Is it a test?
Let's hope that the Director doesn't open a sealed envelope that says, "It was an injected test signal". This has happened before.
After weeks of speculation, the stage is set for Laser Interferometer Gravitational-wave Observatory (LIGO) boffins to announce their findings. The LIGO Scientific Collaboration has briefly popped its head over the parapet to say it'll come clean about what it has (or hasn't) found on Thursday at the National Science …
I doubt they would open the envelope in front of the world, and with the paper already printed in Nature, just to find "that was a test". I suspect the envelope-opening ceremony happened in private at a LIGO meeting some weeks ago, given the time that rumours have been circulating.
I read another article that said they'd seen three signals. Surely they didn't inject three tests?
If there are three events that gives hope that when they add the third detector there will be plenty of candidate events. The third detector will allow triangulating the exact position so they can visually confirm the observations (I assume something like two black holes merging or a black hole swallowing a neutron star is going to leave some obvious evidence in the gamma or Xray spectrum)
I assume something like two black holes merging or a black hole swallowing a neutron star is going to leave some obvious evidence in the gamma or Xray spectrum
I'm not sure you can count on that. This is two black holes. The two black holes will have been orbiting each other for a long, long time, gradually approaching each other as they lose energy by gravitational radiation. I think that they may have hoovered up almost all matter surrounding them a long time ago. Since both objects are already black holes, even the actual merger event won't emit anything except gravitational radiation (on the basic principle that nothing can get out of an event horizon).
It's a totally different story if there's a neutron star being torn apart by a black hole. That's the sort of event that you want to observe from a very, very long way away. E = mc^2 and something approaching a sun's worth of mass would be converted into energy and emitted as concentrated beams up the axis of rotation over a rather short span of time. The ultimate death ray.
with a range of... what?... a couple dozen light years?
No. Thousands of light years. Possibly tens of thousands. An ordinary supernova is dangerous if it happens within a few tens of light-years. A GRB emits considerably more energy into a tightly collimated beam. Either might explain certain puzzling mass extinction events in Earth's geological history.
I wasn't serious about aiming one.
After the fiasco with the BICEP2 team a couple of years ago it's nice to see a science project taking their time to make sure the data is right and the conclusions are sounds.
Fundamental science doesn't need hyperbolic announcements, it needs a measured and careful approach to announcing findings with lots of cross-checking, otherwise they end up looking stupid.
No - it requires journalists to have some clue about what they are reporting on, or to take the scientists words and not ignore the ones they don't understand.
Since that isn't likely to happen they have to say nothing for a long while - because "initial results" gets translated to "confirmed discovery" when it really means "there was a squiggle in the data, we're not sure why yet"
"...it needs a measured and careful approach to announcing findings with lots of cross-checking, otherwise they end up looking stupid."
But you can't do too much cross-checking without telling people about it. And the more people you tell, the more likely it is the media will hear and turn their spotlight your way. (IIRC this was partly what happened to BICEP2 -- it leaked to El Graun. But they were also in competition with the people they needed to cross-check with.)
You said *snigger* "hyperbolic" *snigger* In a story about *snigger* *snigger* relativity *snigger*
The BICEP2 team were just as much to blame. They even staged a video where they went to tell Andrei Linde about their discovery.
Yes, journalists get the bit between their teeth and tend to gloss over a lot of stuff, but the BICEP2 team screwed up badly by over-hyping what they had before it had been checked.
It's not something they actually want to keep secret. They just don't want to be misreported, so they talk only to other scientists who hopefully know better than to get themselves misquoted by the popular media. Witness the gradual popular-media "discovery" of the Higgs boson. First "hints of", then "possible", "probable",... which actually mapped reasonably well onto the number of sigmas' worth of data they'd acquired.
This rumour sounds like the news might be more instantly definite but I'm happy to wait until Thursday.
If there has been a number of non-gravitational wave events that triggered one detector but not the other, how certain are they that the event that triggered both detectors was not the random coincidence of two non-gravitational wave events ?
Before claiming proof of gravitational waves either multiple events need to be detected or considerably more than 2 detectors used - 1 event on 2 detectors is suggestive but not proof.
But it depends on what you mean by 'signal'. If you are just talking a 'blip' then yes coincidence would be difficult to rule out. However if you are talking timing, amplitude and signal characteristics (shape, frequency, rise and fall) then it is possible to be very confident with one even from two detectors.
The article suggests a confidence level of 5.1 sigma, I hope science at that level would have considered the number of events required to back their findings.
I am afraid it is precisely this kind of analysis and speculation that leads to media embellishment of matters still part of the scientific debate.
They haven't actually announced anything yet. Lets wait for the paper to be released hey?
I suspect it's unlikely that a false positive with the same shape would happen to both detectors, let alone happen to both simultaneously. The 5.1 sigma is the quantification of that; it's something like a 0.00003% chance it's down to chance (although the implementation of
erf() I've just pulled off the internet looks suspect at high sigma).
If there are two black holes gradually(?) orbiting in towards each other then both detectors will be picking up a synchronized sinusoidal perturbation with a phase shift between them introduced by the speed of gravity (assumed to be the same as the speed of light) and the motion of the Earth. Further, since the orbiting black holes are losing energy by gravitational radiation, the period of the gravity wave and its intensity will both gradually be increasing, on top of the modulations caused by the motions of the Earth.
Surely it's too much to hope for that they have observed the actual merger event? Really good test of GR and black hole theory, if they have.
"Surely it's too much to hope for that they have observed the actual merger event? Really good test of GR and black hole theory, if they have."
Our primitive detectors are really only capable of detecting the last few minutes of such a collision, so I'm guessing they have a detection pattern like the one in the referenced article , on both detectors.
Its also possible that under certain conditions radioactive decay could be affected by gravity waves, in fact it is required due to SR and its effects on time.
The effect would of course be tiny but for very short half life (ie minutes) isotopes there should be a slight difference between identical samples before, during and after an event.
Perhaps this could also explain some of the strange observations of apparent changes in 54Mn half life just before very large solar flares (which would also cause gravity waves of a lesser magnitude)
Gravity waves traveling at the speed of light from the location of the flare trigger deep within the star get here first before the visible effect can propagate, similar to the way neutrinos from a supernova get here shortly before the light does.
I'm sure it has been asked before, but wouldn't an alien FTL drive generate gravitational waves when entering/exiting a hyperspace window?
I've got some calculations here which suggest the effect might be detectable maybe 60 LY away, obviously if their engines are badly out of sync it will be pretty obvious.
Maybe we should look at the LIGO data from earlier especially those two "minority report" events and see if this is possible: HFGWs might look completely different because the Moon or other astronomical body could possibly shield one detector?
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