The fabric of spacetime may be frothing with gigantic gravitational waves, and the possibility has sent physicists into a tizzy. A potential signal seen in the light from dead stellar cores known as pulsars has driven a flurry of theoretical papers speculating about exotic explanations.

The most mundane, yet still quite sensational, possibility is that researchers working with the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), which uses the galaxy as a colossal gravitational-wave detector, have finally seen a long-sought background signature produced when supermassive black holes crash and merge throughout the universe. Another interpretation would have it originating from a vibrating network of high-energy cosmic strings that could provide scientists with extremely detailed information about the fundamental constituents of physical reality. A third possibility posits that the collaboration has spotted the creation of countless small black holes at the dawn of time, which could themselves account for the mysterious substance known as dark matter.

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