Currently there is a huge rift in the world of physics between the laws that govern the small things and those that govern the big things. Our knowledge of what happens on the tiniest scale is called quantum mechanics, while our knowledge of the big things — on the scale of spacetime and gravity — is covered by general relativity. The hitch is that the two theories are fundamentally incompatible.

Therefore, the next big leap for physicists is to find a unifying theory of the cosmos that can combine our understanding of the two worlds, a so-called "theory of everything." A number of compelling theories are currently vying for space in this theoretical colosseum. For instance, one such scenario involves thinking of gravity in terms of packets of energy known as gravitons.

But another intriguing new scenario that scientists are increasingly considering is the idea that spacetime is a super-slippery fluid, reports Inside Science. According to this theory, the properties of gravity would emerge from the overall behavior of this fluid, rather than its individual parts, similar to how the flow of water can be explained by fluid equations rather than by the properties of the individual molecules that make it up.

This would link the quantum world with the world of gravity because it would eliminate the need to reduce one to the other, but still offer an explanation for how the properties of gravity can emerge from its most basic constituent parts. 

Spacetime couldn't act like just any fluid, though. Spacetime would have to be super-slippery. It would have to be so slippery, in fact, that it would have almost no friction or viscosity whatsoever. This kind of fluid is what physicists refer to as a "superfluid." Superfluids are so slippery that they make water look as slow as molasses by comparison.

The reason that spacetime couldn't be a viscous fluid is because if it was, then it would rapidly dissipate the energy of photons and other particles along their paths, which is not what is observed.

Even so, it could help to confirm this fluid theory of gravity if spacetime had at least a little bit of viscosity. Scientists have therefore proposed analyzing gamma rays and high-energy neutrinos from deep space to see if any of their energy has dissipated, even by just a tiny measure. Such a finding would be a big boost to the idea that spacetime is a fluid.

"This model provides a significant new probe of the nature of spacetime and possible quantum gravity theories by using high-energy astrophysical observations," said theoretical astrophysicist Floyd Stecker at NASA's Goddard Space Flight Center, in Greenbelt, Maryland.

The anti-intuitive but bedazzling ways that modern theories of physics attempt to explain our cosmos are truly fodder for the imagination. Perhaps we, and everything else in the universe, are awash in a super-slippery sea, whirling, sliding, percolating through a cosmic waterpark of sorts. At the very least, such an idea has the potential to make existence seem that much more wondrous and fun.

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