Scientific American 2019-04

April 2019, ScientificAmerican.com 49

Physicists attempting

to unify the theories of

gravity and quantum

mechanics have long thought practical experiments

were out of reach, but new proposals offer a chance

to test the quantum nature of gravity on a tabletop

By Tim Folger

Photographs by Mattia Balsamini

QUANTUM

PHYSICS

IN BRIEF

To unify the famously uncooperative theories of

quantum mechanics and general relativity, scien-

tists will likely have to reach down to the unimagin-

ably small realm of the “Planck scale.” Practical

experiments probing this scale have long been

thought impossible, but several new proposals

stand to change that.

Physicists are hoping that by making extremely

precise measurements of gravity in small-scale set-

ups—experiments that will fit onto a tabletop in a

laboratory—they can detect effects from the inter-

section of gravity and quantum theory.

The experiments aim to show whether gravity

becomes quantized—that is, divisible into discrete

bits—on extremely tiny scales.

GRAVITY IN

THE LAB

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