One of the biggest mysteries in physics today is that of dark matter and dark energy, those shadowy entities that we can't see or identify, but which current theories suggest make up about 95 percent of the cosmos. It's a bit of an embarrassment, really, that such a big chunk of existence often elicits shoulder shrugs from our most brilliant minds.

But now, there's hope. One Oxford astrophysicist, Jamie Farnes, thinks he might have a solution for why our universe seems to be composed of such shady substances, and it's an idea that promises to explain dark matter and dark energy in one fell swoop, reports The Conversation.

Or, perhaps more appropriately, one fell goop.

Instead of dark matter and dark energy, Farnes posits a single, unifying substance that he calls "dark fluid." And like some sort of syrupy slime from the netherworld, dark fluid behaves unlike anything else in the known universe.

When you push dark fluid, it moves toward you instead of away. When you pull it in, it repels. It's basically a real-life physics rendering of the Upside Down (for those familiar with "Stranger Things" lore).

Although instead of being inhabited by mythical demogorgons and mind flayers, Farnes' dark fluid-filled Upside Down is composed of negative mass. It's like putting a minus sign on the universe.

Why negative mass makes sense

A negative mass substance might sound deeply anti-intuitive, but it has surprising explanatory power. For instance, one of the biggest unexplained mysteries in the universe is the observation that galaxies spin way too fast for the force of gravity to counteract. Like any roundabout in a playground, galaxies should fling apart as they spin. This is why scientists think there must be more matter in galaxies than they can see, i.e., dark matter.

But if we instead posit the existence of a negative mass substance, a dark fluid, that reacts to the outward force of spinning galaxies, not by flinging apart, but by pulling in, then we can account for our observations.

Dark energy, which is the mysterious force that scientists posit to explain the observation that our universe is expanding at an accelerated rate, can also be conveniently explained with dark fluid. Farnes found that computer models of the universe that include a negative mass substance behave in the same way that dark energy is supposed to act, with far less mystery attached.

So is this it? Has Farnes solved the mystery of dark matter and dark energy?

Maybe.

Dark fluid offers a compelling theory, but even Farnes admits it could be totally wrong. It will take real-life empirical observations, rather than compelling speculations, before anything can be known for sure. But so far, the evidence is promising.

"The theory seems to provide answers to so many currently open questions that scientists will — quite rightly — be rather suspicious," writes Farnes. "However, it is often the out-of-the-box ideas that provide answers to longstanding problems. The strong accumulating evidence has now grown to the point that we must consider this unusual possibility."

The mystery of dark matter and dark energy might just have been solved
Oxford scientist posits a unifying "dark fluid" that explains many of the current mysteries in astrophysics.