The Beauty of Gravitational Waves with Corey Gray

Spark Science Podcast

The Beauty of Gravitational Waves

 

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Regina Barber DeGraaff:  Welcome to Spark Science where we explore stories of human curiosity.  I’m your host, Regina Barber DeGraaff.  I teach astronomy and physics at Western Washington University and I’m not ashamed to say I know very little about gravitational waves.  We’re lucky enough to learn about this groundbreaking physics from Corey Gray, who’s the lead operator at Laser Interferometer Gravitational Wave Observatory, or LIGO, as we will be saying it from now on, in Hanford, Washington. 

 

He was there at the start and he’s an awesome science communicator.  He was featured on NPR recently because of his expertise and also because of the project he’s doing with his mother.  They are currently translating LIGO press releases into Blackfoot. 

 

So let’s find out more about gravitational waves and when they were detected. 

 

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Regina Barber DeGraaff:  Corey, welcome to our show and we’re going to talk about what is LIGO stand for and what is your position at LIGO? 

 

Corey Gray:  OK, first off, LIGO stands for Laser Interferometer Gravitational Wave Observatory.  The LIGO project consists of two gravitational wave detectors or observatories.   One is in Louisiana, near Baton Rouge.  The second observatory is just over the mountains from you, kind of near the Tri-Cities, and this is the LIGO Hanford observatory.  And here, my position is lead operator for the operator team that we have.  The operators are basically the people who drive the machine when we’re collecting data.  So I’m the lead operator at the LIGO Hanford observatory. 

 

Regina Barber DeGraaff:  There’s been a lot of talk in the news about what are gravitational waves and I kind of want to give our listeners and our views the best maybe summary of a gravitational wave is first before we get into how you got into this position. 

 

Corey Gray:  So my background, I only have a bachelor’s in physics a long time ago, so I’ve kind of had to learn the big ideas of science just on my own and how to explain it, because I was hired to basically help build this machine.  So everything for us starts from Albert Einstein and his general theory of relativity.  When he released that to the world, that was back in 1915 in Berlin, and the crux of it, or the big things that are related to LIGO are just how he came up with a completely different way of explaining how gravity works. 

 

So, instead of objects being attracted to each other via a force from Sir Isaac Newton, Einstein described gravity as how matter affects the space around it. So, all objects bend the space around them, depending on how big or how dense they are with their mass.  And so if you just take a star or you take a planet, they will bend the space around them, and then that’s kind of a static example, but if you take it next level, what happens if you move that object in space?  If you move that object that’s warping the space around it, it’s going to actually wiggle the space around it as well.  So instead of just warping the space around it, if you move that object, it’s going to generate these wiggles in the space around it, and those wiggles are what gravitational waves are.  

 

For the most part, base is a very stiff medium, so you need to have very large objects accelerating in space to be able to observe them.  If you were a black hole, if you had a big, heavy object like a black hole or a neutron star, you accelerated them in space, they would generate big wiggles or big gravitational waves, and their effects would be very violent and those waves would actually destroy you. 

 

But because of the nature of these waves, and because these types of events are so, so far away, if you do the math, the amplitude of the size of those wiggles become monumentally small by the time they reach us where the earth is in our universe. 

 

So Einstein did that work.  He went through the math of calculating certain type of source, maybe two stars, and then looked at how big the two waves they would generate as these stars crashed into each other.  When he did it like on the back of an envelope way back in the 1916, the size of those waves were just so tiny that he thought that there’s never going to be a chance that they would ever be detected, but things have changed since 1916, so different sources have been conceived.  So, ideas of bigger, heavy objects, such as black holes and neutron stars, so sources have gotten a lot bigger and a lot more violent, and so they make bigger splashes in space time.  And then, just technology has also improved in the last century as well. 

 

So both of those different pasts have gotten us to a point where a century later, the first gravitational wave detections were directly detected back in 2015, so close to a century after Einstein conceived this whole thing. 

 

Regina Barber DeGraaff:  I really like that description and I think that later on we’ll kind of get into this difficulty imagining, as humans imagining this idea of a gravitational wave, because as a physics professor, we kind of play around with elastic, and some elastic sheet, or something like, you know, a trampoline material.  And you kind have some heavy object in the middle of your trampoline. 

 

Corey Gray:  Yes. 

 

Regina Barber DeGraaff:  You know, you throw a marble and it looks like it’s orbiting around this really, really heavy spherical object in the middle of the trampoline.  We kind of use this analogy, but you have this two-dimensional analogy, you have to extrapolate that to three-dimensions of reality, which, I was talking to my 10-year old, and she was asking about black holes and I was like, “Well, it’s something that rips through reality.” 

 

Corey Gray:  I like that. 

 

Regina Barber DeGraaff:  And she’s like, “What?!”  We’ll come back to these analogies that physicists use.  And I want to ask you about interferometer, because as a physics professor, explaining what an interferometer is, which what you’re saying is you’re observing tool, it’s not trivial to explain that.  It’s kind of complicated.  So we’ll come back to that.  So, for our listeners, don’t worry.  We’re going to come back to that science. 

 

But I like to ask every single scientist the same question.  So you’re working on these revolutionary things in science.  What made you want to do this?  Like, as a child, was there an event that was like “science!”  Why did you study physics?  Why did you go into this field? 

 

Corey Gray:  I guess role models played a part for me and my experience.  My father was a self-taught electrical engineer, so he was my first role model.  But I guess when I was in high school, one of my heroes was a TV character by the name of MacGyver and he was a character who was into physics and tried to solve a lot of things without violence and weapons and things.  He used his mind.  He had a degree in physics.  So I wanted to be like an Native American MacGyver.  I think that’s where my path started with physics. 

 

Regina Barber DeGraaff:  So when you got into physics, what surprised you and what didn’t surprise you?  Like, as you got into your under grad, first where did you go, but two, when you went into it, were there things that you weren’t expecting? 

 

Corey Gray:  It was just intimidating.  I always knew it would be intimidating.  I knew it would be hard.  But that wasn’t a surprise.  I went to a small state school in northern California, called Humboldt State University.  I’m really glad I did that, because it was a very small university so that made just interactions with the professors really good, and the other students.  Just the classes were pretty small. 

 

So as far as surprises?  Yeah, that’s a good question.  A lot of negative things that I experienced was just in my own head, just knowing that I’m not pursuing something that’s hard, and always questioning myself, “Should I keep doing this?  Can I still do it?”  And then not seeing people who are like me, not seeing other Native Americans in physics.  So I think those are the things that were always going through my head.  “Am I ever going to graduate?”  Just those fears that I had as an undergrad.  Those are the main thoughts I had. 

 

Regina Barber DeGraaff:  Yeah, but you eventually got this position at LIGO and was this one of your first positions related to physics out of school? 

 

Corey Gray:  Yeah, this was my first job right after graduating.  I did have several internships.  So when I talk to students, or when I do outreach trips, big things, I always try to tell students just the importance of internships, because those are the first experiences I had working in science and two of them were physics-related.  So internships are important.  And so yeah, this is basically the first job that I… I think it was the second job that I applied for right after graduating.  I have been her since 1998, so I’ve been here a long time. 

 

Regina Barber DeGraaff:  Was there somebody that was instrumental in helping you get this job, getting your internships?  We always say “get internships,” but the path to do that is hard. 

 

Corey Gray:  I know.  I wish I had a better answer.  I wish I could say that I had a mentor because I know that a lot of students I meet nowadays, they do have a better network of mentors.  I didn’t really . . . I learned about certain organizations, such as SACNAS, which is the Society for the Advancement of Chicanos and Native Americans in Science.  There’s a similar group called AISES, which is for Native Americans in science.  And those organizations have conferences where they have like career fairs or exhibit halls where you get the opportunity to meet a wide variety of universities and just other types of exhibitors and get ideas for careers, internship, or summer research opportunities.  So I guess those networks, those organizations are big thing. 

 

I remember my first semester away from home in southern California, being up in Humboldt by myself, I don’t know if I had tears coming out of my eyes, but I was at a point where I was like on the phone with my mom saying “I don’t know if I can just be here anymore.”  Around that time when I was just thinking of moving back home, that’s when I found this group called Intercept, and it’s just a science organization for Natives.  They saved me, because they were like another family and they introduced me to those other networks that I talked about, AISES and SACNAS. 

 

So organizations like that I think were very important for me with my collegiate experience, and then also with the summer research and also finding my job as well. 

 

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Regina Barber DeGraaff:  Welcome to Spark Science, where we’re talking about gravitational waves with Corey Gray, lead operator at LIGO in Hanford, Washington. 

 

I went to school here at Western in the ’90s, in 1999, and I remember there was an alumni that was talking about LIGO and they were like, “Any day now, we’re going to find a gravitational wave.” 

 

Corey Gray:  Really? 

 

Regina Barber DeGraaff:  And then I went to WAZZU for my PhD and I remember there’s definitely a connection with LIGO at WAZZU, Washington State University, because they’re close to Hanford.  And they were like, “Any day now.”  You know, this is in 2006/2005.  But what I’m saying is that it was such a new thing.  You got this job in 1998 but this idea of detecting this mythical gravitational wave, it was such a big thing.  It was so exciting. 

 

People kept their excitement for over a decade with just nothing to prove for it.  But they were just like, “It’s going to happen any day now!”  That’s what I remember. 

 

So what do you remember from the beginning?  Because you were there basically when it was growing, so what was it like at the beginning of this thing that was so new? 

 

Corey Gray:  So, you knew more than I did about LIGO, because back in ’98, I had no real idea about what LIGO was or what it did.  I did look in my astronomy undergrad text and there’s just a small paragraph about gravitational waves and that was it.  So, it was totally new to me. 

 

So my job was just an excuse or a way to get out of southern California.  So, I just saw the job announcement from Cal Tech up in Washington State.  It sounded like a really cool opportunity and I didn’t know much about it.  So 1997 is when the ground broke, or that’s when both observatories’ construction was complete and so I got here around that time.  For both observatories, they were now having operations and now they were hiring people to help basically build the first detector that we had. 

 

So I got to be on that part of the project and that was probably the first five years, I don’t know, three to five years was focused on a lot of kind of manual labor, I mean learning how to drive a forklift, operate an overhead crane, learning about torque values for certain kinds of screws, learning a lot of hands-on things. 

 

So that’s what I learned.  My job was very focused.  I mean, we were very schedule-oriented.  We had a lot of deadlines that we had to keep to, so that was the first few years.  That phase of LIGO was called Initial LIGOs, so that was the first detector that we made.  And it was mainly a kind of proof of concept type of situation, so we just wanted to build this huge, complex machine and then see if it could run. 

 

Around 2002, that’s when we turned it on, Initial LIGO, and then off and on, we would collect data.  Back then, we called them “science runs.”  That’s when we would have both of our machines in Louisiana and Washington collecting data.  And we would go, it would be three months at a time, or six months.  There was one time when we did a couple of years.  And then we take breaks and work on the machine to try to improve its sensitivity. 

 

Through all those years of data that we collected, there was no detections that we made.  But then we turned off the machine in 2010 and that is when we built Advanced LIGOs.  So we used the same vacuum system, the same basic shell for the detector was used, the same infrastructure, or vacuum system.  Everything was gutted out out of Initial LIGO and then we spent the next five years assembling and installing all the hardware for advanced LIGO, so 2010 – 2015. 

 

So an interferometer, it’s not a new setup.  It’s not a new — I say machine or detector.  It’s an optical setup that’s over a century old.  Very simply, it’s just the light hits the beam splitter, the splitter splits the light into these two twin waves that move down paths that are perpendicular to each other, so what you have is a big L shape path that both those beams go down.  And then they hit a mirror, which could be either inches away, or in our case, it could be four kilometers away, hits that mirror, and then that wave returns back.  For our machine, it resonates in these four-kilometer long arms, but eventually the light from both of those twin waves recombine with each other and interfere with each other and the output of that interference is what you look at with an interferometer. 

 

The thing that’s really good, or why interferometers are so good for what we’re doing is that with those mirrors that you have at the end of the arms, any time, minute little changes that they make, we can see very easily at the output, or where its sensor is, or where your eye is.   Whatever way you’re looking at the output, you can see very tiny effects very easily at the output of it.  And that’s why interferometers are so kind of catered for looking for these tiny signals called gravitational waves. 

 

Regina Barber DeGraaff:  Right.  So basically there’s this interference between these two light sources and you’re saying that what we see on that stream, that inference, that pattern, is affected by the movement of those mirrors at the end of those paths? 

 

Corey Gray:  Yeah.  Also, I like to think of interferometers as like a ruler, because all we’re doing is looking at length changes in that four-kilometer — the arm distances.  So, from here to four kilometers down either arm I’m looking at, we can resolve a lank difference, which is 1,000 times smaller than a proton diameter, that’s how sensitive these machines are.  And we need that sensitivity because gravitational waves are on the other side of the universe and by the time they pass right through the earth, they’re super, super tiny and that’s why we need this very sensitive ruler. 

 

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Regina Barber DeGraaff:  Welcome back to Spark Science, we’re talking with Corey Gray, lead operator at the Laser Interferometer Gravitational Wave Observatory. 

 

So, just to kind of explain to our listeners, why are those two mirrors changing distance?  What are we measuring, right? 

 

Corey Gray:  Yeah, so when the gravitational waves pass through the universe, as they’re moving through, there is violent events happening all the time and these waves are passing through the earth at the speed of light all the time, but we just haven’t had an instrument that’s sensitivity enough to sense their effect.  So when a wave passes through the earth, what it’s going to do is actually change the distance in each of the arms, just very minutely, and those mirrors at the end of the arm will move, depending on what type of wave is vibrating them, or what type of violent event on this other side of the universe is vibrating them. 

 

So when a wave passes through the earth, it passes right through our detector, and it moves our mirrors in a certain way that we would see that wave form, or that wiggle, with our detector.  That’s the output of our machine. 

 

Regina Barber DeGraaff:  Right, so we have these two detectors, one in Louisiana, one in Washington, because we want to see that same wave going through two different points, right?  

 

Corey Gray:  Exactly.  Yeah, yeah.  You want to see the same wave signature, the same identical signal on both of our machines.  Because if you just had one machine and just had the one here in Washington, there could be other things that move our machines.  I mean, there are trucks that drive by our observatory.  There are earthquakes on the other side of the planet.  Anything magnitude 5ish wiggles our mirrors around.  Storms out in the Pacific or in the north Atlantic also move our machine as well.  So there are all these other noise sources that move our machine certain ways. 

 

The beauty of having multiple detectors is that if you see a certain wave pattern on one machine and you also see it on the other one, that’s going to give you an idea that what you saw was not local and it was cosmic in nature.   So we have Washington and Louisiana here.  The signal that they both see has to be within 0.010 seconds, or 10 milliseconds, and that’s because gravitational waves move at the speed of light.  So if you have a signal that’s seen within that window, then that’s a good likelihood that it was maybe cosmic in nature.  You also have to do more analysis to do it. 

 

And then another thing is that when both of our machines, we have super computers that look at the data, at both machines’ output, pretty much in real-time, so that within about two to three minutes, so if they see a signal on both, they’re going to look at all these templates that are different types of wave forms for different types of sources.  So there’s thousands of different digital fingerprints of possible events that could be what we see on our machines. 

 

And the analogy I like is like with my phone, one of my most favorite apps are the music or song recognition apps, so like Shazam.  What Shazam has is, it has all of these templates of a song.  So it’s like a digital fingerprint.  It uses the microphone as its sensor and it takes that data from the microphone and then matches that to all of these templates of songs over the last century. 

 

That’s kind of what happens with LIGO and then the super computers that analyze the data matches the “songs” of these theoretical types of sources to the actual data from the real sources that we might record. 

 

Regina Barber DeGraaff:  It’s funny, because my brain instantly went to the negative, right?  “I’m looking for the sources that are definitely not what we’re looking for.”  There are little earthquakes, cars, and when I ask the question, your mind went right to the positive, which is like, “Hey we have these models for what we want to detect that are most likely going to be two neutron stars orbiting or colliding or two black holes or something like that. 

 

Corey Gray:  Yeah.  The types of detections that we have made so far have been from binary systems, so we’ve had a total of 11 detections.  Ten of them have been from a binary black holes, so with two black holes that are orbiting each other for millions of years, and it’s only at the very last fraction of a second where you get the biggest burst of gravitational waves that the signal is loud enough to move both of our machines. 

 

And so the templates that we make are just focused on that last second, right when the merger happens.  So those templates get matched to our data.  And I also forgot the other detection we’ve had is two neutron stars.  So everything that we’ve detected so far has been binary systems, two objects orbiting and crashing into each other, merging into each other. 

 

Regina Barber DeGraaff:  And like you said earlier, really, really massive binary objects. 

 

Corey Gray:  Yes.  I just gave a TED Talk recently and one of the stories that I liked, or I didn’t even really think about was one that happened kind of a couple years before that first detection happened.  At that point, my mindset was that I was very focused on the specific tasks I had.  One summer, which I think was 2011, I went for a hike with a friend who was also a coworker, grad student from MIT. 

 

And as we were on the trail hiking up to the mountain, I remember, just to make conversation, I asked him, “So, how likely do you think that it will be that we will make a detection?”  And without skipping a beat, “Oh, within the first year after we turn on the machine, we are going to make at least two or three detections.”  And he just didn’t hesitate at all.  He just said, “Yes, we are totally going to make a detection” and he went into the statistics about it and that’s when he kind of starting losing me and that’s when I started losing my breath, because just thinking about, that’s when I thought of the bigger picture.  I think that was the first time I had the thought that, “Wow, this might actually happen in my lifetime.” 

 

So I still didn’t know, but that was I think the first time I thought that maybe this could happen.  So fast forward just three or four years after that, that’s when our lives all changed here, because that’s when we had our first detection. 

 

Regina Barber DeGraaff:  And there are going to be more, right?  Because like you said, it shuts down sometimes and then you modify things.  At LIGO, you’re trying to make this detection, your observatory more and more sensitive and the press release that came out in December says that this spring, we’re going to turn it on again and it’s going to be even more sensitive, so there should be even more detection. 

 

Corey Gray:  That is the hope.  So, yeah, that’s why we’re busy right now.  We have just a few more weeks before we return to observing, or collecting data, because we’ve been off since September 2017, so now we’re at a point where we have both of LIGOs detectors.  We have another separate observatory in Italy, Virgo, so all three of these detectors are ready to go online and collect data.  And because of the sensitivity improvements, we expect the rates to increase for the number of detections we make.  So that will be exciting.  It will be cool to see the new detections.  Maybe there will be different types.  

 

I mean, there are other sources that are out there.  There are super nova, explosions, and then there are things we just don’t even have an idea about.  That’s what we hope for, just the big surprises that’ll be just something that we had no idea about.  And then just the frequency.  We’re going to have a lot more detections because of the reach that is going to be made possible by the improved sensitivity.  We’re going to be able to reach farther out into the universe. 

 

Regina Barber DeGraaff:  There’s going to be some that are orbiting.  When is that going to happen? 

 

Corey Gray:  I think that’s on the order of decade, so I don’t know if it’s ten to 20 years for when they have these satellites that will be millions of miles apart from each other, just looking at a different window of frequencies, versus what we look at. 

 

Regina Barber DeGraaff:  I want to pivot just really quickly looking to the press releases that come out of LIGO, you had said, or somebody else had told me that your mother actually translates them.  Can you talk more about that and how we’re trying to expand this idea of LIGO, not just to like an elite group of people, but to everyone. 

 

Corey Gray:  Yeah, definitely.  So when I think of everything . . .  I mean being part of this project has been very cool, and just the work I’ve gotten to do, I’m proud of that, but I think the thing I’m most proud of is to actually have had the opportunity to work with with my mother.  And it started with that first detection.  So that first detection was . . . oh, I should show you my tatoo.  This is the first detection, actually.  So you know what a beta looks like? 

 

Regina Barber DeGraaff:  Oh wow, we’re going to take a still of this and put it on our Instagram so that our listeners can at least see it. 

 

Corey Gray:  Yeah, so that detection happened in September 14th, 2015.  We took five months to finally announce it.  So we had to make sure the signal was real, we had to write a paper, and then we needed to think about how we would share it with the world.  So, two weeks before we announced it in February of 2016, the idea of the press release came out and how we wanted to share it in as many languages as possible.  

 

And just because I’m mom’s son, and I know the importance of language to her, the idea of translating that scientific document into an indigenous language was just something I thought of.  So we were under embargo at that time, that five months, we couldn’t say anything about this crazy, exciting thing in our lives, but two weeks before, I was able to ask permission to see if my mom could see that press release before we announced and the other LIGO people that I work with were totally excited and they said, “Of course, you can totally do that.” 

 

Me and my mom are Blackfoot, or Siksika, that’s a tribe in southern Alberta, and my mom is a speaker, so she is fluent.  She’s made a dictionary for us, her kids.  And she spent about a week or two working on translating this, I think about a two page press release in the Blackfoot.  And she got help from other family members and a lot of words can be translated word-for-word, but there are other words that there is no Blackfoot translation, so she had to become kind of a poet of astrophysics and come up with these Blackfoot words, like “gravitational waves” or “general theory of relativity.”  She came up with words for that in our language. 

 

Regina Barber DeGraaff:  She must be a linguist.  Like, she like basically get a degree, because that’s like a dissertation, right? 

 

Corey Gray:  Exactly!  No, totally!  Yeah, so her work is cool.  And then she’s translated several other press releases since then.  And like I said, I didn’t think of it at the time, but just have the opportunity to work with your mother was something . . . somebody mentioned that to me and I was like, “Oh wow, that is kind of a cool thing.”  And last June, me and my mom actually presented at an indigenous language conference, so it was kind of cool to get to give a talk with my mom.  She was definitely a star of the show. 

 

Regina Barber DeGraaff:  I mean, that’s really heart-warming that you got to work with your mom and you got to spread your culture and like actually have it acknowledged by LIGO, like you just said, that they were all for it.  Along those same lines, I think what you’re trying to do with your mom is kind of show that science isn’t just for one group of people. 

 

In your experience, I mean, you were talking about MacGyver.  Is there any other people or ways in which science is represented in popular culture that you like or that you don’t like that has been happening lately, maybe related to black holes or gravitational waves or anything? 

 

Corey Gray:  I have so many heros that are just coming out.  I mean, there are a lot of other physicists that I think are just doing amazing things.  And it’s not just the work they are doing, but just for them being out there and doing the work that they’re doing.  There are other native physicist.  LIGO has about 1,200 members and for most of the 17 years that I’ve been here, I was the only native.  There’s a grad student at Cal Tech who’s Navajo, so now I have another native person who is a member of the project. 

 

There’s just heros like that, just being as a youth see people who are like you is such an important thing.  And I can name off all of my other heros, but that’s one thing.  So just seeing representation improving is a huge thing. 

 

I like movies.  I like just seeing things in movies that maybe inspire me.  I’m sure they inspire others, but the movie Contact is one that a favorite of mine.  And just to have a main protagonist be a female and be just so inspiring and smart and a total hero and runs that whole story, I think is also an important thing as well.  So I think popular culture and then in science to be able to have that representation improving and seeing more diversity in roles, in both of those areas, is a huge thing. 

 

Regina Barber DeGraaff:  Well, and I think your mom translating these press releases and LIGO being open to translating it to as many languages as they possibly can, is, I think in my personal opinion, it shows our scientific culture being more open at least to have these conversations. 

 

Thank you so much for talking to us and calling in.  Good luck with all the data coming in.  It’s going to be a flood! 

 

Corey Gray:  Yes!  That’s the hope. 

 

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Regina Barber DeGraaff:  We want to thank Corey Gray for sharing his time and helping us learn about gravitational waves and we hope to speak to him again soon. 

 

Spark Science is sponsored by WWU and created in partnership with KMRE.  Spark Science is recorded on location and in Bellingham, Washington, at Western Washington University.  The producers are Suzanne Blaze, Regina Barber DeGraaff, and Robert Clark.  Student editors are Julia Thorpe, Andra Norton, and Sarah Cokeley. 

 

Additional editing is done by WWU video services.  If there’s a science idea you’re curious about, post a message on our Facebook page, or Tweet us at Spark Science Now.  Thanks for joining us.  And if you want to listen to past episodes, visit sparksciencenow.com. 

 

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