The Observer

Wheeler’s hunch is that the universe is built like an enormous feedback loop, a loop in which we contribute to the ongoing creation of not just the present and the future but the past as well. To illustrate his idea, he devised what he calls his “delayed-choice experiment,” which adds a startling, cosmic variation to a cornerstone of quantum physics: the classic two-slit experiment.

The outcome of the experiment depends on what the physicists try to measure: If they set up detectors beside the slits, the photons act like ordinary particles, always traversing one route or the other, not both at the same time. In that case the striped pattern doesn’t appear on the film. But if the physicists remove the detectors, each photon seems to travel both routes simultaneously like a tiny wave, producing the striped pattern.

Wheeler conjectures we are part of a universe that is a work in progress; we are tiny patches of the universe looking at itself— and building itself. It’s not only the future that is still undetermined but the past as well. And by peering back into time, even all the way back to the Big Bang, our present observations select one out of many possible quantum histories for the universe.

– excerpts from article found here here http://discovermagazine.com/2002/jun/featuniverse

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