At the heart of a black hole, physics as we know it collapses. Gravity, space and time merge into an inextricable tangle, creating conditions that defy our understanding. But if we can't visit a black hole, maybe we can bring a piece of it to Earth. A team of researchers from the University of Nottingham did it, creating for the first time a "quantum vortex" in a helium superfluid at ultra-low temperatures. A pioneering experiment (I link it here) which could open a window into the deepest secrets of the universe.
Superfluid, a dive into the unknown at -271°C
Imagine immersing yourself in a bath of liquid helium, cooled to temperatures just above absolute zero (-273,15°C). Don't forget your costume, please. Once “soaked,” you would discover that matter behaves in strange and wonderful ways, acquiring quantum properties that defy common sense. And it is precisely in these extreme conditions that the researchers created their “mini-black hole”: a swirling vortex in the superfluid, a quantum tornado that drags everything with it.
It wasn't easy. At these temperatures, helium develops an innate resistance to the formation of large vortices, preferring to fragment into myriad tiny “quanta” that tend to spread out. To overcome this obstacle, the team had to confine tens of thousands of these quanta into a compact object, resulting in a swirling flow of record intensity in the realm of quantum fluids.
When spacetime starts dancing (in the superfluid)
What does this experiment have to do with black holes? Well, more than you might think. According to Einstein's general theory of relativity, black holes are not just massive objects, but actual distortions of spacetime. And when a black hole rotates, it drags the very fabric of the universe with it, in an effect called “frame dragging” or the “Lense-Thirring effect.”
And it is precisely this strange cosmic ballet that the researchers managed to reproduce in their quantum tornado. The tiny waves generated on the surface of the superfluid, in fact, mimic the way in which the gravity of a rotating black hole influences the surrounding spacetime. A fascinating parallel, which opens the way to new study possibilities.
Through the quantum mirror
I want to make it clear, even if anyone who reads these articles without stopping at the title knows it well: the helium vortex is not a real black hole. It will not suck us into its event horizon, nor crush us into a singularity. But it is a model, a lens through which we can peer at some of the most exotic phenomena in the universe.
He explains it well Silke Weinfurtner, leader of the Black Hole Laboratory where the experiment was conducted:
Now, with our most sophisticated experiment, we have taken the research to the next level, which could lead us to predict how quantum fields behave in curved spacetimes around astrophysical black holes.
Shall I try to translate? This quantum tornado could be our mirror Alice, a portal to a world where the laws of physics bend and twist in unimaginable ways. A world that, until yesterday, we could only dream of exploring.
A step at a time
We are only at the beginning of the journey: the Nottingham experiment is a first, pioneering step towards simulating quantum physics in curved spacetime. It will take years, perhaps decades, before we can replicate all the gravitational vagaries of a real black hole in the laboratory. A lot of superfluid will pass under the bridge.
Every journey, however, even the longest, begins with a single step. And this first step has already taken us beyond the limits of what we thought possible. We can look the unknown in the eye and, perhaps, begin to understand it.
Perhaps, one day, we will be able to create real "black holes in a test tube", replicating on a small scale all the mysteries and wonders of these cosmic titans. Perhaps we will learn to navigate the currents of spacetime, dancing on the edge of the event horizon.
To infinity and beyond, right?
