What if spacetime were a kind of fluid? This is the question tackled by theoretical physicists working on quantum gravity by creating models attempting to reconcile gravity and quantum mechanics. Some of these models predict that spacetime at the Planck scale (10-33cm) is no longer continuous – as held by classical physics – but discrete in nature. Just like the solids or fluids we come into contact with every day, which can be seen as made up of atoms and molecules when observed at sufficient resolution. A structure of this kind generally implies, at very high energies, violations of Einstein’s special relativity (a integral part of general relativity).
In this theoretical framework, it has been suggested that spacetime should be treated as a fluid. In this sense, general relativity would be the analogue to fluid hydrodynamics, which describes the behaviour of fluids at a macroscopic level but tells us nothing about the atoms/molecules that compose them. Likewise, according to some models, general relativity says nothing about the “atoms” that make up spacetime but describes the dynamics of spacetime as if it were a “classical” object. Spacetime would therefore be a phenomenon “emerging” from more fundamental constituents, just as water is what we perceive of the mass of H2O molecules that form it.
Stefano Liberati, professor at the International School for Advanced Studies (SISSA) in Trieste, and Luca Maccione, a research scientist at the Ludwig-Maximilian University in Munich, have devised innovative ways of using the tolls of elementary particle physics and high energy astrophysics to describe the effects that should be observed if spacetime were a fluid. Liberati and Maccione also proposed the first observational tests of these phenomena. Their paper has just been published in the journal Physical Review Letters. Via Liquid spacetime: A very slippery superfluid, that’s what spacetime could be like.