It Might Be Possible To Detect Gravitons After All

Arthur T Knackerbracket has processed the following story:

Detecting a graviton - the hypothetical particle thought to carry the force of gravity - is the ultimate physics experiment. Conventional wisdom, however, says it can't be done. According to one infamous estimate, an Earth-size apparatus orbiting the sun might pick up one graviton every billion years. To snag one in a decade, another calculation has suggested, you'd have to park a Jupiter-size machine next to a neutron star. In short: not going to happen.

A new proposal overturns the conventional wisdom. Blending a modern understanding of ripples in space-time known as gravitational waves with developments in quantum technology, a group of physicists has devised a new way of detecting a graviton - or at least a quantum event closely associated with a graviton. The experiment would still be a herculean undertaking, but it could fit into the space of a modest laboratory and the span of a career.

[...] Currently, Albert Einstein's general theory of relativity attributes gravity to smooth curves in the space-time fabric. But a conclusive graviton detection would prove that gravity comes in the form of quantum particles, just like electromagnetism and the other fundamental forces. Most physicists believe that gravity does have a quantum side, and they've spent the better part of a century striving to determine its quantum rules. Nabbing a graviton would confirm that they're on the right track.

But even if the experiment is relatively straightforward, the interpretation of what, exactly, a detection would prove is not. The simplest explanation of a positive result would be the existence of gravitons. But physicists have already found ways to interpret such a result without reference to gravitons at all.

[...] It's hard to experimentally probe gravity because the force is extremely weak. You need huge masses - think planets - to significantly warp space-time and generate obvious gravitational attraction. By way of comparison, a credit card-size magnet will stick to your fridge. Electromagnetism is not a subtle force.

One way to study these forces is to disturb an object, then observe the ripples that travel outward as a consequence. Shake a charged particle, and it will create waves of light. Disturb a massive object, and it will emit gravitational waves. We pick up light waves with our eyeballs, but gravitational waves are another matter. It took decades of effort and the construction of the colossal, miles-long detectors that make up the Laser Interferometer Gravitational-Wave Observatory (LIGO) to first sense a rumble in space-time in 2015 - one sent out by a collision between distant black holes.

[...] It would take another conceptual leap to go from a gravitational wave detector to a detector for individual gravitons. In the recent paper, which appeared in Nature Communications in August, Pikovski and his co-authors outlined how the graviton detector would work.

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