It sounds like the setup for a joke: If radio waves give you radar and sound gives you sonar, what do gravitational waves get you?

The answer may be "GRADAR" — gravitational wave "radar" — a potential future innovation that could use reflections of gravitational waves to map the unseen universe, say researchers in a paper acknowledged to Physical Review Letters. By searching for these signals, scientists may have the option to track down dull matter or faint, fascinating stars and find out about their profound insides.

Astronomers regularly use gravitational waves — voyaging ripples in the texture of space and time itself, first recognized in 2015 — to watch cataclysmic events that are difficult to study with light alone, such as the converging of two dark holes (SN: 2/11/2016).

Yet, physicists have also had some significant awareness of a seemingly useless property of gravitational waves: They can take a different path. Einstein's theory of gravity says that spacetime gets twisted by issue, and any wave passing through these distortions will take a different path. The upshot is that when something emits gravitational waves, part of the signal comes straight at Earth, however some could show up later — like a reverberation — subsequent to following longer paths that twist around a star or whatever else weighty.

Scientists have always thought these later signals, called "gravitational glints," should be too frail to even think about recognizing. Be that as it may, physicists Craig Copi and Glenn Starkman of Case Western Reserve University in Cleveland, Ohio, took a jump: Working off Einstein's theory, they determined how strong the signal would be when waves scatter through the gravitational field inside a star itself.

"Shockingly, you seem to get a lot bigger result than you would have expected," Copi says. "It's something we're still attempting to understand, where that comes from — whether it's authentic, even, because it just seems unrealistic."

In the event that gravitational glints can be so strong, astronomers could possibly use them to follow the insides of stars, the group says. Researchers could try and search for massive bodies in space that would otherwise be impossible to identify, similar to globs of dull matter or solitary neutron stars on the other side of the observable universe.

"That would be an extremely thrilling test," says Maya Fishbach, an astrophysicist at Northwestern University in Evanston, Ill., who was not engaged with the study.

However, there are still reasons to be cautious. Assuming this peculiarity stands up to more point by point scrutiny, Fishbach says, scientists would have to understand it better before they could use it — and that will most likely be troublesome.

"It's an exceptionally hard estimation," Copi says.

Be that as it may, similar challenges have been defeated previously. "The entire story of gravitational wave identification has been that way," Fishbach says. It was a struggle to do all the math expected to understand their measurements, she says, however presently the field is taking off (SN: 1/21/21). "This is an ideal opportunity to truly be innovative with gravitational waves."