Browsing the forums and some of the links posted there, I have come across two different ideas regarding what could be called "resurrection technologies". I apologize if this topic seems a bit too far-fetched, in the realm of sci-fi, to be posted in the physics sub-forum. I hope it's not. I think of it as "hard sci-fi" I guess, and the theoretical possibility of it or lack thereof as physics issues.
I feel that despite it's "we are so not there yet, and possibly will never be" character, this is an important topic. For one thing, even though it would be beyond unwise to want to bet on such possibilities for ourselves when we have notably cryonics around, for many people that would be the only chance of indefinite longevity. Many of us just won't get lucky enough to get cryopreserved under fair conditions (fire, lost for months in the Andes before getting recovered, etc, etc...). And anyway cryopreservation is out of the question for all the people already, well, no longer present.
The basic idea is to somehow get access to what constitutes a person's mind/consciousness at the moment of their death in order to reconstitute said mind/consciousness at a later time. It is based on the materialist view of mind, the notion that consciousness arises from the functioning of the material brain. Personally, I agree with that, but someone who does not would I think regard this whole topic irrelevant.
I know of only two proposals about how to do this (maybe you know of others?):
1) what I'd call "Time Retrieval", that is using some kind of time machine in order to access what is deemed needed for satisfactory reconstitution. That could be:
- only information; say, where and in what state are each atom in the person's brain
- or matter, probably transferring the atoms themselves from "back then" to "right now". Although I already see some quantum mechanical notions making this last point a bit murky, since elementary particles at least are generally not considered to have their own identity; maybe simply cloning the quantum state of these atoms could be put in this category.
In a very very loose sense, there is already an effort underway to achieve such Time Retrieval, sort of. I don't know how far Ron Mallett, a physicist at the University of Connecticut, has gone with his project but he has proposed a specific scheme for a time machine, Space-time Twisting by Light. His life-long motivation for constructing a time-machine has been to save his father's life, although not by TRing him, rather by travelling to the past himself and warning him against what eventually caused his death (so, by changing the past, which would be yet an entirely different ball-game I think since it would probably require that the universe allows the existence of several "timelines").
Also, Ron Mallett's plan for a time machine, like that suggested by Kip Thorne using a wormhole and moving its mouths in the appropriate manner, can at best give access to the moment the time machine was created. So a plan based on a scheme like that would not help Ron's father, as he realized after he had the initial idea.
The general "time-retrieval" scheme hinges on the nature of time, which we can't do much about. If the so-called "presentist" view is correct, i.e. the view that only the present exists, it can't work. Philosophers of physics still debate about these things so in this sense the jury is out. My impression is that special and general relativity have been tilting the balance against presentism in these debates, that it seems an unlikely proposition at this point. But of course even if the past exists somewhen out then, that still doesn't mean we can find a way to access it.
2) getting the information about the past state, this time by retrodicting it.
To me it seems this requires three ingredients:
- powerful enough computing abilities. I think this is what the "quantum" in the "quantum archeology" scheme comes in, that quantum computing would hopefully give us the ability to do that.
- equations that allow us to retrodict well enough. I can't imagine how "well enough" could fail to mean "exactly" as opposed to statistically. I probably lack imagination, but right now that's where I'm not all that optimistic. If we want to figure out the positions and states of atoms, surely that involves quantum mechanical laws. Those are not exactly famous for being exact in that sense. They are not deterministic when it comes to the future, and no better at retrodicting a past state from the known present one. Now there might be a sliver of hope that this may depend on the interpretation of quantum mechanics considered. Off the bat, the only thing I can think of that might turn out to be of help if it turns out to be correct is the two-state vector idea of Yakir Aharonov and Lev Vaidman - but I don't understand it well enough to say whether even that would help. They give a review of it here. Notice what they say at the end, they don't interpret their work the same way either, Vaidman thinks it provides a picture consistent with the Many World Interpretation, Aharonov has a different view - which I think might imply determinism in the usual, classical sense but again I'm not sure. This impression of mine is why I think if the universe is that way the equations may allow us to retrodict.
- data. To predict things, we need initial data. To retrodict, we would surely need "final" data, wouldn't we?? If the aim is to find out the state and positions of atoms in a specific part of space on say January 17th 50 BC at 3:02:57:94 etc... time of Rome, those have encountered lots of interactions with other atoms, photons, etc... in the meantime. We would need to find the states "now" of all those, and those they interacted with, and those those interacted with etc... It basically seems to me we'd need the states of all the atoms and relevant particles in some choice of "now" ("now" is not a well-defined notion per se in relativity, it depends on how you move) whose boundaries in space would correspond to the intersection of this "now" with the light cone starting from "back then". If so... gulp. I'd be somewhat tempted to err on the pessimistic side at that point.
Now I don't think that is quite what the scheme known as "Quantum Archeology", which involves retro-diction, has in mind. I've browsed through passed threads and it seems to me that people have very different schemes in mind when they discuss the topic. I think they are all interesting to consider in their own right, but I'm just all the more confused regarding QA per se. From what I've read there, I don't think either that it is quite the same idea as that described in novels such as Dan Simmons' Hyperion (I think Asimov came up with the idea first but I can't remember?) of a rough simulation of the person, using information gleaned from historical sources.
Is the idea of QA to somehow not retrodict at the level of atoms and subparticles, and instead based on the notion that we do not need to do that, that the information we need can be retrodicted well enough from a more macroscopic level, (perhaps thanks to emergence?)?
There seems to have been some nice links posted before on this site, that seemed to provide a nice introduction to the "quantum archeology" scheme for newbies. Unfortunately they are broken. Does anyone know of clear, if possible concise explanations of how the idea would work?
