Welcome, friends! Here we are, waiting for another gravitational wave announcement, and we’re so excited!
Last time one of these came through, it was for a collision between two black holes pinpointed with the greatest accuracy yet, so we’re champing at the bit for this new announcement to drop – and we know this one is going to be massive.
9:30am EDT: It’s 0:30am here in Australia, so we’re basically running on coffee and excitement. But it’s always fun to stay awake for these announcements – and this one’s going to be so worth it!
The big press conference at the National Press Club in Washington DC is starting in 30 minutes. We’ll embed a live stream link down below as it gets closer!
9:31am EDT: While we wait for the announcement in less than half an hour, let’s run a refresher course to entertain ourselves and prepare for the big news.
Gravitational waves are a lot like waves in water, or soundwaves in the air, except they’re rippling across spacetime. When a massive event happens – like two black holes colliding – it’s like dropping a stone into a puddle.
Ripples race out across the universe in all directions at the speed, theoretically at least, of light.
9:35 EDT: In all our excitement we forgot to mention that you should keep refreshing this page to get the latest updates! (Also, sorry in advance for any egregious typos. We made popcorn to celebrate and it’s getting in the keyboard.)
9:37 EDT: Gravitational wave astronomy is still extremely fresh! We only got the first ever confirmation that gravitational waves exist last year, in February 2016.
It was one of the biggest astrophysical discoveries in the previous hundred years, and may remain that way for another hundred. It’s a huge deal – confirming predictions Einstein made in his theory of general relativity 100 years earlier in 1916.
9:40 EDT: T minus 20 minutes! Hang on, we’re getting the live stream link verrry shortly.
Meanwhile, a bit more trivia: three of the scientists behind the discovery were just awarded the Nobel Prize in Physics earlier this month. Rainer Weiss of MIT and Barry C. Barish and Kip S. Thorne of CalTech represented over 1,000 scientists who participated in the discovery.
Today, over 1,200 and around 100 institutions around the world participate in the LIGO Scientific Collaboration.
9:43 EDT: Let’s talk more about the science! Here’s how the gravitational wave detectors work:
LIGO’s detectors are known as Michelson interferometers. A laser beam is shone at a mirror down. This splits the beam. Part continues going forward; part splits off to the side. They’re bounced off mirrors on the other side, and meet back in the middle, cancelling each other out. This meeting is called interference.
If the arms change length, as they do when a gravitational wave hits, one beam will take longer to travel back to the middle and the two beams won’t cancel each other out. The resulting light continues on and is picked up by a photodetector.
LIGO’s interferometers are the largest in the world, with arms 4 kilometres (2.5 miles) long.
9:45am EDT: The music just started on the livestream! We’re embedding it at the bottom of this article so we can all watch together.
9:50am EDT: 10 minutes to go! We’re loving this jazz.
9:52am EDT: This new gravitational wave astronomy has progressed amazingly fast, by the way.
Until earlier this year, only the two detectors were operational. This meant that scientists could only pinpoint gravitational wave events to a very broad swathe of sky.
But in August a third detector was added – Advanced Virgo. This allows triangulation. Gravitational waves don’t hit every detector simultaneously. The order in which detections occur, and the length between them, lets scientists calculate the location with much more accuracy.
It was this third detector that showed a much smaller area for the fourth gravitational wave event.
9:55 EDT: FIVE MINUTES! The music is getting more groovy!
9:57 EDT: Okay, we’re only a few minutes out, time to address some rumours.
That fourth gravitational wave event was a huge deal – but it wasn’t what we were expecting. In August, University of Texas astrophysicist J. Craig Wheeler tweeted out that there was a new LIGO detection with optical counterpart.
As in, something we could actually see to go along with the gravitational wave detection.
Greater accuracy is fantastic – but what did Wheeler mean? Did he get something wrong? Or was there another announcement to come…? WILL OUR SOX GET BLOWN OFF?