X-Message-Number: 17962
Date: Sat, 17 Nov 2001 12:19:22 EST
Subject: MWI and waves

Mike Perry favors the MWI (Many Worlds Interpretation) of quantum theory, and 
he has lots of distinguished company--maybe now even a majority of the most 
qualified people. But there remain plenty of expert skeptics and plenty of 
problems. (No, I'm not an expert.)

I have not been able to get an answer from Deutsch on the following--possibly 
because my question is just too stupid, who knows. Anyway:

In "The Fabric of Reality" Deutsch seems to rely for proof of MWI mainly on 
single-photon interference. (You get different diffraction and interference 
patterns with different arrangements of slits, even if only a single photon 
at a time is involved.)

He says that "shadow" photons (in other universes) interfere with "tangible" 
photons (in our universe). (Likewise with all objects or systems of any kind 
and any size.) Well, the first problem is that--as far as I can see--he 
offers no mechanism for this interference. Interference is classically 
understandable as a wave phenomenon, but he never mentions waves, just one 
photon interfering with another. This doesn't cut it.

Secondly, there is no quantitative discussion. Perhaps this was because the 
book was intended for popular reading, but there should at least have been 
some reference to it. How many shadow photons interfere with each tangible 
photon? Do tangible photons also interfere with each other? If there are an 
infinite number of identical universes, as well as other infinities of 
different ones, as he appears to say, this quantitative question seems 
formidable, even though infinities can be ordered in the sense of measure 

One main argument of the MWI people is that a particle classically cannot 
interfere with itsefl, and yet this appears to happen. But we know there are 
so-called basic quantons (such as photons and electrons) and phenomenological 
quantons, such as phonons and several others. Phonons act like particles in 
certain ways, but result from wave phenomena in ordinary material media. It 
is possible--I would even say probable--that underlying the "basic" quantons 
are so far undiscovered structures which can support wave phenomena giving 
rise to (say) photons or electrons in somewhat the same way that waves in 
gases or liquids or solids give rise to phonons. 

As far as quantum computation is concerned, if all quantons are 
phenomenological, then perhaps we are just dealing with another kind of 
analog computer, which can indeed work tremendously faster than an ordinary 
digital computer.

I remind readers that if MWI (or the Deutsch version of it) is correct, then 
apparently there always have been and always will be infinite numbers of 
identical copies of you, as well as infinities of nearly identical copies, 
and further infinities of miserable, tortured ones, and other (smaller) 
infinities of blissful ones. You are already immortal, very happy and also 
very unhappy, no matter what you do or don't do.

By the way--many thanks to Mike for his generous donation to the James Swayze 
fund. Tangible, not shadow.

Robert Ettinger
Cryonics Institute
Immortalist Society

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