Space trembles: quantum particles are to blame ⚡ экспресс
In postquantum theory, classical gravity connects with quantum matter, causing spacetime to fluctuate stochastically (randomly). The authors broke these fluctuations down into simple components (spin-2 and spin-0 modes) and showed the theory is mathematically consistent. By computing the noise of the Newtonian potential, they compared it with data from the LISA Pathfinder mission and constrained one parameter of the theory; the other is constrained by the stochastic gravitational-wave background. Amusingly, the jittering of spacetime resembles the Brownian motion of pollen, just on a Universal scale.
In one model, spacetime is a smooth lake, and quantum particles are fish swimming in it. Their motion inevitably creates ripples. The math insists that the water trembles — otherwise the theory collapses. This trembling is strictly ordered and comes in two types. One wave is like gravitational waves, the other like compression waves. Both spread out like ink in water. Scientists calculated the trembling's strength and checked it against data from the LISA Pathfinder probe, which senses forces a billion times smaller than the weight of a grain of sand. The mysterious noise picked up by the instrument fits the calculations exactly. Moreover, background gravitational waves in the expanding universe put a cap on the trembling: if it were stronger, we would have already noticed extra ripples. It seems the fabric of reality constantly quivers because of quantum particles, and future detectors will hear its breath.
🎯 LISA Pathfinder was so sensitive it could measure a force comparable to the weight of a bacterium on Earth. The mysterious excess noise it detected could be the first hint of the quantum trembling of spacetime.