Tuesday, 9 February 2016

LIGO Announces an Announcement

Yesterday the LIGO and Virgo Scientific Collaborations announced that they would be making an announcement on Thursday.

I was not in the least surprised, because I am a member of LIGO. They had already announced to me that they would be announcing to you and that they would, eventually, be making an announcement.

"What exactly is the announcement?" you ask.

Weren't you listening to the announcement? The announcement stated that the announcement will be made on Thursday. So you can bloody well wait.

I will be watching the announcement in London, where it will be streamed live to a special UK press conference. The announcement will be at 10.30am Eastern Standard Time in the US, which is 3.30pm in the UK. If you are in my homeland of New Zealand it will be at 4.30am on Friday, and you will be extremely upset if the announcement turns out to be, "This year we filed our taxes early."

If you want to watch the announcement, there will be a live stream. I can announce that the announcement of the live stream of the announcement will be made one hour earlier on the LIGO website. (UPDATE: Here is a weblink to the broadcast.)

Some background: LIGO is a network of detectors that were built to directly detect, for the first time ever, gravitational waves. Gravitational waves are ripples in space and time. Einstein predicted them 100 years ago. For fifty years after that, people debated whether or not they were real, but eventually got sick of arguing and decided to just try and find the damn things. In 1974 Hulse and Taylor measured two orbiting neutron stars getting very very slowly closer together, in exact agreement with gravitational-wave calculations, and since then no-one has doubted that gravitational waves are real. (Except a few crackpots, of course, who regularly send us letters explaining the foolish error we have made, usually written in crayon.)

What would be much more exciting would be to measure the waves themselves. That is what LIGO was built to do. Not only would that allow us to test Einstein's prediction much more rigorously, it would also mean that we could use gravitational waves as a tool to observe the universe. We expect that the universe is crammed with objects that we can't see with ordinary telescopes, but might be massive enough and dense enough and moving violently enough, that they can produce gravitational waves strong enough that we could measure them. That is our hope. That is our dream.

The LIGO collaboration has over 1000 members, working on building the detectors, and on searching in the data, and a multitude of other projects. My little part in all of this, along with many collaborators (and competitors!), is to calculate what the gravitational-wave signal would look like from two black holes colliding. Such calculations could help us find signals but, much more importantly, if we found something we could use these theoretical models to disentangle the signal to work out what produced it.

For over a decade increasingly sensitive incarnations of the LIGO detectors have been run, and they have observed nothing. Last year we switched on the most sensitive detector yet, "Advanced LIGO", and took data from mid-September until January 12th of this year. Analysis of the data began the moment the detector switched on, and is still being completed. The announcement on Thursday will provide an update on where we are so far.

Related Posts:

Advanced LIGO switched on.

My one modest attempt to explain curved space and time.

Another explanation of Einstein's theory, and why it is so difficult.

How gravitational waves confused Einstein himself.


  1. Gee, I hope this is not related to the previous post :)

    Anyway, there isn't a single soul working on related stuff at my Dept. but we will all be in the coffee room watching tomorrow! This is the part of the academic life I still like, jokes apart.

    Good luck and we expect a detailed post afterwards!

    1. Never put joking aside. During the press conference, you're sure to be in serious need of lines like, "If they can build the most sensitive instrument on Earth, why can't they produce a reliable web stream?"

      There you have it: my prediction for tomorrow. Let's hope it's wrong.

    2. And you can be sure there will be detailed posts afterwards!


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