triangle. Who sets up the shot? The devil is a pool shark!
  • When people talk about "time flowing backward" or "moving through time" what they are really meaning is "I want to step outside this point of reference (time) as if it no longer effects me and then step back in at another point". This doesn't work with any other dimension so why should it work with time? In fact it contradicts the meaning of "dimension". If you move to the left you end up to the left and you also have to pass all the points in between in that journey to the left. If you ended up to the right or didn't pass the points in between that wouldn't make sense. Time, as a dimension should be the same. If you go forward you experience it forward. If you go backward YOU CAN'T TELL because you would experience it backwards (unexperience it). Going backwards and thinking you could experience it forward doesn't make sense. Time may flow backward but we won't notice it because we would be going backwards with it.
  • Thank you for the book reference. I will check it out.

    But my argument was more than just an appeal to an authority. I accepted that reversed-timelike things might happen if the future state were highly ordered/tightly constrained. I explained that his example was flawaed. Now you tell me: Why should I expect a highly ordered Big Crunch?

    Anomalous: inconsistent with or deviating from what is usual, normal, or expected
  • The examples stated in the news story (i.e. eggs uncracking, organisms becoming younger) do not make sense. If this area of space has time that is constantly flowing backwards, how could the egg have ever cracked? How could the organisms become older? For this to happen, time must be swaying back and forth in a pendulum-esque motion, rather than just going in one direction.
  • From my understanding, he doesn't get around the second law of thermodynamics... he doesn't have to. The second law of thermodynamics is a boundry condition set forth on the system. If we changed the boundry condition so that we are not moving towards entroy, but away from it, then we have have a reversal of the second law. From what I ascertained, the law is a boundry that has been placed on our space-time. Because to us time moves forward (or what we view as forward) doesn't mean that it can't move in an opposite (again, what we view as opposite) direction for another object. This is where the application of boundry conditions occurs.
  • In a universe whose interactions respond to future conditions rather than past conditions, wouldn't the "future" conditions be experienced as the past?

    The "cause" of gas diffusion in our time-forward universe is that at time 0 it was in some unlikely state (past boundary condition), and it migrated to a more likely state by time 1. In a time-reverse universe, the "cause" of gas un-diffusion would be that at time 1 it must be in some unlikely state (future boundary condition), so it will migrate there from some likely state at time 0.

    But, being a time-reverse universe, the "cause" of the future condition will be an even-more-future condition, and so on, and so on. In such a universe, the "record" of time would be a record of future conditions. Since we define "past" time as time that we have experienced, i.e. that we have a record of, it seems to me that the time perception in a time-reversed universe would be precisely the same as our time-forward perception.

    So, a universe where future conditions will "cause" natural phenomena IS a world where past conditions did "cause" natural phenomena.

    Correct or crazy?
  • Yes, we are viewing time relative to us. So, since we have defined our state of being as going forwards, we view the opposite as going backwards.

    I don't think you'd need another concept of time, just the understanding that we are moving in one direction in time. Therefore, by definition, moving in the other direction would be backwards.

    How does that work?

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