"Quantum shadows: The mystery of matter deepens"
Link to New Scientist
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"One day in 1978 must have been quite something for [a scientist called] John Archibald 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 skip introduction go to 8.5 minutes, and to skip the wave-particle history lesson go to 19.5 minutes.)