Why You Should Care About Gravitational Waves
Gravitational waves are tiny ripples in the fabric of space-time. Albert Einstein predicted their existence in 1916, based on his theory of general relativity, but doubted any technology could confirm them. Just under a century later, on September 14, 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected gravitational waves generated by a collision of two black holes 1.3 billion years ago. Since then, gravitational-wave science has been a burgeoning field, opening horizons for understanding far-flung celestial objects and the nature and evolution of the universe. Astronomy has become “multi-messenger,” with new conveyors of info (including cosmic rays and neutrinos) adding to what telescopes collect in visible light and other electromagnetic wavelengths.
LIGO’s a large-scale physics project with two instruments, one in Louisiana, the other in Washington state. Each is L-shaped, with concrete arms four kilometers (2.5 miles) long, enclosing metal vacuum tubes through which lasers travel, bouncing among mirrors to amplify their power, their photons registering on a sensor. Subtle variations reveal that a gravitational wave has hit. Detection of gravitational waves now occurs several times a week. (Incidentally, “gravity waves” are an unrelated phenomenon that occurs in liquids.)
Having two detectors, far apart, enables LIGO to distinguish gravitational waves from other phenomena, such as earthquakes or traffic, that might cause vibrations in the sensitive instruments. Since gravitational waves travel at the speed of light, the instruments receive them no more than 10 milliseconds apart; a longer interval, or detection by only one instrument, would point to a different cause. Using two instruments, moreover, allows the source of a gravitational wave to be pinpointed, offering wide coverage of the sky and triangulating with help from smaller detectors in Italy and Japan (and one planned in India). Analysis of the waves provides info about sources, such as black holes and neutron stars.
The U.S. is the dominant force in gravitational-wave science; no other nation has comparable facilities or workforce. This cutting-edge research has practical benefits beyond the intellectual elevation of probing cosmic mysteries. LIGO has generated innovations in lasers, optics, sensors, materials, and computational techniques. The project develops employee skills applicable in various fields, in science and beyond, and bolsters education through field trips, classroom activities, and teacher development.
LIGO is funded by the National Science Foundation, part of the federal government, with operations contracted to MIT and Caltech. The Trump administration’s budget proposal for the NSF, which Congress will consider this autumn, would cut the science agency’s overall annual funding by 56 percent, from $9 billion to $3.9 billion, reducing LIGO’s funding by 39 percent, from $48 million to $29 million for fiscal 2026. The administration directs that the NSF “will operate only one of the two [LIGO] sites,” without specifying which one.
The administration has stated that its proposal for the science agency budget “reflects a strategic alignment of resources in a constrained fiscal environment” and “prioritizes investments that can have the greatest national impact.” That LIGO wasn’t scrapped altogether may reflect awareness within the administration that the project has scientific importance, as was recognized in the awarding of the 2017 Nobel Prize for Physics to early developers of the LIGO effort. But cutting the budget to keep only one of the detector sites open is a bizarre move, likened to saving money by ordering eyeglasses with one lens.
“With only one of the detectors active, you can only do less than a quarter of the science,” said astronomer Lieke van Son at a recent event at the Simons Foundation in Manhattan, where she and film director Kyle Finnegan had a public screening and discussion of a short film they made, titled Who Cares About Gravitational Waves? This was part of a Simons Foundation project called Symbiosis, in which pairs of scientists and filmmakers working on a two-week deadline made short films explaining scientific topics.
Who Cares About Gravitational Waves?, also available on YouTube, takes a whimsical tone. The film opens with scenes of people around New York City, as van Son narrates: “There could be a wave going through you right now. Through all of us. This guy. Her. These guys. Even this guy,” the camera finding a man in a park with an eccentric hat. Gravitational waves are too minuscule to harm people, explains van Son, whom a screen title describes as a “black hole stalker.” “Gravitational waves are recording the last moments of an epic dance performed by dead stars,” she says, explaining that black holes are relics of massive stars and offer insights into stellar lives, much as she, who’s from the Netherlands, can get glimpses of the lives of other Dutch people, and her own fate, by looking at tombstones.
Gravitational-wave astronomy, she says in the film, offers hopes of answering “big questions like: Where did we come from? How’d the universe begin? Why is the F train always late? What’s that smell?” The camera pauses on a steaming New York sewer grate.
In the post-screening discussion, though, van Son was blunt in discussing the proposed budget’s implications for gravitational-wave science. “We’re taking American leadership in this field, and we’re throwing it in the trash,” she said. “It’s like taking the microscope and throwing it in the trash. There’s no reason to throw it in the trash, other than people don’t know that this [science] is happening.”
—Kenneth Silber is author of In DeWitt’s Footsteps: Seeing History on the Erie Canal. Follow him on Bluesky