A new technique to detect gravitational waves not only promises to reveal ripples in spacetime — it might redefine how we understand gravity itself, using light from the farthest reaches of the cosmos.
Key Points at a Glance
- CU Boulder astrophysicist seeks gravitational waves using quasar motion, not pulsars
- Gravitational waves warp spacetime in multiple directions, not just along our line of sight
- Darling’s work may detect “wiggling” quasars using Gaia satellite data
- Method could help test fundamental theories of gravity and galaxy formation
Imagine the universe as an endless ocean, with invisible ripples constantly flowing through it — waves so vast they stretch over decades, altering the very structure of space and time. These are gravitational waves, and they’re produced by some of the most dramatic events in the cosmos: collisions between supermassive black holes. While we can’t feel them, we might be able to see their effects. And now, a new approach from astrophysicist Jeremy Darling at the University of Colorado Boulder could help us do just that.
Darling’s work focuses on a cosmic background hum of gravitational waves, the kind that permeate the universe at all times, subtly distorting spacetime. In a study published in The Astrophysical Journal Letters, he lays out a novel strategy: instead of relying on pulsars like previous studies, Darling uses quasars — the luminous, energetic cores of distant galaxies — to detect these elusive signals.
The twist? He’s not just looking for waves that stretch space in one direction, but those that twist and ripple across all three dimensions. “Gravitational waves operate in three dimensions,” Darling explains. “They stretch and squeeze spacetime along our line of sight, but they also cause objects to appear to move back and forth in the sky.”
To visualize it, picture quasars scattered across the night sky as fixed reference points — except they’re not quite fixed. Gravitational waves, like the wake of distant black hole mergers, can bend the light from these quasars, making them appear to “wiggle.” It’s an effect so subtle it’s like detecting the growth of a fingernail on the Moon — from Earth.
This cosmic wiggling hasn’t been spotted yet, but Darling believes it’s only a matter of time and data. His approach relies on highly precise measurements from the European Space Agency’s Gaia satellite, which has been cataloging more than a million quasars since its launch in 2013. By pairing quasars and tracking how their positions change relative to one another, Darling aims to identify minuscule shifts that could be caused by gravitational waves bending their incoming light.
That’s no small feat. Earth itself is hurtling through space — orbiting the Sun at 67,000 miles per hour, while the Sun whips around the Milky Way at over 850,000 miles per hour. Disentangling the effects of Earth’s own motion from the apparent motion of distant quasars requires astronomical levels of precision and statistical rigor.
In 2023, the NANOGrav collaboration achieved a breakthrough by using pulsars — rotating neutron stars that emit regular radio pulses — to measure the gravitational wave background. Their data captured how gravitational waves stretched and compressed spacetime along our line of sight. But Darling’s method complements this, targeting the lateral motion that would be missed by pulsar timing arrays.
“We’ve only been listening in one direction,” he notes. “This lets us see the whole picture.”
Why does this matter? Because understanding gravitational waves isn’t just about exotic astrophysics — it’s about testing the very framework of physics itself. There are competing theories about how gravity works at the most fundamental level, and each predicts different “flavors” or modes of gravitational waves. Some might twist space like a corkscrew; others might warp it like a trampoline.
Detecting these subtle variations could help confirm or refute ideas from string theory, quantum gravity, or modifications to Einstein’s general relativity. It could also illuminate how galaxies form and evolve, how black holes grow, and whether there are forces in the universe we’ve yet to discover.
While Darling hasn’t observed definitive signals yet, his method is poised for a leap forward. In 2026, Gaia is expected to release a vastly expanded dataset — five and a half additional years of high-precision quasar measurements. That treasure trove could finally contain the wiggle evidence needed to confirm the presence of gravitational waves moving in multiple dimensions.
“If we can see millions of quasars,” he says, “then maybe we can find these signals buried in that very large dataset.”
In a universe constantly in motion, Jeremy Darling is listening for a new kind of rhythm — one that could change our understanding of space, time, and everything in between.
Source: University of Colorado Boulder
