[TheOtherHobbes]

The problem with Many Worlds is that it doesn't place a bound on the number of worlds, so you can't derive the Born Rule from it.

That's quite a serious issues. And arguments against that - like Self-Locating Uncertainty, or Zurek's Envariance - look suspiciously circular if you pull them apart.

There's also the issue that if you don't have a mechanism that constrains probability, you can't say anything about the common mechanism of any of the worlds you're in. Your world may be some kind of lottery-winning statistical freak world which happens to have very unusual properties, and generalising from them is absolutely misleading.

There's no way of testing that, so you end up with something unfalsifiable.

[spot5010]

There’s papers that “derive” Born’s rule from the many worlds interpretations, e.g. https://arxiv.org/abs/1405.7907

I don’t claim to understand them though. I have tried.

[Nevermark]

> The problem with Many Worlds is that it doesn't place a bound on the number of worlds, so you can't derive the Born Rule from it.

I have no idea what this means.

Is there a bound on anything in reality, in terms of scale? Beyond its own laws?

I am reminded of how often in history, too much time, or too much scale, were unsuccessful arguments against many theories we accept today. Those critiques died without any need for special arguments, because they don't have a logical basis.

Also, there are not a number of many "worlds". That is a reflection of poor naming. There is an interleaving of all interactions, so if you zoom out, a smeared landscape across all configurations, from the plank scale up.

Because the connections involve both intersection (entanglement) and union (alternate paths), we get bifurcation of classical sized paths (dense entanglements), while the individual particles continue unconcerned by how they appear to create different classical histories at large scale.

And yes it is experimentally validated. This is the theory that everyone accepts in the lab, even as larger scales of experiment continue to progress.

But some people have difficulty believing/visualizing that it continues to work at larger scales. Despite no scale limitation in the theory, no scale related violations ever suggested experimentally, and the strong likely that scale limitations would produce new physics in at-scale observations of our cosmos if they did exist.