# Probability in MWI

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Has it really been shown that probability laws would work under MWI?

Anything that can theoretically happen under the laws of physics would seemingly have a probability of infinity/infinity of happening under MWI.

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Many-worlds is an interpretation of QM. The probabilities are the probabilities you calculate in QM.

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52 minutes ago, swansont said:

Many-worlds is an interpretation of QM. The probabilities are the probabilities you calculate in QM.

But if everything (except things that are literally impossible under the laws of science) is bound to happen under MWI, an infinite amount of times, isn't the probability of everything essentially 100%?

Edited by Orange6
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4 minutes ago, Orange6 said:

But if everything (except things that are literally impossible under the laws of science) is bound to happen under MWI, an infinite amount of times, isn't the probability of everything essentially infinity?

Infinite probability makes no sense. Probability is between 0 and 1. So the probability of non-impossible things approaches or is 1, i.e. it happens in at least one of the worlds.

(That echoes a saying in particle physics: that which is not forbidden is mandatory.)

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18 hours ago, swansont said:

Infinite probability makes no sense. Probability is between 0 and 1. So the probability of non-impossible things approaches or is 1, i.e. it happens in at least one of the worlds.

(That echoes a saying in particle physics: that which is not forbidden is mandatory.)

I think what he means is that, if every possible outcome is realised - albeit in different branches of the multiverse -, then what is the physical meaning of probabilities? Technically speaking, the probability for each outcome should be 1, because it is realised with certainty somewhere - irrespective of the fact that the various outcomes cannot be connected in any way.

I’m not an expert on the MWI, but I think this is a valid objection, which I seem to remember having seen raised in the literature as well.

Edited by Markus Hanke
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5 hours ago, Markus Hanke said:

I think what he means is that, if every possible outcome is realised - albeit in different branches of the multiverse -, then what is the physical meaning of probabilities? Technically speaking, the probability for each outcome should be 1, because it is realised with certainty somewhere - irrespective of the fact that the various outcomes cannot be connected in any way.

I’m not an expert on the MWI, but I think this is a valid objection, which I seem to remember having seen raised in the literature as well.

Exactly. The probability of any event under MWI is seemingly infinity/infinity, which is an improper fraction.

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You can only access one universe in the MWI interpretation. That an even happens in one of them doesn’t actually effect you, unless it happens in yours. So the probability of something happening in all of the universes is not a useful calculation.

And, as an interpretation, you don’t have to use it if it doesn’t help you understand things.

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Oh, I see.  You are asking this question because you don't understand how to calculate probabiities.

What you are saying is equivalent to "If I cross the street in the middle of the block, there are two things that can happen- either I get killed or I don't.   Therefore the probability of getting killed is 1/2."

Given an infinite number of universes, we can still calculate what percentage of them have a given property.

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I, myself, have won the lottery several times, in 'other' universes.

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I think the Many World Interpretation of QM is another form of the "blows up to infinity" problem with theoretical physics equations that are "in trouble".   Or does anybody think my intuitive characterization is inaccurate.

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23 hours ago, POVphysics said:

I think the Many World Interpretation of QM is another form of the "blows up to infinity" problem with theoretical physics equations that are "in trouble".

The MWI is mathematically self-consistent, it being just one possible interpretation of standard quantum mechanics.

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12 minutes ago, Markus Hanke said:

The MWI is mathematically self-consistent, it being just one possible interpretation of standard quantum mechanics.

The only way a MWI could ever exist would be in some virtual quantum state.  In other words, if you were arguing that all possibilities exist because there are quantum waves that describe all possible futures, then it would sound very similar to some kind of metaphysical Astral plane which, is basically just asking for quantum waves to store a lot of information; that's not too tall of an order.

But when you ask each quantum possibility to have 10^74 joules (the approximate energy of the universe), then you run into problems.  The first big problem is a storage problem.  Where do you put all these new universe?  How do they not interact with established universes?  Some people have argued that these MWI universes are a trillion light years away.  But then you have to explain how a causal result of a choice can show up a trillion light years away, how it violates the speed of light.  The MWI interpretation violates laws of physics; has storage issues, and is unpleasant to behold; aesthetically unpleasing.

But if you wanted to say that information content of your choices can be stored in quantum waves, than that is far easier to accommodate.  But I have no idea if there is a maximum amount of information that can be stored in quantum waves.

I actually have my own interpretation of quantum mechanics.  Similar to pilot theory.  One of these days I'll start a topic.

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6 hours ago, POVphysics said:

But when you ask each quantum possibility to have 10^74 joules (the approximate energy of the universe), then you run into problems.  The first big problem is a storage problem.  Where do you put all these new universe?  How do they not interact with established universes?  Some people have argued that these MWI universes are a trillion light years away.  But then you have to explain how a causal result of a choice can show up a trillion light years away, how it violates the speed of light.  The MWI interpretation violates laws of physics; has storage issues, and is unpleasant to behold; aesthetically unpleasing.

The quantum states are orthogonal to each other. You don’t have to “put” them anywhere.

The causality is the issue for me. I’ve heard similar objections to Copenhagen with instantaneous wave function collapse, but MWI suffers from this same issue, just in a different firm

But it’s an interpretation, not a theory unto itself.

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On 11/27/2020 at 3:13 AM, POVphysics said:

The only way a MWI could ever exist would be in some virtual quantum state.  In other words, if you were arguing that all possibilities exist because there are quantum waves that describe all possible futures, then it would sound very similar to some kind of metaphysical Astral plane which, is basically just asking for quantum waves to store a lot of information; that's not too tall of an order.

But when you ask each quantum possibility to have 10^74 joules (the approximate energy of the universe), then you run into problems.  The first big problem is a storage problem.  Where do you put all these new universe?  How do they not interact with established universes?  Some people have argued that these MWI universes are a trillion light years away.  But then you have to explain how a causal result of a choice can show up a trillion light years away, how it violates the speed of light.  The MWI interpretation violates laws of physics; has storage issues, and is unpleasant to behold; aesthetically unpleasing.

But if you wanted to say that information content of your choices can be stored in quantum waves, than that is far easier to accommodate.  But I have no idea if there is a maximum amount of information that can be stored in quantum waves.

I actually have my own interpretation of quantum mechanics.  Similar to pilot theory.  One of these days I'll start a topic.

MWI would pretty easily get around the energy problem if the net energy of the universe is zero, as some scientists predict.

However, I have wondered about universes separating faster than the speed of light. That seems to be what MWI predicts, even though I’ve never seen an MWI supporter outright say that.

In any case, QM is very strange, so I wouldn’t say a few counterintuitive things about a theory completely rule it out.

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1 minute ago, Orange6 said:

In any case, QM is very strange, so I wouldn’t say a few counterintuitive things about a theory completely rule it out.

I think if we had the right way to imagine quantum mechanics, it would be easier to understand, even if it's still an object that behaves mathematically.

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3 hours ago, POVphysics said:

I think if we had the right way to imagine quantum mechanics, it would be easier to understand, even if it's still an object that behaves mathematically.

Not everybody understands things the same way. There is no one “right way” when it comes to interpretations. Put differently, the right way is the one that works for you.

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On 11/24/2020 at 2:43 AM, Markus Hanke said:

I think what he means is that, if every possible outcome is realised - albeit in different branches of the multiverse -, then what is the physical meaning of probabilities? Technically speaking, the probability for each outcome should be 1, because it is realised with certainty somewhere - irrespective of the fact that the various outcomes cannot be connected in any way.

I’m not an expert on the MWI, but I think this is a valid objection, which I seem to remember having seen raised in the literature as well.

Does this make the assumption that 'every possible outcome' is a finite number? Perhaps there are an infinite number of possible outcomes, in which case I would assume that the probability for each outcome is something less than 1.

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7 hours ago, Orange6 said:

In any case, QM is very strange, so I wouldn’t say a few counterintuitive things about a theory completely rule it out.

QM, as a theory, is self consistent, and is not counterintuitive at all; it is a differing paradigm ( or basis of thinking ).
The 'interpretations', which try to describe QM, and relate it to common everyday occurrences, struggle to be sensical.
( my cats really hate the Copenhagen interpretation, and get upset when I try putting them in a box with cyanide )
Don't take the multiple interpretations too literally.

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4 hours ago, swansont said:

Not everybody understands things the same way. There is no one “right way” when it comes to interpretations. Put differently, the right way is the one that works for you.

There is a "right way" to do physics; it's the way that leads to new experimental data.

10 minutes ago, MigL said:

The 'interpretations', which try to describe QM, and relate it to common everyday occurrences, struggle to be sensical.

As an example, the expectation values for momentum and position can be calculated.  https://en.wikipedia.org/wiki/Expectation_value_(quantum_mechanics)

If we were going to calculate the expectation value of a particle in a box, all we're trying to do is predict where it is or what is it's momentum.  It's very similar to looking at a house and wondering where the home owner is; or maybe a better metaphor is fish in the ocean.  What are the odds of catching a fish in any particular volume of ocean, moving at whatever velocity and direction (momentum), under the waves.  The fish are not traveling between universes or creating new universes.  They're just under the waves where we can't see them.  Similarly, the Pilot Wave theory assumes they are just particles traveling about in the quantum waves.  , https://en.wikipedia.org/wiki/Pilot_wave_theory

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1 hour ago, POVphysics said:

There is a "right way" to do physics; it's the way that leads to new experimental data.

But we’re discussing interpretations, which is not “doing” physics. It’s making sense of QM.

1 hour ago, POVphysics said:

As an example, the expectation values for momentum and position can be calculated.  https://en.wikipedia.org/wiki/Expectation_value_(quantum_mechanics)

If we were going to calculate the expectation value of a particle in a box, all we're trying to do is predict where it is or what is it's momentum.  It's very similar to looking at a house and wondering where the home owner is; or maybe a better metaphor is fish in the ocean.  What are the odds of catching a fish in any particular volume of ocean, moving at whatever velocity and direction (momentum), under the waves.  The fish are not traveling between universes or creating new universes.  They're just under the waves where we can't see them.  Similarly, the Pilot Wave theory assumes they are just particles traveling about in the quantum waves.  , https://en.wikipedia.org/wiki/Pilot_wave_theory

And what does this have to do with MWI?

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2 minutes ago, swansont said:

And what does this have to do with MWI?

The many world interpretation is not relatable to nature or to what we commonly experience with the outside physical world.

3 minutes ago, swansont said:

But we’re discussing interpretations, which is not “doing” physics. It’s making sense of QM.

The physics community always proclaims that QM is weird!  Which means that you don't understand what's happening.  But IMO, quantum mechanics is no more magical than just to realize that point particles are being bathed in a medium of expanding gravitons.  I would make the argument that expanding gravitons are 4D point particles (unlike other mediums which are made of 3D particles - which is what the Michelson Morley experiment assumes.

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2 minutes ago, POVphysics said:

The many world interpretation is not relatable to nature or to what we commonly experience with the outside physical world.

You speak only for yourself, of course. MWI isn’t meant to apply to what “we commonly experience” if you aren’t a physicist

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6 minutes ago, swansont said:

You speak only for yourself, of course. MWI isn’t meant to apply to what “we commonly experience” if you aren’t a physicist

Physics is either founded on empirical evidence, or it's no better than astrology.

Incidentally, if wave functions = expanding gravitons, then wave functions DO NOT COLLAPSE.  They expand, at the speed of light, beyond the quantum system; essentially they escape quantum systems by expanding, not collapsing.

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Getting tired of these 'expanding gravitons' ( as I'm sure Swansont is also ), which are not real gravitons.

How about you tell us what evidence you have for their existence ?
And if a ( graviton predictive ) theory, how about posting some math ( or a link, if you don't do LaTex, like me ) and some other testable predictions to back it ?

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34 minutes ago, POVphysics said:

Physics is either founded on empirical evidence, or it's no better than astrology.

Which has nothing to do with the topic. Focus, please.

Just now, MigL said:

Getting tired of these 'expanding gravitons' ( as I'm sure Swansont is also ), which are not real gravitons.

How about you tell us what evidence you have for their existence ?
And if a ( graviton predictive ) theory, how about posting some math ( or a link, if you don't do LaTex, like me ) and some other testable predictions to back it ?

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