The reference frames from which observers view quantum events can themselves have multiple possible locations at once — an insight with potentially major ramifications.

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 frames has a storied history in classical physics: Isaac Newton, Galileo and Albert Einstein all relied on them for their studies of motion. A reference frame is essentially a coordinate system (a way of specifying positions and times relative to some zero point, or “origin”) that might itself be in motion. Einstein used reference frames to develop his theories of relativity, which revealed that space and time are not fixed backdrops to the universe, but rather elastic entities that can stretch, scrunch and warp.

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