Time Travelling Bruce

[cosmicfish]

Originally Posted by mmartin798

You are correct in the BEM does perceive multiple pasts, but not infinite. Only the pasts that are created when he travels back to a previous point in a established worldline. The 1989 war is a case in point.

That was my point - not that he experiences infinite pasts, but rather that he experiences multiple pasts when your proposed multiversal theory claims only one past.

Originally Posted by mmartin798

So BEM only has one past to enter, though he knows there have been different ones.

But what is the mechanism of this? If there is only one "past" at a time, then when he goes backwards in time he creates a new past, so there are multiple, realized "pasts" even if only one appears accessible at a time.

Let's consider time travel between the years 1960, 1980, and 2000. If our intrepid traveler starts in 1980, the years 1960-1980 are that single, fixed past. If they then travel to 2000, all of 1960-2000 are now that single, fixed past. But when they travel back to 1960, any change means replacing all of that 1960-2000 past with some new past. The old past is not probability or theory, it actually existed and must now be replaced by something else that is, again, neither probability nor theory. This goes back to the Energy issue I raised earlier - collapsing probability is potentially a zero-energy issue, but replacing one concrete past with another isn't.

Originally Posted by mmartin798

When he goes into the future, he can only chose between ones that are most likely to happen, not go into ones that are highly unlikely, like the universe where all the world leaders simultaneously disintegrate from a statistical improbability of thermodynamics. It is this limitation that makes it impossible for him to go to a future where his family still exists. If he goes back and tries to stop the 1989 in a different way, he is still not assured that it would bring his family back, or that the Project would have more time to prepare or succeed.

This is the way I have structured time travel for my game and, just to mess with BEM, Krell has a slightly different way to messing with the future for his own ends.

I like the idea of probability influencing what he can do - just as it would take less energy to knock something balanced precariously on a perch than it would to do the same to something entrenched firmly in the ground, it makes sense that whatever energy Bruce gets to use would have the most effect spent in conjunction with "temporal potential" (to coin a term) than opposing it. But I am still not sure how that squares with the fact that the probability curves were already collapsed as soon as he traveled into the future in the first place.

[mmartin798]

Originally Posted by cosmicfish

But what is the mechanism of this? If there is only one "past" at a time, then when he goes backwards in time he creates a new past, so there are multiple, realized "pasts" even if only one appears accessible at a time.

The way to think of this is from BEM's perspective. Let's first make some definitions. Let's let A(0) represent a point on a worldliness where time travel begins and A(t) represent a point on a worldline at time t from A(0).

Originally Posted by cosmicfish

Let's consider time travel between the years 1960, 1980, and 2000. If our intrepid traveler starts in 1980, the years 1960-1980 are that single, fixed past. If they then travel to 2000, all of 1960-2000 are now that single, fixed past.

So if we let A(0) = the year 1980, then A(t<0) is indeed a single, deterministic path. But when our time traveler decides to go to time t, there is no single path. So they choose one from the available worldlines and choose a point, A'(t). The choice is limited by the light cone that extends from any given point A(t). Any worldlines outside the light cone are not accessible. So our traveler is not creating the worldline that contains A'(t), but simply goes to A'(t) which is already on an accessible worldline. Once the traveller arrives at A'(t), it becomes A(0) and again there is just a single deterministic worldline for all A(t<0). So we agree here.

Originally Posted by cosmicfish

But when they travel back to 1960, any change means replacing all of that 1960-2000 past with some new past. The old past is not probability or theory, it actually existed and must now be replaced by something else that is, again, neither probability nor theory.

So now our traveller is going to A(-40). As this is a simple deterministic route, no problem. But now when we reset this to be A(0), the additional information that the time traveller beings back, will change the probability of the worldline and normal time may follow a different path. So we have three worldlines that all exist. The first would be the one that started in 1980 and would have progressed along a worldline, on which "future" events would be on, that we will call A1980(t). The second is the worldline that contains choice the traveler made and all "future" events from that point we can call A'1980(t). The third worldline is the one that will be followed after bringing back the information, A'1960(t).

So we have three worldlines that co-exist, but the people in the worldlines only know about the one they have always been on. Therefore, only BEM knows there have been differences. So quite literally, BEM perception is reality. But because his available choices of worldlines is limited, there is only so much change he can effect. Also, this is what caused him to lose his family. The change in worldline that was introduced when he stopped the 1989 war moved him to a point where his family only exists outside of his lightcone. He has no way to get back to them, unless he goes and stops himself from preventing the 1989 war, but that will put him on yet another worldline and still may not be able to reach them. Who knows, maybe he has tried it many times and just can't get back to them. It's kind of sad. But if we look at this from his family's perspective, he disappeared one day and just never came back.

Most of this heavily draws on work by David Deutsch and presumes a multiverse. Though Deutsch's work has been criticized because even though his models do eliminate things like the Grandfather paradox, it suffers from a knowledge paradox that Deutsch's model cannot solve. But since this is just a game, close counts.

If you are interested, here are some published papers:
http://thelifeofpsi.com/wp-content/u...utsch-1991.pdf
http://www.academia.edu/6059479/The_...of_Time_Travel
https://conjecturesandrefutations.co...f-time-travel/

[mmartin798]

For those not going to read the articles, one the the implications of this form of time travel is that within most of the closed timelike curves (CTCs) created by BEM, there will be more than one BEM. I assume most will be working in concert with each other, but this does leave open the possibility that Krell is BEM from a "different" worldline. Just food for thought.

[tsofian]

Maybe the problem is word infinite. If so let's just remove it and go multiple. In an infinite series of universes all possible outcomes are found an infinite number of times. If there are just a large number of universes then the distribution of outcomes will be distributed by likelihood.