[ExI] Many Worlds (was: A Simulation Argument)

[John K Clark]

"Damien Broderick" <thespike at satx.rr.com>

> If you fire a single photon and register its arrival at a detector one
> meter away, you know precisely how long it should take to arrive
> *if it goes straight there*.

The trouble is the word "precisely". It you use a low energy photon that
means it will have a large wavelength and that means there will be some
ambiguity over exactly when it hit the detector. If you use a high energy
photon it will have a small wavelength so there will be less ambiguity
about when it hit, but more about exactly where that is because the
photon will pack quite a wallop.

Me:
>>I think you're mixing Feynman's Sum-over-histories and
>> Everett's many worlds.

You:
> I'm assuming they cash out the same way

I don't recall Everett adding up his worlds to get any numerical result,
and in Feynman's Sum-over-histories the thing you're summing up is
not a position or a trajectory or even a probability, it is the quantum
wave function and that is the square root of a probability.

Being a square root means it can and does have negative terms in it
and even imaginary terms, and that means the quantum wave function
is not a scalar like simple probability but a vector with an intensity and
a direction, and that means you can not just add up 2 independent
probabilities to figure the probability both will happen the way we
usually do, and that means two very different wave functions can
yield the same probabilities.

The electron that went through slot A and the one that went through
slot B will have different quantum wave functions, but they could and
sometimes do yield the same probability, hence the weird stuff when
they hit that photographic plate.

And Feynman never said the universe split or the observer split; he
wasn't even sure if all those bizarre paths had any physical
significance, he thought it could just be a mathematical trick that
happened to work.

> Some commentators deny that Everett's model meant entire universes

Everett came out with his theory in his PHD thesis, it was very long and his
thesis advisor John Wheeler (the man who coined the term "black hole")
made him cut out about half of it and encouraged him to say things like
"many histories" instead of "many worlds" because he thought it sounded
less kooky.

> due to relativistic constraints, if for no other reason.

I don't see how relativistic constraints enter into it.

  John K Clark