How do you tell proto-science from pseudo-science?

My impression is that MW vs. other theories are not a disagreement about the math, but about how the math should be interpreted.

Just sticking to the quantum interpretations discussed in the sequences, Everettian/MW quantum mechanics has 1 fewer postulate then Copenhagen quantum. The question as to whether they are empirically identical is still open- no one has derived the Born probabilities in many worlds. Until someone does, no one really knows what many worlds predicts. Most pop-science sweeps this under the rug- including the sequences.

The inability to derive the Born probabilities is THE key area where many worlds fails, and its a technical problem with the physics/math.

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.

IIRC, less than half of physicists believe in the Copenhagen interpretation, and more than half of the rest believe in MWI. At any rate, actual physicists who ascribe to MWI are not rare, and if your conjecture had anything going for it, I'm sure one of them would have thought of it. I'm under the impression that we have good theoretical reasons to believe that such interactions cannot happen. Making up statements that sound plausible given a few other assertions you've heard, without first understanding the technical details behind those assertions, is a poor way to generate hypotheses.

The main alternative paradigm to dark matter is modified gravity (above all, MOND, Modified Newtonian Dynamics). Modified gravity theories usually involve a change at the classical level, but it has been suggested that the galactic rotation curves, etc., might be due to some specifically quantum effect. In quantum field theory, a classical force field generated by an object is understood in terms of virtual particles emitted by that object, the quantum details can cause the field to exhibit properties different from the classical approximation, and maybe virtual gravitons do something funny when they are summed on galactic scales.

If you could explain such quantum modifications to gravity on astronomical scales, as a result of interaction between Everett worlds, then you could have something like your MWI theory of dark matter. The real problem with that, is in finding a coherent causal account of inter-world interaction.

ETA By the way, I suspect that your idea of how MWI gravitational leakage would work, uses paradigms from the wrong multiverse "level". In string theory there is the idea of membranes in hyperspace, each with its own matter attached, and with gravity being the one force that can cross hyperspace. So what we can see in space might be just one brane, and the dark matter could be matter on other nearby branes. I suspect that you're thinking of the MWI multiverse in similar terms - a stack of worlds, with some gravitational interaction between neighbors.

But in QM, quantum interference involves whole configurations at once. Suppose you have two entangled particles x and y, that are far apart in space. Schematically, their combined wavefunction will be x1 y1 + x2 y2 + x3 y3 + ... where the x's and y's are different possible wavefronts for the individual particles, and xi yi is a formal product of two such individual wavefunctions. The point of nonlocality is that the combined wavefunction of the two particles is simultaneously susceptible to changes at the x end and to changes at the y end. It's a nonlocally defined entity whose manifestation as x and y can't be reproduced by influences that travel through the space between x and y - that's the lesson of Bell's theorem.

So the brane-like scenario of locally propagated gravity leaking between worlds that are neighbors in a hyperspace, doesn't capture the nonlocality of quantum effects. What would be needed, is a type of Bohmian many-worlds theory, in which the nonlocal quantum force of Bohm (which allows Bohm to reproduce QM within a neo-classical ontology of determinism and definite trajectories), comes from some sort of nonlocal inter-world interaction. MWIers really ought to be investigating this sort of model, especially modified versions of it that approach locality.

The fact that MWI isn't generally accepted doesn't mean that there a sizable chunk of physicists who do accept it. I'm not even sure that you need to accept it to run the relevant equations.

The problem with using agenda as a heuristic is that it could be claimed most scientists have one. Perhaps if you divided agenda into subcategories, some of those could be useful, like political or religious agenda.

How do you tell whether those who claim it's pseudoscience are more reliable than those who claim it's not?

It's not accepted by the majority of the scientific establishment, so it's not "science". However, it's claims don't violate known physical law.

Whether something is a science has nothing to do with whether it violates physical law for which a consensus exists within the scientific community.

Paranormal is a much better word to describe those claims.

When Feynman made up the term cargo-cult science one of is prime examples was rat psychology research. Those researchers where doing experiment but the didn't do them in a way that really tested the claims they were investigating.

Pseudoscience is when you claim that there scientific evidence for a claim when there isn't. You aren't a pseudoscientist for investigating a hypothesis.

It's not accepted by the majority of the scientific establishment, so it's not "science". However, it's claims don't violate known physical law.

As ChristianKI already said, whether something strictly violates known physical laws is a poor criterion for telling science from pseudoscience. According to that criterion, paradigm-breaking physical theories such as Einstenian relativity and quantum mechanics would have been pseudoscience when they were presented, while lots of medical snake oil (including literal snake oil) would be not.

f someone says that it has a 5% chance of working, and they'd be willing to pay 20x the cost of cryonics to cure themselves of a disease, that seems to fall within "arguably reasonable".

But it hasn't been established that cryonics has a 5% chance of working, or even a 0.25% chance.

Victor Stenger, who authored the other PDF in the line you quoted, seems to have his head on reasonably straight. And even if Tipler's beliefs are pseudo-scientific, the math involved in the two PDFs seems to check out, as best I can tell, without any reliance on anything on the pseudo-scientific side.

I haven't had the time to read it yet, and this is not my field of expertise, but AFAIK attempts to reduce quantum physics to classical physics have been around since quantum physics exists, and they have always turned out to be unsuccessful. Even Einstein dedicated a large part of his research to that goal, to no avail.
Thus I don't expect any of them to succeed anytime soon. Past a certain point it stops being proto- and it starts to become largely pseudo-.

This seems like a non-obvious statement to me. Kidney function is dependent on fine microstructure: http://en.wikipedia.org/wiki/Renal_corpuscle

The size of each corpuscle is about the same as the size of a neuron.

Moreover, human kidneys can't be reversibly cryopreserved by current methods.

Yes.

It's also true, though perhaps irrelevant, that we don't actually care whether kidneys are restored. If my kidneys are damaged and a surgeon successfully transplants Sam's kidneys into my body, I'm basically OK with that... I don't especially want my kidneys, I just want kidneys. I suspect that's true of most people.

If my brain is damaged and a surgeon transplants Sam's brain into my body, the corresponding thing is much less true.

That being said, I expect that >99% of my cognitive function, memories, etc could be replaced by Sam's and I would be OK with that as well, even if I make the OKness evaluation with my current brain. Identifying the <1% for which that isn't true is a tricky project, though. That being said, I expect I'm very atypical in this respect.

Sorry, you've made a bad comparison. Randi hasn't raised that money for a Paranormal X-Prize. The Brain Preservationists, by contrast, have strictly empiricist criteria for deciding who wins the incentive prizes.

Reference: http://www.brainpreservation.org/content/competitors

As availability heuristic-appointed representative of the LW community, I also disapprove.

I disapprove.

I see what you did there.

I'd say It's similar to vetting ideas by their level of approval among the general public, except, I think, rather better. However, if you're not going to solve it for yourself anyway and going to be on the internet anyway, you might well figure out what the domain expert consensus is in roughly the same amount of time and that would be better still.

That's not what it means.

I think Vladimir is making the point that the categories you're using don't give much useful information when applied to your examples. It would be better to narrow down and make precise various different criteria for judging whether an idea is worth pursuing or not.