SPACE-TIME'S frothy nature could be blurring the cosmos. If our views of gamma-ray bursts halfway across the universe are intrinsically fuzzy, as some predict, then the finding could help unite the twin pillars of theoretical physics: quantum mechanics and general relativity.
The two theories disagree about the texture of the universe, with relativity saying space-time is smooth and quantum mechanics claiming it is grainy, especially on small scales. Peacemaking "quantum gravity" schemes, like string theory, are notoriously hard to test, but do predict that space-time should be frothy at close range.
This "quantum foam" would only show up at scales of 10-35 metres, far too small to observe directly. But it might jostle the paths of photons enough for us to observe its effects across the universe.
"They're very small perturbations, but they add up," says Eric Steinbring of the National Research Council Canada in Victoria.
In 2003, Richard Lieu at the University of Alabama in Huntsville looked for this blurring in optical images of galaxies from the Hubble space telescope, but found nothing significant. Others have since argued that our ability to observe far more distant objects at all means the foam's effects must be weak or non-existent.
But Steinbring says that high-energy photons – belonging to gamma rays and X-rays – could be perturbed by even weaker fluctuations in the quantum foam (http://ift.tt/17pXIme). He tweaked the equations that describe how tiny uncertainties due to the foam add up as a photon crosses space, and compared his predictions with gamma-ray data from NASA's Fermi telescope. The results are consistent with some blurring, he says.
"I take it as a promising result," says Lieu. "Quantum gravity is the ultimate in excitement."
This article appeared in print under the headline "Key to quantum gravity may lurk in cosmic haze"
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