Is Space a Kind of Sea?

What if everything is a ripple on something we cannot see?

Look at a wave rolling across a pond. The wave is real. You can measure how fast it moves and how much it carries. But the wave is not a thing sitting on the water. It is something the water is doing.

Now ask the strange question. What if an electron is like that? Not a tiny brick, but a pattern in something deeper. Some physicists take this seriously, and they got there through very cold liquids.

What we know for sure

Cool helium down far enough and it turns into a liquid. Cool it further and it becomes a superfluid. A superfluid flows with no friction whatsoever. Start it swirling and it just keeps going.

A Russian and Finnish physicist named Grigory Volovik spent his career on such liquids. He noticed something startling. The math for ripples inside superfluid helium looked oddly familiar. It looked almost exactly like the math for particles in our own universe.

Even better, fluids can copy gravity. Make a fluid flow faster than its own waves travel. You have built a horizon. Sound cannot escape it, the way light cannot escape a black hole. In 2016 Jeff Steinhauer measured the faint glow leaking out of one such laboratory horizon.

What scientists are testing right now

So here is the big idea. Perhaps our own space is a superfluid too. Every particle would then be a ripple in it. Scientists are testing this idea, and it is far from settled.

The test is clever. A real liquid has a resting state, a way of sitting still. If space were a liquid, that would leave a fingerprint. Light of different colors should travel at very slightly different speeds.

So astronomers watch enormous flashes called gamma-ray bursts, billions of light years away. After such a long trip, even a tiny difference would show up as a delay. Scientists measured this carefully. The colors arrive together.

That result matters. It rules out the simple versions of the idea. The careful versions survive, and that is where the work has moved.

Why it matters

There is a prize hiding here. Add up the energy that empty space should hold and you get a colossal number. Then look at what astronomers actually see and you get a tiny one. The two disagree by a staggering amount.

It is one of the biggest open questions in all of physics. A superfluid kind of space might answer it neatly. Nobody would have to fiddle the numbers to make it work.

Your turn

If you were a ripple, could you ever find out what you were rippling on? What experiment could a ripple possibly do?

Nobody has settled this. The measurements keep getting sharper. Perhaps you will take the next one.