In the Quantum World, Even Points of View Are Uncertain

Imagine standing on a railway platform watching a trolley go past. A girl on the trolley drops a bright red ball. To her, the ball falls straight down. But from the platform, you see the ball traverse an arc before hitting the trolley floor. The two of you observe the same event, but from different reference frames: one anchored to the trolley and the other to the platform. The idea of reference…

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