Question

Is there a possibility that there is an universe where time flows from future to past ?

Answer 1

i think it can't be possible..

Answer 2

isn't the concept of multi-verse is every possible variation.

Answer 3

look at twin paradox, if u have twins who traveling around the universe with velocity close to the speed light. When your twins is back, u will be older than your twins. so your twins is comes to the future. But there isn't possible to return to the past.

Answer 4

well, nothing is impossible but if you can prove that with a mathematical equation, that'll be totally acceptable..

Answer 5

look at the time dilation\[\Delta t=\Delta t'\div(1-v ^{2}/c ^{2}),\ \Delta t=time \ experienced \ by\ someone \ in \ earth \] \[ \Delta t'=time\ experienced\ by\ your\ twins \] with v = your twins velocity and c= speed of light..

Answer 6

just like i said before.. time just go positively..

Answer 7

wont the twin paradox work just the opposite way in such an universe

Answer 8

i still don't understand yet all of general theory relativity, but if time is the fourth dimension like they said. go to past is possible. Just like negative direction in cartesian coordinates..

Answer 9

It depends what you mean. From a purely grammatical point of view, the question seems self-contradictory, since the direction time flows DEFINES "past" and "future." It isn't possible for time to go from future to past, because that is grammatically contradictory, like saying a car accelerates to a stop, or a man ages into a baby.

But what you may mean is to ask whether it is possible for a universe to exist in which events happen in the direction of decreasing, not increasing, entropy. For example, men do turn into babies and go back into their mothers' wombs, rusted-out cars do return to factory-fresh newness, then become disassembled, the steel converted to iron ore and coke, which are then buried in the ground, and so forth -- the movie of our universe, only run backward.

There are two answers to this question, the theoretical and the practical. From a theoretical viewpoint, it depends on whether the space of possible states of the universe is infinite or finite. That is, is there an infinite number of ways to arrange the positions and velocities of the particles in the universe, or not? (It may be a very very large number, of course, but it may not be infinite.)

If the number of states available to the universe is NOT infinite -- because, for example, there is not an infinite number of particles in the universe, or the universe does not occupy an infinite space --then NECESSARILY given enough time, the universe will retrace its earlier steps, and that means indeed that events will happen in the direction of decreasing entropy. People (if they existed) would grow younger, cars would unrust, and so forth.

From the practical point of view, however, this is absurd. "Given enough time" means time on a scale that staggers imagination. The entire lifetime of the universe so far would be unmeasureably small by comparison. We are talking about lengths of time so long they cannot be written down except in complicated math formulae. For any imaginable practical purpose, it is flatly impossible for a universe to evolve in the direction of decreasing entropy because the inescapable and simple laws of probability rule against it. Of all the bazillion possible behaviours of the huge collection of particles that make you up, ONLY one (or very few) result in your growing younger, and all the rest result in your getting older. Even if one of the weird getting younger paths was followed for a few moments, the sheer number of the getting older paths mean that you will, on the whole, always get older.

Answer 10

@Carl_Pham one question. what do you think about back to the classical age.. are that possible?

Answer 11

Not sure what you mean, lasaz. Are you asking whether human society could evolve back towards the level of technology and population, et cetera, of roughly 1 AD? Sure. We used to imagine it as a good possibility all the time during the Cold War, as a consequence of a big thermonuclear exchange. There is no guarantee that humanity progresses always forward, and indeed sound theoretical arguments why it should, from time to time, regress.

Or are you asking if you personally could experience Classical Greece, while the rest of the universe continues on in the 21st century? That answer to that is no, unless Einstein was badly wrong. You and Classical Greece are what the physicists call outside each other's light cone, meaning there is no possible way in which you (or they) can experience each other's events as simultaneous. This is not to say that if you had been born somewhere else, in a very different frame of reference, you could not be experiencing Classical Greece right now, while the rest of us are experiencing the 21st century. But if that were so, you would be unaware that anything odd was going on -- you would certainly not be aware of the 21st century going on for us. Roughly speaking, you can't be one and the same person and experience both Classical Greece and the 21st century within one ordinary human lifetime.

A more interesting question is whether Classical Greece still, in some sense, exist, since certainly there is a reference frame which sees the troops amassing at Thermopylae right now, from our point of view. This is part of the problem of relativity. Since we can no longer define one single stream of time for the entire universe -- we cannot say today is Monday, April 30, 2012 absolutely everywhere for all observers -- then in what sense do events in any one obsever's future or past fail to exist, since they are in SOME observer's present? Food for thought.