# timeless quantum immortality

post by Algernoq · 2015-12-06T04:14:17.784Z · score: 2 (9 votes) · LW · GW · Legacy · 52 comments
Summary: The world looks normal despite Quantum Immortality, because the most likely Universe in which you're immortal is one where your immortality doesn't require much luck.

Recap of Quantum Immortality: The Many-Worlds Interpretation of Quantum Mechanics states that every time some event is observed (e.g. a coin flip), the Universe splits into separate universes, one for each possible outcome (e.g. Heads universe and Tails universe), and the conscious observer will find themselves in one of these universes (e.g. either see the coin come up Heads or see it come up Tails) with a likelihood proportional to the number of ways this event can happen (e.g. you'll probably never see a coin land on edge). Quantum Immortality states that my consciousness will follow the path of branchings in which it survives (e.g. if I set up a highly reliable system that will kill me if the coin ever comes up tails, I can flip and flip the coin and I will only ever see it come up heads).

New idea: Let's take a timeless perspective, and ask "what entire life path am I most likely to observe, from the set of all possible life paths?" Quantum Immortality restricts me to observing life paths in which I do not die. Some life paths are more probable than others. It's not clear what this probability is, but simpler life paths seem more likely than others (e.g. I'm more likely to observe a life path that can be described with any of many sets of physical laws and initial conditions, and less likely to observe a life path that requires a unique, complicated description.) I'm most likely to observe a world that follows physical laws all the time, in which many different sets of simple physical laws could create the world I see. I'm less likely to see a world in which I get improbably lucky.

Thus, I expect to live forever but I don't expect to get lucky.

2nd new idea: Let's generalize this timeless perspective across multiple individuals and lifetimes. Zooming out again and looking at the set of all possible evolutionary paths for a lifeform: it's most likely that I'm one of a lifeform that exponentially grows about as rapidly as possible. Over a long time horizon, the most numerous lifeform is the one that has the highest rate of growth. Thus, because I am conscious and Quantum Immortality appears to be correct, there's a good chance that I will spawn huge numbers of conscious immortal beings during my infinitely-long life.

comment by Luke_A_Somers · 2015-12-06T16:08:23.859Z · score: 8 (8 votes) · LW(p) · GW(p)

The Many-Worlds Interpretation of Quantum Mechanics states that every time some event is observed (e.g. a coin flip), the Universe splits into separate universes, one for each possible outcome (e.g. Heads universe and Tails universe), and the conscious observer will find themselves in one of these universes (e.g. either see the coin come up Heads or see it come up Tails) with a likelihood proportional to the number of ways this event can happen (e.g. you'll probably never see a coin land on edge)

This is false and misleading in various ways.

1) in MWI, splitting events are gradual, in the sense that the relevance of one 'world' to another continuously drops from 'high' to 'utterly negligible' without a sharp cutoff. There is a connection to observation, but it's a confusing one that MWI ought to be helping one avoid making.

2) splitting events produce thermodynamically large quantities of worlds.

3) the likelihood is indeed a sum over the various paths, but the coefficients on the paths are complex-valued and span many orders of magnitude. I grant that these details might normally not be relevant for such coarse-grained matters as biology, but if you're going to survive, say, a heavy object smacking into your head at high speed, this is going to be a major issue - all of your survival paths are much smaller than the fatality paths.

4) Nothing is keeping you off of such doomed states, so once you find yourself in one, you're about to get really lucky (or die). Nothing except going timeless, but...

5) You can't both take the timeless perspective and invoke quantum immortality. QI is all about the subjective case, and the timeless perspective requires, among other things, not taking the subjective case.

comment by Algernoq · 2015-12-07T07:52:54.684Z · score: 2 (2 votes) · LW(p) · GW(p)

Thanks for the criticism.

summary: If, hypothetically, I tried to catch a terminal-velocity bowling ball with my face, your theory says I would experience the bowling ball doing nonfatal damage and then stopping just before killing me, and my theory says I would experience changing my mind and getting out of the way of the bowling ball. It looks like our key disagreement is whether Quantum Immortality only operates over short timescales. You say it only acts in an instant, and I say it acts over long time intervals as well.

longer argument: I'm not convinced by your argument yet. Specifically:

1) I agree that two worlds may be very similar or very different or many places in between. However, my consciousness observes exactly one world at once. Do we have a disagreement about reality, or only about word definitions?

2) I agree that splitting events produce massive numbers of worlds (I have no idea how many, but I'm guessing no more than the volume of the Universe divided by the cube of the Planck length). Does this invalidate my argument (that I'll live forever without appearing to get lucky)?

3) I agree that the likelihoods are a sum over various paths whose magnitude ranges from approximately 1 to approximately 0. I also agree with your intuition that if I ended up in a situation with a high-velocity bowling ball partially inside my head then my survival paths are much much less likely than my death paths. However, my argument is that Quantum Immortality works backward in time, if that makes sense. For example, consider all the ways I can walk through a bowling alley -- a 10-minute-long time interval. Quantum Immortality means I will not experience death during that 10 minutes. Looking at all of the different worlds in which I don't die in the bowling alley, it's most probable I'll find myself in one where I walk safely and nothing weird happens, and really really improbable that I'll throw a bowling ball straight up in the air and then try to catch it with my face and then have the bowling ball spontaneously lose its momentum right before impact. This looks like where we disagree. This is clearer in your next point...

4) I'm kept off of those doomed states by Quantum Immortality. I disagree with you here, and I'll make two arguments why...

4a) My conscious experience already averages over large lengths of time relative to quantum processes. The brain runs at about 10Hz. In the time it takes for one neuron to fire, many many quantum processes have time to happen. Since my consciousness only collapses the universal wavefunction once every 1/10th second, I see no problem with looking at the problem as if my consciousness only collapses the universal wavefunction once every 10 minutes, or once every lifetime.

4b) When I look at the real world, it looks like I'm kept away from doomed states. Why was I so ridiculously lucky as to be born in the current era, where human immortality is a possibility for the first time in history? Timeless Quantum Immortality provides an answer: because it's more probable that I'll live forever from the World I experience now, than it would be for me to live forever from most other worlds. Being born an ancient Sumerian or a dolphin would require many more improbable events to get me to immortality. Being born in a post-Singularity culture where immortality already exists would require a more complicated Universe. My existence looks like it's one of the most likely ones of the set of all possible Universes in which I don't die.

4c) I go to sleep (lose consciousness) and wake up again. QI seems to predict that I would never fall asleep, because I stop observing when I'm asleep and so I couldn't observe that instant. Timeless QI has no problem with me falling asleep and then observing I'm alive and awake hours later.

5) QI is all about the timeless perspective because it requires looking at worlds splitting into other worlds from a perspective outside of time. I'm just doing what regular QI is already doing, just on a longer timescale.

comment by Luke_A_Somers · 2015-12-07T23:06:16.750Z · score: 2 (2 votes) · LW(p) · GW(p)

1 - word definitions. This was one of those that was not wrong, but unclear.

2 - another point that was kind of sketchy-looking. It wasn't directly wrong, but it looked overly simplified. You'll see why in a few points.

I'm guessing no more than the volume of the Universe divided by the cube of the Planck length

A better limit would be not more than 2 to the power of that. Hilbert space is very, very large.

3 - this seems to be going out of order.

Quantum Immortality means I will not experience death during that 10 minutes

Regular old Quantum Immortality takes as an axiom that you cannot experience death. If you could, then the whole thing falls to pieces.

As for the universe putting you in a safe place, well then, you are fortunate. How does this argument apply to people who die? Did they not have subjective experiences? What makes them different from you?

4 - the heart of the matter

Since my consciousness only collapses the universal wavefunction once every 1/10th second

This is seriously, majorly wrong, and the reason I complained about point 2. Your brain decoheres a zillion times per second. Your consciousness is far, far, far into the classical regime.

Observing does not cause collapse. Events which cause the wavefunction to split into dynamically separate parts do, and those happen at the same rate in a system regardless of how you cut it.

QI seems to predict that I would never fall asleep

Depends on how you formulate it, doesn't it? Anyway, arguing against regular QI does not argue for your variant.

QI is all about the timeless perspective because it requires looking at worlds splitting into other worlds from a perspective outside of time

That doesn't look like immortality to me. It looks like you dying eventually. You look at the history of your lifeline and it peters out, little by little, sometimes more at once than other times. Those decreases? Those are dying. The only way QI works is if you ignore the parts that died, and the only justification I've seen for doing that is by locking your viewpoint to your subjective experience. That's what allows you to discard any cases where you don't survive. If you're looking from a distance, you see a whole lot of dead you-s out there.

comment by Laszlo · 2015-12-11T11:24:21.004Z · score: 1 (1 votes) · LW(p) · GW(p)

As for the universe putting you in a safe place, well then, you are fortunate. How does this argument apply to people who die? Did they not have subjective experiences? What makes them different from you?

I believe the argument goes that they, too, are immortal... from their own perspective. Your consciousness traces its worldline, taking branches where you stay alive, and theirs does the same, but picking worlds where they stay alive. In other words, you can see them die, and they can see you die, but the consciousness, the qualia of the person who's supposedly dying is not there; it's gone down a different worldline.

I think that the theory is cute and quite seductive, but quite clearly wrong. The problem is, for example, brain damage: does quantum immortality allow you to experience Phineas Gage-type brain damage, or doesn't it?

Also, I've been blackout drunk in college, and if quantum immortality is a thing, it's not clear why my consciousness didn't trace a path through the universes where I wasn't blackout drunk. It was, after all, a loss of self, even if it was only temporary. The arguments QI uses for keeping you alive could be used equally easily to prove that you cannot become blackout drunk.

comment by Luke_A_Somers · 2015-12-11T13:33:57.986Z · score: 0 (0 votes) · LW(p) · GW(p)

I believe the argument goes that they, too, are immortal... from their own perspective.

That was my point. The above QI argument broke that by going timeless and universal.

comment by Algernoq · 2015-12-08T06:56:33.332Z · score: 0 (0 votes) · LW(p) · GW(p)

Thank you again for the thoughtful reply.

Your brain decoheres a zillion times per second. Your consciousness is far, far, far into the classical regime.

Observing does not cause collapse. Events which cause the wavefunction to split into dynamically separate parts do, and those happen at the same rate in a system regardless of how you cut it.

Eh? Observing is the only thing that causes collapse.

I agree that there are constant tiny thermodynamic events that, if observed, could cause decoherences a zillion times a second. But, usually these events are not observed.

Decoherence is me finding out which world I end up in, and this only happens as quickly as I think, once every ~1/10 seconds when I'm awake.

I'm guessing you would say that decoherence is my brain ending up in some world, and this happens every time any entropy-increasing chemical event happens.

How can I experimentally tell the difference between these? It's not obvious because even a high-speed detector requires me to read the readout with my (slow) brain. From my perspective, the detector doesn't collapse any wavefunctions until I look at it. I agree with you that if I looked at another brain I would see that brain decohering / doing thermodynamic stuff all the time. I also agree with you that if I looked at my own brain I would see my own brain doing a bunch of stuff really rapidly. You would say that my brain decoheres as quickly as a detector measures it. I would say that my brain decoheres only as quickly as I notice detector readouts. Until I look at the detector, my brain and the detector are in a superposition of states with different possible detector readouts.

I don't know how to test this.

comment by Luke_A_Somers · 2015-12-08T21:50:24.505Z · score: 4 (4 votes) · LW(p) · GW(p)

That isn't the relationship between decoherence and observation.

Decoherence events are when a quantum system splits into multiple parts that are no longer dynamically accessible to each other. At this point, they are in different worlds.

Observation events have to be decoherence events. Observation has no other role in quantum mechanics other than that in order to observe, you must decohere.

So, whether or not you observe things, you are in some world of dynamically mutually accessible states, and this will evolve into many dynamically inaccessible components with or without your observing it. By the time you've observed anything, it's way too late to get from one to another.

comment by Algernoq · 2015-12-09T09:20:21.891Z · score: 0 (0 votes) · LW(p) · GW(p)

In that case, it seems like Quantum Immortality doesn't work.

And here I thought I was safe. Dammit.

comment by Luke_A_Somers · 2015-12-09T17:15:23.334Z · score: 1 (1 votes) · LW(p) · GW(p)

Well, the nice form you described here doesn't work. The kind of lousy usual form does, with the usual caveats.

comment by Algernoq · 2015-12-11T06:44:34.612Z · score: 0 (0 votes) · LW(p) · GW(p)

I agree provided the many-worlds interpretation is correct, which seems likely.

If the consciousness-causes-collapse interpretation is correct (which seems less likely), then the special form I described might still work. But I can't count on it.

comment by gjm · 2015-12-07T13:44:04.157Z · score: 1 (1 votes) · LW(p) · GW(p)

it's more probable that I'll live forever from the World I experience now

This also explains why you find yourself in a world that has already perfected immortality technology.

... Oh, wait.

[EDITED to add: I see that you sort-of addressed this "... would require a more complicated Universe". But I don't understand that at all. How would it require a more complicated universe?]

comment by Algernoq · 2015-12-11T06:58:26.647Z · score: 0 (0 votes) · LW(p) · GW(p)

It's a flawed argument but if for some reason there was a high complexity penalty to being born in an older Universe then it could be more likely to be born in a younger Universe where immortality technology has not quite been invented yet.

comment by OrphanWilde · 2015-12-11T14:16:43.208Z · score: 0 (0 votes) · LW(p) · GW(p)

my consciousness observes exactly one world at once.

How sure of that are you, anyways?

comment by mwengler · 2015-12-09T16:01:53.344Z · score: 0 (0 votes) · LW(p) · GW(p)

If, hypothetically, I tried to catch a terminal-velocity bowling ball with my face, your theory says I would experience the bowling ball doing nonfatal damage and then stopping just before killing me, and my theory says I would experience changing my mind and getting out of the way of the bowling ball.

So from the perspective of a you that I can talk to after the near miss with the bowling ball, your description makes sense. But it also makes sense to me. We are both in the universe where you changed your mind before the bowling ball hit you and you got out of the way.

But from the perspective of me in the world where you got hit by the bowling ball and died in pain, your consciousness did whatever consciousnesses do when people die. Presumably it felt the fear when it noticed he inevitability, felt the impact and then the pain, and then stopped working as the neurons in the brain stopped working, some from immediate injury, others more slowly form loss of viable environment.

The worlds in which people die exist. I am in a world where billions, of people have died. A small number I have seen die with my own eyes, a larger number I have seen soon after they died, a much larger number I know of by reliable report.

This immortality you speak of: if there are identical twins and a the age of 5 they are crossing the street and one is hit by a bus,has not some individual died? If you live in a world with MWI, and at the age of 5 for one conscious version of you the universe splits, and in one of those branches EVERY new universe generated ends in your death at a finite age at least 20 years later, while in the other branch there are some branches where you go on forever, than have there not been at least one conscious version of you which will last 20 or more years, but not infinitely, that will die?

This idea that your consciousness jumps from the dying world to somehow mystically join with the version of you in a different world is anti-intuitive at best, and non-scientific or religious at worst. Nothing else jumps between worlds once they have split, why would consciousness? There is already a consciousness in the world you want to jump to with different experiences than yours as you face your last seconds of life, how is there room for your consciousness to pop on over to the other universe to escape death?

Your theory strikes me as the opposite of timeless. Your theory seems to come down to, if I ask my 10,000 year old self about the worlds, I am always going to get an answer in which I lived at least 10,000 years. But if you ask your 20 year old self about the world, then almost all the answers you get are going to be about worlds in which you live less than 100 years, I say that based on the observation that the people other tyan you that you see, way over 99% of them are dying before age 100.

A QI belief in infinite life seems indistinguishable from any other regligious belief in infinite life, at least in regards to conformity with evidence, logical plausibility, and some amount of wishful thinking.

comment by Algernoq · 2015-12-11T07:02:00.930Z · score: 0 (0 votes) · LW(p) · GW(p)

I don't know if anyone else is conscious, but if they are, and they die in my branch of reality, then in my theory they experience a branch of reality in which they continue living.

seems indistinguishable from any other regligious belief in infinite life

I agree it's pretty similar. I have to accept the consciousness-causes-collapse interpretation, and it's a short hop from that to full-on theism.

comment by Viliam · 2015-12-07T17:24:33.095Z · score: 0 (0 votes) · LW(p) · GW(p)

my consciousness observes exactly one world at once

On macroscopic scale, yes. Trying to observe a particle in the double-slit experiment could change your mind (you might realize you are observing an interaction of multiple worlds, differing only in the trajectory of the observed particle). This is probably irrelevant for everyday life, but using the word "quantum" reminds people that it's at least technically not true.

It could possibly become more relevant in a very far future, approaching the heat death of the universe, if we take the immortality literally.

my argument is that Quantum Immortality works backward in time, if that makes sense.

Seems to me like an example of selection bias. Some of your future you's will die, and the rest of them will happily exclaim: "I knew I was immortal!" The question is whether this is a "correct" way to describe reality (and what specifically "correct" means in this context).

comment by Algernoq · 2015-12-11T07:20:20.545Z · score: 0 (0 votes) · LW(p) · GW(p)

The "Wigner's Friend" experiment has some interesting examples that physicists already thought about.

whether this is a "correct" way to describe reality

I'll find out in about 100 years.

comment by gjm · 2015-12-11T11:18:13.822Z · score: 0 (0 votes) · LW(p) · GW(p)

If you commit to flipping coins and shooting yourself dead as soon as you get a tail, you will also (in the same sense) "find out" that your coin has an astonishingly large bias towards heads. Are you sure this is a good notion of "finding out"?

(This is just the same point as Viliam's last paragraph was making, but it seemed worth trying it from a different angle.)

comment by Gurkenglas · 2015-12-06T10:11:02.580Z · score: 5 (5 votes) · LW(p) · GW(p)

Corollaries: You expect to never try to exploit QI, because most of the anthropic weight ends up in the timelines where you didn't try to. If you are the sort of person who would try to exploit it regardless of this argument, you're likely never to come into the position to do so - for example, you, or the population of your Earth, might never think of it. If your Earth has thought of it, that is bayesian evidence QI doesn't work in the first place. (So is your being the sort of person that would exploit it.) Yay for newcomblike problems.

comment by solipsist · 2015-12-07T05:49:07.301Z · score: 1 (1 votes) · LW(p) · GW(p)

I set up an experiment to test quantum anthropics.

Flip four quantum coins. If they all came up heads, stop. If any of them came up tails, flip 5 more coins and (using mnemonics) think really hard about the exact coin flip sequence. If I find myself in a universe where first four coins came up all heads, then with p < 0.0625, quantum weirdness kept me from finding myself in one of the universes the state of my consciousness split me 512-ways.

I got access to a quantum random number generator, resolved to do the experiment, called a friend and told them I was about to do the experiment, and... chickened out and didn't do the experiment.

I do not know how to interpret these results :-/

comment by Algernoq · 2015-12-07T08:20:22.187Z · score: 2 (2 votes) · LW(p) · GW(p)

I love this forum.

If I understand the experiment, your theory is that quantum weirdness makes it more likely to see four heads in a row because you resolved to flip many more coins if you don't.

Sounds fun. I'll flip four coins (actually use a string of 0's and 1's that's 4 bits long). If I don't get four heads, I'll generate a 10-digit sequence and memorize it. Let's explore this frontier!

I did it. It didn't work. My new favorite number is 1 1 0 0 0 0 0 0 0 1.

Reality hack failed.

Let's try again. If I don't get 4 heads, I'll memorize a 20-digit number.

It didn't work. My other new favorite number is 1 0 1 1 0 1 0 0 0 0 1 1 0 1 1 1 1 1 1 1.

I wonder if there's a better way to test this theory.

comment by solipsist · 2015-12-07T15:30:04.370Z · score: 0 (0 votes) · LW(p) · GW(p)

I'm not sure if coin flips are quantumly random, or just hard enough to predict. Feels like coins would still work as well in a Newtonian universe. I tried to go with something that something that is clearly caused by quantum effects, like measuring if electron is either polarized up or down or down. Luckily, there's an app for that.

comment by Lumifer · 2015-12-07T15:40:41.268Z · score: 1 (1 votes) · LW(p) · GW(p)

I don't see any reason for physical coin flips to be provide quantum randomness. This is a better source.

comment by gjm · 2015-12-07T16:42:07.605Z · score: 0 (2 votes) · LW(p) · GW(p)

There are plenty of processes in Newtonian mechanics that amplify small differences. (E.g., in a game of snooker or billiards, it doesn't take many bounces before quantum fluctuations have a substantial effect on where the ball goes.)

Coin flips in particular aren't great, though. A skilled coin-flipper can, I think, get any result they want with close to 100% reliability, which suggests that at least some superficially-plausible-looking kinds of coin flip don't amplify small differences enough.

comment by Lumifer · 2015-12-07T18:41:26.725Z · score: 1 (1 votes) · LW(p) · GW(p)

E.g., in a game of snooker or billiards, it doesn't take many bounces before quantum fluctuations have a substantial effect on where the ball goes.

That's not obvious to me. Evidence..?

E.g. the three-body problem is unsolvable in classical mechanics, without the need to postulate quantum anything.

comment by gjm · 2015-12-07T21:14:23.222Z · score: 1 (1 votes) · LW(p) · GW(p)

That's not obvious to me.

It wasn't intended to be obvious, merely true. But (1) I'm merely repeating something I heard from someone I thought credible, so it might turn out to be wrong, and (2) as I recall, "not many" is still rather more than one ever sees in practice in actual games.

So, is it right? I can't readily find anything on the web where the calculations are done, and I'm too lazy to do them properly myself. What I can find is a good look at a related problem, which gets us at least part of the way.

So, the (excellent) book "The SIAM 100-digit challenge" by Bornemann et al provides solutions to ten problems of the following form. "Here is a mathematical question whose answer is a number. Find the number to at least 10 significant figures". One of the problems, whose proximity to the billiards question should be clear enough, is as follows. Put a perfect circular mirror of radius 1/3 around every (integer,integer) point in the plane. Fire off a photon starting at (1/2,1/10) with velocity (1,0). Where is it after 10 units of time? The answer isn't particularly important, but it turns out that (1) in that time it bounces 17 times and (2) the growth of any initial error is about a factor of 10^11. That suggests about a factor of 4 per bounce.

So, the next question is what quantum effects do to the initial trajectory of a snooker/billiard ball. The following is surely not the best way to answer that question, and I suspect it yields a considerable underestimate, but let's see. Consider the first bounce. A change in either the position or the momentum of the ball will alter the angle it bounces at; for balls of mass m and radius r moving at speed v, a change in position by dx will change the angle by something of order dx/r, and a change in momentum by dp will change the angle by something of order dp/(mv). So the angle uncertainty has to be at least something of the order hbar/(mvr), which is probably somewhere around 2x10^-31 radians.

So if a "substantial effect" means, say, 0.1 radians, that means ... actually somewhere around 50 bounces, which is distinctly more than the number I thought I remembered. So maybe the bit of folklore I heard was wrong; or maybe I misunderstood or misremembered it; or maybe a better estimate of the effects of quantum phenomena on a billiard ball gives a much larger value.

the three-body problem

... doesn't have a closed-form solution in classical mechanics, but that's an entirely separate question from whether it amplifies small quantum effects enough to be useful for generating usable quantum randomness. (I think the answer to that depends on the details, but in any case gravity is weak enough that any 3-body system you make is going to be made up of massive objects moving on rather long timescales; it'll be much less practical as a quantum randomness amplifier than a system of bouncing billiard balls. Of course both are ridiculous choices anyway.)

comment by Gurkenglas · 2015-12-13T12:47:15.095Z · score: -1 (1 votes) · LW(p) · GW(p)

Here's how I predict your setup to work, and shame on you for chickening out:

http://sketchtoy.com/66313589

You start doing the experiment, you flip four coins, 15/16 of you memorize a sequence, 15*32 of you memorized pairwise probably different sequences. In the end, you have a probability of 15/16 to find yourself having memorized a sequence. If QI works and half of you who find a tails in a first four coins commit suicide, start-experiment-you only has a 15/17 chance to find themselves having found tails and failed to kill themselves.

comment by solipsist · 2015-12-13T15:27:01.467Z · score: 0 (0 votes) · LW(p) · GW(p)

What do you mean by "commit suicide" here? Memorize the results of 5 more coins?

comment by Gurkenglas · 2015-12-13T15:36:21.362Z · score: 1 (1 votes) · LW(p) · GW(p)

No, that would do nothing to the anthropic weights of each subtree. I meant ending your life as part of the thought experiment. Why would memorizing numbers do anything special?

comment by cousin_it · 2015-12-11T16:33:28.609Z · score: 3 (4 votes) · LW(p) · GW(p)

I've kind of switched to the view that I'm an observer-moment (OM) rather than an observer. There could be a giant probability distribution over all OMs that's based on complexity or something else, I don't claim to understand it.

Since some OMs remember being other OMs, we imagine a single thread of continuity pointing backward. (If minds could merge, we'd get creatures that remember being both Alice and Bob, so their past would look more like a tree, but we don't have the right technology yet.) Since we are also inductive learners, we imagine that continuity points forward as well. Since that seems to contradict physics, we compromise and say "okay, I have multiple actual futures, but there's gotta be a probability distribution over the next OM".

But I don't see why such a distribution must exist! At most, you have a distribution over OMs that have an (imperfect, possibly false) memory of being your current OM. You could call it immortality, but I'm not sure that's the right way to think.

Wow, that was a mouthful. Hope that makes sense to anyone else...

comment by RichardKennaway · 2015-12-14T13:26:07.421Z · score: 0 (0 votes) · LW(p) · GW(p)

The continuing identity of a person seems to me the same sort of thing as the continuing identity of a physical object, and not particularly problematic. The paradox of Theseus' ship is as easily dissolved as that of unheard falling trees.

I have a day-to-day continuity that I do not have with any part of anyone else since I was born, in just the same way that the chair I am sitting on does not have any continuity with any other chair more recently than when it was assembled on a production line.

To ask whether a person who has undergone a massive change of personality or mental capacity is the "same" person is like asking whether a wrecked car is the "same" car as it was before it was wrecked. To ask whether a person still exists when they are asleep is like asking whether a performance car is still a performance car while it is sitting in the garage.

comment by MrMind · 2015-12-14T11:30:23.247Z · score: 0 (0 votes) · LW(p) · GW(p)

Since some OMs remember being other OMs, we imagine a single thread of continuity pointing backward.

I have a problem with the word 'imagine' here. Let's say that an OM is composed of the space-time slice roughly one second long and the volume of your brain wide. In this interval, the OM accesses neurons that store some particular memories, those of past OMs.
Why that happens? Unless you are a Boltzmann brain, it's because the state of those neurons has been causally originated from the state of the world in the past where there was another OM very 'near'.
Now the problem is that, having already identified myself with an OM, I could very well imagine of having been that OM who originated the state of my neurons, or the past OM of Britney Spears, whose influence on my neurons is negligible (ehrm... in a proper sense). I feel that calling both those instances with the same word is deleting a very important and cogent information.

comment by gjm · 2015-12-06T10:28:01.417Z · score: 3 (3 votes) · LW(p) · GW(p)

In so far as this argument works (I'm talking here about idea 1) surely what you should be expecting is to live for ever without getting luckier than should be necessary to keep you alive all that time, which might still be outrageously lucky by normal standards.

[EDITED to fix a stupid autocorrect typo -- I had "ask that time" instead of "all that time".]

comment by Algernoq · 2015-12-07T07:55:04.577Z · score: 0 (0 votes) · LW(p) · GW(p)

Counterexample: I go to sleep (lose consciousness) and wake up again. QI seems to predict that I would never fall asleep, because I stop observing when I'm asleep and so QI would force me into universes in which I don't fall asleep. Timeless QI has no problem with me falling asleep and then observing I'm alive and awake hours later.

comment by gjm · 2015-12-07T10:29:47.499Z · score: 2 (2 votes) · LW(p) · GW(p)

I don't think advocates of QI generally mean by it what I think you're taking it to mean.

comment by Algernoq · 2015-12-13T11:51:17.413Z · score: 0 (0 votes) · LW(p) · GW(p)

In terms of conscious experience, dreamless sleep and death feel similar, as far as I know.

comment by ike · 2015-12-06T04:22:28.400Z · score: 3 (3 votes) · LW(p) · GW(p)

You're equivocating between MWi-QI, which entails the same physical laws, and something like Tegmarks MU, which doesn't. You should pick one, or explicitly note when you switch.

comment by Algernoq · 2015-12-06T05:10:25.288Z · score: 1 (3 votes) · LW(p) · GW(p)

This distinction is irrelevant to the main point: I expect to experience living forever without experiencing unusual luck. This is true regardless of whether MWi-QI or Tegmark's MU theory is more accurate.

comment by ike · 2015-12-06T11:25:00.507Z · score: 1 (1 votes) · LW(p) · GW(p)

The specific example is wrong in mere MWI, as is some of the comments here.

If we fix the physical laws as constant, and merely vary over the wave function, it's not clear how "unlucky" worlds are more likely, or what a lucky world would look like. I think you should change the reference from mwi to mu, or else explicitly analyze both.

comment by kilobug · 2015-12-07T08:46:30.752Z · score: 2 (2 votes) · LW(p) · GW(p)

The MWI doesn't necessarily mean that every possible event, however unlikely, "exists". As long as we don't know where the Born rule comes from, we just don't know.

Worlds in MWI aren't discrete and completely isolated from each others, they are more inkstains on paper, not clearly delimited blobs, where "counting the blobs" can't be defined in non ambiguous way. There are hytpothesis (sometimes called "mangled world") that would make worlds of too small probability (inkstains not thick enough) unstable and "contaged" from "nearby" high probability world.

But the main issue is that as long as we don't have a formal derivation of the Born rule inside MWI, we can't make any formal analysis of stuff like QI. We are left with at best semi-intuitive analysis of what "MWI" does mean, but QI being highly counter-intuitive, a semi-intuitive analysis breaks down there.

comment by qmotus · 2015-12-07T14:26:00.963Z · score: 1 (1 votes) · LW(p) · GW(p)

We don't know how to derive the Born Rule in MWI, or even if it is possible to derive it. However, uncertainty goes both ways, and that's definitely no way to dismiss QI. Is there any actual reason to suspect that MWI is true, but QI isn't (apart from, maybe, mangled worlds)?

Because I lack the necessary mathematical understanding, I've never really understood what mangled worlds actually says. What does it mean when you say that a world's probability is "too small", and does mangled worlds say that these worlds never actually come into existence, or just that they eventually disappear?

Also, is there something wrong with Sean Carroll's attempt?

comment by MrMind · 2015-12-09T08:44:53.255Z · score: 0 (0 votes) · LW(p) · GW(p)

Also, is there something wrong with Sean Carroll's attempt?

It works only in a very limited setting. Here's my analysis.

comment by turchin · 2015-12-06T10:58:08.244Z · score: 2 (2 votes) · LW(p) · GW(p)

If you logic is correct, most likely I will find my self in the world there I can be immortal technically. And it is true: I signed for cryonics and strong AI creation is probably inside my life expectance, so I very likely will be immortal in this world.

comment by MrMind · 2015-12-10T09:14:02.274Z · score: 1 (1 votes) · LW(p) · GW(p)

Is this a correct summary of your idea?

"If MWI is true, then all the possibilities in which the universal wave function can split are realized, and there will be branches where I live for a very, very long time.
Out of those branches where I am 'quantum immortal', those where the immortality is due to normal occurences will be much more probable than those where the law of (classical) physics are explicitly violated.
For example, in the branches where I do not die hit by a bowling ball in the head, those where I simply decide not to go bowling are more probable than those where the ball simply stops mid-air or tunnels through my body."

comment by Algernoq · 2015-12-13T11:55:24.054Z · score: 0 (0 votes) · LW(p) · GW(p)

That summarizes the "what" of the idea. The "why" part is that classical physics violations are improbable so timelines with lots of classical physics violations would be improbable.

comment by MrMind · 2015-12-15T08:23:07.071Z · score: 1 (1 votes) · LW(p) · GW(p)

Well, it falls under the very known problem of any MWI: how can we say that some branch is improbable if all are realized?
Unless you reverse it: a branch is more improbable the more it violates classical mechanics.

comment by qmotus · 2015-12-07T10:30:13.891Z · score: 0 (2 votes) · LW(p) · GW(p)

I really hope someone will do some serious philosophy about Quantum Immortality soon. The only thing I've seen is an article (a very pessimistic one) about it by David Lewis from about 15 years ago. It just feels way too important to be left to random lesswrongers to speculate on.

comment by Algernoq · 2015-12-13T11:56:53.977Z · score: 0 (0 votes) · LW(p) · GW(p)

The 20th-century physicists speculated a lot about it. Schrodinger's Cat, the Wigner's Friend problem, etc. But in the absence of a test for consciousness they mostly went on to other things.

comment by qmotus · 2015-12-13T12:52:47.565Z · score: 1 (1 votes) · LW(p) · GW(p)

I've never heard that it occurred to any of them (aside from Hugh Everett) that quantum mechanics might imply something like quantum immortality, though.

comment by mwengler · 2015-12-06T16:04:14.595Z · score: 0 (0 votes) · LW(p) · GW(p)

I think your argument is wrong.

If in my young age I am present in zillions of different universes, am I not conscious in each one of these? Am I not just as much a conscious being in the universes in which I die tomorrow, as I am in the universes in which I will die next week, as I am in the universes where I will live for 3000 years?

So what life path are you most likely to observe? You are most likely to "observe" ALL of them. If you were to pick one at random, what is the lifespan of the one you are most likely to pick? You would need to know the distribution of lifespans across timelines to answer that question. There are many distributions where your most likely choice would be a rather short lifespan, and many where it will be one of the very long ones, and probably even some distributions where the most likely one will be an infinite lifespan. But I don't believe you have suggested any way to estimate which case applies to your hypothetical MWI universes.

comment by entirelyuseless · 2015-12-06T16:11:33.176Z · score: 0 (0 votes) · LW(p) · GW(p)

This does not work as a response. Sure, you will observe all of them. But at no moment in any of those lives, will you be dead, and you will be sick and dying at relatively few moments in those lives. So you will rarely observe the situation where you are about to die.

comment by entirelyuseless · 2015-12-06T13:37:24.721Z · score: -1 (3 votes) · LW(p) · GW(p)

Note that if this is true, it is true for everyone who was ever conscious. So a religious person could argue that your argument favors their religion, since their religion implies subjective immortality without luck, whereas without religion someone in the middle ages would have needed a great deal of luck indeed.