Gravity can snap and reconnect like the sun's magnetic field, study finds

In a prior study, published in Physical Review Letters earlier this year, the pair applied this framework and found that gravitational fields can form two-dimensional structures called gravitational field sheets. One dimension of a sheet stretches through space; the other stretches through time, so each sheet is the trail a line leaves as time passes. A snapshot at any instant catches each sheet as a line, much like the field lines drawn around a magnet. And under certain conditions, these sheets evolve without breaking or changing their connections.

The takeaway: gravity, written in the right mathematical language, produces rope-like structures that behave like magnetic field lines frozen in plasma.

What did the new study find?

The new paper shows the frozen-in rule doesn't always hold. "Gravitational field sheets can break and reconnect in a different arrangement, much like magnetic field lines do in plasmas," Comisso said.

The researchers also drew a careful boundary around the effect. Breaking the frozen-in rule doesn't, by itself, guarantee reconnection. Sometimes the sheets merely slip relative to the flow carrying them, staying intact because they remain frozen into a different flow. Genuine reconnection happens only when no such alternative flow exists.

The team derived equations describing how quickly the reconnection can occur and how it affects the transfer of energy and momentum. In general relativity, gravity and matter can trade energy and momentum, with only their combined total conserved — and the study shows reconnection changes the local rate of that exchange. Reconnection also alters gravitational helicity, the gravitational counterpart of a quantity measuring how twisted and interlinked magnetic field lines are. Frozen-in sheets keep their helicity fixed; reconnection can create or destroy it.

"Everything follows from Einstein's general relativity," Comisso said. "Einstein developed his theory more than a century ago, and it has passed an extraordinary number of experimental tests. Yet even after more than a century, there are still new insights to be gained from those same equations."

The takeaway: pure math, drawn from a 1915 theory, predicts a new kind of gravitational behavior.

Could black hole collisions show it?

What could trigger gravitational reconnection in nature remains an open question. The candidates the researchers suggest include the singularities thought to lurk at the hearts of black holes, the combined effect of gravitational ripples too small to track individually, and quantum effects linked to Hawking radiation — the faint glow black holes are predicted to emit.

"We're still at the beginning, but one of the most interesting possibilities is that gravitational reconnection could play a role in extreme events, such as the merger of two black holes or the collision of neutron stars," Comisso said. "These are environments where gravity is extremely strong and the geometry of spacetime changes dramatically."

Such collisions send out ripples in space-time called gravitational waves, which detectors such as LIGO, the Laser Interferometer Gravitational-Wave Observatory, have been recording since 2015. "We'd like to understand whether gravitational reconnection could contribute to transferring energy, and whether it might leave a recognizable signature in gravitational waves," Comisso added. "We don't know the answers yet, but these are questions that we can now begin to investigate."

The takeaway: this is early-stage theory, but it hands gravitational-wave astronomers a concrete new question to chase.