Infinite Parallel Universes

[Qubit]

Hello there, I am new to the forum. I have read relatively widely on the topic of physics, but i do not have formal qualifications in science. I am looking for an outlet to express ideas about the physical universe, whether on large or small scales, and this site seems quite good for that. In engaging in discussions with you i hope to crystallise my view of the universe (which currently includes the hypothesis of God). I do not wish to be imposing, considering that you may have spent alot of your life learning about these things, and i hope my lack of formal education will not be a hindrance to you, whoever you are.

 

I have read a few posts and replies so far, but felt the best thing to do would be to start a new topic, just to get going.

 

The question I wish to put to hypography is about the science related idea of infinite parallel universes. It is thought that as a consequence of Schroedinger's cat that at each moment in time the universe undergoes a split of some kind. Kaku talks about the possibility that wormholes could lead to parallel universes. Now, whether this is science or not, I would say that there is only one universe. I say this because if there are infinite universes extending all the way back from the big bang, and these include all the possibilities we could have, why hasn't there been a universe which has discovered how to connect to other universes and thus discovered our own? (remember, "infinite" is very large!) I suspect that were there infinite parallel universes, we would certainly know about it.

 

That is the essence of my query. Please be gentle!

 

Thanks, Dan.

[sanctus]

Welcome!

 

No infinite is bigger than "very large". Your argument for a sole universe can be falsified in the following way:

 

infinity is such that it can include infinities. This means, with respect to your argument, that there are an infinite number of universes where the discovery on how to connect universes was made. But there are also an infinty of universes where this was not the case.

 

More to the physics of parallel universes, if I remember right the theories predicting it are actually also predicting an upper bound for the number of paralell universes (a very high number but smaller than infinity) and hence in this case there is no necessity that there is a universe which figured out how to connect to other ones.

 

In both cases (infinite or very high number of parallel universes), even if there is a parallel universe where someone discovered how to connect to parallel universes, it is not guaranteed that they ever visited ours...

[sanctus]

And thinking about it a bit more, I realised that there is another issue. If parallel universes are just all the possibilities of the outcomes of all events til now (one possibility per universe). Then a parallel univrse can be in contact with other parallel universes only if such a contact is actually a possibility! Having an infinite amount of universes still does not make an impossible thing possible.

 

In other words, your argument actually implies that it is possible to connect parallel universes, which we do not know to be true (or false).

[Qubit]

Thank you for your comments, my friend. And in fact they were most helpful, in that you took the logical step regarding infinity that i failed to take. To me it is all about possibilities and i would say in response to you that although there may be an infinite number of universes in which none have the ability to connect to others, there are also an infinite number of universes which have. This brings to mind a superposition of universes which collapse under quantum observation and produce just one. This is where the whole thing becomes philosophical if we are not careful. However, i recognise the sum over paths theory in which the possibility of parallel worlds is implicit in the wavefunction of this one (prior to collapse), and without trying to point to an intuitive dogma of observational capacities (by which i mean consciousness) I still believe there is just one universe which is the one we observe. The possibility of parallel univereses is simply a matter of human freedom and foresight/insight.

[CraigD]

Welcome to hypography, Qubit/Dan! :) Please feel free to start a topic in the introductions forum to tell us something about yourself. I’m guessing from your member name that you’re interested in quantum computing - so am I.

 

The question I wish to put to hypography is about the science related idea of infinite parallel universes.

A good starting point on the subject – one that a lot of science-literate people know – is Max Tegmark's classification scheme. This scheme divides the kinds of things people mean when they refer to “parallel” or simply “other” universe into 4 “levels”:

1. ”Beyond our cosmological horizon” – Simply put, stuff that’s too far away to be seen with any possible technology. There could be an infinite number of universe with physical laws the same as and thus histories similar to ours, but so far away we can never know anything about them.
   
2. With different physical constants/laws – Like level 1, but with different – perhaps very – physical laws than ours. Universe where things as we know it in ours wouldn’t be physically possible.
   
3. Per the Many-Worlds interpretation of quantum physics – The “splitting” universe model Hugh Everett wrote about in 1957 PhD thesis. Every time, anywhere, an particle interaction occurs that could have one outcome or another, the universe splits into one where one outcome occurred, and another where the other did. According to this (and despite lots of literature from impressively credentialed folk, most philosophers but some even physicists) there are not an infinite number of “other worlds”, but a very, very, large number of them. It’s possible, in principle, to count the current number – just calculate how many quantum mechanical interactions have occurred, and raise 2 to that power. ;)
   
4. ”Ultimate ensembles” – Every universe that is possible to describe using mathematical physics.
   

The definition of “other universe” Tegmark used for this scheme requires that there be no way of getting information or anything else between these multiple universe. If, for any reason, you can get stuff between “universes”, then according to Tegmark’s scheme, they’re not really separate universe, but simply hard-to-connect parts of our universe.

 

So theories like brane theory, which describe our universe as just one of many (possibly infinitely many) “floating” in a higher-dimensional bulk, aren’t using the term “universe” in the same way Tegmark’s classification is.

 

It is thought that as a consequence of Schroedinger's cat that at each moment in time the universe undergoes a split of some kind.

This describes Tegmark’s level 3 universe scheme, the MWI-based one.

 

Kaku talks about the possibility that wormholes could lead to parallel universes. Now, whether this is science or not, I would say that there is only one universe. I say this because if there are infinite universes extending all the way back from the big bang, and these include all the possibilities we could have, why hasn't there been a universe which has discovered how to connect to other universes and thus discovered our own?

If you’re “playing by the rules” of the MWI, then by definition, the parallel universe can’t connect. The key point here is that the MWI isn’t a physic theory suggesting that the spitting it describes is physically real, but an interpretation of a physics theory, a way of better understanding, quantum mechanic’s vexingly counterintuitive “measurement problem”. Its intellectual predecessor, the Copenhagen interpretation, depict all but one of the MWI’s many universes as “collapsing” as each interaction outcome is measured, leaving a person (such as 1950s PhD student Hugh Everett) with a nagging feeling of “why?” As a real physics prediction, however, a universe where one collection of outcome measurements happened can no more “connect” with another if we use the MWI to help ourselves make sense of quantum mechanics than if we use the Copenhagen Interpretation, where we’d be imagining connection a non-existent “collapsed” universe to a single “what really happened” one.

 

Now, whether this is science or not ...

The study of traversable wormholes is certainly science, in that lots of well-respected scientists have seriously studied them. Their conclusions fall short of confidently deciding whether they can possibly exist or not. The best-developed wormhole theories – which I’d ascribe to Kip Thorne (see his 1994 book Black Holes and Time Warps: Einstein's Outrageous Legacy for an account of this interesting story) more than Michio Kaku, as Thorne and his grad students did most of the work on them, though I expect Kaku understands the work well – require that, for them to exist, some kind of stuff (usually called “exotic matter”) that’s gravitationally repulsive be “threaded” through them. Nobody has much of an idea how or if such stuff could exist, though most suspect that if it can, it has something to do with the Casimir effect.

 

Serious science about wormholes has, IMHO, made about as much progress as it can – which is to say not much – because physics really has no good theory reconciling gravity (which is well-described by General Relativity) with quantum mechanics – that is, a good theory of “quantum gravity”. As a successful theory, QM just ignores gravity, which, since it’s mostly concerned with describing how individual subatomic particles interact with one another, where the effects of gravity are negligible, isn’t a big practical problem. However, when your try, and Thorne and other have, to use QM to figure out how to build a wormhole, or if it’s even possible, the failure of QM to describe gravity becomes a huge problem!

[Qubit]

Thank you CraigD for your interesting reply and kind welcome. I will post an introduction when i have more time.

 

The taxonomy of universes is something I've vaguely heard of and i guess I'm mainly interested in level three where the universes split. What I learned among other things from your reply is the idea that a universe which can connect to another universe is not really another universe - something i hadn't thought about.

 

A friend of mine says infinite universes (IUs) is not science because they cannot be observed... of course, I disagreed stating the MWI of QM. Also IUs are rarely even discussed in philosophy it seems, because what's the point? I heard of IUs from science anyway, so they must be science, as you pointed out above.

 

I have heard of the Casimir effect and find it fascinating that distance between objects causes a force, however I lost the thread when you applied this to IUs. It's not your fault; some things I just don't understand. It occurs to me that despite the beauty of the theory of many worlds there still can only be one universe. The whole idea of many worlds seems to a question of choices and free will. We always ask what would happen if 'this' was different or that was different, but essentially it all comes back to the same thing. The infinite universe theory has to boil down to a theory of the unknown (or 'ignorance') which seems necessary for humanity, like a law that says we will always be ignorant about some things because we have to be, or we would know the future and we'd be gods and that would never do.

 

Also, I'm just thinking, does the possibility of IUs have anything to do with determinism? I ask because without the idea of infinite universes (as a cognitive thing) seems to frame the human conception of existence... well, not existence - more the capacity to choose and have freedom.

 

Sorry if it seems i philosophise too much. I firmly believe philosophy has a say in the world of thinking.

 

Thanks, Dan.

[Guest MacPhee]

I think you're right. The idea of infinite parallel universes is a cognitive thing. That's to say, it comes from human imagination.

 

Human imagination can invent all kinds of possible worlds. We seem to have an innate drive to make things up. That's why we have fiction writers. Such as Isaac Asimov, who pleasingly displays a future Galactic Empire. Or George Orwell who depressingly portrays a nightmare Socialist world. Our writers can imagine endless possibilities.

 

But that doesn't make any of them true. They're just a modern kind of fairy tale. Fantasies. Dream worlds. Myths.

 

In reality, there's probably only a single Universe. We're trying to understand it, and discover how it works. We've made good progress. Our development of hard rational Science and Maths has got us a long way. By sticking to the facts, and the observed evidence.

 

Mystical concepts such as "parallel universes" seem unhelpful, and unscientific. As if we were retreating to Astrology or the Numinous.

 

Where's the evidence for such things?

[Aethelwulf]

 

The question I wish to put to hypography is about the science related idea of infinite parallel universes. It is thought that as a consequence of Schroedinger's cat that at each moment in time the universe undergoes a split of some kind. Kaku talks about the possibility that wormholes could lead to parallel universes. Now, whether this is science or not, I would say that there is only one universe. I say this because if there are infinite universes extending all the way back from the big bang, and these include all the possibilities we could have, why hasn't there been a universe which has discovered how to connect to other universes and thus discovered our own? (remember, "infinite" is very large!) I suspect that were there infinite parallel universes, we would certainly know about it.

 

That is the essence of my query. Please be gentle!

 

Thanks, Dan.

 

 

To be more precise, it has to do with the wave function interpretation, rather than the Cat Experiment. The Cat Experiment shows the wave function smears objects out as probabilities, but at the core of the matter it has to do with how you interpret it.

 

Every time, in the parallel universe model, when an object smears over spacetime represents how many universes it corresponds to, it is only when a measurement is made on the system does the system split apart.

 

Wormholes, which are theoretically-possibility, could lead to other universes... only if other universes actually exist. Kaku is a parallel universe enthusiast so I can understand why he would announce this idea as being very factual... truth is, we don't know if other universes exist, let alone if we can even measure another universe.

 

Universes, in reply to your question about them extending to the big bang, is that universes have what is called ''self-contained time frames,'' that is, they all tick away time at different rates... no universe has the same time you see.