The void is deceptive. William Unruh showed that an accelerating observer perceives the vacuum as hot. The effect resembles the particle birth near black holes, predicted by Stephen Hawking, but instead of spacetime curvature, acceleration is at work. Yet for massive particles — electrons, for example — the heat is suppressed: it's like trying to hear the ring of a ship's hawser. Even at accelerations close to light speed, the signal is weakened by an unimaginable 10⁹ orders.

The solution: replace the detector with a super-light double. In a superconducting circuit, an 'effective mass' is created — an almost weightless ghost of a particle. It's like taking the thinnest guitar string: it responds to the slightest touch. Just so, the ghost particle under acceleration chisels thermal glow out of the vacuum, detectable by lab instruments.

An unexpected twist: the Unruh effect is the mathematical twin of Hawking radiation, but while the radiation of black holes is almost impossible to observe, this experiment turns quantum heat into something tangible. For the first time, we will be able to see how acceleration births entropy where previously there was only curvature.