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[Radish]

man sits down before a gun, which is pointed at his head. This is no ordinary gun; it's rigged to a machine that measures the spin of a quantum particle. Each time the trigger is pulled, the spin of the quantum particle -- or quark -- is measured. Depending on the measurement, the gun will either fire, or it won't. If the quantum particle is measured as spinning in a clockwise motion, the gun will fire. If the quark is spinning counterclockwise, the gun won't go off. There'll only be a click.Nervously, the man takes a breath and pulls the trigger. The gun clicks. He pulls the trigger again. Click. And again: click. The man will continue to pull the trigger again and again with the same result: The gun won't fire. Although it's functioning properly and loaded with bullets, no matter how many times he pulls the trigger, the gun will never fire. He'll continue this process for eternity, becoming immortal.

Go back in time to the beginning of the experiment. The man pulls the trigger for the very first time, and the quark is measured as spinning clockwise. The gun fires. The man is dead.

But, wait. The man already pulled the trigger the first time -- and an infinite amount of times following that -- and we already know the gun didn't fire. How can the man be dead? The man is unaware, but he's both alive and dead. Each time he pulls the trigger, the universe is split in two. It will continue to split, again and again, each time the trigger is pulled his thought experiment is called quantum suicide. It was first posed by then-Princeton University theorist Max Tegmark in 1997 (now on faculty at MIT). A thought experiment is an experiment that takes place only in the mind. The quantum level is the smallest level of matter we've detected so far in the universe. Matter on this level is infinitesimal, and it's virtually impossible for scientists to research it in a practical manner using traditional methods of scientific inquiry.


Do you agree with this theory?

[Radish]

What this is saying is that there is an endless amount of alternate universes and that each time he pulls  the trigger a different result plays out on a different universe.

[plustax]

While I certainly think it's an interesting theory, I don't see how it's feasible.Where would the matter of this entire second universe come from?

[Radish]

well it's going back to the two worlds theory which says


The quantum suicide thought experiment is based on and seeks to prove what has become an increasingly accepted interpretation of quantum physics, the Many-Worlds theory. This theory was first proposed in 1957 by a doctoral student at Princeton University named Hugh Everett III. The theory was scorned for decades until fellow Princetonian Max Tegman created the quantum suicide experiment, which lends support to the interpretation According to the Many-Worlds theory, for each possible outcome to an action, the world splits into a copy of itself. This is an instantaneous process Everett called decohesion. It's kind of like a choose-your-own-adventure book, but rather than choosing between either exploring the cave or making off with the treasure, the universe splits in two so that each action is taken.

One vital aspect of the Many-Worlds theory is that when the universe splits, the person is unaware of himself in the other version of the universe. This means that the boy who made off with the treasure and ends up living happily ever after is completely unaware of the version of himself who entered the cave and now faces great peril, and vice versa.

This is the same case with quantum suicide. When the man pulls the trigger, there are two possible outcomes: the gun either fires or it doesn't. In this case, the man either lives or he dies. Each time the trigger is pulled, the universe splits to accommodate each possible outcome. When the man dies, the universe is no longer able to split based on the pulling of the trigger. The possible outcome for death is reduced to one: continued death. But with life there are still two chances that remain: The man continues living or the man dies. When the man pulls the trigger and the universe is split in two, however, the version of the man who lived will be unaware that in the other version of the split universe, he has died. Instead he will continue to live and will again have the chance to pull the trigger. And each time he does pull the trigger, the universe will again split, with the version of the man who lives continuing on, and being unaware of all of his deaths in parallel universes. In this sense, he will be able to exist indefinitely. This is called quantum immortality.

So why aren't all of the people who have ever attempted to kill themselves immortal? What's interesting about the Many-Worlds interpretation is that according to the theory, in some parallel universe, they are. This doesn't appear to be the case to us, because the splitting of the universe isn't dependent on our own life or death. We are bystanders or observers in the case of another person's suicide, and as observers we're subject to probability. When the gun finally went off in the universe -- or version -- we inhabit, we were stuck with that result. Even if we pick up the gun and continue shooting the man, the universe will remain in a single state. After all, once a person is dead, the number of possible outcomes for shooting a dead person is reduced to one.

But the Many-Worlds theory stands in contradiction to another quantum theory, the Copenhagen interpretation. In the next section, we'll look at this theory and see why it changes the rules of quantum suicide.

[Uberstache]

Interesting, but you can't really prove anything with a thought experiment. The Greeks had a perfectly acceptable, if complex series of mathematics to prove that the universe was composed of hollow celestial spheres.

[TheMan]

I think it's important to note that int he original thought experiment, the man isn't immortal, but will eventually die in all possible universes unless there's a possible universe where he is actually immortal and wouldn't die even if the gun did go off anyway.

[SJZexpat]

If I may ask, what exactly is your question?

All I get right now is that you're posting stuff that you cut-and-pasted directly from here without attribution, and then asking what others think.  But, as of right now, I don't know what your thoughts are on the matter, and I almost thought that the long, dry explanations given were your own work.

But there was too much punctuation for that to be true, and the voice sounded a bit off.

Do I believe in this theory?  Sure, I guess it's possible. But given all the variables that could go one way or another at any given point in time, I don't know how that would work or how we could ever test anything like this.

It's also been the fodder for countless episodes of a  variety of sci-fi theories, which is where, I imagine, most folks picked it up from.

Where exactly do you stand on it, Radish?  Can you speak on it without quoting others?

[Rambo]

Hows this science thing work nowadays? I thought to be a valid theory it had to be in some way falsifiable. It sounds like to me you could run this test a million times and if the gun fires you're in a universe where it fired and if it didn't well I guess we're in a universe where it did. Its not really a very good theory if theres no way to test it.

[cheesemonster]

Is this like the Shrodinger's cat question?  There is a cat in a box and it is either alive or dead, but until you find out which, both possibilities exist?

[Ross]

It's not quite the same as we know the answer to that question. The cat is both alive and dead until it's been observed.

The many worlds theory is a way to reconcile the randomness that is related to the Schrödinger's cat problem. A lot of people, myself included, don't like the idea that a particle's state is unpredictably random, when measured. If the electron's spin is up, I feel like there should be a reason that it isn't down. With the many worlds theory, the reason the spin isn't down is because it is down, in another universe.

I'm mentally satisfied thinking that this is the way things are. Unfortunately, there's no way to tell if it's true or not.

[SJZexpat]

Correct me if I'm wrong, but wasn't there a case about 10 years back or so where a subatomic particle existed in two places for a split second?

Does anyone else remember this?

I thought I'd read it in Scientific American.  There was blurb about there being equal probabilities of the particle going in one direction or another after being fired or accelerated toward something that would force it to break one way or the other. And for a fraction of a second there were two particles until it resolved into one.

Does that ring a bell for anyone else?

[Captain Jack Ellingsworth]

So why aren't all of the people who have ever attempted to kill themselves immortal? What's interesting about the Many-Worlds interpretation is that according to the theory, in some parallel universe, they are. This doesn't appear to be the case to us, because the splitting of the universe isn't dependent on our own life or death. We are bystanders or observers in the case of another person's suicide, and as observers we're subject to probability. When the gun finally went off in the universe -- or version -- we inhabit, we were stuck with that result. Even if we pick up the gun and continue shooting the man, the universe will remain in a single state. After all, once a person is dead, the number of possible outcomes for shooting a dead person is reduced to one.

This may be nitpicking, but it would seem that by this theory, continuing to shoot a dead person WOULD create new universes; ones in which the person had only been shot once, had been shot twice, and so on.

I don't mean that to be facetious, and I don't give this theory any support, but it seems arrogant of human life to assume that universes would only be created whenever it hinges on a person being brought closer to or further from death.

I'm relatively sure that wasn't the intent of what you said, but I would think that if we assume the basic premise of this theory is true, then continuing to shoot the person would create new universes, as would performing or not performing any action. That is to say, there would always be another universe where you hadn't performed that action, or had, or had performed it differently, or had performed it while sporting a full-on mohawk. I would think this to be true even if that thing had no major effect on that universe (such as shooting a dead man doesn't make him more dead) and that as long as there was a possibility for any sort of difference at all, there would be an alternate universe where that difference had occured.

Obviously, that last one regarding the mohawk is a silly example, but I think that by the theory, it is a valid one. Do I understand the theory incorrectly?

I'm not intending to belittle it or promote it, I'm merely curious.

[Rambo]

I believe the point of the thought experiment is not that life is the important part. I mean, you could perform the same action where its a balloon instead of a human head. What makes the thought experiment interesting is that if this is right theoretically this means there is a universe where you are immortal. I think... Maybe I'm missing the point myself.

[Captain Jack Ellingsworth]

But from what I understand, it does not even matter whether it is a balloon or a head, or if there is even a gun!

There are theoretically an infinite number of universes in each of which a different possibility is realized.

It is not even relevant that he has a gun. Merely existing and being alive gives him the possibility of always being alive, if he should happen to be in that universe where he never dies.

Is this accurate if the theory is assumed to be valid?

[Rambo]

Yes. I think the whole situation was just to show an odd quirk of quantum theory (were it true) where someone could be immortal. If the multiple worlds theory is correct every time a particle moves there is another universe where it took an infinite number of different paths.

[Captain Jack Ellingsworth]

So is there any reason to believe this theory to be accurate or anything this is based on other than a scientist or philosopher lounging around the house one Sunday afternoon and thinking, "Man, it would be sweet if I had a mustache. Or a pet rabbit.", or a kid saying "I want strawberry ice cream, but I also want vanilla. But I can't have both... Or can I?"

That question is perhaps worded a little too absurdly for HB, but what I mean is, is there honestly any reason to support this theory?

[Rambo]

Well... theres an entire field devoted to quantum theory. And some evidence to back it up, though its mostly... anecdotal? I dont really know what word to put. Theres like observational evidence of what it predicts and so far its been eerily spot on, but with the tools available to us theres no way to actually test it.

For instance this was what a poster higher up was talking about, 1 photon existed in 2 places and interfered with itself, and now they're doing further testing of what quantum theory predicts.

[Ross]

The only reason to support Many Worlds is that it sounds nice and provides a tidy solution. There's no hard evidence. Alternatively, quantum theory has lots of hard evidence.

Regarding the point of the thought experiment:

*Contains spoilers for the movie The Prestige*
The immortality is unimportant. Every time the subject pulls the trigger, it creates a universe where they shoot themselves. The subject is bizarrely able to kill themselves over and over and over again. Just like in the Prestige where the magician drowns his clone over and over again. This creepy idea is the point of the experiment.

[Rambo]

Can you expand on the hard evidence? I was under the belief that quantum theory couldn't be directly tested, we could only test its predictions.

[Captain Jack Ellingsworth]

Didn't he say there was no hard evidence?