Not only might spacetime be a fluid, some say, but perhaps a slippery one at that:
Now researchers suggest that if spacetime is a fluid, it must be an extraordinary kind of fluid known as a superfluid. These findings could help test models of quantum gravity.
A superfluid is a fluid that flows with virtually zero friction or viscosity. In comparison, water might seem as slow as molasses. Liquid helium can behave like a superfluid when cooled to temperatures just a few degrees above absolute zero, the coldest possible temperature.
Scientists have looked for paradoxical or unlikely predictions in models that treat spacetime as a fluid in order to support or disprove these models. For instance, past research suggested that photons might travel at different speeds depending on their energy if spacetime is a fluid.
The researchers found that if spacetime was a viscous fluid, it would rapidly dissipate the energy of photons and other particles along their paths. Since astronomers can see photons traveling from stars and galaxies located billions of light years away, Liberati and Maccione’s calculations revealed that if spacetime is a fluid, it must be a superfluid. More.
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