A stone falls into a well, and a second later, a splash. A star falls into a black hole, and disappears beyond the horizon, leaving only a ripple in space. But what if the bottom of the well is not a dead end but a passage? In the usual picture, matter compresses into a point of infinite density — a singularity. Here, the equations break down like a watch caught in a concrete mixer.

The authors replaced this point with a quantum viaduct. In their model, a black hole does not end in a dead end but continues as a tunnel into another universe — thanks to corrections from the theory of "safe gravity." The key element is the parameter ξ (xi), which acts like a volume knob for quantum effects. The larger it is, the more noticeable the "terrain" near the horizon changes.

A particle orbiting such a hole traces intricate patterns: zooms (dips toward the horizon) and whirls (loops around the center). These loops resemble the steps of a dancer who sometimes spins in place, sometimes dashes across the edge of the stage. The quantum parameter ξ lengthens the whirl phase — the dancer lingers in a pirouette before moving to the next circle. Orbital frequencies shift, and this changes the rhythm of gravitational waves emitted by the system.

When a light object (say, a neutron star) falls into such a hole, it sends waves in the millihertz range, like bass notes from a cosmic organ. Detectors LISA, Taiji, and TianQin, which will start operating in the 2030s, will be tuned to exactly this register. Calculations showed: as ξ increases, the signal amplitude grows monotonically, and the phase shifts. In other words, the quantum bridge not only changes the volume but also disrupts the rhythm, and this can be eavesdropped.

Thus, the particle's dance reveals the geometry of the abyss. The final chord is not a splash but a pure note by which we will know whether a black hole has a bottom.