Ask a Physicist

If gravitational waves are successfully detected, can we expect that knowledge to lead to new kinds of technological advancements?
Submitted by Jo from the USA

Even though we haven't detected gravitational waves yet, there have already
been technical advancements spun off from the search effort.

The first spinoff I know of is from the 1970s and is called Pound-Drever locking. It was a big practical improvement in using laser interferometers to measure small distances. In principle an interferometer measures length changes by letting the mirrors swing freely and counting the light/dark cycles in the output (the light leaking out of the end) to see how many light wavelengths a mirror moved. In practice an interferometer is more sensitive if you keep it locked, or force the length between the mirrors to stay a certain number of wavelengths of light of the laser that's beamed into it. And it's easier to keep it locked if you mess up the laser very slightly. You can see how much the mirrors want to move due to gravitational waves (or anything else) by watching how much power is needed to hold them in lock. Ron Drever developed it with LIGO in mind, but people working with other precision measurements quickly saw its potential and now it's fairly common in industrial settings.

Then there are engineering things. LIGO's 4km arms have been called (correctly) "the biggest holes in the Earth's atmosphere." Building them pushed vacuum technology to the limit and then redefined the limit. The engineering firms who did it learned lessons I'm sure they'll apply on future projects, which will look easy by comparison.

These spinoffs would have happened eventually even without the search for gravitational waves. But having that exciting goal attracted some very bright people to work on the problems who otherwise would have been interested in something else. And because the gravitational wave application is much more challenging than the practical applications, these people had to push much harder than if they were working on the practical stuff directly. Similarly, I don't expect the eventual detection of gravitational waves to directly produce any practical spinoffs. But the excitement it will generate will get more people interested in pushing lasers and vacuum technology and other things related to detection, which will indeed produce practical spinoffs.