Thread: What happens when time meets antitime?

Ha, the Curious Universe of Benjamin Button.

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?

This is the 'mistake' some are making. Time wouldn't be 'moving backward' in either of the universes. Time would be following the 'rules of physics' (as we currently know them). While universe A may appear to be moving in one direction and universe B may appear to be moving in an exact opposite direction, time in both universes would be moving in the same direction. It is up to us to figure out this apparent paradigm.

A useful experiment to envision, to illuminate the nature of the phenomenon under discussion, is to envision , within the forward universe and prior to the opening of the window, a thermal cell consisting of two blocks of material almost touching , the other faces of which are covered by a good thermal insulator. We will assume that the blocks are at the same temperature. There is a like block in the backward universe, so situated that when the "magic window" opens (as viewed in either universe), the half that pertains to the universe of the observer but which is on the far side of the window, is disconnedted by vanishment, being replaced by the corresponding half of the other universe's pair. So that, for the duration of the openness of the window, the near half from the observers' universe is facing the opposite half of the other universe's pair. This means that we now have a system in which two blocks in an opposite time state, each well insulated except one face, are closely facing one another and able to thermally communicate by radiation. Now we know that under ordinary circumstances, two blocks facing one another in such a manner will tend to equalize in temperature. But that means in the direction of increasing time. In this situation, the blocks do not agree on in which direction time is increasing. So what axre we to expect? My present analysis is, that as views from, say, the forward universe, all radiation originateing from the block from the backward unverse is travelling backward, therefore cannot increase the temperature of the forward block. The forward block, however, can radiate and loses temperature in the direction of its forward time. Thus it would seem that there is a unidirectional transfer of energy from the forward block to the backward block, resulting in the former becoming cold and the latter becoming hot. Is that consistant with what would be seen in the backward universe? The heating of the backward block takes place in the direction of increasing forward time, which is to say, in the direction of decreasing backward time. That is in agreement with what a backward observer should see: to his viewpoint, the temperature of the backward block should be higher at earlier times, losing heat as backward time advances, which is in agreement with what has been previously said. Thus it seems to be self consistant that in either universe, each blocks will appear to be warm before the window opens, then will lose heat to the other while the window is open, and then be cold after the window closes. That of course at first seems to violate the conservation of energy (The exchange of heat between two hot bodies results in two cold bodies) but that is not so because the times are proceeding oppositely, so the process must be rather described as the tranfer of heat from a hot body to a cold body in such a way that the cold body is now the hot body and vice versa, which conserves energy.

However, I am unsure whether this analysis is complete. It has not looked into the question of a quantative calculation of the process. On thinking of that, I am not sure I know how to proceed.

Originally Posted by Atomic-S

A useful experiment to envision, to illuminate the nature of the phenomenon under discussion, is to envision , within the forward universe and prior to the opening of the window, a thermal cell consisting of two blocks of material almost touching , the other faces of which are covered by a good thermal insulator. We will assume that the blocks are at the same temperature. There is a like block in the backward universe, so situated that when the "magic window" opens (as viewed in either universe), the half that pertains to the universe of the observer but which is on the far side of the window, is disconnedted by vanishment, being replaced by the corresponding half of the other universe's pair. So that, for the duration of the openness of the window, the near half from the observers' universe is facing the opposite half of the other universe's pair. This means that we now have a system in which two blocks in an opposite time state, each well insulated except one face, are closely facing one another and able to thermally communicate by radiation. Now we know that under ordinary circumstances, two blocks facing one another in such a manner will tend to equalize in temperature. But that means in the direction of increasing time. In this situation, the blocks do not agree on in which direction time is increasing. So what axre we to expect? My present analysis is, that as views from, say, the forward universe, all radiation originateing from the block from the backward unverse is travelling backward, therefore cannot increase the temperature of the forward block. The forward block, however, can radiate and loses temperature in the direction of its forward time. Thus it would seem that there is a unidirectional transfer of energy from the forward block to the backward block, resulting in the former becoming cold and the latter becoming hot. Is that consistant with what would be seen in the backward universe? The heating of the backward block takes place in the direction of increasing forward time, which is to say, in the direction of decreasing backward time. That is in agreement with what a backward observer should see: to his viewpoint, the temperature of the backward block should be higher at earlier times, losing heat as backward time advances, which is in agreement with what has been previously said. Thus it seems to be self consistant that in either universe, each blocks will appear to be warm before the window opens, then will lose heat to the other while the window is open, and then be cold after the window closes. That of course at first seems to violate the conservation of energy (The exchange of heat between two hot bodies results in two cold bodies) but that is not so because the times are proceeding oppositely, so the process must be rather described as the tranfer of heat from a hot body to a cold body in such a way that the cold body is now the hot body and vice versa, which conserves energy.

However, I am unsure whether this analysis is complete. It has not looked into the question of a quantative calculation of the process. On thinking of that, I am not sure I know how to proceed.

Unless I'm mis-understanding your statement, you've stated that the blocks are already equalized temperature-wise and thus there should be no 'thermal communications'.

Some clarification: There are actually 4 blocks, two in one universe and 2 in the other. In any one universe at such times as the window is not open, its two blocks are facing each other, and I said "in thermal equilibrium", which I probably should not have said inasmuch as that statement runs afoul of later conclusions. I was mainly making a rhetorical point, which is, that when the window opens, the universes exchange views so that each is looking into the other, such that one block of the forward universe is now facing one in the backward universe (and that the other two are in a like relationship, a feature I did not mention above because i thought it unnecessary to discuss the second opposite pair at that point in the agument, inasmuch as it would presumably replicate what was going on with the first opposite pair.) (When the window opens, a traveler in the forward universe passing through it would find himself in the backward universe, but then if he makes a 360 degree circuit around some portion of the window boundary and heads throuhg it again, he would be back in the forward universe). (Note therefore that two pairs of blocks cannot see one another at any time). Perhaps a better way to analyze this problem is to set the initial conditions at the time halfway between when the window opens and closes. Both observers will agree on when this time is, since it is halfway between. And to state, that at that time, one forward block at a certain temperature as measured in the forward unverse, faces a backward block at the same temperature as measured in the backward universe. (The non-mentioned pair, in the "other" side of the window that cannot be seen from this view, can be assumed to be in the same state). Then we would analize, given these conditions, what conditions must exist at other times.

Originally Posted by Atomic-S

Some clarification: ... And to state, that at that time, one forward block at a certain temperature as measured in the forward unverse, faces a backward block at the same temperature as measured in the backward universe. (The non-mentioned pair, in the "other" side of the window that cannot be seen from this view, can be assumed to be in the same state). Then we would analize, given these conditions, what conditions must exist at other times.

This is what has me confused...if the both blocks in Universes A & B are at "the same temperature" then I don't see any "thermal equilibrium" taking place. However, if Universe A blocks are of the same temperature and Universe B blocks are of the same temperature (but different than Universe A) then thermal equilibrium can take place. But I think, overall, I understand what you are getting at....

This is what has me confused...if the both blocks in Universes A & B are at "the same temperature" then I don't see any "thermal equilibrium" taking place. However, if Universe A blocks are of the same temperature and Universe B blocks are of the same temperature (but different than Universe A) then thermal equilibrium can take place. But I think, overall, I understand what you are getting at....

The suggestion is worthwhile. I spoke of all the blocks being at the same temperature merely for convenience, but we need not do so. In fact, going with your suggestion that the blocks in the two universes be at different temperature adds a useful new feature to the problem, which we would want to examine eventually.

Thinking further about the problem has led me to the following additional observations: The stipulation that the universes be able to interact in an antiparallel manner through a window that does not open during the beginning of either, and that each universe begin with a "big bang" of very low entropy, could be contradictory. To see why, let us try to examine a simplified version of this problem. This simplified version was made necessary by thinking about exactly how one would attempt to solve the problem, which did not seem to be lending itself to any identifiable method. Then it occurred to me that the problem likely requires detailed tracking, in some sense, of particle motions. That is hard to do unless the problem is simplified.

So to simplify it, I envision simply Universe A being a box having ideally reflective walls, and in the box is a regularly-arranged set of little balls, in contact, and having ideal mechanical properties: all collisions between them are perfectly elastic. Additionally we can envision each ball being surrounded by a perfectly conservative, radial, and attractve force field that acts over a short distance. The exact form of this force need not concern us. The balls are all touching and assembled together in the form of a "crystal". The universe "begins" by the crystal moving as a whole toward one of the vertices of the box. When it reaches the vicinity of the vertex, some of the balls will collide with walls, causing the crystal to break up and the balls start going in various directions. Assuming we avoid an extremely symmetrical starting conditions, the probable further evolution of the system will be one of increasing chaos, until the situation reaches statistical equibrium. Universe B can be envisioned as being likewise constructed (except the exact form of its initial crystal, or the exact direction of its initial velocity, will be assumed to be different, in order to avoid possible mathematical difficulties that could arise out of perfect symmetry). Universe B lies alongside Universe A. The two universes never communicate with each other except during a certain time interval, when the wall that separates them is removed, allowing balls to move from one to the other.

Now to relate this to the previously stated problem, we would specify that at the mid-time of the "open" interval, statistical equilibrium would exist throughout the joined boxes. That approximates the previously stated equality of temperature. Our problem is to figure out, on the basis of these stated conditions, the entire history, in both directions, in both boxes.

The problem will require calculating the paths of every ball. Doing so will involve applying the force law between them, from some known state, and integrating forward or backwards as applicable. We have three known states: The initial state of A, the initial state of B, and the midstate. (Actually the midstate is not fully known, but its statistical properties are). If we start at the beginning of A, we have no problem until A-time reaches the moment of opening (as seen in A) of the window. At that point, balls from B can enter the picture, but we do not know how they move. To find that out, we could calculate from the beginning of B, and that would take up us through when the window opens in Universe B (which is when it closes in Universe A). But we can't go further than that because then A's balls come into the picture, and we do not know how A's balls are moving at the end (as seen in A) of the interval, which is the beginning as seen in B.

Messy problems, however, sometime yield to iteration. What we would do is first solve the problem on the assumption that the window never opened. A and B would evolve independently, and we would calculate the ball motions for each independently. That would give us a first approximation for the motions before, during, and after the time that the window would be open. Then using those, we would go back and calculate , with the window open, the motions from, say, the moment in A when the window first opened, using, now, not only the exact prior motions of A, but also the exact motions in B during the same time (that is, the motions that, in B, appear to follow the window opening, but which actually are contemporaneous with the early history in A). There is, however, one slight problem: if we do this, and carry the calculation forward (in A, backward in B) through the time of the open window, the previous calculations, based upon the window being closed during that interval, would appear to be grossly different. Carrying the open-window calculations further, all the way to the beginning of B, would seem to be likely to yield a result utterly at odds with the initial statement concerning the origin of B. And, given the nature of the process, the new conclusion concerning the beginning of B would be, that B would be in a state of complete chaos at its beginnining.

Similarly, we reach the same conclusions concerning the beginning of A: that it too would have to be in complete chaos.

Thus, it would appear that if there exists an interval of interaction between the universes, then neither universe can begin in an orderly state. And therefore if they do begin in an orderly state, then a window between them, linking them in an antiparallel manner, can never exist.

But the problem with that is, the properties of the defined sets seem to clearly be compatible with both an orderly beginning to each, and also an antiparallel linkage.

I can only conclude that something is yet missing in the analysis, although I do not yet know what.

Originally Posted by Atomic-S

Thinking further about the problem has led me to the following additional observations: The stipulation that the universes be able to interact in an antiparallel manner through a window that does not open during the beginning of either, and that each universe begin with a "big bang" of very low entropy, could be contradictory. To see why, let us try to examine a simplified version of this problem. This simplified version was made necessary by thinking about exactly how one would attempt to solve the problem, which did not seem to be lending itself to any identifiable method. Then it occurred to me that the problem likely requires detailed tracking, in some sense, of particle motions. That is hard to do unless the problem is simplified.

So to simplify it, I envision simply Universe A being a box having ideally reflective walls, and in the box is a regularly-arranged set of little balls, in contact, and having ideal mechanical properties: all collisions between them are perfectly elastic. Additionally we can envision each ball being surrounded by a perfectly conservative, radial, and attractve force field that acts over a short distance. The exact form of this force need not concern us. The balls are all touching and assembled together in the form of a "crystal". The universe "begins" by the crystal moving as a whole toward one of the vertices of the box. When it reaches the vicinity of the vertex, some of the balls will collide with walls, causing the crystal to break up and the balls start going in various directions. Assuming we avoid an extremely symmetrical starting conditions, the probable further evolution of the system will be one of increasing chaos, until the situation reaches statistical equibrium. Universe B can be envisioned as being likewise constructed (except the exact form of its initial crystal, or the exact direction of its initial velocity, will be assumed to be different, in order to avoid possible mathematical difficulties that could arise out of perfect symmetry). Universe B lies alongside Universe A. The two universes never communicate with each other except during a certain time interval, when the wall that separates them is removed, allowing balls to move from one to the other.

Now to relate this to the previously stated problem, we would specify that at the mid-time of the "open" interval, statistical equilibrium would exist throughout the joined boxes. That approximates the previously stated equality of temperature. Our problem is to figure out, on the basis of these stated conditions, the entire history, in both directions, in both boxes.

The problem will require calculating the paths of every ball. Doing so will involve applying the force law between them, from some known state, and integrating forward or backwards as applicable. We have three known states: The initial state of A, the initial state of B, and the midstate. (Actually the midstate is not fully known, but its statistical properties are). If we start at the beginning of A, we have no problem until A-time reaches the moment of opening (as seen in A) of the window. At that point, balls from B can enter the picture, but we do not know how they move. To find that out, we could calculate from the beginning of B, and that would take up us through when the window opens in Universe B (which is when it closes in Universe A). But we can't go further than that because then A's balls come into the picture, and we do not know how A's balls are moving at the end (as seen in A) of the interval, which is the beginning as seen in B.

Messy problems, however, sometime yield to iteration. What we would do is first solve the problem on the assumption that the window never opened. A and B would evolve independently, and we would calculate the ball motions for each independently. That would give us a first approximation for the motions before, during, and after the time that the window would be open. Then using those, we would go back and calculate , with the window open, the motions from, say, the moment in A when the window first opened, using, now, not only the exact prior motions of A, but also the exact motions in B during the same time (that is, the motions that, in B, appear to follow the window opening, but which actually are contemporaneous with the early history in A). There is, however, one slight problem: if we do this, and carry the calculation forward (in A, backward in B) through the time of the open window, the previous calculations, based upon the window being closed during that interval, would appear to be grossly different. Carrying the open-window calculations further, all the way to the beginning of B, would seem to be likely to yield a result utterly at odds with the initial statement concerning the origin of B. And, given the nature of the process, the new conclusion concerning the beginning of B would be, that B would be in a state of complete chaos at its beginnining.

Similarly, we reach the same conclusions concerning the beginning of A: that it too would have to be in complete chaos.

Thus, it would appear that if there exists an interval of interaction between the universes, then neither universe can begin in an orderly state. And therefore if they do begin in an orderly state, then a window between them, linking them in an antiparallel manner, can never exist.

But the problem with that is, the properties of the defined sets seem to clearly be compatible with both an orderly beginning to each, and also an antiparallel linkage.

I can only conclude that something is yet missing in the analysis, although I do not yet know what.

I just got back, sorry for the delay. I'll have to ponder this as I also feel something is missing....hmmmm

We could contemplate the problem from the standpoint of Einsteinian world lines. The path of each particle is a world line. viewed this way, the history of a universe starts out with all the world lines parallel until they intersect the boundary, at which point the go off in various directions, becoming more and more tangled. The window poses the challenge of understanding in what way the lines are related in the situation that there can be crossover between the oppositely-oriented bundles during a limited aperture between the universes. If the universes were parallel sewer pipes, with tree roots entering one at a certain point, and the other at a point further down, with the aperture somewhere between, the roots would grow normally towards the aperture; at the aperture, some from one pipe could grow into the other and vice versa, and eventually the situation would be that near the one beginning point there would be a combination of the orignal entry root plus the disorganized strands from the other going back the other way. Translated into the present problem, that would mean that in one universe, there would be not only the orderly beginning of its own particles, but also a haphazard collection of particles from the other universe. The action would appear to be one of the normal growth of the universe's own particles, plus the slow self-reorganization of the particles from the other universe, until the window opend, at which time the particles from the other universe would collect themselves sufficiently to return to their own universe through the window, and that would be the last that would be seen of them in the first universe. The only problem with this interpretation of the problem is that it is inconsistant with a sensible physics; it forces one to conclude that the primary particles (those of the universe in question) act as if the others were not present, and vice versa. In that scenario, however, the others probably can't be seen at all by the first observer. (The conclusion being that, perhaps entropy is decreasing around us all the time in a form of matter that we cannot detect!) The more reasonable view is that the particles can, in fact, interact. (The possibility that the particles from the backward universe are actually antiparticles, supported by the mathematics of quantum mechanics, which say that the reversal of any one dimension of space or time in the applicble equations turns a prticle into an antiparticle, does not alter the basic issue here; matter and antimatter do in fact interact. Also, the difficulty could be removed by supposing that all the particles in the backward universe look like antimatter in that universe, so that they look like matter in the forward universe, and of couse, the matter from the forward universe would look like antimatter in the backward universe.)

If we suppose that the particles of the 2 universes do in fact interact, we are left with knotty problems. Another way to solve them might be to say, yes, the beginnings of both universes is highly ordered, and there is no fundamental distinction between particles belonging to one or the other universe. Thus, each universe is viewed as beginning (including all particles that might be deemed in some sense to belong to the other universe) in an orderly way, although not necessarily ending in an orderly way. The worldline picture of this scenario is one in which a bundle of lines starts out parallel, then becomes increasingly tangled until the aperture is approached, at which point some of the world lines branch across into the other universe, continue on toward its beginning but in the process becoming more closely aligned, until they merge with all that universe's other world lines in a tight bundle. Think of telephone cables: a bunch of wires leaves a wire nut and heads down a conduit. They become tangled as they go. A crossover opening exists, and some of the wires cross over but the others do not. The wires that do head down a second conduit, along with others to yet another wire nut, where they all are neatly connected. Note, however, that the courses of the wires are determined not only by other wires in their immediate vicinity, but also by the fact that some of them at least have been forced into a tight bundle at both connections. The meaning of this as it applies to the motions of particles is that the movement, in some small time interval, of a particle is not affected solely by other particles with which it collides during that time interval, but also by a condition that exists far in its past, and by another condition that exists far in its future, and also by past and future positions of the particles throughout the entire history. This situation implies that an observer would see particles moving in strange ways, being deflected not only by the particles with which it is colliding, but also by forces emanating from invisible events in the past and future. That situation is incompatible with the assumption that the particle motions would be simply those of elastic balls surrounded by a short-range conservative force field.