Why an Electron Can Be in Two Places at Once
Why an Electron Can Be in Two Places at Once — After learning of this experiment, I dwelt long on the fact that the act of seeing is not innocent. The moment we look into something, it has already become other than it was before we looked. Are people not the same? The self that is watched and the self when no one is near are not identical. When we say we know a person, we know only the one face he showed us — not all the possibilities he might have held. Nature tells us this: until we ask, the world lies open in far more forms than we have decided.
If there are two doors and a person walks toward them, he can enter only one. It is utterly obvious. Yet when a single tiny grain called an electron was sent through two slits, it behaved as if it had passed through both at once. How can one thing pass through two places at the same time?
In 1801, in an age that quarreled over whether light was particle or wave, Thomas Young passed light through two narrow slits. On the wall appeared alternating bands of bright and dark. Waves from the two slits met: crest upon crest rose higher, and where crest met trough they cancelled. Light was a wave. So it seemed settled. But a century later, when a single electron stood in light place, all common sense began to crumble.
Electrons were fired through the two slits one at a time, very slowly. Since they went one by one, the wall should have shown one dot at a time. Yet as the dots piled up, the same striped pattern as light emerged. A lone electron, traveling alone, had passed through both slits at once and interfered with itself. More astonishing was what followed. The moment a detector was switched on to see "which slit it went through," the stripes vanished and the electron passed obediently through only one. Unobserved, two; observed, one. Nature showed a different face depending on how we asked.
- Quantum computers harness exactly this "many at once" nature for calculation, feeling along many paths simultaneously where we once solved one path at a time.
- Even our retina sensing of starlight begins as a quantum event — whether one grain of light strikes a molecule or not. The rules of the smallest world sit at the first threshold of our senses.
- Lasers, LEDs, the semiconductors in our phones — nearly every everyday device runs on the rules of this microscopic world. A nature that defies common sense holds up our lives.
分은 칼로 무엇을 갈라 나누는 형상이니, 하나의 전자가 두 길로 갈라져 제 자신과 만나는 중첩의 신비와 통한다.
Meet this hanja in Cheonjamun →After learning of this experiment, I dwelt long on the fact that the act of seeing is not innocent. The moment we look into something, it has already become other than it was before we looked. Are people not the same? The self that is watched and the self when no one is near are not identical. When we say we know a person, we know only the one face he showed us — not all the possibilities he might have held. Nature tells us this: until we ask, the world lies open in far more forms than we have decided.
