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LIGO: The Dawn of Gravitational Wave Astronomy
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Title  LIGO: The Dawn of Gravitational Wave Astronomy 
Title of Series  EuroPython 2016 
Part Number  61 
Number of Parts  169 
Author 
Rollins, Jameson

License 
CC Attribution  NonCommercial  ShareAlike 3.0 Unported: You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal and noncommercial purpose as long as the work is attributed to the author in the manner specified by the author or licensor and the work or content is shared also in adapted form only under the conditions of this license. 
DOI  10.5446/21158 
Publisher  EuroPython 
Release Date  2016 
Language  English 
Content Metadata
Subject Area  Computer Science 
Abstract  Jameson Rollins  LIGO: The Dawn of Gravitational Wave Astronomy Scientists have been searching for the elusive gravitational wave for more than half a century. Hear how they finally found them, and the role that Python played in the discovery.  Scientists have been searching for the elusive gravitational wave for more than half a century. On September 14, 2015, the Laser Interferometer Gravitationalwave Observatory (LIGO) finally observed the gravitational wave signature from the merger of two black holes. This detection marks the dawn of a new age of gravitational wave astronomy , where we routinely hear the sounds emanating from deep within the most energetic events in the Universe. This talk will cover the events leading up to one of the most important discoveries of the last century, and the myriad of ways in which Python enabled the effort. 
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00:00
really happy about who introduced James Rowlands are
00:04
here has been in the image of talking and I think it's so amazing he's been working in the gravitational arch et gravitational waves community for 18
00:14
years like all his professional life and he's going to tell you more about his research on the project and discoveries and all Python was involved so all these very will come emerging rolling if not low the
00:35
hearing was going to produce
00:41
right so yes i'm James Rollins I work of for the light goes project which is a project to detect gravitational waves a brief overview it consists consists
00:55
of these 2 begin a Frommer's which I'll describe in a minute in a self our project and United States MIT although we have many international collaborators 60 institutions thousand
01:09
individuals around the world but the 2 of observatories or separated 1 is in Washington State mothers
01:17
Louisiana 3 thousand kilometers 10 milliseconds
01:24
right so little background about what are gravitational waves of so Einstein's general theory of relativity which is 1 of the most successful physics periods in history basically it's been 100 years this year is the anniversary 100 year anniversary and of it's been basically unaltered since she he gave birth to it it's really incredible and basically the
01:52
idea is that the curvature that gravity is curvature of space time so masses in Spain cause the
02:02
space time to curve and then the curved space time causes masses to change the trajectory and this is this is
02:11
the the only equation in the talk promise and this is
02:15
the Einstein's equation it's the curvature is described by this mathematical logical the tensor over here and then the mass energy content like what what is in spaces is on the other side and its related by this very very small of
02:33
factor which indicates that space is very very stiff it's very hard to bend so 1 of the
02:42
interesting predictions of general relativity is that it predicts there should be waves of gravity and I like this animation the looks kind of little bit sexy but so you can
02:56
imagine that what's happening here is that through the central axis of this too is that is the movement of a gravitational wave a wave is propagating through this 2 or in this direction in which you can see
03:09
what the tube is doing is showing how all the surrounding space time is going to move so perpendicular to the direction of travel the spaces compressing in 1 dimension and expanding in the other and then as the wave moves it does the opposite kind of does that squeezing in
03:27
stretching motion so if you look at the crosssection of the 2 yeah and you put some masses at the edges you'll see that the masses because the
03:38
spaces bending are going to move with the space Friday so how can we how can we use this effect to
03:50
look for the gravitational waves so what we do is we make this device called an inner from a we can use light to measure these these distances
03:59
in space so imagine these these 2 where we have here is a laser a beam splitter and then
04:04
to and if we good if we
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choose the laser beam at the beam splitter that splits the light the light goes to the 2 years and bounces off then comes back to the beam splitter where recombine and what happens is you take this very interesting property of light which is that it can interfere with itself and what you can do is very precisely measure the relative separation of these 2 images so this is the way that you can see the waves going into 2 arms they're
04:43
out of phase at the output port but then wind up
04:46
in the mayor's move they become in phase and so you get the light goes up and down at the output it's really it's
04:54
very simple elegant concept and so how do we use this so we we take
05:03
this very simple concept of laser beam errors and after many many years of development we made it much more complicated because as all you all explain shortly it's it's
05:18
very complicated optical system now and all that but the point of all of these extra optics these extra the folding of the light is to try
05:27
to amplify the signal so 1 thing I'll just point out is that instead of just having the light down to the end and bounce off a neuron come back we actually have cavities In all arms which allow the light to build up bounces and arms many many times and that amplifies the effect of the in moving so then
05:47
eventually after many decades of research this this idea by the way to detect gravitational waves with these Michaelson interferometry came in the in the sixties but and so the physicists to kind of came up with
06:03
this idea started to make very small experiments that were only meter well event that initially they tried to detect them with with borders but I won't go into the whole history but then they start to make small a farmers and kept getting bigger and bigger and bigger and so we got like
06:19
go where the length of the arms is 4 kilometers long so this from here all the way to the end here is 4 kilometers we have 2 detectors like I said 1 is in the desert in Washington and the others in the swamp in Louisiana so this is what it looks
06:37
like inside so this here is inside this
06:41
this central building OK we can observe onto the inside
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there it's a big vacuum system so the whole air from the is enclosed in this big vacuum these big
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these big chambers here
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hold the mirrors is a person 1st scale so it's it's very big big inside here so this
07:05
is 1 of the marriage so you can see at the bottom here that's the mirror the red thing is mere it's about it's about this big the ways 40
07:14
kilograms and its suspended so it's not
07:19
firmly attached to the ground because of course the ground moves a lot and we don't want the motion of the ground to confuse the instruments and make it think it's a gravitational wave so we isolate the mirrors from the ground with these very complicated seismic isolation systems is
07:35
actually this mirrors hung from this mass which is hung from another mass here which is some from another mass here which is found from this table which has you know active seismic isolation system and so this is 1 of the core mirrors this is our our
07:52
laser which can output over 100 watts of continuous like power that doesn't sound like much because you think of a light bulb in your house is 100 watts but the light bulb is outputting light in all directions and this laser beam is focused into a
08:06
very tiny spot and of if you were to get hit by it it was not the not the country of here's a here's what it looks like at the
08:19
output of the unit parameter so actually I where we make the the detection is in this Assembly here where that that that what we call the photo detector that measures the light is inside here
08:32
and so the light goes through the whole order from a comes to this
08:36
Chamber where bounces around them more optics and eventually is caught in this Assembly here and
08:43
here's here's another picture of I think this is another very sexy pictures so this is this is inside the in chamber with the in test
08:52
masses and so you can see this is the test mass
08:58
here this is this what we call the in near and so behind this guy here down down here is not for kilometer long arms and then this whole assembly here is to take a little bit of the light that leaks through the mirror and then it bounces it bounces up
09:15
in here goes up onto another optical Table of here where we measure the light so we actually we actually measure the light in many different
09:23
places throughout the year from there so we're constantly getting of feedback about what's going on inside the instrument right
09:34
so basically life is shit I mean let let like go is just the transducer of the spacetime strain of the movement of spacetime through
09:42
electrical signal that's basically what it is it's really very similar to a microphone and a lot of ways I mean you know microphone when it gets the pressure from the air that causes the microphone to move and we turns that into an electrical signal that we can then digitizing process and listen to well it's very similar with like go and interestingly the
10:06
frequency range that like can detect of use of the motion of space time Is the audio frequency range it's exactly the same bandwidth that you here with your
10:19
years because from about a little less than from like 40 40 hertz up to a couple kilohertz and so this is the this is sort of our primary thing that we measure we look at this scientists and
10:35
like look at these plots a lot so this is called the strain spectrum of like the
10:42
spectral amplitude spectral density and it's basically just a measure of how much power there is at each frequency in the detector so you can see here the gray the gray curve this is what the strain spectrum look like in the initial versions of light at the end of the initial I go of project which ended in 2009 and then in
11:05
2009 we the whole instrument apart and we completely put it back together with all new components to try to make this curve go down
11:15
and that's what we got to do with this black curve basically this is only for 1 instrument the 2 instruments a slightly different obviously so the spectrum is
11:25
a little bit different but it's mostly the same and so this is
11:29
where we are in or 1st observing run which happened in the 2015 with the advanced detectors and then we just talk really briefly about what why do we what limits this and so what we're trying to do is we're trying to make this measurement as sensitive as we possibly
11:47
can and so what we wanna be limited by is actually is physics we don't wanna be limited by the sort of technical noise sources like you know is our amplifier noisy that would be that would be a failure basically we would think of it as a failure of our amplifier was too noisy and so what we have here
12:07
so at the upper the left side in this sort of entrees
12:12
is a is the size
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of noise I mean we can we can try to do we can try to suppress the size of noise as much as we can and what we have to we do it with these suspensions with the seismic isolation tables and so what happens is the the the the ground is moving quite a bit
12:30
and so all of those seismic isolation the isolation systems attenuate that motion and that's why you have this very steep dropoff
12:38
in frequency here add the this
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green trace down here is interesting because that's actually normal motion in the arm test mass so that the actual test mass because it's not at absolute 0 temperature
12:56
is going to be vibrating all of the molecules in the test mass will be vibrating and that is notion that you know will limit how much we can detect and then the red curve is quantum
13:10
mechanical noise on the light itself so the light is not just a continuous wave it's
13:16
actually you know a bunch of individual photons that's a quantum mechanical like is a quantum mechanical
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objects and so those photons the fact that the discrete little packets of energy has has an effect on the the noise so we can't detect you know we we don't detect a continuous stream it's like rain and that rain you know causes the noise so where do we get that ultimately
13:41
so that at the bottom of this this is our strain here and over on the other side is what we call the displacement sensitivity in terms of meters so at the bottom of this curve we have 3 times 10 to the minus 29 meters i'm letting everybody think
14:02
about the number for a 2nd 3
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times 10 to the minus 20 meters that's an incredibly small number and I'm working on like for 18 years and that number still blows my mind 0 what is it what does it mean so here's an
14:17
Adam this is anatomist 10 minus 10 meters and Adam a hydrogen atom is 10 the minus 10 meters we go and this is a proton extended to the edge of a proton that's 10 to the minus 18 meters that's still bigger than that noise were measuring what
14:39
follows that possible it's it's
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crazy at its that's not so I I don't know why would I know we so what is
14:54
it sound like so let's let's put it all together the 1st direct
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erases
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leakage around in the
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detector you can use be on marketing that that's that's we
15:11
can we listen to this in the control room this is the data that we take brought properties
15:17
Newsweek or or this
15:19
like this original or up to all of you you don't like this thing this original all of these very many times those lines are because the
15:30
test masses are hung by these very small fibers that are actually made of glass is the test mass the made of the same material that the
15:39
test methods and so those vibrate like a violin string and so we call them violin modes and so they have those those you know all of those highpitched harmonic and then what we can do as we can start to this so we we tried to filter out the the low frequency
15:59
well we we filter out all of use of these and then about what
16:08
happens when so that that's filtering out all of the things that we know
16:14
are not gravitational waves we get a somewhat lower in the long run going on is right so that's that's what we that's what we detect meanwhile 1 . 3
16:31
billion years this happens so this is a very cool simulation From this collaboration called S access which is simulations of extreme spacetimes and this is to black holes that are
16:47
orbiting around each other and what's behind is just static picture of the milky
16:53
way galaxy just the light of the star field in the background and all this crazy stuff you're seeing is the space
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time that's being curved in war is the is bending the light binning the light that's coming from behind it that's called gravitational lensing and so this is just a way because the black holes a black there obviously in space where there is no there's
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nothing to see really no light so what we what we do is they put this picture behind it so you can see I mean we actually observe things
17:24
like this in the universe today we we observe these these gravitational lensing effect this is obviously a special because of this the the the fact that we're seeing these black holes so the orbit around each other as they orbit around each other they emit emit gravitational waves so this is that this is an animation also from that same
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collaboration of what the waves look like what the representation of the waves as they leave the system to get the 2 black holes order around each other this list with red and yellow is the waves being emitted and as they get closer to the waves get higher amplitude the frequency gets bigger until right at the very end you get this big burst of waves and you just left with 1 black hole at the end so
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then on September 14 which
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is funny because on September 15 we gonna start having assigned from we start observing but we were in
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and we were in a on what we call an engineering right we were getting ready to observe we're very close we're about basically everything was completely ready we hadn't just you know check the box
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and the the I being ms we I
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also got this is a picture of are you there you had a little the chair and so this is actually what was
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measured by the instrument from those from black holes that look like that this is the
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1st detection of gravitational waves and you can see this is basically what the
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signal look like in the hamper detector and this is what it looked like in the Livingston detector however the
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allergens and and yet so that the that the higher pitch the higher pitch version is pitchshifted up so you can sort of you can hear the chirping more but that's that the chop is the frequency getting
19:44
higher as the 2 black holes get closer together and then you
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can hear the amplitude get louder as well and so this is another this
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is this is the plot from our paper that we published this was the 1st part and so you can see up there at the very top is just the waveform that we measured I mean it's literally just you know like a wave file the the next row it is a numerical simulation so we took the we
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took what we measured we tried to reconstruct what we
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think that the signal is based on what we know about you know numeric what we know about general relativity we have lots of complicated algorithms to try to predict what these with the signal will look like and we think that from what we measure we say OK we
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think these are black holes of this mass and they should in in pure form without the noise of the detector look like
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this so that's what's on the 2nd row and then we take the top row and we subtract the 2nd row and we get the 3rd row and you can see all that's left
20:51
is just noise so what is that show it so that there is actually a pretty good match if you take away or prediction of the signal from what we actually measure you're left with basically nothing and so we kind of use that as evidence that's not how we that's not how we prove it but it's nice it's nice but nice thing to see and this is the frequency as as a function of time you can see it's only it's about 200 millisecond long signal and
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the frequency start very low it's something like 40 50 hertz and then it goes up to like 300 hertz and we call this
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signal GW 1509 14 1st gravitationalwave detection so
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then reverse that was that was day minus 1 of our observing run and saw we kept going and then the on boxing day on December 26 which was actually December 25th in the United States everybody started again more email all the sudden and we detected another event this 1 is a little bit different but in the 1st events the 2 black holes are very similar size and this event very very very different and you know the the size difference is bigger and so you have a smaller 1 smaller that's 1 much smaller than the other and so the event
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is much is longer it's over the course of the 2nd we see many more cycles of the events so this is is a little
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bit too complicated but I just wanna show just because this is this is kind of what we show as evidence of the of the proof this this
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these these curves down here what we call the background and we get
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these curves by shifting the data from the 2 instruments relative to each other so that the there's no
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causality between them so you know if you shift them by remember I said that the light travel time between the duty to detectors with 10 ms well shift the data the a 2nd you know so that so that the 1 is shifted for 1 2nd relative to the other there's no way that some you know something that's traveling at the speed of light is going to have a coincidence signal in both of those things so that's how we generate this background we reach shift the
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data and then look for gravitational waves we don't you know we see this very sort of expected of me all
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random random signal and then these are the what we detected during the 1st observing right so over here on the right is the 1st signal
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which is just screamingly allowed it's like a really
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loud we we never expected we would see signals that really we didn't really expect to see single sellouts we made all these but all these time making is very sensitive algorithms to listen to the tiny signals and noise you know like the needle dropping and then we get this really loud signal no whatever so Will it helps us it helps us
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because of course the next 1 was was not allowed and so that's the GAW 15 12 26 the boxing day event and of course people people might have heard about 5
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sigma that's the that's what scientists use to sort of trying to say that something is significant so you can see those they're how how the signal was moved up as you get louder and louder and so we the purple is kind of what we consider actually
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this this black 1 here is the background because of the fact that the 1st signal is actually in the data the 1st signal even if
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you time shifted it is coincident with occasionally with random events and the other detector and because it's so loud it that actually looks like fake fake signals so we have to we remove that and then also in October we got another event that's kind of interesting it's not you know if they if there were no gravitational wave signals although orange boxes would just be on that line and so anything that's off of that line that's a little bit interesting in the further away it is this much more interesting so we have this another event you can see it's only like 2 sigma that's not very strong but you know all that against judge there's some
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numbers so it's kind of incredible to me that with this tiny amount of data we can learn a lot about the system because we know general relativity very well we can run these numerical
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simulations we can sort of reconstruct what it looked like so we can we get an estimate of how far away There's 1 .
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3 billion light years which is 1 10th of the distance to the edge of the observable universe so it's really far this is this is 1 of my favorites here the the big black hole was 36 . 2 that that symbol there in with the circle with the dot is the mass of the sun that's what we
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use frequently in astronomy to measure masses is a scholar solar masses so this black hole with
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36 times the mass of the sun and the other 1 was 29 times the mass of the sun and the final black hole was 62 times the mass of the sun well doesn't take very fancy math to see that that doesn't add up right so what happened there's
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3 solar masses missing that was the gravitational waves so these 2 black holes colliding turn the wheel entire sons they just like completely evaporated the energy and turned it in the gravitational waves that's pretty incredible that's a lot of energy that went into bending the space and then this 1 this and this is just crazy here
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so the luminosity that as a man is another measure of energy
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that we frequently use in astronomy 3 . 6 times 10 to the 56 birds per 2nd that's a that's how much at the very peak how much
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energy per time it was emitting so this the luminosity of the Sun is 10 to the 33 so that's 20 to 23 orders of magnitude bigger than the brightness of the sun and then the higher universe the luminosity of the entire universe if you don't have any crazy events like
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this just the NBA universe is 10 to the 55 words so that at the peak of this event it was brighter than the entire rest of the universe which is this varied these events are very very energetic
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right so that's that's the story like go we where we're currently we took the instruments down again to try to improve them i'm because every time we prove we go out and distance but when we go out and distance that's the volume is the cube so little increase in distance makes a lot of extra volume so we get a lot more potential events so that's why
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we keep trying to improve the sensitivity once we get up toward design to be remember where where where that black curve were not at where we ultimately want be and and explain why we're not there yet but you can come and ask me after the like but if we get to that ultimate design sensitivity we'll see multiple events a week we
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so water big discoveries we hope to see binary neutron stars colliding so you know black holes are just these mathematical g of g general relativity objects but neutron stars have structure and so if we if we see those smashing together we can learn stuff a lots of
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interesting things those might produce electromagnetic waves that we could detect with telescopes which is very interesting and then we got more detectors that will join
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our networks Virgo is rise of French Italian collaboration that will hopefully be taking data soon powder a Japanese collaboration of we have were tried hoping to build another like a detector in India and then of course were planning to make much bigger detectors with longer arms in space all sorts of things like that so this is a pi bond conference I wanted to say a little bit how we use pipeline which is basically everywhere I mean we love Python in in science in general I think but particularly and the gravitational
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wave community it used to be reduced to be all Matlab for various reasons but pipeline is becoming much more popular now so for data analysis off or what we or flagship search research that looks for so compact binary coalescence so compact means very you know Compaq stars or black
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holes neutron stars binary is obviously 2 stars and coalescing use that process where spin
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together and merge so searches for those types of events we use of we use a pipeline called CBC we have another we have another pipeline that's based on G streamer which is actually really cool I like that 1 a lot and we use
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Python in that in that search as well to construct G streamer pipelines that's a streaming pipeline so that 1 is actually used to detect events in real time as we take the data from the instrument but this 1 is is this you know we that's C and we have this
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like algorithm library which is a C library which also has all of these algorithms for generating With the waveforms look like and doing the the the the template being look for those signals in the data that's called Pylab we also have a lot a package called GW part which is you know we used to retrieve data in who do basic signal analysis and plotting of course
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all the plot to see we're done with matplotlib I love that was not problem right yeah from
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simulations we do lot of simulations like the s excess collaboration that made this really cool animations they use Python interface to pair of you pi is the
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interface to this of optical simulation thing that we use that simulates signals and the inner from of course like everybody else in the universe were trying to get in machine learning were little bit behind the curve but you know we're ramping up our reach IPython notebook is anybody here use IPython notebook that's really cool what
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we love i pipeline a book it's but really it's it's awesome and so we've been using
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a lot it's been very useful in our outreach efforts so I I recommend people go to Last . like 0 . org LOS even like open science and and we have lot IPython notebooks were you can analyze the data yourself
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it's the actual they so you can get the actual data that we measure which is just those you
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know basically those wave files which you can listen to and you can filter it's you can extract the signal and plot it it's very cool and I 1 of by the
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very last thing I want to talk about is the instrument control so I'm I'm more on the instruments I help like to help build the unifrom eters and so 1 of the things that I helped put together was our automation system so we have this big optical experiments it takes a lot of coordination to you know control all of the and the seismic isolation systems
32:59
to get to the place where the instrument is sensitive most sensitive to detect the gravitational waves and so all part of and 2nd I just
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mentioned 1 notable deficiency in Python were Matlab still beats Python is in control system analysis but hopefully that will change in the future that telling you something so alright so automation so there is this but just talk about this really briefly is I think it's a really cool usage of Python it's not because I made it I swear but so it's called guardian and it's the automation system for like it's a distributed hierarchy of state machine atomic bombs of my mine fancy description of
33:48
it so this is kind of a
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schematic very very very cartoonish schematic of the instrument so here's the interferometry you got the laser you got the mirrors here you've got our our digital analog digital interface where the user just
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but you know digitalanalog converters that convert electrical signals from the uh the instrument into digital
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signals here we have this real time control system which I won't talk about but which is really cool and if anybody's interested in real time real time Signal analysis and then up at the top is all of this is this automation systems so each 1 of these blue dots represents a 1 of these little automatons that is
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automating part of the time system so it's basically like flipping so we know it's looking at signals and flipping switches and turning virtual novels and stuff like that so each 1 of these little
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blue dots we have a state machine that
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represents you know the automation logic you know basically what happens is we say 0 we wanna go to 1 of those States of there and then this thing looks at this graph and says OK I'm going to go this path to get over there and so
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this is all programmed in Python so we have these these Python modules that describe the instrument commands in these what we call the state classes that's what this God status of God state is just a class that defines 1 of those bubbles in that in that graph over to the right it has a couple of methods that get overloaded so safety is
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the name of new state damped is the name of the new state has 2 methods of
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main and run method I won't into the details of how those are executed but basically they just
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have some commands and them you know flip the switch set this game to be something else turn on these filters stuff like that then we have edges which is a list of tuples
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which just represent connections between the global so you can see these in
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that that basically all of these arrows in the graph over to the right and so this edge would connect the say state to the dance state and so then that whole thing those
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states and those edges is this state what we call the state graph so what guardian dies is it takes the the the modules that describe
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the state process it imports because Python is so powerful and you can get into the import mechanism so easily you can basically load the marginal standards for all of these gods states
36:48
definitions extract all the states look at look for the edges definitions but that all into the network X module which is a really sweet module for doing on this would graph analysis
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Network analysis like this anybody has to do network analysis I highly recommend this package and abilities this graph representations and so then what happens is that that
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graph then gets loaded into the automaton process and that becomes like the brain of the automaton and you say hey guardian go to state down and then guardian looks at the graph and says OK I'm down here and I can just you know very easily figure out how to get to the state that I wanna go to and it just starts to go broke starts
37:38
going and starts executing every state once it's done with 1 state that goes along the edge to the next 1 until it gets to the you know to the final place and I think that the the
37:50
architecture of this is kind of cool because we we use is the multiprocessing library
37:55
which is also not you know I mean Python but on rocks and some users all of the
38:07
interfaces to this stuff is just so clean it's so nice so the main process uses the
38:13
multiprocessing to spawn off the worker process and that worker processes the thing that actually does the execution of the user code that you know since the commands then you do it with the
38:26
multiprocessing instead of the threading because that allows the Damon to have full control over the worker if the if the workers doctors blocking for some stupid reason because scientists are very good at writing computer code then it can just terminated and and reload research on it and you know start over again and we use the shared memory interface
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and the multiprocessing to exchange data between the 2 processes so the commands to the worker go through the shared memory and then the the status of the execution of the user code goes back up to the shared memory the worker process capped catch all of the user exceptions report them back
39:08
to the dam and the Damon won't die it'll just keep sitting there and it'll report to the people in the control room had somebody part of the curve again and you know it makes a makes a you know an error message 1 thing that's kind of cool is that you can completely reload all the code on the fly so you can just send the command to the
39:28
Damon and it'll go in take up take all of the the user code that state graphs
39:36
and all you know just take it'll take that you can even reload as of it it's in the middle of executing a method on the class it can you can even reload that same class so what I will do is it'll just wait till the that tell the method is you know done executing in the meantime it's taking all the activities of that class stuffing it into the new version of the class and when that method is done and it just wants it out and starts executing the new the new version of that of that method with the new version of that class with the new commands in it critical and we use this this epic clientserver this is something that's that's frequently used in physics to large physics experiments to do control of various you know to control of the physics experiments is basically like a light weight the network Message Passing Interface so that said
40:42
some but the amplitude role
40:45
and detection of gravitational waves in the analysis and control of the instruments and on behalf of the entire field I think all of you was much spirited toward most thank you
41:08
very much since I think as slow as it was an amazing like the view into 1 of the huge the biggest discoveries ever in physics i amazing amazing talk thank you very much James think you have again that you can be a problem we can take a few questions if you will 1 of the things that you hear about question 0 yeah I'm happy to take questions yeah where only a final and for questions so
41:34
you get this coming year waiting the frontier so read is it true that when the 1st that the answer came out to us so huge that you thought was a fake some kind of elaborate prank you I asking what I personally doctor that money that what exactly that so that I mean that
41:56
many people in the collaboration well we cost behaved immediately like it was a real events like I was very I don't know it's too crazy it's too too perfect it's too loud it doesn't it's not what we expected to see the 1st events so it took some of us it took me you know like a month to be convinced that it was real but you know we we did a lot of analysis and we've made the detection in September we did not announced until February exactly and that was the 1st that we were just like sitting with thumbs up our asses the whole time we were we were analyzing the crap out of the data trying to figure out is this real or are we completely convinced that this is a real gravitational wave and then when we were ready and we had a really nice paper of then then we decided that announce you don't have to understand that that yeah that
42:49
would be a lot yeah it would I mean we we we thought a lot about that
42:52
like could be malicious good somebody have you know somebody is trying to get 10 year no it's not the end but it's too hard I mean this is 1 of the I mean it's this is not the reason we made 2 detectors but we make 2 detectors far away so that it's really difficult for any sort of terrestrial signal to look the same in both detectors basically impossible people and have a
43:19
question about the actual the utility of those detections like well we know that you can in our studies on the radical events but there had been been reading about it then it's like to what are those signals are incapable of using those signals to use behind things that we can't see actually like you well all I mean and so
43:48
certainly now that we've made the detections so this is why I titled the talk the dawn of gravitational wave astronomy because the point is not just to make 1 detection to prove that the gravitational waves exist that's very cool but what we want to do is we want to see them routinely that's why we continue to work on the detectors we continue to try to make them better so if we can see these events regularly we will start to learn about what produced the events I mean you saw how much we learned just from this 1 event right we learn and what are the masses of the black hole's how far away they are those are just those things alone of very important information to astronomers because they tell us you know the fact that we solve what appears to be the read binary black hole mergers in our 1st observing and not in the neutron star emerges which is something we thought we would see that tells us a lot about what's going on in the universe so astronomically speaking of a lot of information that we can get from each of these signals and from the ensemble of all of the signals that we did hi I think to
44:56
have that stuck this is 2 2 7 2 7 we're where we we're slow
45:03
to upgrade we try to keep you know we try to make things the when a when you know we're trying to do science so we we're not we're not trying to go to the the cutting edge all the time I mean obviously would be we we will go of I would like to go with you know in our system administrators are more conservative than me if you have kind of a model a measure of how
45:27
likely it would be to have to speak you and how how would you repeat this became and how likely that you just detectors 1 next 1 would be properly in year or 10 years or so so I mean we had 2 and a half
45:39
events in 4 months but if you have any models is it that the rows
45:44
has a size and about the the properties of the whole you have these so many sure we have we had
45:50
we have models but and we had models and the but they had very big error bars because we don't know we've never seen gravitational waves particularly for the black holes the error bars for the black holes were there could be thousands a year or there could be 0 so I was like really huge about we had no idea
46:13
and and then we see we see 2 and a half and 4 months so that's that's very promising we will definitely see more as we as we continue
46:21
to so the 1st detection was 1 . 3 billion
46:26
light years away of 3 or 30 times the luminosity of the universe is what was the minimum safe distance that sun and you
46:35
have and I I think that I think that that has been right we we if I don't have the answer to that of off the top of my head but I think that it's something like if you were within you know less than a thousand kilometers from the event you would actually if you'll the gravitational wave in your body so you know but remember these these gravitational waves are tiny it's just like a tiny fraction of a proton size that's that's moving the instrument so it's obviously impossible for humans to feel that it's in which you get really close to the black hole but then at that point you're I don't think would 1 of you I mean it would be really cool
47:15
but it would be the last thing you see probably that that's a big relief thank you have no life at when
47:21
yeah said about women were too much
47:25
I guess the 1st commemorations it's really great to see in planning sound detection and click on and that's in so my question is a hollow and is demands of the black hole is them on independent in a way yet to assume I guess generate the immediate assumes some lack of the physics they have to assume cementing of that growth all things that we only know that you kind of did use altogether were 1 observation so how can these said uh list so the the what we
47:53
deduced from the observation comes purely from general relativity and black holes are actually very simple objects in some sense because they're just purely mathematical you know general relativity predicts that there will be these black holes that you have this very extreme curvature and those you know they don't have many properties there they have a mass they have that could have a charge almost in the real universe would not have a charge and they have spin that could be spending and these black holes were actually we we actually measure the spin of them as well so there's really only these 3 parameters and those of the the inclination of the spin relative to to us so we can use that we can use our knowledge of general relativity and these sort of simple black holes to make predictions of the signal and then that is what we when we look at the data that we we we do we sort of reverse engineer what this single looks like to extract what the parameters are so you don't
48:57
have to assume was in a model for the evolution of the universe for example domain and we don't we don't we we will well we do we
49:03
like to do Bayesian analysis so we have what we call priors where we we we make some assumption about what the distribution is but we like to keep those assumptions to be very broad so we don't wanna bias or search and so we like to assume that you know for the 1st for the placement of the Book of the black holes in the universe we just assume that they're basically isotropic because we don't know we don't know we don't have we we we don't yet have reason to believe that they should preferentially the at some point but that the 2nd black hole the boxing day event was also added very similar distance basically 1 . 3 billion light years so that's very interesting we have 2 detections and they're both from the basically the same distance away there are also kind of similar masses there but you know 10 20 times 30 times the mass of the sun so you know With this is this is what we're learning from these detection and we have like
50:02
the time for 3 more short question so that ratio so has 7 and Fabio has and you'll adoption of open source software also helped in gender and attitudes to opening the data in the output of your calls the year I would
50:26
I would I would I would say if I would flip it basically and say that scientists are by their nature the open wait wait I mean we'd we'd it's a little bit tricky because in academia you know you have to different you have 2 people get a little bit protective because they need their results so that they can get publications so they can get 10 year but you know we that we also want to share and so the the I think you know we open source all of our software now we it's not just that we use open source software but all the software that we write is also open source so all of the all of the of the pi CBC Pylab all of our algorithms goes wrong get hold this automation platform that freely available you know other scientific collaborations can use them if they want so where we're formally firmly invested in open source and obviously we get so much benefit out of it we you know I mean if we that's 1 thing that sucks about Matlab right it's proprietary we have to pay thousands of dollars many many thousands of dollars a year for licenses they change the API is no apparently no reason just as they think they should make people want to buy a new version they make 2 releases a year and you know you have to pay more I mean it's really annoying it's really annoying to work with of honestly and so python is just been huge because of the open source enables us to be more flexible the
52:12
1st was in very quickly the things that you think there are really missing in order to maintain points on the Python of more specifically on by the ecosystem you could use some help what can we do to improve
52:37
I don't know this is doing what you have to have IIIV
52:44
going in particular I mean there's certainly there certainly like I mentioned the controls analysis stuff I mean there you know there's lots of cool signal
52:52
analysis stuff inside by we would like you know to see more expansion of the capability is there you know we we do a lot of very high performance computing stuff we have you know big computer clusters were we do massively parallel analysis of the data on I don't know I mean it's our and that's 1 of the things that's so great about Python whenever you know I wanna do something and I do research can almost always find a quick easy way to do it so so far only them for or their the parallelism is a little bit you know I mean it's kind of specialized because we need to parallelize across computers in a cluster so it's not the same you know I mean obviously there are packages that help do that we we use this we use this platform called of Condor and the people of about that but it's a job scheduling of a system for running analysis jobs on computer clusters we don't our our our our own cluster analysis this not terribly sophisticated it's not like these big numerical simulations where you have to do a lot of sharing of memory between processes spread across many nodes we basically just you know give each computer node each process running on each computer a little chunk of the data and say you look for gravitational wave here you look for gravitational wave here and we just just you know massively parallel that's pretty straightforward what we have to do with the of the reconstruction of the information about the the event that's more complicated right because we have we have we have so you know this 1 small stretch of data where we know that there is an event and we want to extract all the information from so we have to run a lot of models over it and you know do these of integrals over all of these you know all of these different tests so but a little bit for here OK last question
54:57
OK I have a question at about the visualization of the event that the there it it looked like in your model that debt to black holes which are rotating around each other about 30 times and 5 seconds Is there something that actually the same as those of slow down right so they're actually
55:15
it's actually faster than those slower than realtime yeah there there it's they're very fast that's incredible I mean so mean 1 of the 1 of the plots i showed actually
55:26
has but we just go really quick sorry to show 1 thing scripted OK look
55:38
over here this is this is
55:41
the speed of of the black hole the velocity of the black
55:45
hole as of over the speed of light so at the very end of the black holes I mean these are these are macroscopic either you know the bigger 30 code
55:55
solar mass things is moving at half the speed of light I mean it is it is it's not I mean what's going on in that region of space is who
56:07
that's crazy there were thank you very much thank you
00:00
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