13.8 billion years ago, the universe swirled in a waltz. The right turn was forbidden. Today, the echoes of that cosmic ball reach us as a barely perceptible ripple in spacetime — gravitational waves. Their existence was predicted by Albert Einstein.

In the first moments after the Big Bang, during the epoch of inflation, the hypothesis of Alan Guth, quantum fluctuations were stretched to cosmic sizes. This created scalar perturbations. They, in turn, spawned gravitational waves, merging into a stochastic background — a cosmic hum pervading all of creation.

Yet this noise carries more than just fundamental tones. The interaction of perturbations produces overtones — non-Gaussianity. It encodes the asymmetry of the dance. To hear the symphony, we need interferometers of unprecedented sensitivity: the Einstein Telescope with 15-kilometer arms and the Cosmic Explorer with 40-kilometer arms.

Ilaria Caporali's group simulated a year of observations with such a network. Numerical simulation combined with Bayesian analysis allowed them to estimate how accurately the non-Gaussianity parameters fNL, τNL, and ˜τNL can be recovered. The results were promising. For the local bispectrum template: fNL = 6.9+3.0-4.0, τNL = 10.2+5.4-5.2 at 68% confidence level. Crucially, they reconstructed the degree of circular polarization Π(f). It showed significant chirality at frequencies above 50 Hz: the early universe indeed twisted waves in one direction.

This discovery connects inflationary physics with profound problems. The same mechanism that broke parity could have generated the excess of matter over antimatter. Enhanced scalar perturbations could have collapsed into primordial black holes — candidates for dark matter. Thus, gravitational waves become a key to the hidden mass. With the launch of new detectors, physicists will read the score of the forbidden dance. The prohibition of the right turn will be decoded. And the first steps of the cosmos will be understood.