WE ARE ALL CREATIONIST NOW:

Over the past hundred years, numerous experiments on elementary particles have upended the classical paradigm of a causal, deterministic universe. Consider, for example, the so-called double-slit experiment. We shoot a bunch of elementary particles -- say, electrons -- at a screen that can register their impact. But in front of the screen, we place a partial obstruction: a wall with two thin parallel vertical slits. We look at the resulting pattern of electrons on the screen. What do we see?

If the electrons were like little pellets (which is what classical physics would lead us to believe), then each of them would go through one slit or the other, and we would see a pattern of two distinct lumps on the screen, one lump behind each slit. But in fact we observe something entirely different: an interference pattern, as if two waves are colliding, creating ripples.

Astonishingly, this happens even if we shoot the electrons one by one, meaning that each electron somehow acts like a wave interfering with itself, as if it is simultaneously passing through both slits at once.

So an electron is a wave, not a particle? Not so fast. For if we place devices at the slits that "tag" the electrons according to which slit they go through (thus allowing us to know their whereabouts), there is no interference pattern. Instead, we see two lumps on the screen, as if the electrons, suddenly aware of being observed, decided to act like little pellets.

To test their commitment to being particles, we can tag them as they pass through the slits -- but then, using another device, erase the tags before they hit the screen. If we do that, the electrons go back to their wavelike behavior, and the interference pattern miraculously reappears.

There is no end to the practical jokes we can pull on the poor electron! But with a weary smile, it always shows that the joke is on us. The electron appears to be a strange hybrid of a wave and a particle that's neither here and there nor here or there. Like a well-trained actor, it plays the role it's been called to perform. It's as though it has resolved to prove the famous Bishop Berkeley maxim "to be is to be perceived."

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