Thread: What happens when time meets antitime?

Imagine 2 big bangs. Each generates a universe. Nobody in one can know of the other; their spacetimes are nonintersecting. However they lie closely parallel in a certain interval of each. And they are expanding in opposite temporal directions. (The bangs are widely separated by any measure). Now imagine that in a certain subset of the regions of close parallelism, a "slit" is formed in each 4D manifold, and that the spacetime of each is disconnected there from its own, and joined to the corresponding spacetime of the opposite universe. (Think of 2 pieces of paper, and you cut a slit in each, and then join one to the other at the slit, so that geodesic travel becomes possible from one to the other at that junction.) This "slit" occupies a certain time interval in each universe, and not elsewhere. The effect that will be seen within one of the universes by an observer is that, for a time, everything will look perfectly normal. Then, when the time arrives corresponding to a boundary of the "slit", the observer will see, when looking through a certain planar region in space ("Window"), the things that he previously was viewing through them, suddenly become replaced by objects in the other universe. This is because the observer has now entered the time corresponding to the cross junction. The "magic window" will of course have a peripheral boundary, such that if the observer looks in a direction outside it, he will still see objects pertaining to his own universe; but if he looks through it, he will see objects in the other universe. The "magic window" will remain open during a time interval corresponding to the temporal extent of the "slit", and then will close when the clock ticks past that limit, restoring the normal view.

And because of symmetry, an observer in the other universe will see the same phenomenon, as measured on his clock.

However, because the universes unfolded in opposite directions, when they join, times are moving in opposite directions; that is, as entropy in one increases, entropy in the other decreases. (We will assume that nothing is exchanged between the universes during the time the window is open other than light.) Now the direction of entropy has a lot to do with how we percieve things, what we know under what circumstances and what times; and we are acquainted with only one direction of that. The question to be explored now, is, given the fact that entropy is evolving in opposite directions in the two universes, what does each observer see, and what can each know, and what kind of messages can be sent, and what physical phenomena may arise, during the time that the window allows light from these oppositely evolving regimes to reach each other?

Originally Posted by Atomic-S

... And they are expanding in opposite temporal directions. ... However, because the universes unfolded in opposite directions, when they join, times are moving in opposite directions; that is, as entropy in one increases, entropy in the other decreases....

One would think that time would be travelling in the same direction no matter what direction the universe was travelling.

Answer a simpler questions first, about just one of the universes. In the universe where entropy is decreasing, what does an observer see?

It would be good to know that, because the observer of the OP is either going to be in that universe, or looking into that universe.

It's unlikely the observer would see anything at all. The other universe could not have started at the Big Bang, or it would be expanding just like ours. If it is collapsing, it started from whatever the end point of our universe is. Since the projected duration of our universe is many times its current age, all you would see is empty space with perhaps a few distant radio sources.

If your slit happened to open on a universe in the same general condition as our own, it's still unlikely you would see anything. All light emitters would become absorbers. Your sensory equipment would only function if you also were moving backwards in time.

In the forward universe, a flash of light can be aimed through the window. In the backward" universe, that light will appear to be traveling back through the window toward its source, because time is reversed. Meaning that in the backward universe, it will be difficult to identify any source of it, but it will have an unambiguous destination. If, in the backward universe, an opaque object is placed in the beam, the beam should strike the object on the side toward its apparent source (howsoever indefinite), causing the light to be absorbed or scattered on that side. But, if it had been so interrupted, then it could not, to a backward observer, then proceed through the window to its actual source in the forward universe. So we have the curious contradiction that if, from the forward universe, a beam of light is flashed at an opaque target in the backward universe, then the beam cannot exist between the source and the target. This contradiction would seem to suggest that the experiment is impossible in principle. However, that is contradicted by the original hypotheses, all of which seem supportable in principle, namely: (1) That if one universe such as ours can exist, then a second could also exist, and that (2) making a junction between them is possible in principle, and (3) there is nothing preventing that junction from being made so as to join them in an antiparallel manner. Ergo, the experiment must be possible in principle.

One detail escaped my notice: If an opaque barrier exists in the backward universe, then when the light is sent there from the forward universe, it never can (I think!) progress further than that. Therefore, to a backward observer, the light would appear to spontaneously arise out of the target and travel from there through the window towards its original source. Of course, for light to spontaneously arise out of an opaque target is a reversal of entropy. But what does that say about the molecular state of the target?

Answer a simpler questions first, about just one of the universes. In the universe where entropy is decreasing, what does an observer see?

It would be good to know that, because the observer of the OP is either going to be in that universe, or looking into that universe.

There are two observers: one in the regular universe and the other in the reversed universe. To each, things in his own universe look normal, but in the opposite universe, presumbly not.

If an opaque barrier exists in the backward universe, then when the light is sent there from the forward universe, it never can (I think!) progress further than that. Therefore, to a backward observer, the light would appear to spontaneously arise out of the target and travel from there through the window towards its original source.

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Of course, one complication is that the target, from the viewpoint of the forward observer, differs in a certain fundamental way from such a target in his own universe: its entropy (apart from the light beam) is reversed from his viewpoint. Does light interact with such a target the same as it would under normal conditions?

If time was moving backwards in one ... then wouldnt the Big bang be more of a Gran finalle ... a big crunch of sorts .... rather than a starting point?

Originally Posted by Atomic-S

Imagine 2 big bangs. Each generates a universe. Nobody in one can know of the other; their spacetimes are nonintersecting. However they lie closely parallel in a certain interval of each. And they are expanding in opposite temporal directions. (The bangs are widely separated by any measure). Now imagine that in a certain subset of the regions of close parallelism, a "slit" is formed in each 4D manifold, and that the spacetime of each is disconnected there from its own, and joined to the corresponding spacetime of the opposite universe. (Think of 2 pieces of paper, and you cut a slit in each, and then join one to the other at the slit, so that geodesic travel becomes possible from one to the other at that junction.) This "slit" occupies a certain time interval in each universe, and not elsewhere. The effect that will be seen within one of the universes by an observer is that, for a time, everything will look perfectly normal. Then, when the time arrives corresponding to a boundary of the "slit", the observer will see, when looking through a certain planar region in space ("Window"), the things that he previously was viewing through them, suddenly become replaced by objects in the other universe. This is because the observer has now entered the time corresponding to the cross junction. The "magic window" will of course have a peripheral boundary, such that if the observer looks in a direction outside it, he will still see objects pertaining to his own universe; but if he looks through it, he will see objects in the other universe. The "magic window" will remain open during a time interval corresponding to the temporal extent of the "slit", and then will close when the clock ticks past that limit, restoring the normal view.

And because of symmetry, an observer in the other universe will see the same phenomenon, as measured on his clock.

However, because the universes unfolded in opposite directions, when they join, times are moving in opposite directions; that is, as entropy in one increases, entropy in the other decreases. (We will assume that nothing is exchanged between the universes during the time the window is open other than light.) Now the direction of entropy has a lot to do with how we percieve things, what we know under what circumstances and what times; and we are acquainted with only one direction of that. The question to be explored now, is, given the fact that entropy is evolving in opposite directions in the two universes, what does each observer see, and what can each know, and what kind of messages can be sent, and what physical phenomena may arise, during the time that the window allows light from these oppositely evolving regimes to reach each other?

I was thinking the exact same thing. The Universe where antitime exsist would only be called antitime in our view, and if this was the case then everything would come into exsistance from nothing. People would materialize out of nowhere and have knowledge of everything and as their time decreased everything would be lost. This would continue to occur until the entire universe collapsed into itself.
That would be cool to see.

Originally Posted by tom

If time was moving backwards in one ... then wouldnt the Big bang be more of a Gran finalle ... a big crunch of sorts .... rather than a starting point?