Re:many worlds

Loren Haarsma (
Fri, 19 Sep 1997 13:53:00 -0400 (EDT)

Glenn wrote:
> I have touched on what I will say before, and I don't remember the results,
> so I may step onto a landmine I stepped on a year ago. The problem I have
> with the many-world hypothesis is that it would have a universe (ours) in
> which I am a Christian. There would be others in which I am a Christian.
> But there would be still others in which I decided to become an atheist
> during my crisis of faith a few years ago. Thus, in the multiverse (the
> existence of all universes) there is are many non-christian Glenn's and many
> Christian Glenn's. What then does redemption mean? I don't know the answer.

This raises several interesting theological points. But first, I think
it's important to distinguish quantum many-worlds theory from
cosmological "inflationary" many-universes. Some versions of inflation
theory suggest that during the inflationary epoch, many different
causally-disconnected universes (potentially each with different
physical laws) were created. This is very different from the quantum
many-worlds hypothesis, which claims that each quantum measurement (or
"collapse of the wave function") causes multiple nearly-identical
universes to spring into existence, continually, even as your read

Suppose quantum many-worlds is true. Does it then follow that there are
some universes in which I am a Christian, and some in which I am not?
Not necessarily. I don't think our decisions correspond in any
meaningful way to quantum measurements. I seriously doubt if our brains
are quantum devices any more than the computer on my desk or a

But let's go a step further. Let's suppose that quantum many-worlds is
true AND that our decisions correspond in some way to quantum
measurements, so that any decision we supposedly make splits the
universes. In that case, the theological problem seems to be a loss of
Free Will. Who-we-are-right-now is no longer dependent upon our past
choices the way we usually think of choices; instead, who-we-are-right-
now is simply the victim of our previous quantum world-history. Is a
loss of Free Will a problem for Christianity? Interestingly enough,
some theologians such as Jonathan Edwards have argued "No." It might be
worth checking out their arguments.

> Here is the landmine. Assuming two things, neither of which is certain, we
> may get a test of the many-world hypothesis. The two things are 1. the
> invention of a quantum computer and 2. the solution of a mathematical
> problem of more than a certain complexity.
> A calculation requires the manipulation of a physical object. In the case
> of computers it requires the manipulation of electrons and atoms. Now,
> there are 10^80 particles in the universe. Assuming that a quantum computer
> is capable of solving in 5 minutes a problem requiring 10^500 calculations.
> The question would have to be asked, where are all the particles which are
> being manipulated in these calculations? The obvious answer to most would
> be the manipulations of particles in other universe's. This the solution to
> this kind of problem would be considered evidence of the other universes. An
> interesting easy level article is Tim Folger, "The Best computer in All
> Possible Worlds,' Discover, Oct, 1995, circa p. 95

The question that needs to be asked about our hypothetical quantum
computer is: Is it solving a problem which requires 10^500 calculations
*by a conventional computer*, or is it solving a problem which actually
requires 10^500 calculations, period. I strongly suspect the former is
true. The idea behind this particular quantum computer, as I understand
it, is to cleverly design a physical situation such that the measured
eigenstate of the quantal system corresponds to the solution of a
mathematical problem -- a problem which *conventionally* would require
10^500 calculations. (All the incorrect answers would evaporate in a
puff of canceled complex phases.) This is not the same as *actually*
doing the calculations. The way in which an electron finds its proper
energy eigenstate in a hydrogen atom may be mysterious, but I think it's
safe to say that it isn't performing calculations to solve the Dirac
equation. Is this hypothetical quantum computer really any different
from a glorified hydrogen atom?

Loren Haarsma
Occasional Quantum Philosopher (at least in this universe)