On Outreach...

In my last post, I mentioned that I recently visited Ole Miss to give a colloquium on outreach for their physics department.  Later that night, I also gave a talk at a local bakery on multi-messenger astronomy (public events like this are called "Science Cafes").  The colloquium on outreach was interesting to do since it made me organize my thoughts from my experiences here at LIGO (and this blog was featured) and I wanted to share my thoughts on engaging students and discussing religious issues in general.

The beginning of my colloquium at Ole Miss.

ENGAGING STUDENTS

I specialize in being the scientist that people talk to when they visit LIGO.  That includes taking visitors on a tour of the control room (where all the science happens).  I think everything I talk about is immensely interesting, but some of my visitors (especially the younger ones) will disagree.  So, how can I make this interesting for them?  Usually, anything that is gross (yet age appropriate) will get their attention.

One of the features of LIGO I like to point out is our outstanding vacuum system.  LIGO has 300,000 cubic feet of volume in a vacuum that is 8x better than the vacuum of space the space station is currently orbiting in (that is a trillionth of the atmospheric pressure you are sitting in now).  For some visitors, this is impressive; for others, not so much.  Then I talk about how your blood would boil if you went into our vacuum without a spacesuit.  And I put a little dramatic emphasis on the "boil" part.  Now I've got their attention!

Why would our blood boil if we were inside LIGO's vacuum?

The reason that blood would boil in our vacuum isn't because of temperature.  Rather, it is because our blood stores oxygen and carbon dioxide in solution.  How much it can store is dependent on the pressure that surrounds our body.  Going from atmospheric pressure to 1/1,000,000,000,000^th that pressure would allow the oxygen and carbon dioxide to be released from solution in the form of bubble.  Hence, it "boils".  To give an example that most of us encounter in our daily lives, this "boiling" is similar to what happens when you open a 2 liter bottle of soda (or pop, or Coke depending on where you live) - you release the pressure in the bottle and the bubbles come out of the drink.  Another example that many people have heard of is deep sea divers suffering from the bends when they surface too quickly.

RELIGIOUS ISSUES

In one of my first blog posts, I stated that I don't want to argue religious issues here.  I want to make clear that I am not making any statements for or against a view, I simply want to talk about DISCUSSING religious issues when the come up.

Many people who visit LIGO have strongly held religious convictions.  Fortunately, there is very little controversy over LIGO science and religion.  The one concept that can have religious implications if the Big Bang.  This theory (and I mean a scientific theory that is supported by evidence, not a hunch) states that the Universe was once contained in a very dense, very small ball and time effectively started in a large explosion.  This is at odds with many types of creationism.  While this can yield lively debate, that is not something I am interested in doing with visitors; my goal is to talk about science and what LIGO can reveal about our Universe.

My goal when faced with situations like this is to treat everyone with respect no matter what their beliefs are.  Just like it is unlikely for them to convert me to their worldview (assuming it is different from mine), I know it is unlikely for me to change theirs.  So I define what kinds of questions science can and cannot answer: science only ever asks "How?" not "Why?".  For the "Why?" you need to turn to philosophy and religion.  With respect to the Big Bang and creationism, I point out that evidence exists to support the Big Bang in the Cosmic Microwave Background.  But, even if this is not the relic light from the Big Bang, something created it and whatever it was may have also created gravitational waves.  So, while one of our documentaries claims that we are seeking the gravitational waves from the Big Bang (and many other sources), we are really seeking the gravitational waves from whatever created the Cosmic Microwave Background.

Some have accused me of skirting the subject in the way I handle religious issues and they are mostly right.  I try to respect everyone and re-frame the contentious issue in a way that doesn't conflict with religious beliefs and is still true to the science.  But I think it is also important to make the distinction in what science can and cannot do.  Some people believe that science tries to disprove God but the truth is it can't.  Science also can never prove God.

The Likely End to a Space-Based GW Detector

LISA...

(The video below is large [~44 MB] and dated, but gives good background on the motivation and specifics of a space-based gravitational-wave detector:)

About this time last year, I wrote a blog post about the NASA withdrawal from being a full partner in the LISA (Laser Interferometer Space Antenna) with the ESA (European Space Agency).  At that time, it meant that US scientists would still be able to receive funding to develop research programs and contribute to the LISA effort but the ESA would be responsible for the bulk of the work.  This withdrawal by NASA was caused by the poor state of the agency's funding and the cost of the James Webb Space Telescope.  For all of us in doing research in gravitational waves, it was a horrible setback; LISA was once a flagship mission of NASA's Physics of the Cosmos program and the best hope we had of detecting low frequency gravitational waves (< 10 Hz). 

This then led the ESA to redevelop their plans for a new version of LISA (that is referred to as eLISA but is officially known as NGO [New Gravitational-wave Observatory]) in order to lower the cost of the mission by at least 20% and preserve as much of the science as possible.  This new design was published in their "Yellow Book" at the beginning of the year which included, among other things, only 2 arms in a triangular formation (previously there were 3 arms and each corner pair of arms could function as an independent detector), reduced distance between satellites (1 million kilometers instead of 5 million), and a new orbit which is similar to the LISA orbit (in orbit around the Sun about 20^o behind Earth in its orbit) but will allow the detector to drift away into the solar system over time.  Below is a short movie illustrating a few orbits - the "drift away" is not noticeable:

The newly designed eLISA/NGO received the highest science ratings of the projects up for funding at the ESA.  However, the ESA Science Programme Committee has concerns about the technological readiness of eLISA/NGO to fly in the 2020 time frame and has passed it over to recommend the JUICE (JUpiter ICy moons Explorer).  This is likely the last nail in the coffin for a space-based gravitational-wave detector in the foreseeable future.  (Note:  NGO can be considered for future launch opportunities but that is way down the road.)  There is a slight chance that the recommendation could be rejected in favor of gravitational waves when the 19 member states of the ESA make the final decision on May 2.  However, I heard the news of this recommendation from a friend who specializes in LISA science and he didn't seem hopeful for the 11th hour pardon.

I wonder what will happen to the LISA Symposium that is supposed to take place in Paris at the end of May...  Or for that matter, the LISA Pathfinder mission (which will demonstrate the basic abilities that LISA would have needed to have) which is scheduled to launch on June 30.

UPDATE:  I've heard from a LISA colleague that LISA Pathfinder is still a go!  Thanks!

***

On a more uplifting front, I had the wonderful opportunity to speak at Ole Miss (this link will take you to their gravity research group - they do great work!) about the importance of outreach, useful skills for it, and different ways to do outreach (and this blog was featured!).  That night, I also got to demonstrate my points by giving one of their monthly public science cafes.  This experience gave me the chance to really consider what it is that I have been doing professionally for the last 5 years...  What have I learned?  What mistakes did I make?  What surprised me?  What ideas can I pass along on how to do outreach to those who are expected to do it but aren't afforded the extra time like I am?  I'm thinking about posting a summary of my thoughts and speaking points in next week's post (unless something else newsworthy happens in the mean time)!

Q: How do we know gravitational waves really exist if we've never directly detected one?

Today's question is one that has been asked of me repeatedly while giving tours of LIGO and talks on the science we do:

How do we know gravitational waves really exist if we've never directly detected one?

One question I often get while discussing LIGO science with others is, "How many gravitational waves has LIGO detected?"  Well, the answer to that is none - yet.  But, we also didn't expect to detect any yet.  During our last science run, we were able to detect gravitational waves that change the length of LIGO's arms about 10,000x smaller than the diameter of a proton.  Even though this is almost an unthinkably small distance, this is considered a big gravitational wave at Earth (where these gravitational waves are produced in the depths of the Universe, they are incredibly strong - strong enough to rip you apart) and therefore a rare one - so rare that we statistically didn't expect to see one in the amount of data we collected.  (Of course, the Advanced LIGO upgrade will change that!)

So, if we have yet to make a direct (meaning measured with our own instruments) detection of gravitational waves, how do we know that they really exist?  After all, this is a lot of effort and resources going into the search!  Well, we have seen the effects of gravitational waves on astrophysical systems in the Universe.

In the early 1970's, a pulsar (a very dense star that has beams of radio waves coming out of the magnetic poles) was discovered in the constellation Aquila at the Arecibo radio telescope in Puerto Rico.  The beam of radio waves passed over the Earth 17 times every second.  After observing this star for a while, it was discovered that some of the radio pulses came a little late and others a little early.  The periodicity of these arrival times indicated that the pulsar had a companion star and they orbited around each other (together, this system is known as PSR B1913+16 [referring to its sky coordinates]).  After further observation, it was found that the orbit of these stars around each other was gaining speed indicating that the stars are getting closer together (this is just like how a figure skater starts spinning with their arms extended at their sides and then, as they pull their arms to their body, they spin faster).  This can only happen if energy is being carried away from this system of stars.

The only energy loss that matched what the researchers, Taylor and Hulse, observed was the energy carried away by gravitational waves.  After about 20 years of making observations on this system, their measurements consistently matched the energy loss caused by gravitational waves.

This plot shows the change in the periodic time of closest approach (periastron) of this pulsar system compared to when the first observations were made in the early 1970's.  The red dots are observational measurements and the blue curve is the prediction from general relativity given the emission of gravitational waves.

This provided evidence of the existence of gravitational waves and won them both the 1993 Nobel Prize in physics.  Unfortunately, LIGO will not be sensitive to this particular pulsar system for about 300 million years even with upgrades to the detector.

Now that we know that gravitational waves really are out there, we want to detect them affecting our own instruments so that we can learn more about the sources that made them (after all, we know exactly what is going on for the source above).  Gravitational waves have encoded in them information about what made them very much like how radio waves can have music encoded on them.  Just like without a radio you can't hear the music, without detectors like LIGO, we can't learn more about what made these sources.  Gravitational waves can be emitted by things that don't produce light, like black holes, so we will be able to see them in ways traditional astronomy (astronomy using light) never can.  On top of all that, gravitational waves can travel through matter and emerge unchanged - basically, there is no such thing as a gravitational wave shadow!  So we will be able to observe things in the Universe that will forever be obscured to traditional astronomy.

***

Note that I have added 2 new pages (listed just below the blog banner): "Ask a Question!" and "Contact".  If you have a question you would like to ask, please fill out the form in "Ask a Question!".  If you would like to contact me, please fill out the "Contact" form.  Of course, you are more than welcome to leave comments to any blog post and start conversations with other readers!

No "Faster Than Light" Neutrinos

SCIENCE AS A PROCESS

Most people see science as purporting itself to be infallible and they can twist this perception for many reasons (e.g. "See, they didn't see what they thought they saw so science cannot be trusted.").  The truth is that science is a process.  It must be reproducible by others.  Sometimes, an experiment comes around that seems to defy the current understanding of science and people are quick to jump and accuse science of being unreliable.  Really, when results like this come to light, it is the duty of other scientists to scrutinize the results: to try to reproduce them and, if they cannot, try to find where the errors in the original experiment occurred.  Most of the time, radical findings are disproved.  When they are not, this is an exciting time for science to learn more about the world around us!  We scientists often spend as much time trying to disprove things as we spend trying to prove them.  Truly revolutionary results often exploit a subtlety in a theory (which in science means a highly tested and verified description of how something works and NOT a hypothesis or guess as it is sometimes used in everyday language) or law that opens the way to a deeper understanding.  Science is not created or invented by scientists - the Universe has its properties and we simply pursue the discovery of them so we can understand better how it works.

THE "FASTER THAN LIGHT" NEUTRINOS

While at the APS April Meeting this past week, there was a lot of excitement (see the talk abstracts in this session) about the "faster than the speed of light" neutrinos that the OPERA collaboration claimed to have observed.  There was extra excitement since there was a final resolution at the beginning of the meeting along with a little drama.  There were even talks on how to use this new coverage as a great outreach opportunity to illustrate science as a process (don't think of the scientific method that you were taught in school - science almost never follows that prescription but it is a good starting point).  I've had many people bring this up to me when I talk about how gravitational waves are expected to travel at the speed of light but could travel slower - never faster.  Then there is usually someone who asks about the new neutrino results and this is when I get to talk about how science is a process.  So, I've decided that I would dedicate today's blog post to the subject matter.  Spoiler alert: there are NO "faster than light" neutrinos!  If you are interested in a very good discussion of these results, disproof, and aftermath, read more about it here.

***  What is a neutrino?  ***

A neutrino is a virtually massless particle that interacts so weakly with matter that it can travel right through any matter with only a few (of billions and billions) interacting with matter.  The neutrino has never been directly detected but we know when one interacts with matter because it produces other subatomic particles or radiation.  Every second, about 10,000,000,000,000 (that's 10 trillion) neutrinos from our Sun pass through every square foot when the Sun is directly overhead.  Those neutrinos pass right through you and, since they so rarely interact with anything, you don't notice a thing. 

Because neutrinos are virtually massless (I say virtually because there is evidence they they do indeed have mass, but it is so small that it hasn't been accurately measured) they can travel at or so near the speed of light that we haven't measured evidence of them traveling slower.  This agrees with special relativity: only massless particles can travel the speed of light and massive particles can only travel slower (there are theoretical particles called tachyons that can only travel as slow as the speed of light and travel faster otherwise - these have never been observed).

***  What is the OPERA experiment?  ***

The OPERA experiment used a beam of neutrinos created at CERN on the Franco-Swiss border to send to the OPERA detector in Gran Sasso, Italy.  That's right, the beam of neutrinos was shot right through the intervening earth between these 2 sites.  Since the distance is known to high precision, the time it takes the neutrinos to arrive at OPERA is directly related to their speed.  It appeared that they were measuring their arrival about 60 nanoseconds (0.00000006 seconds) before they should have if they traveled at the speed of light. 

***  What did we know about the speed of neutrinos before OPERA?  ***

There have been many experiments that have observed neutrinos traveling at the speed of light.  These experiments have been both Earth-sourced (where we create and then detect the resulting neutrinos) and Universe-sourced.  A spectacular example of using neutrinos from space was the detection of neutrinos that preceded the supernova 1987a.  They arrived 3 hours before the light from the stellar explosion did.  This is what is expected because neutrinos are created when the matter in the star collapses before the supernova explosion.  If neutrinos traveled as fast as the OPERA collaboration claimed to have observed them traveling, then after traveling the more than 160,000 light years to Earth they would have arrived 4 years before the accompanying light we observed.

***  Should OPERA have published their result?  ***

So, was the OPERA collaboration wrong to publish their observations?  Absolutely not (in my opinion at least)!  Nowhere in their paper did they claim that they have found a fault with the current understanding of the physics - they simply couldn't disprove their own observations so they opened their experiment up to the scrutiny of the scientific community.  They even recognize the controversial results and their desire for scrutiny of their experiment in their paper (which can be read in full here):

"Despite the large significance of the measurement reported here and the stability of the analysis, the potentially great impact of the result motivates the continuation of our studies in order to investigate possible still unknown systematic effects that could explain the observed anomaly. We deliberately do not attempt any theoretical or phenomenological interpretation of the results. "

THE RESOLUTION TO THE CONTROVERSY AND THE FALLOUT

In the end, it was found that a loose fiber optic cable and an error in their timing produced the superluminal (fancy way of saying 'faster than the speed of light') observations.  THERE IS NO EVIDENCE TO SUPPORT THAT NEUTRINOS CAN TRAVEL FASTER THAN THE SPEED OF LIGHT.  Also, the ICARUS experiment (located in Gran Sasso with OPERA) independently reproduced the experiment and found no faster than light neutrinos.

The heads of the collaboration resigned their post on March 30 (just a few days ago) after a vote of no confidence.  There were scientists in the collaboration who felt the publication of the results was premature, and that not everything that was done was good experimental procedure.  It seems that the resignations were the result of their rush to publish the paper, more than what they published.

Crawfish Boils and On the Road Again...

Last week's post came to you from the LIGO-Virgo Meeting in Boston, MA.  This week, it is coming to you from Atlanta, GA.  I just arrived here for the APS April Meeting.  My room is a beautiful corner room with two great views!  So I've chosen the better view from one of my windows:

Actually, I am here a day early so that I can attend the Professional Skills Development Workshop which is designed to improve the communication and negotiation skills of women physicists.  I'm looking forward to this as, while I would love to improve my communication skills, I really feel that I need to develop negotiation skills.  I am currently working to transition my current postdoc position (which is temporary by definition) into a more permanent position, not only because I love my work and the opportunities I have here, but my husband also works at the LIGO Livingston Observatory as an engineer.  The fact that I am this early in my career and living under the same roof with my husband, who is also happily employed in his field, is almost unheard of.  This is known as the two-body problem - when two academic professionals are challenged to find a way to find jobs together; I plan to write a blog post on this later.  That being said, I almost want to jump and any offer that can be scrapped together for me - the last thing I want to do is ruin the good thing I have going.  This is exactly one of the reasons that women tend to make less than men, even in physics - we undersell ourselves.  While I have no intention of trying to wring every penny I can out of a new position, I want to make sure that I am at least being compensated properly for my work.

As for the APS April Meeting, I will be giving a talk on the latest burst gravitational wave all-sky search results.  The information for my talk is here and the "plain English" science summary of the paper is here.  Once I give my talk, the presentation will be publicly available on the LIGO Document Control Center (DCC).  I will also be attending the APS Forum on Education Executive Committee Meeting and this will be the last of my term.  I have more than enjoyed the others I was privileged to serve with and it has been wonderful to get a chance to spread my wings a little more in physics education.  Of course, I have days and days of interesting talks and other activities to look forward to.  I will make sure to Tweet points of interest so make sure to follow me @livingligo.  You can also follow others' Tweets from the meeting using the hashtag #APSapril.

Between my trips to Boston last week and this one to Atlanta, I did get to be home in Baton Rouge for a few days.  Yesterday, the observatory staff was updated on the large scale status of the Advanced LIGO upgrade by the program leader, David Shoemaker.  While that was very informative (all is going well), the best part of the day of the crawfish boil we had outside afterwards.  For those of you who don't live in the American South (specifically the deep south), crawfish/crawdads/mudbugs/crayfish (but don't call them the latter around the natives lest you truly out yourself as not one of them) are essentially small freshwater lobsters that yield about the same amount of meat in their tail as a shrimp.  The meal takes "family style" to a new level: everything is served in heaps and you get a tray instead of a plate and it is heaped with the crawfish, sausage, corn-on-the-cob, and potatoes.  Oh yeah, and you don't get utensils.  This is a get-your-hands-dirty kind of meal.  Here is what my lunch looked like (before I started tearing the little critters apart - the communal aftermath from everyone at the table wasn't nearly as pretty):

This is considered a "dainty" portion.  A few other tips on how to fit in as a local:

• Don't sit while you eat crawfish - you stand so that the juice that can sometimes explode out of the body when you separate the tail from the head doesn't get all over you.
• Suck the heads!  Once your remove the tail, don't through away the top part of the body - that's where all the best flavor is.  As I have never done this myself, I am not sure if they are referring to the seasoned boil that remains inside or if they actually suck the "stuff" out.  To me, it just looks like the poor thing is trying to escape!
• Again, don't call them crayfish.

And a point of common sense - take your watch off!  Mine still smells like crawfish!

March LIGO-Virgo Meeting in Boston

So, I am at the LIGO-Virgo Meeting in Boston right now.  As you may (or may not) know, our two collaborations are very close knit.  We schedule our upgrades to be around the same time, we always share our data, and we collaborate on our science to get the most from our work.  Being a part of a big international collaboration is exciting and gives you a new perspective on international politics - in science they exist, but are much easier to deal with since we are all working for the same goal.

Here is the gorgeous view from my hotel window:

Personal Complexes:

Another thing about being one of over 800 scientists and engineers working on a project is that you can feel small.  I've written before about the Impostor Syndrome - when people who are fully qualified and competent feel inadequate.  Sometimes, these meetings bring those feelings back to me.  Every time someone comes to me and asks me what I do, I feel like my worth is being weighed.  But it absolutely isn't!  After all, I do the same thing to new colleagues that I meet and I am only interested in learning more about them and maybe working with them in the future.

I was starting to feel inferior while I was traveling here...  I was sitting at my gate during a layover and a colleague I consider a friend was sitting in his seat diligently working on his computer.  What was I doing?  Reading a vampire book.  The self-loathing voice in my head immediately chimed in with, "See, there is someone who is deserves the esteem of the collaboration.  He works hard and makes the most of his time.  What are you doing?  Reading a book about things that don't even exist!"  As I was resigning myself to mediocrity, he put his computer aside and started talking with me.  During our short conversation, he paid me the most unexpected complement.  I'm not going to repeat it here, but I was speechless and ecstatic at the same time and tried not to tear up.  I smiled and thanked him because his words forced me to think well of myself (not that I told him that).  If he is reading this, you know who you are and what you said even though you don't know how much it mattered to me - THANK YOU!

I've been trying to work more on these issues but I don't ever expect to completely get over feeling inferior to my peers.  Not that I really want to - I've met many scientists who thought they were a divine gift to science and I can't stand them (even if they are right)!

The Science:

The final data analysis from our last data run is finishing up and we've been talking about these results and preparing for the demands the MUCH more sensitive Advanced LIGO and Advanced Virgo detectors will place on our analysis infrastructure.  This has been a time of reorganization.  I gave a short talk about the functionality of the gravitational wave simulation software (called GravEn) I wrote while I was a graduate student.  This has been the standard software we've used to measure the sensitivity of of our burst data analysis methods.  We are also taking time to consider if there is a better way of doing it.  So far, it seems like GravEn is still the bee's knees and that makes me very happy!  (The science summary of the last burst data analysis paper is here.  The plots that show the sensitivity of our methods to different kinds of signals [the second and the third] were made using the simulations I produced.)

There have also been talks on the status of LIGO, Virgo, GEO, the Japanese KAGRA detector, and the status of what used to be the LISA space-based detector (this was a partnership between the ESA and NASA until budget issues forced NASA to cancel being a full partner).  There is progress being made on all of these fronts - even LISA (which is now led by the ESA and known as NGO for the New Gravitational-wave Observatory).  Every where you walk around the conference hotel, you see small groups working together on a project and a few very tall people in red uniforms (the Wisconsin Badgers are staying in our hotel for their NCAA Sweet 16 game tonight against Syracuse).

What Would YOU Like to Ask a LIGO Scientist/Engineer?

As part of a talk on the collaboration's outreach activities, this blog was featured!  (Those who don't know my science work will often still know me as the "Living LIGO Lady".)  It was also announced that I would like to feature interviews of gravitational wave people (scientists, engineers, etc.) on this blog.  When I originally started writing this, I wanted to make science human and accessible.  I feel like I am running out of human things about me to talk about (I'm not all that interesting).  But there are so many others with different backgrounds and stories that I would like to share with you.  I already have a list of questions I am thinking about asking (not all of them will be mandatory, of course) but I want to invite you to tell me what questions you would like to as a LIGO person?  Tweet them to me @livingligo or leave a comment here (below).  You can also email me at amber@livingligo.org.  I'm thinking of using my husband, a mechanical engineer for LIGO, as a Guinea pig (he can't cook and likes to eat, so I think I can convince him :P ).

Until next week!

Q: What does LIGO look like?

Today's question comes to you from the site statistics search terms used to find this blog:

What does LIGO look like?

FROM THE OUTSIDE:

LIGO is BIG!  Instead of being looking like a traditional observatory with a dome and telescope, LIGO looks for gravitational waves (small changes in the gravity of the Universe as they pass by Earth like a ripple on a pond) by comparing the lengths of two arms, each 4 km (or almost 2.5 miles) long.  A gravitational wave will compress space in one direction (say, East-West), expand space in the other (North-South), and alternate back and forth between compression and expansion in these directions.  Below is an animation (from Wikipedia) on how a ring of matter can be compressed and expanded in orthogonal (at 90^o) directions:

To best observe this stretching, LIGO is an "L" shaped detector (although many of the students that visit tell me it is shaped more like a "corner" since each side is the same length).  Because the facility is so large, it is hard to get it all in a single image.  Below is an aerial image of the LIGO Hanford Observatory in Washington state (which is in the eastern desert part of the state):

... and the aerial view of the LIGO Livingston Observatory in Louisiana (where I work):

Google has wonderful satellite images of the sites (click here to view the Livingston site).  A noticeable feature of the Livingston site is that there are large rectangular bodies of water along the arms:

During construction, the arms needed to have an elevation above the 500 year flood line (meaning that the probability of there being a flood reaching that elevation is once every 500 years).  To do that, soil needed to be excavated from the sides to build up where the arms would be built.  In Louisiana, the water table is so near the surface that whenever you dig a hole, even a shallow one, it will most likely fill up with water.  (The locals here aren't impressed about that, but being a Northerner who loved to yell down her family's water well as a child to hear my echo, the thought of gardening and hitting water is unique!)  Another reason that the arms needed to be built up above the surface is to correct for the Earth's curvature.  Assuming the Earth is a perfect sphere (which it isn't), the Earth curves down away from the corner of LIGO a little over 4 feet over its 2.5 mile long arms.  Since the beam tubes were we shine the laser in are only about 4 feet in diameter, if we didn't ensure that the ground under the arms was perfectly flat (not flat with the curvature of the Earth), the light would never reach the ends!

ON THE INSIDE - The Control Room

So, that's what LIGO looks like from the outside.  Now, let's look at what it looks like from the inside.  The heart of the observatory is its control room where almost anything inside of the detector can be changed with the press of a button (and I've learned the hard way that you can also "break" LIGO with a press of a button as well - oops!).  Below is one of my favorite pictures (not just because I am in it) since you can see almost all of the control room in this image:

I liked this image so much that I purchased a print and it is proudly framed in my office. [Image by Roger Zettler of The Advocate newspaper (Baton Rouge, LA); published on 25 February 2010.]

Just behind me (I'm the woman standing in the front of the image) is the on-duty scientist (left - Peter Saulson of Syracuse University) and the on-duty operator (right - Danny Sellers).  The operator maintains the instrument in working order and responds promptly to any malfunctions while the scientist ensures the quality of the data.  Together they make sure that there is as much good quality data as possible.  You can also see that there are projections of graphs and videos on the back wall (top of image) and the side walls.  These let those working in the control room know at a glance how the instrument is behaving.  Currently, this control room is being renovated in preparation for the completion of Advanced LIGO.

FROM THE INSIDE: The Interferometer

Finally, there is the detector itself (also known as an interferometer - the "I" in LIGO).  Below is an image of the corner of LIGO where laser light is split between the 2 arms:

The following is a large video (~33 MB - so it may take a little while to load) that shows views of the interferometer from the inside and the outside.  I made this in July 2008 when the upgrades for Enhanced LIGO were finishing up.  There is no audio to accompany this video, as I use it when I give talks about LIGO and narrate it live.  An index is located below the movie describing what you are seeing and when.

Video Index:

0:00-0:12 - This is the input portion of LIGO.  In the far back of the image, in the white room, contains our main laser source.  The laser is infrared (wavelength = 1064 nm) so it can't be seen by the eye but it is powerful enough to permanently blind you.  In front of this white room is a pink draped room.  This is a portable clean room and inside the air is filtered so that less than 100 6-micron particles are floating around every cubic foot.  Basically, you will never see any dust motes in there.  This is needed to help ensure that the vacuum inside of LIGO (which is the largest sustained ultra-high vacuum in the world - to the best of my knowledge) isn't contaminated.  (When the camera moves to the next view, you will see the top of another portable clean room and the HEPA filters that push air down into it.)

0:20-0:27 - This is the corner of LIGO.  In the center chamber is an instrument called the beam splitter that does just what it says: it lets half of the light pass through it and go into one arm while the other half of the light is reflected off of it into the other arm.

0:30-0:34 - This is the X-arm (the arms are named after the X and Y axis of a standard [Cartesian] graph) of the interferometer where the light that is transmitted through the beam splitter goes.  This metal tube continues through the wall and outside.

0:34-0:59 - This is the X-arm as seen from the roof.  The video zooms out to the end of the arm where there is a building that houses the tip of LIGO and the mirror that reflects the light back.  The concrete barrier that protects the metal beam tube (as seen in the previous view) is also seen.  This concrete barrier protects the tube from the environment (like lightning strikes).

1:03-1:11 - The Y-arm where the light reflected off of the beam splitter travels.

1:11-1:35 - The view of the Y-arm from the roof.

1:40 - The light from both of the arms combined again at the beam splitter (seen here).

1:40-2:03 - The combined light from both of the arms goes to the output where the interference pattern (the brightness of the light) is measured to determine if the lengths of the arms changed compared to each other.