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 (opens a new tab) 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.
“It’s something that can be reached in a few years of research,” said Matteo Fadel (opens a new tab), an experimentalist at the Swiss Federal Institute of Technology Zurich (ETH Zurich) who was not involved in the proposal.
“It’s a very original proposal and well thought-out,” said Frank Wilczek (opens a new tab), a Nobel Prize-winning physicist at the Massachusetts Institute of Technology with a long-running interest in graviton detection. “It would be real progress in the field.”
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.
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