Hi everyone! We are very excited about the upcoming press release (10:30 EST / 15:30 UTC) from the LIGO collaboration, a ground-based experiment to detect gravitational waves. This thread will be edited as updates become available. We'll have a number of panelists in and out (who will also be listening in), so please ask questions!
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Links:
YouTube Announcement
LIGO
Gravitational wave primer by Discovery
Gravitational wave primer by PhD Comics
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FAQ:
Where do they come from?
The source of gravitational waves detectable by human experiments are two compact objects orbiting around each other. LIGO observes stellar mass objects (some combination of neutron stars and black holes, for example) orbiting around each other just before they merge (as gravitational wave energy leaves the system, the orbit shrinks).
How fast do they go?
Gravitational waves travel at the speed of light (wiki).
Haven't gravitational waves already been detected?
The 1993 Nobel Prize in Physics was awarded for the indirect detection of gravitational waves from a double neutron star system, PSR B1913+16.
In 2014, the BICEP2 team announced the detection of primordial gravitational waves, or those from the very early universe and inflation. A joint analysis of the cosmic microwave background maps from the Planck and BICEP2 team in January 2015 showed that the signal they detected could be attributed entirely to foreground dust in the Milky Way.
Does this mean we can control gravity?
No. More precisely, many things will emit gravitational waves, but they will be so incredibly weak that they are immeasurable. It takes very massive, compact objects to produce already tiny strains. For more information on the expected spectrum of gravitational waves, see here.
What's the practical application?
Here is a nice and concise review.
How is this consistent with the idea of gravitons? Is this gravitons?
Here is a recent /r/askscience discussion answering just that! (See limits on gravitons below!)
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Stay tuned for updates!
Edits:
The youtube link was updated with the newer stream.
It's started!
LIGO HAS DONE IT
Event happened 1.3 billion years ago.
Data plot
Nature announcement.
Paper in Phys. Rev. Letters (if you can't access the paper, someone graciously posted a link)
Two stellar mass black holes (36+5-4 and 29+/-4 M_sun) into a 62+/-4 M_sun black hole with 3.0+/-0.5 M_sun c2 radiated away in gravitational waves. That's the equivalent energy of 5000 supernovae!
Peak luminosity of 3.6+0.5-0.4 x 1056 erg/s, 200+30-20 M_sun c2 / s. One supernova is roughly 1051 ergs in total!
Distance of 410+160-180 megaparsecs (z = 0.09+0.03-0.04)
Final black hole spin α = 0.67+0.05-0.07
5.1 sigma significance (S/N = 24)
Strain value of = 1.0 x 10-21
Broad region in sky roughly in the area of the Magellanic clouds (but much farther away!)
Rates on stellar mass binary black hole mergers: 2-400 Gpc-3 yr-1
Limits on gravitons: Compton wavelength > 1013 km, mass m < 1.2 x 10-22 eV / c2 (2.1 x 10-58 kg!)
Video simulation of the merger event.
Thanks for being with us through this extremely exciting live feed! We'll be around to try and answer question