Date: Sun, 22 Jul 2007 18:00:46 -0400 (EDT)
From: "Keith F. Lynch" <kfl at KeithLynch.net>
To: WSFA members <WSFAlist at KeithLynch.net>
Subject: [WSFA] Re: "Fifty Years of the Ultimate Quantum Strangeness"
Reply-To: WSFA members <WSFAlist at KeithLynch.net>

"Elspeth Kovar" <ekovar at panix.com> wrote:
> Michael Walsh wrote:
>> http://www.nature.com/nature/journal/v448/n7149/index.html

>> There's also a book review section by Gary Wolfe:
>> http://www.nature.com/nature/journal/v448/n7149/full/448025a.html

> I (belatedly) took a look at this and discovered that I couldn't get
> any of the articles, just the index, without paying.  Damn.

I noticed the same thing.  Judging by the URL, this appeared in Nature
magazine, so you should be able to read it in any library which
subscribes to that well-know scientific journal.

But even without reading it, I know what it's about.  Fifty years ago,
Hugh Everett wrote a dissertation on a new explanation for quantum
weirdness.  A good example of quantum weirdness is the following:

Light is both particles and waves.  If light goes through a pair of
parallel slits, you'll get an interference pattern, as the light waves
that went through one slit are alternately in phase and out of phase
with light waves that went through the other slit.  A sensitive enough
detector can detect a single photon, a particle of light.  So what
happens when you make the light dim enough that there is only one
photon?  It invariably lands in what would have been one of the bright
bands of the interference pattern, not in one of the dark bands.  But,
intuitively, a photon had to have gone through one slit or the other,
and whichever slit it went through, no light was going through the
other slit to interfere with it.  So why does the photon always land
in what would have been a bright band of the interference pattern,
never in what would have been a dark band?  Sure enough, if you block
one of the slits, there's no longer any preference -- the photon is
equally likely to land in either location.

Another example is the fact that in quantum physics, unlike in
Newton's or even Einstein's theories, knowing the position and
velocity of everything relevant isn't sufficient to predict what will
happen next.  Identical experiments can have different results.  (It
obviously took a lot of work to rule out the possibility that there
was some relevant variable that just wasn't being noticed that was
different between the experiments.  All such hidden variables were
eventually ruled out, to almost everyone's satisfaction.)

Hugh Everett's explanation was that whenever a quantum event could
happen in more than one way -- a neutron decays, or doesn't; a photon
goes through one slit or through the other -- the universe splits in
two, and both branches continue on.  In other words, there are vast
numbers of parallel worlds in which pretty much anything that's
physically possible actually happened.  Worlds in which the South
won the Civil War, etc...

This wasn't just abstract irrelevant theory to Hugh Everett.  He
believed that we are all immortal, as our consciousness would follow
whichever branch we didn't happen to die on.  So he smoked and drank
and ate all the wrong foods, confident that nothing bad could happen
to him.

Maybe he's still alive in some alternate, but in this one he died 25
years ago at age 51.  And after his death, using the same reasoning,
he daughter committed suicide with the intention of rejoining him.

I'm honored to have known him personally.