When a distant galaxy sends us light, it dims with distance, and from that dimming, we can tell how far away it is. Gravitational waves work in much the same way: the farther their source, the weaker the ripple in space that detectors on Earth pick up. But if our world has hidden dimensions, gravity might 'leak' into them, and the waves would fade faster than usual.

The authors took a catalog of 141 mergers of compact objects, black holes and neutron stars, and compared the measured loudness of the waves with distances to galaxies from the GLADE+ catalog. This method is called a 'dark siren': unlike optical flashes, it doesn't require seeing light from the collision. If gravity leaks into a fifth dimension, the waves weaken more than general relativity predicts.

The scientists introduced two parameters: the number of dimensions D and the transition scale $R_c$, at which gravity changes its behavior. The analysis yielded D = 4.38 with a fairly wide uncertainty range — from 3.37 to 6.29. This means the data don't yet contradict the usual four dimensions. The value of $R_c$ remained almost unconstrained: the transition scale could be very large, and current detectors simply don't feel it.

The conclusion is cautious: four-dimensional general relativity has held up again. But the dark siren method is just beginning to gain strength. With each new catalog of observations, sensitivity will grow, and someday we might see that very kink in the wave's fading — a sign that space is more complex than it seems.