Thursday, March 29, 2012

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!

Thursday, March 22, 2012

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  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!

Thursday, March 15, 2012

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?


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 90o) 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.

Thursday, March 8, 2012

Solar Flares and Space Weather

There has been a lot of buzz about the large solar flare that was observed on March 7th (this is one of the strongest flares observed - read about this specific flare here).  Most of the interest in this, other than it is an awesome thing to see, is that the material that was ejected from the Sun can interfere with satellites (like the GPS satellites you need to find your way around unfamiliar locales), power grids, and electromagnetic communications (like radio).  Before I get started, below is a great video of the solar flare using different kinds of light (the Å symbol, called an angstrom, on the left side of some segments of this video is a unit of wavelength equal to 10-10 meters):

While this is truly an event to behold, there is more to it than just its beauty.  Below is a short video on what you are seeing in this video and how the flare may affect us here on Earth:

The effects of astronomical events interacting with the Earth is called space weather.  (NOAA even studies space weather and you can check the current space weather conditions anytime at NOAA Space Weather Prediction Center.)  If you live north (or south) enough above the Equator (about 70o or so in latitude) , you may have seen the aurora (known as the aurora borealis [northern lights] if you are north of the Equator or the aurora australis [southern lights] if you are south).  This light display is caused by charged particles from space interacting with the Earth's magnetic field (called the magnetosphere).  This interaction directs the charged particles towards the north and south poles of the Earth.  When the particles strike atoms of our atmosphere, they excite electrons in atoms that make up our air; light is produced when these excited electrons release this excess energy.  Since our atmosphere is made up primarily of nitrogen and oxygen, the colors of this light are usually red (from nitrogen) or green (from oxygen).  This recent solar flare is starting to interact with the Earth now and brilliant aurorae are expected.  Since I am posting videos today, below is a spectacular time lapse video of the aurora borealis by National Geographic (there may be a short advertisement before it starts - sorry!):

I bring all of this up, not only because it is timely and interesting, but also because space weather affects LIGO.  Space weather often produces particles that shower down on the Earth's surface called cosmic rays (even though most of the particles are not from space but are produced when very high energy particles from space smash into the atmosphere and produce showers of new particles from this interaction).  Of particular concern to us is what would happen if a shower of particles are produced near or within one of our mirrors.  Could this cause a vibration big enough for the detector to be sensitive to?  If so, could the motion look like a gravitational wave signal?  A paper published in 2008 investigated this (which you can read here if you are REALLY interested).  It was determined that a strong shower could indeed move our mirrors enough for us to notice, but a strong shower like this is rare.

Even though the effect is rare, so is detecting a gravitational wave (at least until Advanced LIGO is completed).  For the "Big Dog" event - when we last thought that we may have really detected a gravitational wave but it was later shown to be a blind test of our detection methods - the possibility that space weather could have affected our results was thoroughly investigated (along with many other things like one of us turning to the dark side and fraudulently adding this signal to the detector).  As it turned out, it was a "clear" space weather day for that event.

Remember to check the NOAA Space Weather Prediction Center for updates on the effects of this recent solar flare here on Earth!

Thursday, March 1, 2012

On Leap Years and Keeping Time

I hope everyone had a good leap day (I know it isn't a holiday, but it is even rarer since it only comes about every four years).  In honor of this, I am discussing why we have leap days and different calendar systems.  I'm not sure what you think, but while I find all of this fascinating, I'm happy this isn't something I study for a living!

There are many different calendar systems that base themselves on the periodicity of different things - most of them having an astronomical origin like the Sun, Moon, or even Venus.  The system in most use today is the Gregorian calendar (at least for international commerce in countries that use a different system).  This is a solar calendar that assigns a date to every cycle of day and night.  This has the advantage of syncing up well with the normal human sleep cycle.  However, the Earth does not revolve around the Sun in an integer number of days.  While our normal year has 365 days in it, it actually takes the Earth 365.242374 days (and the length of a day is slowly increasing) to orbit the Sun.

If we did not correct for that extra fraction of a day, the seasons would slowly start changing later and later on the calendar.  Over an average human lifespan, say 75 years, the equinoxes and solstices (start of seasons) will be a little more than 18 days later at the end of that 75 years than at birth.  This year, the summer solstice is on June 20.  If we never have another leap day, summer will start on Christmas (December 25 is 188 days after June 20) in 776 years.  I know you and I wouldn't be around to see that, but on the human history scale of things this is very significant.

But our leap year every year that is evenly divisible by 4 system is overcompensating for that extra fraction of a day it takes Earth to orbit the Sun.  So exceptions to the every 4-years rule must be made: every year divisible by 100 is NOT a leap year EXCEPT if it is divisible by 400.  That is why 2000, even though it was divisible by 100, was not a leap year since it was also divisible by 400.

The reason I am going into this on this blog about LIGO is that keeping time is VERY important to us.  It is also important to astronomers in general.  There have been many revisions and changes to the calendar over the years (before the Gregorian calendar, most of Europe used the Julian calendar) and this can complicate figuring out how long it has been since something happened.  So that we don't have to worry about these complications, astronomers use the Julian date system (which is different from figuring out the date on the Julian calendar mentioned above).  This system assigns a date to every day consecutively (there are no months or years).  For example, today is 2455988 (any fractional parts would  correspond to the time of day).  Day 0 is assigned to be January 1, 4713 BC (this is roughly around the beginning of human recorded history).  This makes it is very easy to figure out how many days there have been between events; for example, I was born on 2443787 so I am 12,201 days old (today).  Here at LIGO, we use a system called GPS time which counts the number of seconds since January 6, 1980 (I wrote a post about this here).  In GPS time, I was born on -39489840...  Now I feel prehistoric!

Remember in the first paragraph when I mentioned the day is getting longer?  One of the predictable reasons for this is the effect of the tides on the Earth cause it to rotate a little slower over time (this is called tidal breaking).  Other factors that are not as predictable can also effect the length of a day, like the motion of the molten mass inside the Earth.  A 2004 earthquake was so powerful that the length of the day became 2.68 microseconds shorter.  There are also unpredictable reasons we don't understand that cause the length of the day to change (in 1999 it changed by about 1 microsecond and we don't know why).  But, factors like this cause there to be such a thing as a leap second (there will be a leap second on June 30 this year).  Date systems like Julian dates and GPS time are not affected by this unless you want to convert back into normal dates and times - here at LIGO we make sure that all of our computer programs keep up to date with the leap second corrections.


Yesterday (leap day) I was leaving work by way of a staircase in the back of my building.  This faces the woods and there is a single light above them so you can see your way at night.  This is a prime place to find the varied kinds of moths that are indigenous to the area because many of them are attracted to the light and some die during the night.  I guess I got a leap day treat yesterday when I saw this moth I have NEVER seen before with beautiful pink and yellow colorings:

I looked this up later and discovered that this is a rosy maple moth.