The quantum world is weird and illusive. Is it a trick of the light that scientists can’t determine if ours is a world of waves or particles?
When Ice melts in your hands and pools at your feet, do you question that it is water slipping, dripping through your fingers? Are you even surprised by its metamorphosis?
Just as water can be observed in more than one state, matter, in general, can apparently change states. The double-slit experiment shows that small matter is a wave until the wave becomes a particle; the wave changes to a particle, apparently, through participation with an observer.
Bruce Rosenblum and Fred Kuttner in their book, Quantum Enigma describe the puzzle this way:
“A small object is sent into a pair of well-separated boxes. Looking into the boxes, you always find the whole object in a single box, and the other box empty. According to quantum theory, however, before the object was observed, it was simultaneously in both boxes, not wholly in a single box. An interference experiment, which you could have chosen, would have established that. By your free choice, you could establish either of two contradictory prior realities.”
How can something be in two boxes at once? A wave can be in more than one place, but a particle is in one place only, right?
The is it a wave or is it a particle question still disturbs physicists in the 21st century, almost a century after the discovery of quantum mechanics. The main problem remains: does the wave collapse to a particle due to observation? What counts as an observer? Does the wave collapse at all? Could something else explain the quandary posed by the double-slit experiment?