A clap of the hands compresses the air, and it flies outward — the simplest shock. In space, exploding stars play the role of hands: their shock waves sharply compress gas and trigger chaotic mixing — turbulence. But exactly how explosion energy transfers into eddies of different sizes has long remained a puzzle, because spotting details in distant nebulae is very difficult.
To peek into this process, physicists built a miniature model. Two targets made of carbon-hydrogen mesh were irradiated with a powerful X-ray pulse lasting 30 nanoseconds. The mesh vaporized, and from each target a plasma flow rushed toward the center at speeds tens of times the speed of sound. The flows met after 75 nanoseconds, and at the impact site a layer of churning gas about 4.5 millimeters thick formed — roughly the size of a pencil eraser.
The most surprising discovery was that the vortices remembered where the impact came from. If you yank a tablecloth sharply, the folds first run along the pull and only later tangle. Here it was the same: in large vortices, motion remained elongated along the collision axis, and this anisotropy persisted even at smaller scales. Kinetic energy split roughly as 70% into swirling motion and 30% into compressions and expansions, as if the energy from a handclap mostly went into spinning the air rather than heating it.
This experiment is a bridge between terrestrial measurements and astrophysical phenomena. Now we know that shock-driven turbulence is not completely chaotic: it carries the imprint of the explosion that created it, and that imprint can be discerned even in fine details. Understanding this will help model more accurately how chemical elements mix in supernova remnants, how new stars are born, and how energy is distributed in galactic gas.
The turbulent layer in the experiment existed 15 times longer than it takes sound to cross it — all the while, vortices kept tangling without damping out.
In Peter Watts's novel 'Blindsight', alien ships use turbulence as both a weapon and a means of camouflage — much like in this experiment, where vortices retain a memory of the attack direction.