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There’s this experiment in quantum physics that shows the weird dual nature of atoms: sometimes particles, sometimes waves. If you fire enough bullets at a (bullet-proof!) screen with a couple of slits in it for them to go through, eventually you’ll get a pattern on the wall behind the screen that shows two bands of bullet-holes, one for each slit, with a bulletless band inbetween. So if atoms are particles, mini-bullets, then if you do the same kind of thing with atoms you get the same three-band pattern on the ‘wall’. But in fact when they fire atoms – just one at a time, so they don’t hit each other – at a two-slitted screen in this way, they get an interference pattern on the ‘wall’ behind, as if what they’d fired were waves, not particles, that had gone through both slits at once.