# B Is anything possible in the many worlds interpretation

#### IvicaPhysics

In the many worlds interpretation of Qm, is there one universe in which I am a horrible murderer, for example?

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#### Mentz114

Gold Member
In the many worlds interpretation of Qm, is there one universe in which I am a horrible murderer, for example?
After you commit (theoretically) your first horrible murder the universe will split another infinity times. So there will be an infinite number of them.

Whether you do this or that in some alternative universe is not specified by the interpretation, which leads to much (pointless) argument.

#### OCR

In the many worlds interpretation of Qm, is there one universe in which I am a horrible murderer, for example?
Whether you do this or that in some alternative universe is not specified by the interpretation, which leads to much (pointless) argument.
Lol... also, maybe ?... there is one universe in which you are just a horrible murderer, for example? [COLOR=#black].[/COLOR] [COLOR=#black]..[/COLOR]

#### PeterDonis

Mentor
In the many worlds interpretation of Qm, is there one universe in which I am a horrible murderer, for example?
It depends. The MWI says that, whenever a measurement is made on a quantum system that is in a superposition of eigenstates of that measurement, the universe splits into multiple copies, one for each eigenstate, i.e., one for each possible measurement result. (Here "result" doesn't just mean the new state of the system, but the state of the measuring device, of all the people who observe the device's output, etc.) So for there to be a universe in which you are a murderer, there would have to be some kind of quantum measurement process like that involved in the events that led up to your being a murderer, or not, depending on how the measurement came out.

The assumption of many MWI proponents seems to be that the above is an obvious consequence of the MWI, but I'm not sure. There is an ongoing discussion in another thread on this topic; here is a recent post of mine there:

#### PeterDonis

Mentor
is there one universe in which I am a horrible murderer
I should also mention that there is another issue here, namely, what defines "I" in this hypothetical? In other words, suppose that there is some alternate MWI branch in which there is a horrible murderer; how do we know that that murderer is "you"? Presumably that person will have a very different personality and history from the "you" that posted the OP in this thread. So what makes them count as the same person?

This is not really a question of physics, or at least not solely a question of physics. But I bring it up for completeness.

#### Dxoutkast

After you commit (theoretically) your first horrible murder the universe will split another infinity times. So there will be an infinite number of them.

Whether you do this or that in some alternative universe is not specified by the interpretation, which leads to much (pointless) argument.
Who gave you this premise of infinity? That's not true, it would be divided a finite amount of times, if the interpretation was correct, in quantum theory discrete regions of space have finite amounts of energy. The probability of DNA-based life is greater than zero; and if the number of types of DNA-based living things is finite (because the size of the DNA molecules cannot be arbitrarily large ,the number of possible histories in each region is finite because the energy in each region is finite and, according to quantum mechanics, energy is quantified.

#### PeterDonis

Mentor
according to quantum mechanics, energy is quantified
That's not correct as you state it. What is correct is that some systems (basically, bound systems) have discrete energy levels; but others (such as free particles) do not. Also, even most bound systems with discrete energy levels have an infinite number of them, so you can't conclude from the fact that the energy levels are discrete that a measurement of energy can only have a finite number of possible outcomes, which is what you would need to conclude to make "it would be divided a finite amount of times" true.

Moreover, whether or not a system has discrete energy levels doesn't matter unless you are measuring its energy. But whatever observable corresponds to "determining whether so-and-so commits a murder" is not going to be a measurement of energy. What we would need to figure out is whether that particular observable had only a finite number of possible outcomes, or an infinite number. The latter is overwhelmingly more likely, which is why @Mentz114 implicitly assumed it in his post.

#### Michael Price

In the many worlds interpretation of Qm, is there one universe in which I am a horrible murderer, for example?
Yes - everything consistent with the boundary conditions and laws of physics happens. Loosely speaking, everything possible happens.

#### hilbert2

Gold Member
The things that are not possible even if MWI is true include having a particle of electric charge $e/2$ or a repulsive gravitational interaction in one of the infinitely many universes.

#### DarMM

Gold Member
This question is quite hard to answer for reasons @PeterDonis mentioned.

You'd have to know what exactly what is possible given the current electric charge, angular momentum etc of the world.

If you know that anything possible within those constraints can occur.

#### Mentz114

Gold Member
Who gave you this premise of infinity? That's not true, it would be divided a finite amount of times, if the interpretation was correct, in quantum theory discrete regions of space have finite amounts of energy. The probability of DNA-based life is greater than zero; and if the number of types of DNA-based living things is finite (because the size of the DNA molecules cannot be arbitrarily large ,the number of possible histories in each region is finite because the energy in each region is finite and, according to quantum mechanics, energy is quantified.
If we have two indivduals, then one presumes both individuals continue to exist in the splitting of their respective universes. It becomes difficult to track any individual or to count the universes in which they exist when all possible splittings are considered. Without specifying some kind of counting procedure your argument is speculation.

"Is anything possible in the many worlds interpretation"

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