Puzzling GW190521 could be wormhole echo from parallel universe, study suggests

In 2019, scientists detected GW190521, a gravitational-wave burst lasting less than 10 milliseconds that did not exhibit the rising chirp typical of binary black-hole inspirals. A preprint by researchers led by Qi Lai of the University of Chinese Academy of Sciences proposes that the event could be an echo from a collapsing wormhole connecting our universe to a parallel one. The authors caution that the wormhole explanation is not the most likely, but it cannot be ruled out.

GW190521 stands out in the gravitational-wave catalog because the resulting black hole weighed about 141 solar masses and the signal lacked the gradual increase in amplitude that normally marks black holes spiraling toward each other. The event was detected by the network of LIGO and Virgo observatories, and scientists say the data barely fit the standard scenario of two black holes merging directly without a prolonged inspiral. Lai and colleagues quantified what a wormhole-connected echo would look like and compared it with the actual signal, finding that the wormhole model cannot be ruled out by the data. While the study notes the conventional collision explanation fits better, the difference is not statistically decisive enough to exclude a wormhole interpretation.

Gravitational waves are ripples in spacetime produced when massive, dense objects accelerate, such as black holes in binary systems. Einstein’s theory predicts that these waves propagate at light speed and can be detected far from their source using highly sensitive interferometers. The LIGO detectors use laser light shot down two 4-kilometer-long arms, with the light recombined to measure tiny changes in distance caused by passing waves. In a robust network, identical signals should appear in both detectors almost simultaneously, despite local noise such as raindrops, earthquakes, or wind.

The wormhole hypothesis imagines a scenario in which the collision of two black holes briefly creates a throat linking our universe to another. If so, the ringdown signal produced in the other universe could pass through the wormhole and emerge in ours as a very short-duration echo pulse. The researchers modeled this possible imprint and compared it to GW190521, alongside a standard collision model in our own universe. They concluded that the data do not decisively favor either explanation, leaving the wormhole scenario as a viable, though not preferred, hypothesis. A confirmation would have profound implications, potentially offering the first direct glimpse into a universe beyond our own.

Beyond this specific event, the finding underscores how gravitational-wave astronomy continues to test the limits of current theory. The standard picture—binary black holes spiraling inward, producing a characteristic rising chirp—has explained roughly two dozen notable detections. Yet GW190521’s abrupt end and the unusually large remnant mass keep researchers attentive to alternative interpretations and exotic physics. The ongoing accumulation and analysis of data from LIGO, Virgo, and, in the future, additional detectors, will be essential to determine whether wormholes exist as physical realities or remain speculative constructs in theoretical models.