What have the LIGO team detected?

The LIGO team announced the results from the States but there was a special meeting for British-based journalists and academics in London and this is where Graihagh Jackson met Norna Robertson from Cal-tech who's helped to detect these elusive things...

Announcement - Ladies and Gentlemen.  We have detected gravitational waves.  We did it.

[Applause]

Graihagh - But how did they do it?

They announced the results from the States but there was a special meeting for us Brits in London and this is where I met Norna Robertson from Cal-tech who's helped to detect these elusive things...

Norna - The event that we saw was two black holes which were orbiting each other in a double system.  So that they're going round each other and they're also moving toward each other because they're losing energy as they're orbit each other and so they speed up and go round and round faster and faster until they finally merge.  And it's that final inspiral and merger which happens in a fraction of a second that produces a big burst of gravitational waves.

Graihagh - And that rippled across the universe to us.  How long does it take to reach us though?

Norna - The event happened something like one billion years ago, a billion light years away and it's taken all that time to ripple across space towards us and pass through the Earth on September 14th, 2015.

Graihagh - It's quite remarkable really, isn't it?

Norna - It is remarkable.  It's wonderful.  There have been many, many people involved in developing detectors and developing all the analysis techniques and, for all of us, this is really a momentous occasion.