By Chethana Janith, Jadetimes News
If we track explosions from malfunctioning warp drives, we could finally discover where E.T.s are hiding.
If a warp drive explodes in deep space, will anybody hear it? Probably not, but new research suggests that humans could one day detect the ripples in spacetime such a catastrophe would create, potentially aiding the search for alien life.
Warp drives that enable spacecraft to travel at near light speeds are a fixture of science fiction, famously allowing Star Trek’s Federation crews to boldly go where no one has gone before. But scientists have long theorized how a real-life warp drive might work, the most famous example being the Alcubierre drive, a design that Mexican physicist Miguel Alcubierre, Ph.D., put forth in 1994. This type of drive would form a bubble around travelers, contracting the space in front of it and expanding the space behind it to leap across the cosmos.
In a preprint study posted online in June, a team of researchers hailing from the U.K. and Germany posed the question: If an alien civilization is using an Alcubierre drive, could we detect it by looking for the gravitational waves such a system might emit? After all, the Pasadena, California-based LIGO Lab-home to the world’s largest gravitational wave observatory, can pick up the perturbations in spacetime generated by highly energetic events like black hole mergers and supernovas.
So why not alien technology?
According to the researchers’ calculations in this new work (which has not been peer-reviewed), humanity really could pick up on signs of an alien warp drive, but only with a new generation of gravitational wave observatories.
Astrophysicist Katy Clough, Ph.D., and her co-authors came up with the idea of simulating a warp drive’s gravitational wave signature seven years ago. They were inspired by Star Trek, she says, and in particular by the occurrence of warp “breaches” in the show’s universe.
An Alcubierre drive, which theoretically would require negative energy (a repulsive gravitational force, rather than an attractive one) and exotic forms of matter to work, wouldn’t greatly perturb spacetime while operating correctly. Technically, even driving a car on Earth generates gravitational waves (anything that accelerates does), but they’re too small to be detected or have much of an effect on anything. But the waves that reach our planet from space are typically caused by violent events or the movements of massive objects, like a spinning neutron star. A malfunctioning Alcubierre drive would qualify, too.
“If you put exotic matter into forming a warp bubble, it will naturally disperse over time. So, hypothetical aliens would need some kind of containment mechanism to keep it in place. And we don’t know what that is,” Clough explains. “We said, well, in Star Trek, it always happens that you have a warp-drive containment failure. So why don’t we just go with this idea?”
In a warp-drive containment breach, Clough says, all of the contained energy and matter would spill out and create the kind of messy oscillations that generate gravitational waves, like someone splashing around in a pool. This would be, to say the least, unpleasant for the ship’s occupants.
A warp-drive collapse in Andromeda, the nearest galactic neighbor to the Milky Way—could be detectable on Earth.
“You’d get stretched and squashed, and ultimately, it would be nasty,” Clough says.
Clough says the project seemed “fun” to the team at first, but that it quickly became very complicated. The main problem, Clough says, was choosing equations that both led to a stable evolution in the simulation and made physical sense.
That accomplished, Clough’s team found that a warp breach on a kilometer-sized ship traveling at 10 percent of the speed of light (30,000 kilometers per second), would create a “very distinct” gravitational wave signal. It could be detected from up to 1 megaparsec away, or 3.26 million light years, meaning a warp-drive collapse in Andromeda, the nearest galactic neighbor to the Milky Way, could be detectable on Earth.
Luke Sellers, Ph.D., lead scientist at Applied Physics—an independent research group based in New York City and Stockholm that has proposed its own warp drive designs and studied the search for alien life in gravitational wave signals—says the work from Clough’s team is a “welcome addition” to the field. The study “just makes sense,” he says, particularly the insight that an Alcubierre drive could blow apart.
One day, he said, “we could have a menu of all these exotic SETI-type gravitational wave signals” to look for, “one of which might be a very large propulsive mechanism, and one of which could be this warp drive explosion.”
The Next Generation
Assuming that aliens have figured out how to make an Alcubierre drive and one explodes within range of our observatories, there’s still a problem: none of our existing detectors are equipped to pick up high-frequency gravitational waves.
Gravitational wave detection is still “a really new field,” Clough says. “It’s really like the beginning of electromagnetic observations, where we’re just looking at one frequency band.”
Caltech and MIT’s ground-based LIGO observatory, for example, debuted in 2002 and eavesdrops on frequencies in the range of 10 Hz to 1 KHz. (If a 1-KHz wave was sonified, it would sound like a high-pitched whining tone.) NASA and the European Space Agency’s planned space-based LISA observatory, which is expected to launch in the 2030s, will listen in on even lower ranges. An exploding Alcubierre drive would emanate waves at a frequency of about 300 KHz, which, if it was a sound, would be outside the range of human hearing.
“There aren’t that many well-motivated astrophysical targets at those kinds of [higher] frequencies,” she explains. “There are some exotic things, like primordial black holes or signals from the early universe, so there are proposals to try and build detectors in that range. This is another potential argument for building those detectors.”
Indeed, in 2021, a team of over two dozen scientists from around the world, including institutions like LIGO and CERN, argued in a paper that observatories targeting high frequency ranges would allow us to look for signs of novel physics in the early universe, for example.
“It stands to reason that you want to probe that vastness as much as possible, if you want to have a chance to detect something,” says Sellers, the scientist from Applied Physics. On top of new detectors, a “pipeline” for SETI searches involving machine learning algorithms could be beneficial, he says.
The paper’s conclusions also come with some caveats. The work covers a very specific scenario with carefully chosen parameters, including the type of warp drive. It’s “an example, and not the template to look for,” Clough says. Still, her team expects that the frequency range of the gravitational waves would carry over to other designs.
“It could be the case that, once we get these better detectors, there’s a really loud warp drive signal that you can see even if you didn’t already know what you’re looking for,” Sellers says. “And if that happens, it’s conceivable that we could actually reverse engineer what system they’re using.”
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