Forget particles and waves. When it comes to the true guise of material reality, what's out there is beyond our grasp
"If you haven't found something strange during the day," John Archibald Wheeler is said to have remarked, "It hasn't been much of a day." But then, strangeness was Wheeler's stock in trade. As one of the 20th century's leading theoretical physicists, the things he dealt with every day - the space- and time-bending warpings of Einstein's relativity, the fuzzy uncertainties and improbabilities of quantum physics - were the sort to boggle the minds of most mere mortals.
Even so, one day in 1978 must have been quite something for Wheeler. That was when he first lit on a very strange idea to test how photons might be expected to behave. Half a century earlier, quantum physics had produced the startling insight that light - everything in the quantum world, in fact - has a dual character. Sometimes it acts as if made of discrete chunks of stuff that follows well-defined paths - particles. At other times, it adopts the more amorphous, space-filling guise of a wave. That led to a question that exercised Wheeler: what makes it show which side, and when?
It took a while for the test Wheeler devised to become experimental reality. When it finally did, the answer that came was strange enough. Now, though, the experiment has been redone with a further quantum twist. And it's probably time to abandon any pretence of understanding the outcome. Forget waves, forget particles, forget anything that's one or the other. Reality is far more inscrutable than that.To read more, click here.