When astronomers first spotted gravitational waves, the entire scientific world was thrilled. This was something we’ve been expecting for years, but finally confirming the theory was highly exciting. Now, just a few months after that, they’ve discovered another signal, confirmed with a confidence level of over 99.99999%.
The discovery was made by LIGO (Laser Interferometer Gravitational-Wave Observatory), an observatory dedicated to gravitational waves, composed of two identical interferometers located in the US. The first phase of the project wasn’t fruitful, but an updated phase was launched in September 2015. It didn’t take long before the first discovery.
“Just the fact that we’ve now seen more than one [gravitational wave source] is very exciting,” said MIT’s David Shoemaker, who led the Advanced LIGO construction program. “It takes us out of the ‘gee whiz, could it be true?’ mindset to yes, this is a tool that we can use.”
Black holes only form from the largest of stars. Some of these holes form a pair, orbiting around each other and gradually getting closer while losing energy in the form of gravitational waves, until a point is reached where the process suddenly accelerates. When that happens, the two merge together into a single black hole, releasing a very distinctive signal in the process – it’s this signal that was detected the first time.
Astronomers thought that this is a very rare phenomenon, as you’d expect. But the fact that they’ve detected a similar process might suggest that it’s not that rare after all – either it’s a huge coincidence, or black hole pairs are much more common than we suspected.
Prof Neil Turok, director of the Perimeter Institute for Theoretical Physics in Waterloo, was also thrilled – saying that it’s one of the few pure “Eureka” moments. The potential applications for this, he continues, are hard to grasp at the moment.
“Just think of radio waves – when radio waves were discovered, we learned to communicate with them. Mobile communication is entirely reliant on radio waves. For astronomy, radio observations have probably told us more than anything else about the structure of the universe. Now we have gravitational waves we are going to have a whole new picture of the universe, of the stuff that doesn’t emit light – dark matter, black holes,” he said.
“For me, the most exciting thing is we will literally be able to see the big bang. Using electromagnetic waves we cannot see further back than 400,000 years after the big bang. The early universe was opaque to light. It is not opaque to gravitational waves. It is completely transparent.
“So, literally, by gathering gravitational waves we will be able to see exactly what happened at the initial singularity. The most weird and wonderful prediction of Einstein’s theory was that everything came out of a single event: the big bang singularity. And we will be able to see what happened.”
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