"Whither existence?" a real constructivist

[Ian Murray]

[NYTimes]
[snip]
Back in his office Dr. Wheeler busied himself at the blackboard
with a diagram that is emblematic of quantum weirdness, and of his
hope for constructing the universe and its laws
"higgledy-piggledy," as he likes to call it, out of nothing.

It is called the double slit experiment. In it an electron or any
other particle flies toward a screen with a pair of slits. Past
the screen is a physicist with a choice of two experiments. One
will show that the electron was a particle and passed through one
or another slit; the other will show that it was a wave and passed
through both slits, producing an interference pattern. The
electron will turn out to be one or the other depending on the
experimenter's choice.

That was weird enough, but in 1978 Dr. Wheeler pointed out that
the experimenter could wait until after the electron would have
passed the slits before deciding which detector to employ and thus
whether it had been a particle or wave. In effect, in this
"delayed choice" experiment, the physicists would be participating
in creating the past.

In a 1993 paper Dr. Wheeler likened such a particle to a "great
smoky dragon," whose tail was at the entrance slits of the chamber
and its teeth at the detector, but in between - before it had been
"registered" in some detector as a phenomenon - was just a cloud,
smoky probability.

Perhaps the past itself is such a smoky dragon awaiting our
perception.

He wonders if the delayed choice experiment is a prescription for
how the universe can be built up from information, as in a cosmic
game of 20 questions, a series of yes-no decisions resulting from
billions upon billions of quantum observations. It's a concept
that has gone by many names over the last few decades from
"genesis by observership" to "participatory universe" to the
current fashion, "it from bit."

Typically there is a diagram, a cartoon actually, which consists
of a giant U with an eyeball on top of one stem looking back at
the other. The skinny unadorned end of the U is the Big Bang, he
explained, tracing his finger along the loop.

"The model of the universe starts out all skinny and then gets
bigger," he said. "Finally it gives rise to life and the mind and
the power to observe, and by the act of observation of those first
days, we give reality to those first days."

< http://www.nytimes.com/2002/03/12/science/physical/12WHEE.html >