Thursday, January 26, 2012

Q: How can gravitational waves help mankind?

UPDATE:  [11 Feb. 2015] Gravitational waves have been detected!  Read more about it here.

@HughScot asked:
What do you hope to discover about gravitational waves that will help mankind in the future?
There are many things that we hope to observe through gravitational waves especially since they have the advantage of being able to travel through matter and come out the other side unchanged, unlike the different forms of light used in traditional astronomy.  This gives us the opportunity to observe things that do not emit light, like black holes or to observe systems that would otherwise be obscured by intervening material.

But this question asks how gravitational waves will improve mankind in the future - as in what are the applications of gravitational waves.  I get this question often when I am giving tours of the facility.  Well, the primary use of gravitational wave observations will be to understand our Universe better.  Most people's reactions to this are that our efforts can better used for other endeavors.  But this view is a little short sighted.  One of the things we forget is that when we understand more about the Universe in general, we know more about the world around us.  We are a very small part of the Universe, but we are a part of it nonetheless.

One of the direct uses for gravitational waves will be to use them to turn the Universe into our own laboratory.  There are many things that we cannot replicate on Earth, like the dense cores of neutron stars.  Under extreme conditions like this, nuclear physics and thermodynamics can theoretically do some interesting things.  However, we can't investigate those directly because we cannot create these environments ourselves.  That's when we turn to the Universe for our laboratory!  Prime candidates that will allow us to use gravitational waves to investigate this include pairs of neutron stars merging into one star, starquakes on these stars, or even rapidly rotating neutron stars with "mountains" on them (and I put mountains in quotation marks because neutron starts are believed to be so perfectly spherical that a deformation a few millimeters [a quarter of an inch or so] is 'huge').  Knowing the details of how nuclear physics and thermodynamics changes in these environments can have applications on Earth, although I can't tell you what they are yet.

Another application of gravitational wave observations will be testing Einstein's general relativity.  Even though gravity is the force that holds the Universe together, we have a very difficult time testing it since it since it is also the weakest force in the Universe (there is no negative mass to cancel the effects of positive mass like happens between positive and negative charge).  Since the mass needed to conduct experiments to test general relativity is so great, lab experiments are very few.  Again, we must turn to the Universe to be our lab.  Directly observing gravitational waves with LIGO and detectors like it will allow us to perform tests on general relativity that we have never been able to before.  For example, it is expected that gravitational waves travel at the speed of light but there really isn't anything in the theory that constrains them to that speed (they could travel slower).  Detecting gravitational waves with multiple detectors across the planet and observing light from the same source in the sky would allow us to test this.  (By the way, even though general relativity is difficult to test, every time it has been tested it has proven to be right!)

We already use an application of general relativity in our everyday lives: a consequence of special and general relativity is that time passes a different rates based on the speed of an observer or the strength of the gravitational field that the observer is in.  No matter what, your time will always be the same, but you may observe the clocks of others who are at rest or traveling slower than you ticking slower than yours (this tutorial does an excellent job of explaining how this time dilation works).  If corrections for this effect are not taken into account, the clocks on GPS satellites would quickly become out of sync and the GPS in you car, etc. would not be able to accurately locate you!

Besides the benefit to mankind due to the information the gravitational waves themselves will bring us, we have also developed a significant amount of new technology to make LIGO work.  We have developed new seismic isolation techniques that allow less than 1 billionth the energy of normal ground vibration into our instruments, we have required and received the most precisely polished mirrors, and we have developed new suspension and control systems to stabilize our optics.  These are just a few of the advancements the search for gravitational waves have made.  I am sure that there are many other applications for these new developments (although I haven't explored them myself).  Using technology developed for other purposes is a well known phenomenon in science and technology call spin-off technology.

In conclusion, we will never be able to commercialize or weaponize gravitational waves themselves.  However, they will carry information to us about some of the most extreme environments in the Universe which we can use as a laboratory for environments we cannot create here on Earth.  This information can tell us more about how the physics around us works in subtle ways that can have profound implications.  What those are are yet to be seen.  That's the exciting thing about science - you never really know the full potential of new discoveries until after the fact.

Today's picture is of an engineer (my husband Derek Bridges) dressed in clean room garb (so as not to contaminate the equipment that will be placed into LIGO's interior vacuum).  The blue stands he is leaning on are part of the seismic isolation system mentioned in the text above and the big steel chamber behind him is one of the many used to contain LIGO instrumentation in its vacuum.  This picture was taken at the Advanced LIGO testing lab at MIT.

I hope this answered your question!  If not, please feel free to ask me more about this or anything else!

Thursday, January 19, 2012

First Software Engineering Run for Advanced LIGO

Most of the visible work on Advanced LIGO has been revolving around the installation of new instruments that are needed to increase the sensitivity of LIGO about 10 fold.  While this is exciting, it can feel a little like being on the outside looking in for data analysts like myself.  But there is still much to prepare for!

The first step in that preparation starts in a few days with the first Software Engineering Run (which we abbreviate ER1 - there's longish, boring story on why it isn't being called SE1).  The goal of this is to start testing our computing infrastructure and data analysis methods with simulated data (remember, Advanced LIGO is still not complete).  For this first run, we will be simulating the channels of data that would contain information about a gravitational wave.

But what is a channel?  Just like channels on a TV, LIGO has many different data streams called channels that report on basically everything involving the instrument.  Besides the channel that will carry information about gravitational waves, we also have channels of data from seismometers that tell us how the ground is moving beneath us, channels from microphones placed around the detector that tell us about loud noises like thunder that can cause vibrations in the detector, and channels that tell us how different places on a mirror inside of LIGO is moving (and we can combine channels like this to tell if the mirror is moving up, down, sideways, front to back, rolling, etc.).  This is just the beginning of the channels we record at LIGO (there are hundreds per detector)!  We use these to cancel out unwanted movement and to double check if a potential gravitation wave is real or caused by vibrations in our environment (we would be less likely to claim a detection around the time that our seismometers indicate a train moving on the tracks a few miles away from the detector here in Louisiana).

So, we are starting out small with ER1 and focusing on just the gravitational wave channels (with simulated gravitational waves included to give the detection software a workout).  In the future, more of the Advanced LIGO channels will be simulated and included in the run.  We plan on having about 5 or 6 of these runs until Advanced LIGO is ready to give us all of the channels for real.  But, the transition from Software Engineering Run to Engineering Run should be seamless.  Engineering Runs precede Science Runs to allow us to work out any bugs in the real detector before we start using the data for science purposes - but data from engineering runs is handled like it would be if it were science data.  As more subsystems in LIGO are installed and producing data, the simulated data for those channels will be replaced with real data.  The only difference between the last Software Engineering Run and an Engineering Run will be that none of the data is simulated anymore.

It is anticipated that, by having these ER runs, that the computational infrastructure for Advanced LIGO will be ready to handle the new demands of the more sensitive detector.  We are entering a new era in LIGO where detections will be expected on a fairly regular basis (once the detector has been tuned into its design sensitivity).  We need to be able to respond quickly to potential detections to alert others in the astronomical community and for us to vet the detection in a time efficient way.  We want to be able to clear detections off of the table, so to speak, before others become backlogged.  Honestly, I am excited at the prospect of this since I have worked with LIGO since it took its first science data and I remember collaboration meetings being focused on how to make the data clean enough that we could see more than just instrumental artifacts or environmental contaminants.  Now I'm thinking about backlogged detections!

LIGO has several supercomputer clusters and one of them is located right here at the LIGO Livingston Observatory.  So, I went downstairs (from my office) and took a few pictures of our cluster today:

Above is a picture of the computers facing the front of the room.  Since these computers produce a large amount of heat and noise, they are isolated in their own room which also allows for the efficient use of extra air conditioning (and noise containment).  This is an odd room to be in because of the noise but also because of strong air currents moving the heat around.  The wind is noticeable and it can change quickly between a warm breeze to a cold one as you walk.

This is a close look at the computers in the racks (as we call the large rectangular container).  Each one of the horizontal shelves is a computer.  Many computers are used simultaneously to search LIGO data for gravitational waves.

This is the back of the rack shown in the previous picture.  If you are ever chilly, this is the place to stand since the heat pushed through the fans from the computers is dumped here.

Thursday, January 12, 2012

Broken New Year's Resolution and Priorities for 2012

I really do know better than to make New Year's resolutions.  Truly.  But there is one thing that I want to do more of and that is to make more blog posts.  I've noticed that it is easiest for me to make posts on Thursdays so I resolved to post weekly on Thursday.

Then last Thursday happened...

I woke up with the most painful migraine I've had (at least in recent memory).  I felt like my head was going to explode all morning and early afternoon and when I finally took the correct meds (when you are alone and trying to keep your brains in your skull, you tend to lose a lot of common sense) and felt better, but not well, I was thoroughly exhausted.  I think I was asleep more hours than I was awake that day.  Between that and the fact that I had to write a last-minute abstract to present some new LIGO results at the upcoming APS April Meeting, my blog post never happened.

But, today is a new Thursday and the first new blog post of the year!

I hope everyone had a pleasant holiday season.  I didn't murder any family members so I'm counting mine in the win column (I'm kidding - I would never harm my family!).

So, what have I been doing as a LIGO scientist this year?

  1. I've had a few projects in the works that I am trying to wrap up and complete (I love starting new and exciting projects and documenting completed computer programs is not exciting to me).  One of the things that has been simmering for a long while now is a survey of the LIGO Scientific Collaboration to assess the members' feelings on its diversity and climate (working environment).  I created and administered a similar survey just for us who work at the LIGO Lab (I am on the LIGO Lab Diversity Committee).  The point of surveys like these are to identify areas that can be improved to make everyone's working experience better and to find out what we are going right.  This survey is in a fairly-mature format and should be ready to release in the coming weeks.
  2. There is a paper I have half written on multi-messenger astronomy and LIGO that I am targeting to  publish in The Physics Teacher.  This has been half done for a while now because other life issues have gotten in the way.  Notably, work and making an application to move up the career ladder and secure myself something more permanent (all postdoctoral positions are temporary like medical residencies - I talk about this a little in my post about "Becoming a Physicist").  This is high on my list of priorities for the near future. 
  3. There is a new initiative in LIGO to write outreach abstracts (summaries) of the scientific papers we publish (like this one).  The papers themselves are almost always on the arXiv server (I can think of only 1 exception) and anyone can read these for free.  That is all well and good, but these papers are meant to be read by other experts and are horrible to wade through for someone who doesn't do that sort of thing for a living.  We are trying to make our results more accessible to everyone and these abstracts are written so that everyone can know what science we are doing.  I've been working on the outreach abstract for the paper discussing the methods employed to rapidly alert telescopes to search for possible optical counterparts to gravitational wave detections (this is the link to the scientific paper).  I've talked about working on this project before here.  When this abstract goes live, I will write more about it and discuss the other abstracts that have been written.
  4. There are also numerable data analysis and software simulation projects that need to be further developed, but I won't go into those here (if you really want me to, let me know in the comments - I may tell you about it later anyway even if you don't).
  5. I also still work extensively with the Science Education Center here at Livingston.  Yesterday, I traveled to a elementary school in Amite, LA to talk to about 120 kindergarteners over the course of the day.  Besides the fact that they were adorable and very interested, I had the cutest ambush of my life - a 20 little kid group hug! :)  And only a few of them where taller than my hips.  Little things like this (besides getting to discover new things about the Universe) is what truly makes my job amazing!
  6. Finally, I have only a few questions left to answer from my previous call for questions!  These will be answered in the coming weeks.  If you have anything you would like to know about, let me know.  Also, I was thinking about having guest blogs from other LIGO scientists, engineers, etc.  Is that something you would be interested in?  (My husband is an engineer at LIGO Livingston with me, so I have one person that I can probably bribe into doing this.)  There are many different specialties here so this may be interesting.  Let me know!

Hope to hear from you soon!


Today's picture comes from my office and its new vampy inhabitants:

From left to right: Vampire Julius from Paul Frank, Count Chocula from the cereal of the same name, and The Count from Sesame Street
You may remember from previous posts that not only do I have a nearly unhealthy love for vampire books, but I also have a collection of stuffed undead (do NOT call them dolls).  Here is a previously posted picture of my office with a few of the figures in the background:

And another of my name tag covered light (which really doesn't function so well as a light since I've added even more tags) with a few other figures: