# A Does the MWI require "creation" of multiple worlds?

#### stevendaryl

Staff Emeritus
... needed (and meaningful) only in MWI.
That's actually not true. We have to make similar assumptions in classical physics, but they are just not made explicit.

#### A. Neumaier

That's actually not true. We have to make similar assumptions in classical physics, but they are just not made explicit.
No. In classical physics, we approximate probabilities by relative frequencies, in the same way as we approximate exact positions by measured positions. By regarding a relative frequency as an approximate measurement of the exact probability, no assumption about alternative worlds need to be made.

#### stevendaryl

Staff Emeritus
No. In classical physics, we approximate probabilities by relative frequencies
How do you know that's a good approximation? You don't. In classical probabilities, a sequence of flips of a fair coin can give you a relative frequency of anything between 0 and 1. We assume that if we flip enough times, then the relative frequency will settle down to 1/2 in the case of a fair coin. But that is the assumption that our world is a "typical" one.

#### A. Neumaier

How do you know that's a good approximation?
How do you know it in case of high precision measurements of position? One generally assumes it without further ado, and corrects for mistakes later.

In classical probabilities, a sequence of flips of a fair coin can give you a relative frequency of anything between 0 and 1.
In theory but not in practice. If one flips a coin 1000 times and finds always head, everyone assumes that the coin, or the flips, or the records of them have been manipulated, and not that we were lucky or unlucky enough to observe a huge statistical fluke.

We draw conclusions about everything we experience based on observed relative frequencies on a sample of significant size, and quantify our remaining uncertainty by statistical safeguards (confidence intervals, etc.), well knowing that these sometimes fail. Errare humanum est.

But that is the assumption that our world is a "typical" one.
Nobody ever before the advent of MWI explained the success of our statistical reasoning by assuming that our world is a typical one. Indeed, if there are other worlds, we cannot have an objective idea at all about what happens in them, only pure guesswork - all of them might have completely different laws from what we observe in ours. Hence any statements about the typicalness of our world are heavily biased towards what we find typical in our only observable world.

#### stevendaryl

Staff Emeritus
How do you know it in case of high precision measurements of position? One generally assumes it without further ado, and corrects for mistakes later.
I can't tell whether you actually have a disagreement, or not.

In theory but not in practice. If one flips a coin 1000 times and finds always head, everyone assumes that the coin, or the flips, or the records of them have been manipulated, and not that we were lucky or unlucky enough to observe a huge statistical fluke.
That's the assumption that our world is "typical". So you're both making that assumption and denying it, it seems to me.

#### A. Neumaier

That's the assumption that our world is "typical". So you're both making that assumption and denying it, it seems to me.
No.

In common English, to call something typical means that one has seen many similar things of the same kind, and only a few were very different from the typical instance. So one can call a run of coin flips typical if its frequency of heads is around 50% and atypical if it was a run where the frequency is outside the $5\sigma$ threshold required, e.g., for proofs of a new particle (see https://physics.stackexchange.com/questions/31126/ ), with a grey zone in between.

This is the sense I am using the term. All this happens within a single world. It is not the world that is typical but a particular event or sequence of events.

But I have no idea what it should means for the single world we have access to to be ''typical''. To give it a meaning one would have to compare it with speculative, imagined, by us unobservable, other worlds. Thus calling a world typical is at the best completely subjective and speculative, and at the worst, completely meaningless.

#### Derek P

No.

In common English, to call something typical means that one has seen many similar things of the same kind, and only a few were very different from the typical instance. So one can call a run of coin flips typical if its frequency of heads is around 50% and atypical if it was a run where the frequency is outside the $5\sigma$ threshold required, e.g., for proofs of a new particle (see https://physics.stackexchange.com/questions/31126/ ), with a grey zone in between.

This is the sense I am using the term. All this happens within a single world. It is not the world that is typical but a particular event or sequence of events.

But I have no idea what it should means for the single world we have access to to be ''typical''. To give it a meaning one would have to compare it with speculative, imagined, by us unobservable, other worlds. Thus calling a world typical is at the best completely subjective and speculative, and at the worst, completely meaningless.
Just remember, hair-splitting is irrelevant to world-splitting.

Funnily enough I can understand Steven's language in what appears, admittedly to my vague sort of mind, to be perfectly well-defined terms. Personally I translate "typical" into something useful about confidence limits.

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#### almostvoid

Gold Member
There is no collapse in Many Worlds.
aren't the many worlds theoretical-

#### almostvoid

Gold Member
??? @StevenDarryl was describing the smooth evolution of the emergent worlds. It was not even remotely a reformulation of MWI.

You may believe so but MWI asserts exactly the opposite.
See this article - but only if you don't mind Vongher's provocative style.
that article above--See this article--- - fails simply because the use of Wikipedia makes research infotainment. Plus a lot of thought experiments. Neumaier has it spot on-

"Does the MWI require "creation" of multiple worlds?"

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