More than a century ago, Albert Einstein published his Special Theory of Relativity, positing that when massive objects accelerate in space, they produce small wrinkles, similar to sound waves, that move through the fabric of space-time.
These wrinkles, called gravitational waves, travel through the universe at the speed of light and carry information about the epic cosmic phenomena that created them, such as massive collisions between two black holes, two neutron stars or one of each. Studying these waves could offer scientists clues about how such prodigious movements occurred. Even the gravitational waves made during the Big Bang—scientists have theorized—are still rippling through the universe, detectable with the right technology.
Now, scientists hope, the right technology has finally come along—and its name is LISA.
“The first time I wrote a proposal for LISA was 31 years ago,” Karsten Danzmann, a physicist who leads the LISA Consortium and is director of the Max Planck Institute for Gravitational Physics, says to Nature News’ Elizabeth Gibney. “People thought it was ridiculous. I said, ‘Just you wait.’”
@ESA adopts two ambitious space science missions: Venus voyager #EnVision and gravitational wave surfer #LISA.— ESA Science (@esascience) January 25, 2024
“These trailblazing missions will take us to the next level in two extraordinarily exciting areas of space science and keep European researchers at the forefront of… pic.twitter.com/MFjiqCS4pw
LISA, or the Laser Interferometer Space Antenna, is a new mission from the European Space Agency (ESA) that earned formal approval on Thursday. The go-ahead is the effective starting gun for contractors to begin building the required spacecraft and technology to get the project off the ground.
“If we imagine that, so far, with our astrophysics missions, we have been watching the cosmos like a silent movie, capturing the ripples of spacetime with LISA will be a real game-changer, like when sound was added to motion pictures,” LISA project scientist Oliver Jennrich says in a statement.
Comprising LISA’s hardware will be three nearly identical spacecraft that will sit 2.5 million kilometers (about 1.6 million miles) away from each other in space, trailing the Earth as it orbits the sun. Positioned to form the universe’s strongest shape—an equilateral triangle—the trio of spacecraft will exchange laser beams. And inside each one, a 4.6-centimeter (1.8-inch) gold-platinum cube will rest.
Set almost like a tripwire for cosmic sound, the laser beams will be sensitive to even the most subtle of gravitational waves—anything with wavelengths between 300,000 kilometers (186,400 miles) and three billion kilometers (1.86 billion miles). When waves affect the beams, the golden cubes will be moved ever so slightly—even just billionths of a millimeter—and the motion will register as data scientists can use to determine the direction the waves were coming from.
“LISA will give us a panoramic view, allowing us to observe a broad range of sources both within our galaxy and far, far beyond it,” Mark Clampin, director of the Astrophysics Division at NASA, says in a statement. “We’re proud to be part of this international effort to open new avenues to explore the secrets of the universe.”
NASA scientists will be contributing partners to the LISA mission, which will begin construction in January 2025 and is set for a 2035 launch date.
Gravitational waves were first detected in 2015 by the ground-based Laser Interferometer Gravitational-Wave Observatory (LIGO). Scientists picked up on a collision between two black holes 1.3 billion light years away, culminating a decades-long search to witness what Einstein had predicted.
Since that first discovery, scientists have detected myriad more cosmic signals using LIGO, and LISA is expected to add to these discoveries. The new technology will also fill gaps where LIGO has been limited—it will potentially observe supermassive black hole collisions and detect leftover “ringing” from the universe’s birth by peering back to just seconds after the Big Bang.
“This is almost a sci-fi sort of instrument,” Valeriya Korol, an astrophysicist at the Max Planck Institute for Astrophysics and member of the LISA collaboration, tells Nature News.