Eliezer came up with a good analogue in Where Physics Meets Experience and Where Experience Confuses Physicists.
To summarize, the universe is a three-dimensional sheet in a four-dimensional universe. It's predicted that it occasionally splits into two thinner sheets. The probability of being in a sheet is measured to be proportional to the square of the predicted thickness.
The Copenhagen interpretation claims that, once the sheets have separated beyond a certain distance, one of them completely vanishes for no adequately explained reason. It's not known how far apart they have to be, beyond that it's further than you can detect a parallel universe.
The Many Worlds Interpretation claims that all the sheets continue to exist. No explanation is given for why you end up in the thicker one at that rate. It's just assumed that there's a better reason than that one universe ceases to exist.
It's just assumed that there's a better reason than that one universe ceases to exist.
"One universe ceases to exist" doesn't explain why the universes survive with that probability either.
This was one of the points raised in the QP sequence. You can't say "MWI doesn't explain these probabilities" as evidence for Copenhagen, because Copenhagen doesn't explain them either.
(I don't actually know the physics, I'm just repeating the teacher's password.)
There are a great many ideas which don't have enough carefully-measured evidence to be sufficiently confirmed as scientific fact and accepted as such by the scientific community (a recent joke was "While the Higgs Boson has not been discovered yet, its mass is 125 GeV"), but don't have enough carefully-measured evidence to be ruled out yet, either. Do any of the tools of the LW community help narrow down which ones are more worthy of consideration than others?
Eg:
* Cryonics as an arguably reasonable bet for its cost: proto-science
* Cryonics as a surefire way to achieve immortality: nigh-certainly pseudoscience (unless it's the method by which your Everett Immortality keeps you alive)
* Using math to demonstrate that taking classical physics and adding determinism results in MWI-style quantum physics: proto-science.
* Using math to demonstrate that quantum physics proves Christianity is true, from a certain point of view: pseudo-science
* Tubulin might self-organize into microtubules capable of computation on a sub-neuron scale: Possibly proto-science
* Tubulin architecture is 'quantum' in nature and that is what gives rise to consciousness: Probably pseudo-science
* 'Quantum consciousness' means anything is possible: Downright silly
* The E8 Lie group can provide a system for organizing the properties of subatomic particles: Proto-science, perhaps
* Heim theory is useful for predicting particle masses: Pseudo-science, probabilistically
* Using the Bullet Cluster to claim that dark matter is a better theory than Modified Newtonian Dynamics: proto-science
* Claiming that dark matter is made of 'anapoles': Proto-science, perchance
* Suggesting that dark matter is actually gravitational leakage from MWI 'parallel universes': You tell me. (But if it's true, then since I can't seem to find any previous serious discussion of this idea, I get to name part of it after myself, right? :) )
These may not be the best examples, but they're the closest ones I can think of to the boundary. If you know of any better ones, feel free to comment with them.