h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Entry: Parallel Universes: A Beginner's Guide to Proving Their Existence (with the Added Bonus of Immortality) - A2528444
Author: Baryonic Being - U234603

This could conceivably be considered a controversial submission. I must stress that the concept presented in the entry is as grounded in scientific fact as any other entry in the Edited Guide, even it sounds somewhat different.

I should warn the reader that the article is also largely concerned with death, and I could not avoid but use arguably violent references to death in a fairly liberal fashion, so please give your opinion on this.

I am also in doubt about my use of the words 'we' and 'you' in the entry. As far as I am concerned they simply serve the purpose of addressing the reader directly to make them feel involved, and to give a friendlier atmosphere, so I trust they are not in violation of the Writing Guidelines.

I have also used a direct quote of a physicist within the entry. I presume that since I have cited it as a direct quote it is within my right to use it as evidence and it does not breach the copyright of the book I found the quote in?

Could you also give your opinion on the title of the entry. I have found it difficult to think of a suitable name.

Thank you very much.

And again, as with my entry on kaons, axions, J/psi, sigma and xi particles, I have in fact copied a section from my Hyperons entry directly into this one for purposes of giving background explanations on the concepts referred to.

Hi BB,

Actually I think this is a really well written article deserving of the Edited Guide, since it is based on good scientific principles. It may not be true of course, but the fact that it is an active theory under discussion by scientists makes it a very good entry for the guide. Surely Schroedinger's Cat must also deserve an entry here somewhere?

All in all I liked it. It reads very well - almost like a detective story, with some very nice touches of humour thrown in. It also works well on the level of explaining very serious science to non-scientists.

I see another assumption that isn't mentioned that maybe you can explain. There could of course be multiple parallel universes where in one, I am sitting here typing at a computer. In another, I am watching TV, and in another I am married to Julia Roberts. Ok. All of those "me"s are consious, presumably, completely oblivious to each other and having a great life. Why does Tegmark make the assumption that your death enables another, or the only available, universe of consciousness to open automatically? I'm a bit confused about this. It seems as if death is still a reality in the quantum world, so why would the world make exceptions in this single case?

I also have a small quibble with the word "immortality" - you are not proving immortality in general, just immortality in a specific case. If the researcher, after having tried the experiment 10 times walked out of the room and smashed straight into an oncoming car, this would disprove his experiment. Also, you could theorise that he keeps going for 90 years, attempting millions of experiments, all the time trying to kill himself, that sooner or later he would die of necrotising fascitis, or pulmonary oedema or something even worse, thus proving that even he was not immortal. Its only a small quibble though (in another universe I am conceivably not even writing this paragraph), so reject it or accept it as you see fit. (I will be comforted that, in at least one universe, you will have accepted my quibble ).

While almost everything in the article is sufficiently well explained, I'm not sure about the Copenhagen Interpretation. I couldn't for the life of me figure out what relevance it had for people in boxes with guns to their heads . I will be the first person to admit that behind my vacant exterior is an even more vacant interior, but there you go.

I hope that helps. Overall I liked the essay a lot!

Woodpigeon

Thank you for your positive feedback!

Taking your points in reverse order (for no particular reason):
The Copenhagen Interpretation is mentioned because it is, according to the physicists working on quantum suicide (if I can put it like that), the opposite of the Many Worlds theory. Hence my last point: 'either they die and the Copenhagen Interpretation is correct; or they live on...'

Secondly, you are right about immortality. I could do the experiment 10 times and indeed I could still get run over by a bus. However, if I were to keep a very condensed 'continuous shooting' quantum gun implanted in my brain, I would effectively be immortal. In other words, the gun would continuously be making random decisions and I would be continously within the universes where I invariably survive.

Thirdly, I think you are asking why it is possible that in the case of death I may suddenly enter another universe. This is a common question and just needs a little bit of complicated imagination to explain. You remember my point about the stack of cards? I say that the 3D universes are stacked on each other in the same way that truly 2D cards are stacked on top of each other. In other words, there is no thickness between one universe and the other because they all occupy the same space, just like cards that are TRULY two-dimensional. Thus it makes no sense to ask how one 'moves into' another universe, because we are already in it.

If you need me to explain any further I would be happy to attempt to condense it into nicely spaced bullet points (if I can! ), which I always find somewhat helpful myself.

Fourthly, I am very glad you liked it.

Hi BB,

No need to bother with additional bullet points - as I say it reads very well already. Bullet points tend to be in the eye of the beholder.

Just a tiny thing. You say "the gun would continuously be making random decisions and I would be continously within the universes where I invariably survive." But, but, em, (gulp) surely you'll still get old and eventually die, sooner or later?

Woodpigeon

Well, Woodpigeon, death from old age is probably encompassed by the theory. It's fairly random, you don't usually know it's about to happen, and it's quick. So you'd probably survive it from your point of view.

However, I have just thought about it all and I realise that even with a little quantum gun in my head I am still vulnerable to death from outside causes. So you were right. I am not immortal. But there is still a way to be immortal, after all, if you stay living in a vacuum with a quantum gun in your head, not moving or interacting very much.

Do you think that this point is worthy of changing the entry somehow?

No, I don't think you need to add it. It was more for my own understanding that I asked the question. Adding it might serve to confuse it a bit. What I like about your entry is that it reads and flows well, so I am reluctant to ask you to change it around too much. Lets see what other people think.

Living in a vacuum - must give that one a go!

I've seen this presented before and it used the classic Russian Roulette setup of a gun with a rotating bit, one bullet and a five empty chambers. Surely that's a lot simpler to understand than the stuff you've got here?

You should perhaps mention that the Copenhagen Model is the 'Standard Interpretation' of Quantum mechanics and is used by most Quantum Physicists. The Many Worlds theory is gaining in popularity, but is still considered unusual, mainly because it is a different philosophical interpretation without actually predicting any different results, so it isn't much use for anything as yet.

Typo: many world's theory --> many worlds theory

I have not heard of the 'Russian Roulette' idea, but it sounds to me as though the person doing the experiment that way could probably tell that they were going to be shot when the wheel slowed its rotation, and it may not work that way.

"it isn't much use for anything as yet"
...except for the immortality theory itself and the fact that it is a core part of theories predicted by the esteemed 'string theory' (or M-Theory). Whilst the many worlds theory may not provide mathematically different results, it is a theory with sufficient physical substance to make it coherent in explaining otherwise messy one-universe quantum mechanics in a clear way.

Thank you again for reading about these fascinating ideas, I'm sure you'll agree.

I like this, BB!

Thank you.

I'm trying to get to grips with the way things would work.

Do the universes diverge from the instant when the random triggering event takes place (put another way, does the split happen before the person actually dies in the 'unlucky' version of the universe), or are they in some kind of superposition until observed.?

Also, thinking about the single-atom-decay trigger, if we take a time period over which the probability of a decay happening is 50%, (for example, an atom of Pu-233, and a time of 20 minutes), at the end of the 20 minutes, are there
a) two universes, one in which decay happened and one where it didn't, or
b) one universe where no decay happened, and numerous universes where the decay happened at a slightly different time.
or
c) Universes existing in some superposition until observation takes place.
or
d) something else?

Potholer, the superposition existing until it is observed is the Copenhagen model. The Parallel worlds model says that the world splits in two at the instant the random event takes place.

OK, so my next question is

If a random event can happen anytime within a defined time period, are there an infinite (or near-infinite) number of universes split off, in each of which the event happened at a different time, and then a single copy of the universe left where nothing happened?

Yes.

Okay.

So, performing the experiment seems likely to generate a large (possibly infinite?) number of universes with a dead subject in.

Also, why is it important that the subject in a 'losing' version of the universe isn't aware of their impending death?
If the 'losing' universe has already split from the 'winning' one, the awareness of death shouldn't affect the subject in the winning version.


On a different angle, presumably universes are splitting off all the time for all manner of quantum reasons, and since quantum causes can have macroscopic effects, it seems likely that history will naturally tend to diverge when considering any pair of once-identical universes, so there will naturally be an ever-increasing branching set of differing universes.

If I commit myself today to doing something dangerous next minute/week/year/whatever, then by the time I get round to doing the dangerous thing, there will be many subtly different daughter universes in which I will end up taking the risk, across which my survival chances will vary. After the risk is taken, there will be some universes in which I am dead, and some in which I am alive.
In what way is the result (universes in which I am alive, and universes where I am not) different from that of the quantum-random driven experiment?

Hello all. Firstly I need to correct Gnomon's definitive 'yes' answer to the infinite universes where one is dead. There would only be an infinite number of these universes if time is not discrete, i.e. there is no smallest unit of time (it's continuous, in other words). However, the general consensus in the physics community is that the Planck time is the smallest unit of time, thereby meaning that time is discrete, and in a given length of time there will be a huge yet finite number of universes where the person in this experiment dies (one universe per instant of possibility that the gun goes off) and one universe where the gun does not go off in the whole period of time.

"why is it important that the subject in a 'losing' version of the universe isn't aware of their impending death?"

When the random element is in action, Tegmark believes that the person in front of the gun would be in a strange schizophrenic superposition of both dead and alive states. At this point, new universes are being created to house the different possibilities (provided that the many worlds idea is correct). If the person doing the experiment were to know of his/her impending doom before it happened, the superposition would be destroyed, and the person would die because there is no longer a certain possibility that they won't (provided the gun will certainly kill them).

There is still a possibility of survival, but as with all macroscopic versions of quantum effects, the probability is exceedingly low.

For your second query:
"In what way is the result (universes in which I am alive, and universes where I am not) different from that of the quantum-random driven experiment?"

In your proposed risk, you will probably not be using a random quantum element. This means that conventional macroscopic physics applies, and therefore the quantum particles involved in the decisions that will construct the macroscopic picture of your risk will be bombarded by 'observations' - i.e. things that destroy their superposition. I think Tegmark is saying that in these circumstances no new universes would be created because there is no quantum uncertainty.

However, it might be the case that universes do create themselves under any circumstance. In this theory, you would perceive yourself to survive the life-threatening ordeal, no matter what outsiders observe you to do. And this is the theory that you would be able to live forever - or at least perceive immortality yourself - simply because in the other universes you are dead and cannot perceive anything.

Complex, isn't it?

Not too complex for the Edited Guide I hope...
It's been in peer review for a week now...

Time IS quantised in peer review - and is measured in Scouts picking cycles!

Of course it is. Have you read the entry yourself, Old Hairy?