Detecting the Temporal Gravitational Wave of Late-Universe Hawking Cascades

Cosmology has long been defined by the Cosmic Microwave Background, the faint radiation echo of the Big Bang. Now, a group of theoretical physicists are searching for a signal that is astronomically fainter and infinitely more profound: The Last Echo. This is the proposed name for a temporal gravitational wave—a ripple not from the past, but propagating backward in time from the far-future end of the universe.

The theory holds that as the very last supermassive black hole evaporates via Hawking radiation, it will trigger a final “cascade” that shakes spacetime itself. This event, occurring in a post-truth world where matter and information have long since decayed, would be the final “truth” of the cosmos. The search for this signal at observatories is, in a very literal sense, a search for ultimate meaning—a definitive confirmation of the universe’s fate. Detecting this signal would not only validate Hawking’s theories on an unimaginable scale but would prove that the beginning of time is inextricably linked to its very end.