davidm

If I understand correctly, block spacetime implies that all events and locations, past, present and future, are on equal footing, and that the concept of passing time is an illusion. If this is so, then time is a dimension like space, and my boundaries in it are my birth and my death, just as my physical boundaries in 3D space are defined by the limits of my body.

If true, isn't it meaningless to say that after I die, I will no longer exist? It would be like saying that because I'm not in Boston but in New York, I don't exist anywhere. It's true that I don't exist in 3000 B.C. or 3000 A.D., but I do exist, eternally, between my birth and death.

My inference is that when we die, it logically follows, if block spacetime is correct, that we immediately begin to re-experience our own lives again, from birth. More, if the Many Worlds Interpretation of quantum physics is true, we will experience every conceivable variation of our lives, within its temporal boundaries. After all, if past, present and future are on equal footing, who else could experience my life but me? The concept of eternal oblivion following death seems predicated on the fallacious notion that time passes.

Is there anything obviously wrong with this hypothesis? Is there any conceivable way that it could be made into a proper, testable theory? Thoughts and comments appreciated. dave.

Calzaer

Nifty! Not exactly how I'd want reincarnation to work, but since when has anything gone the way I want it to?

Would also explain deja-vu!

davidm

I think it's only nifty if you've had a good life.

Also, if MWI really is true, and you were to experience all the potential versions of your life, some of them are going to be really, really bad. Others, of course, will be great.

I'd like to see a refutation of the hypothesis, though. It makes sense to me, but it's not the way I'd like things to work, either.

Jesse

What this comes down to is how you think the mind/matter relationship works. You seem to be suggesting that there is no time in the realm of matter, just a fixed block spacetime, but that time really flows in the realm of mind, like each person's consciousness is a spotlight which moves across the worldline of a physical brain, illuminating different states of the brain in succession and thereby creating a succession of experiences. Then you suggest that when the spotlight comes to point in the worldline where the brain dies, it resets back to the beginning of the brain's history and starts all over again. But why should it work this way? Why not have the spotlight move to the start of a totally different brain's history, leading to a kind of subjective reincarnation? (there would probably be no evidence of reincarnation if this were true, assuming memories are physical while the movement of the spotlight has no effects on the physical world) Why not have it reset each night when you go to sleep, so that we are actually each living the same day over and over again a la groundhog day, but just don't realize it because this recurrence has no effect on our memories? What if it just moved around randomly between different states of different brains, as was suggested in Fred Hoyle's story October the First Is Too Late? You would need some kind of "theory of consciousness" or "psychophysical laws" (of the kind suggested by philosopher David Chalmers in The Conscious Mind) to justify any particular claim about how you think the spotlight of consciousness should move.

davidm

Hi, Jesse, thanks for your reply, and the links.

I don't think the spotlight metaphor is quite right. I have in mind a world line of myself starting at my birth and ending at my death. Each successive moment in the time dimension also has three coordinates in the space dimensions. In effect, there are a vast number of versions of me, stretching from birth to death. My later versions differ from my earlier versions in that each retains memories of the states of the earlier versions. Nothing moves, nothing changes, no spotlight; everything perfectly static and eternal, in the sense that my world line "always" exists between birth and death. The spotlight model is not what I have in mind, because I'm proposing that every version of myself on this world line is currently experiencing consciousness at its particular 4D coordinate. The spotlight model suggests that as the light moves, consiousness in earlier versions is somehow "snuffed out" while later versions are waiting to be lit up. This is too much like passing time. I think Julian Barbour proposes something like this but says the model is not quite block spacetime. I'm not sure how it differs. I don't say that this idea must be right, but it seems a reasonable hypothesis to derive from the block spacetime model. What I'm really interested in is what physics can tell us, if anything, about what happens to us after we die. If the above model is reasonable, it seems to follow that "I" exist eternally in all the configurations of my life, moment to moment, between my temporal boundaries of birth and death. It would seem to follow that these experiences must eternally recur from my own standpoint, though that could be a non-sequitor. You are probably right that we need a theory of consciousness to account for this. I do not think there is a supernatural afterlife but I also think the idea of eternal oblivion after we die is incomprehensible and perhaps even incoherent.

Hope this doesn't sound like babble; I'm in a newsroom at 1 a.m. dave

echidna

But without the spotlight how do you generate the perception of “now” ?

What mechanism would cause us to re-experience our lives from the start after death ? Why not simply play it backwards for instance ? Why should there be any repeat performance at all ?

davidm

Echidna,

I'm saying there is a version of me at, say, 8:00 a.m. on April 9, 1988. There is a version right now, in 2003, at this particular time and location, typing this. There's another version on June 20, 2030, if I live that long. Block spacetime models say all these versions are real, on equal footing. The experience of time somehow sweeping forward from the past to the future is illusory.

When I die, what becomes of these and all the other versions of me between my life and my death? Answer: nothing! They are still there, still experiencing their particular 4D slices of reality. They always have been there. Subjectively, though, we perceive time as sweeping forward from the past to the the future.

It's not that my life will "replay," it's that these versions will continue to exist. I'm suggesting that subjectively, after death, I will re-experience all these "nows" just the way I do currently, sweeping forward from past to future, even though this movement is illusory.

Jesse

But without something like the notion of a moving spotlight, the feeling that your consciousness is "sweeping forward from past to future" is just a pure illusion, so the notion of "re-experiencing" anything "after death" would be meaningless. "You" would just be the experience associated with your brainstate at this moment in time, and you should no more see future brainstates as "you" than brainstates in alternate branches of the multiverse (if the many-worlds interpretation is correct). You'd never experience anything besides what you're experiencing right now, even if your memories and anticipation of the future makes it feel like you have and will.

echidna

David, how does block spacetime account for 2003 feeling as though it is “now” ? Neither 1988 nor 2030 have a feeling of “nowness”. If all three moments are equally real, then it would seem that they should all be experienced simultaneously & equivalently. And yet our consciousness perceives all three quite differently. When you answer using temporal language, surely that can only be meaningful in the context of consciousness. Whether or not the three moments are equal, our consciousness does not perceive them as such, hence the spotlight model.

As such, maybe after your consciousness dies, all those MWI versions live on. But the instant your DNA was “born”, your consciousness began to split into other universes & these multiple consciousnesses will evolve different brain structures and brainstates. The brainstate which gave rise to your typing your last post, does not seem linkable to another brainstate which in another “world”, might have taken offence to my post & flamed me as an ignorant troll.

So when you refer to “me” or “you”, we mean the end product up till this point in time, of brain states which we witness in this universe. There is no evidence that another “me” or “you” in another universe has any mental link to the one in this universe. Indeed given the infinite mental states which the MWI implies, the very notion seems practically impossible.

Back in terms of spotlights, when we die it would seem like that spotlight dies out. There doesn’t seem to be a way to re-illuminate that same spotlight back at another point in time or in another world. The unique nature of that particular spotlight is a function of its own history & without that history, it is no longer the same spotlight.

In short, those alternative “me’s” and “you’s” would be no more “me” and “you” than any other person with a different brainstate.

davidm

Let me simplify by first disentangling MWI from this model. The model I have in mind is potentially valid even if there is a single, nonbranching version of "me" from birth to death.

Let's say my worldline consists of only five points:

1 = my birth.
2 = an experience, along with a memory of my birth.
3 = a second experience, along with a memory of the experience at 2, and my birth at 1
4 = A third experience, along with a memory of 3, 2, and 1
5 = My death. Concsiousness extinguished.

Jesse, I am suggesting that, yes, the notion of consciousness sweeping forward from past to future is in fact an illusion. Block spacetime models posit that passing time is an illusion, so how could consciousness, in the absence of passing time, sweep forward along the time axis?

I'm saying that each of the above five points is consciousness; each one is its own spotlight. The contents of the consciousness of each spotlight differ, in that the "later" points (those further along the time dimension) have memories of the contents of the previous points.

If I could somehow step outside of time and space and look at Reality, I would see this five-point worldline engraved somewhere in the fabric of spacetime. It just IS there, in a timeless and static state. The five individual spotlights never go out. They shine on. But when I say they NEVER go out, I mean, of course, they never go out between my temporal boundaries, my birth and death. On the other sides of those boundaries, they do not exist.

But let's say, for the sake of argument, that they could be turned on and off. Say they turned on randomly, so that the sequence of firing were: 3-5-1-4-2. Would it make any difference to "me" as to how "I" perceived passing time? Would my history appear a jumble of mixed-together past and future states? No. If state 3 turned on first, the content of its consciousness IS an experience, together with a memory of state 2 and state 1. So no matter which order the spotlights fired, from the point of "me," time would "seem" to "flow" logically from a fixed past to an unknown future.

Now what happens when I die? Consciousness is extinguished. But is it? Hypothetically observing myself from outside the spacetime manifold, I see that the five point worldline is intact between the boundary conditions of my birth and my death. Who, then, is experiencing these 4D slices of reality? I am! Who else could be? The mental states of the five points are unique from anyone else's; they ARE me. So, between my birth and death boundaries, I never die. I can infer that this five-point world line is subjectively recurring eternally, though of course I will never recall its past iterations, since none of the contents of the consciousness of the five points contain "memories" of the states recurring. (That is to say, I will never have a deja-vu-like sensation of, "I've done exactly this thing before, many times, and now I'm going to do it all over again.")

Echidna, you ask how block spacetime models account for a feeling of "nowness" in 2003, but not in 1989 or in 2030. I have no idea. The alternative, as you suggest, would be to somehow experience all these states "simultaneously." Maybe the evolved human brain can't handle such overwhelming input, so it coarse-grained reality to chop it up into "now" bits that give the illusion of flow. Maybe it's an anthropic coincidence: without the illusion of "now" and flow, human-style consciousness couldn't exist. But so far as I can tell this is just as much a problem for relativity models of the universe, which imply block spacetime in the first place. We know that there is no universal "now" and that subjective nows can can widly out of sync, depending on one's reference frame. So to ask why my "now" is somehow 2003 and not 2030, might be the same as asking why all of us are creatures experiencing 2003 and not, say, 1500 B.C. or 2886 A.D. Maybe the question has no real meaning, or maybe it will take a deeper understanding of physics and consciousness to find an answer. dave.