Last September 2015, LIGO had its first detection of gravitational waves from a pair of colliding black holes. As soon as the news broke, everyone was sharing the hype and elation of the LIGO scientists. Why was this discovery a big deal?
- It confirmed Einstein’s General Relativity. The theory actually predicted the existence of gravitational waves more than a hundred years ago.
- It proved that binary black mergers exist.
- It opened a whole new field: gravitational wave astronomy. Previously, astronomical observations were only made using telescopes that catch light in the form of radio waves, microwaves, visible light waves, X-rays, or gamma rays. Now, we can use gravitational waves to look at things that do not emit light such as black holes.
LIGO has since made three other detections of gravitational waves created by binary black hole systems. The latest of which was from August 2017. Even more recently, on October 3, three of the LIGO Scientific Collaboration’s scientists – Rainer Weiss, Kip Thorne, and Barry Barish – were awarded the 2017 Nobel Prize in Physics. With all of these exciting news, there’s something even more exciting: You – yes, you – can join in on the efforts to search for gravitational waves! With Gravity Spy, you can become a true gravitational wave hunter from home!
LIGO’s annoying glitches
LIGO’s detectors are extremely sensitive: They can measure the most minute vibrations at a scale 10,000 times smaller than an atomic nucleus, easily earning the title of “Most Sensitive Gravity Experiment in All of Science.” This ultrasensitivity, however, comes at a huge cost. The detectors will log millions of irrelevant environmental and instrumental noises such as a tree falling, a truck passing by, and even a refrigerator in the building!
In order to separate these extraneous data, also known as glitches, from the real astronomical signals that matter, LIGO needs a huge volunteer network of passionate nerds like you. In Gravity Spy, these glitches can be seen as characteristic patterns in a graph called a spectrogram. These glitches come in different forms or morphologies: blip, whistle, paired doves, helix, koi fish, and fifteen others. There may be even more undiscovered glitch morphologies.
Glitch morphologies in Gravity Spy. Image by George, Shen, and Huerta.
Although LIGO already has advanced computers that can spot and classify these glitches, nothing beats human intuition and pattern recognition. Even when they already “taught” these computers how to classify glitches, the computers need human confirmation just to be sure. The glitches have obvious and distinctive characteristics, like how a blip glitch is shaped like a teardrop. However, different blips will have slight differences in shape, roundness, or length. Though our human brain can easily recognize these differences and pass them off as random variations, a computer cannot do that so easily.
By classifying these glitches in Gravity Spy, you’re essentially teaching LIGO’s computers how to recognize the small differences so they can do it on their own. Once the computer sees a new glitch that vaguely looks like a teardrop, it will then refer to the thousands of different blip glitches citizen scientists have classified. If the new glitch looks similar enough to all of them, it will officially be classified as a blip.
LIGO needs more nerds
However, there isn’t just a few thousand of these glitches. Because the detectors are unbelievably sensitive, they generate huge amounts of data (and this comes with a painfully large number of glitches too.) As a result, LIGO needs thousands more people to confirm the computers’ classifications. With citizen scientists combing through the data, the LIGO computers can become smarter at classifying these glitches. With even more nerds, the computers can learn much faster. As of writing, there have been 2,524,491 glitch classifications on Gravity Spy accomplished by 9,888 volunteers – and you can join in too!
What you can contribute
Imagine this. Somewhere in a remote corner of the Universe, two neutron stars are rapidly orbiting each other creating gravitational waves that eventually reach LIGO; but a pesky little glitch was in the data right when the gravitational wave passed.
That would just be infuriating! If you join this initiative, you can help avoid that unfortunate situation. Through your efforts, you can help LIGO scientists learn from these glitches, track their source, and ultimately eliminate them for good. In fact, citizen scientists discovered two new classes of glitches, now called the “paired dove” and the “helix.” In Gravity Spy, you will be taking part in real and groundbreaking science. Your contributions will definitely make a difference as we use gravitational waves to probe farther in the Universe.