The DESI cosmic observatory gathered light from 1,550 exploding stars and millions of galaxies. It was expected that the Universe accelerates unimpeded, like a car picking up speed on a straight road. But the data showed a slight braking.

To catch the signal, astrophysicists tracked the stretching of light from distant objects and frozen density waves from the early Universe. A mathematical algorithm processed the data and favored a scenario where, in addition to dark energy (the repulsive force), a tiny attractive addition is at work. This “brake” eases contradictions: the expansion rate measured by different methods finally begins to align. Edwin Hubble discovered that galaxies are flying apart, and Adam Riess that this flight is accelerating. Now their colleagues are searching for where the brake hides.

The final answer will come from Euclid and DESI. For now, the cosmos is a car that keeps accelerating, even though somewhere beneath the gas pedal a tiny brake awaits.