Echo in a Wormhole ⚡ экспресс
Linear scalar perturbations of a four-dimensional traversable wormhole proposed by Maldacena, Milekhin, and Popov are studied. The geometry consists of an asymptotically flat region of a near-extremal Reissner-Nordström solution, matched with an AdS₂×S² throat supported by charged massless fermions. An effective potential for wave dynamics is obtained; in the tortoise coordinate, it manifests as two extremely sharp and widely separated barriers. These barriers form a resonant cavity and arise from the geometry near the horizons of the wormhole mouths. Analysis of the response to an initial wave packet inside the throat via time-domain integration shows that the late-time signal contains a clear sequence of echo signals. The echo amplitude depends on the orbital number l: modes with large l produce significantly stronger echoes because the corresponding potential barriers are higher and more reflective, leading to more efficient wave confinement in the throat.
A wormhole is a tunnel that pierces through curved space and connects distant regions of the Universe. Recently, Juan Maldacena and his colleagues proposed a working model of such a hole based on a special combination of spatial curvature and quantum particles. Physicists wanted to find out what an observer would hear if they sent a signal into such a tunnel.
It turned out that the wormhole acts like an echo chamber: its throat is sandwiched between two near-black holes—regions with monstrous gravity. These regions act as mirrored walls. A wave that gets inside bounces between them, each bounce producing a new, weaker burst—an echo. The more twisted the wave (the greater its angular momentum), the higher the gravitational barriers become, and the longer the sequence of echoes rings out. A simple, untwisted wave slips through almost without an echo.
This echo pattern is unique: ordinary black holes swallow the signal immediately, without repetition. If astronomers ever detect similar series of gravitational waves or other pulses, it would be a strong hint of wormholes. Curiously, even gravitational tremors passing through the Earth right now could echo in the same way if there were a traversable tunnel nearby.
🎯 The echo from a wormhole resembles the famous 'whispering gallery' in St. Paul's Cathedral: sound, reflecting off curved walls, repeats many times at the other end.
🎬 In the movie 'Interstellar,' the wormhole is a bridge to another galaxy. Now scientists have shown that a real wormhole could reveal itself through a series of echo signals—like a cosmic sonar.