Thursday, May 31, 2012

The Two-Body Problem: Relationships and Physicists


One of the more difficult things about being a physicist in a relationship is that your partner is usually also a professional in a technical field as well.  Working in specialized fields make finding jobs in the same location as your partner difficult.  So many of us have experienced these issues that we have a special name assigned to it - the two-body problem (re-purposing the phrase referring  to the physics of two masses interacting, say in orbit).

The problem isn't about finding work, but finding work working in our specialties.  For example, I am a skilled physics educator and every college and university teaches physics at some level so there are job opportunities for me in that respect.  Of course, these jobs are still very competitive to earn, but you get the idea that there is work out there.  But many of these jobs would likely be strictly or mostly teaching without much in the way of research opportunities.  I could be employed but I would likely not be able to continue my LIGO research which is important to me.  There are about 80 institutions from across the country and around the world that work in the LIGO Scientific Collaboration (click here for a list of these institutions).  While this sounds like many, the odds of not only landing a job at one of these institutions and having fulfilling job prospects for a spouse isn't great.

My two-body problem was made official in 2003.


This is usually most difficult for us academics as we finish our degrees (or when an appointment ends if the relationship started when not a student - mine did so this is what I reference).  For me, it was especially stressful since I finished my doctorate before my husband finished his.  My solution to the two-body problem: take a mini retirement.  He was supposed to graduate next semester so I figured that I would wait for him.  Besides, after writing my dissertation, I was quite burned out on research.  Well, next semester turned into the next next semester and I started to quickly lose my mind as I wasn't nearly as burned out as I thought.  I had a small contract teaching job at Penn State, but it was something that I had been doing for years as a graduate student and it wasn't challenging or time consuming.  Then I discovered vampire books and decided to do a normal person job for fun (almost all of my work previously has been in academia).  One of my students gave me tips on where to apply for a waitressing  job.  I was looking for something in the evening, like in a bar, but I ended up with breakfast/lunch service at a hotel restaurant.  Except for the very early start time (I had to be there for 6 AM, which I know isn't that early, but doesn't exist in my universe), I loved the work!  I met lots of new people and none of them treated me like I was odd because I was a physicist (since they didn't know).  This did come at a potentially steep cost professionally since effectively being out of the field for nearly a year (like I was) is usually career suicide.

Finally, there came a job I was willing to suffer a long distance relationship for - the one I have right now.  It was pure serendipity that they were also hiring engineers with my husband's skills at the same time.  We both got jobs and we are both happily employed at LIGO now.  This is EXTREMELY rare.

Now my concern is maintaining the ability to sleep under the same roof with my husband in the future.  My job here is a postdoctoral scholar is temporary, much like a medical doctor's residency.  I've been at this job for almost 5 years now (I did get promoted to senior postdoctoral scholar after my third year) which is a long time to be a postdoc at the same place.  That's not to say that it's unusual to have several postdoc appointments at different places for more than 5 years.

What to do now?  Well, I am trying to work out a new position but I don't want to jinx by talking about it here now.  This solution would let me stay put but definitely mix things up a bit for me.  Fingers crossed!


To give you an idea of how lucky I am to live with my husband through our transition from student to scientist, I've had two advisors on my way to getting my Ph.D. who both had extended long-distance relationships due to the two-body problem.  The first was Gabriela Gonzalez who left Penn State to go with her husband (also at Penn State) to LSU where he was offered a prestigious position and she would be able to work much closer to LIGO.  Before they found the Penn State (and then LSU) solution to their two-body problem, they worked for about 6 years hours apart from each other (you can read about their story here - you may need to register, but it's free).  When I turned down the opportunity to go to LSU with her (due to my own relationship), I then worked for Sam Finn at Penn State.  He and his wife also spent about a decade apart before they found their solution.

Conclusion, I am lucky beyond belief to not only have a job that I love but to have the one I love with me as well.

Read More:

A Dual Dilemma  (
Is the Husband Going to be a Problem?  (New York Times)
Women in Academia: The Two Body Problem  (Persephone Magazine)

Friday, May 25, 2012

News on LISA and Some Personal Stuff


The LISA Symposium was in Paris this week and the result of this meeting was a strengthening of the efforts to put a gravitational-wave detector into space and the formation of the eLISA Consortium.  Below is a statement issued by the Consortium:

Getting ready for next time:
European gravitational wave community strengthens its space collaboration
During the 9th international LISA Symposium, held May 21 – 25 in Paris, the international LISA* community analyzed the new situation after ESA´s decision to choose JUICE for Europe´s next large space science mission. As the eLISA** mission, despite not being selected, was reported to have been unanimously ranked first by ESA´s scientific review committee in terms of scientific interest, strategic value for science and strategic value for the projects in Europe, the community is in good spirits: this is the first time that any space agency committee has ranked a gravitational wave observatory as its highest scientific priority. In order to prepare a strongest possible bid for the next launch opportunity the community has decided to continue its collaboration as the self-funded and independent eLISA consortium.
Besides preparing for the next competition the consortium will strongly support ESA's LISA Pathfinder mission, whose launch in 2014 will finally open the door to approval of a full gravitational wave mission. LPF will demonstrate key gravity-measuring technologies in space for the first time, preparing the way not only for gravitational wave detectors but also for next-generation Earth and planetary gravimetry.
The eLISA consortium consists of a management board, a steering committee, and working groups in science, technology and data analysis. It represents the European states involved in eLISA, i.e. Denmark, France, Germany, Italy, Netherlands, Spain, Switzerland, and UK. The consortium is led by Prof. Dr. Karsten Danzmann, who chaired the former LISA International Science Team and is a director at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) and a professor at the Leibniz Universit├Ąt in Hannover, Germany.
“Our goal is to keep this highly motivated and effective scientific community together. It has attracted many young and excellent researchers. The knowledge and innovative potential of our community is documented in more than 2000 published scientific papers - we want to keep it working on a strong science, technology and data analysis programme”, says Karsten Danzmann, describing the role of the eLISA consortium.
Colleagues from the US, China and possibly other interested countries will be invited to participate. At the LISA Symposium, US participants presented results on a comparative study of low-cost LISA variants and expressed interest in contributing to an ESA-led mission. And for the first time, a large Chinese delegation participated in the LISA Symposium and announced their scientific interest in a close collaboration on a gravitational wave mission. The Chinese Academy of Sciences and the Chinese Space Agency are developing their own plans for a gravitational wave detector in space.  
LISA*: Laser Interferometer Space Antenna
eLISA**: evolved Laser Interferometer Space Antenna, also known as NGO (New Gravitational-Wave Observatory)


It's been a long while since I posted on here about myself.  One of the reasons I started this blog was that I wanted to humanize scientists and the work they do; you wouldn't believe how often visitors tell me that I'm not what they expected from a scientist (they mean that as a compliment) or that I was more normal than they expected.  I pulled back on writing much about myself simply because I wasn't nearly as interesting as I first thought.  I can be summed up pretty well by: loves vampires, has migraines, and is sometimes insecure about her professional worth.  (This post is even being published a day late because a migraine.)

But there has been some excitement in my life.  Over the last two weeks I have been catching up on all of my routine doctors appointments I have been putting off due to my work schedule and my husband's (and we share a car since we work at the same place).  He was out of town for nearly 2 weeks so I had the car to myself!  I've seen by dermatologist (I am very fair skinned and I get checked out for skin cancer), my gynecologist, my dentist, my cardiologist, and my urologist.  The good news is that everything is going well even though I was up to 6 months behind on being seen.  The bad news is that I've let my depression get the better of me these past few months and I didn't realize what a bad place I was in until I had time to myself.

I've been wondering whether or not to talk about this on my blog since I have had some outright ignorant reactions when I mention that I have depression.  But, May is Mental Health Month and I would like to talk a little about dealing with depression and anxiety and why you should seek treatment if you suffer from this as well.

I was an anxious little kid who was sad a lot.  As I grew up and started to have more adult problems, these tendencies became more pronounced.  It took a traumatic event for a doctor to recommend treatment for depression.  This treatment took some time to work, but when it did I realized that I had basically lived my whole life depressed to some extent and simply thought that was what normal was.  I don't need constant treatment for it, but if I'm not careful depression can sneak up on me so slowly that I don't notice it happening until it becomes horrible.  That is what happened for me recently and even then it took a doctor to bring the point up (I guess I'm not as good at covering it up as I thought I was).  I'm being treated again and things are starting to look brighter.  At least I don't feel alone and isolated even when I am surrounded by friends and colleagues.

My point is, if you think you are depressed or feel anxious for extended periods of time, talk to a doctor, medical or psychological.  I've been told to just "get over it" or called weak because I have sought treatment for my depression.  Well, will power can only help you look like nothing is wrong but you will still be depressed.  And I have discovered that most of the people who call me weak have similar problems of their own that they won't seek help for.  Truly, treating my depression is the best thing that I have ever done and I am not sure if I would be where I am today if I had not.

Thursday, May 17, 2012

Q: What is a Gravitational Wave?

Many times, when we scientists answer this question, we say "ripples on space-time".  It wasn't until I was in grad school that I really started to understand was "space-time" was.  Before that, anytime someone said the word I just nodded with an expression of recognition so I wouldn't look dumb.

So, when I talk to visitors to LIGO, I like to talk about gravitational waves (or, more specifically, space-time) in a different way.  First, let's go back to gravity as Newton described it...


There is a story about how Isaac Newton came upon the realization of gravity, often referred to as "Newton's Apple".  One day, Newton was sitting under a tree in an apple orchard.  This was one of those days when the Moon is visible in the afternoon sky.  He then saw an apple fall to the ground (some versions of the story say the apple fell on his head but I think that is too convenient).  It was then that he realized that the force that drew the apple to the ground without touching it was the same force that kept the Moon in orbit around the Earth.  This kind of force is called action at a distance.  The way two masses communicate the gravitational force between them is with a field (just like the magnetic or electric field).  Every mass (including you and me) fills up the Universe with a gravitational field that gets weaker with distance.  When objects move, the entire gravitational field of the object moves with it and every object in the Universe feels a change in the gravitational force because of this instantaneously.


In Einstein's relativity, nothing can travel faster than the speed of light, including information about where mass is in the Universe.  That means that there must be a change in the gravitational field that moves out into the Universe at a finite speed instead of everything "feeling" the change instantly.  A gravitational wave is really that change in the gravitational field propagating out into the Universe like a ripple on a pond.


So, how is this moving change in gravitational field that is a gravitational wave related to space-time?  First, space-time measures the curvature of the Universe.  It is usually visualized as an elastic grid, but this is a large simplification since space-time would be better represented by an animated 3-dimensional grid - but that is beside the point for now.  When there is no mass, space-time is perfectly flat:

When there is mass present, space-time will be curved:

Consider another much smaller mass approaching this one: it will be deflected by the curvature of space-time.  This is gravitational attraction.

Ultimately, the strength of the gravitational field at any given place corresponds the the steepness of the curvature of space-time there.  In the flat space-time, there is no curvature and no gravitational field.


Now, we can go back to the phrase "ripples in space-time".  Now that we understand more about what space-time is, how it is represented, and how it affects mass moving through it we have a bigger picture of what gravitational waves are.  Any time a mass moves (accelerates - there are some subtleties here), that is going to create a change in the gravitational field (the curvature of space-time) and this change will ripple out into the Universe.

Below is an animation by the Jodrell Bank Center for Astrophysics of a pulsar-neutron star system merging into a black hole.  The green grid represents the surrounding space-time and the gravitational waves on it are evident:

So, what do you think?  Does this make more sense?  Let me know!

ADDENDUM added 15 July 2012:

The elastic 2-dimensional grid, while suitable for discussion here, has several important features that are imperfect for use as an analogy for spacetime.  The first is that an elastic sheet will create a curvature that is related to the object's mass and its size.  However, the size of a mass has nothing to do with the curvature of spacetime.  Another is that a passing gravitational wave will affect a mass but the mass will not continue to 'bounce' on spacetime thus creating more ripples on spacetime (think of a mass bouncing on a trampoline).  There are plenty of other features that make this 2-dimensional approximation imperfect, but these are two of the most important for our purposes.

A better visualization is found in the American Museum of Natural History's short documentary called Gravity: Making Waves (which can be seen in its entirety on my Viewing Fun! page).  This is grid-like scaffolding filling 3-dimensional space in which there is a depression caused by mass.  While it still isn't a perfect representation of spacetime, it is much better than the trampoline approximation above (but also overly complicated for this discussion).  Below is the relevant clip from Gravity: Making Waves (~ 2 MB):

Thursday, May 10, 2012

Q: Why Isn't LIGO Sensitive to GW From the Sun, Moon, or Planets?

Another question I am often asked at LIGO is why we are looking for gravitational waves from the most violent, energetic events in the Universe when the Sun, Moon, and planets are moving around the Earth right beside us.  The reason for this is that there is simply not enough mass (even in our Sun) moving fast enough to produce detectable gravitational waves.  The key here is "fast enough".  Let's look at the sensitivity of LIGO to figure out what is "fast enough"...

Click on this plot for a larger image.

These are the sensitivity curves for all of the LIGO science runs (labeled S1, S2, etc. in chronological order), the design sensitivity for Initial LIGO (iLIGO), and Advanced LIGO (aLIGO).  Remember, like in golf, a lower number is better (more sensitive).  There is a little more to reading this graph:
  • The vertical (Y) axis is in units of strain.  That is just the change in length of LIGO's arms divided by their original length (4 km or 4000 m).  The numbers on this axis on in scientific notation (10-18, etc.).  The negative in front of the super-scripted number (exponent) means the number of places after the decimal place.  For example, 10-3 is the same as 0.001.  103 (note there isn't a negative sign here so this is the number of zeros before the decimal place) is 1000.  10-21 is a strain that corresponds to a change in length of the arms of 1000x smaller than the diameter of a proton.  
  • The horizontal (X) axis is frequency which is measured in units of Hertz (Hz, how many crests of a wave pass by every second).  This is also in scientific notation (like mentioned above).  The spacings of the lines are uneven because this is in log (logarithmic) scale.  The line labeled 102 is 100 Hz, the next unlabeled line is 200 Hz, the next unlabeled is 300 Hz, etc.  Each labeled line is 10x more than the labeled line before it.
The frequencies where LIGO is most sensitive is between 100-1000 Hz (102 - 103 Hz).  At lower frequencies (to the left on the plot) the sensitivity curve takes a sharp turn up to lower sensitivities (remember, a higher plot means lower sensitivity).  This is due to the seismic vibrations that are constantly present on the Earth mostly from the microseism.  The only way to eliminate this noise is to place a gravitational-wave detector in space.

You can see from the sensitivity plot that for our last science run (S6, the yellow-green curve) achieved a sensitivity better than the Initial LIGO design (the black curve just above it).  For Advanced LIGO (the lowest black line) there are several configurations that it can be operated in (more details are here), but the curve represented here produces the best sensitivity over a broad frequency range and is likely to be the general operation state.  Advanced LIGO will have even better sensitivity at lower frequencies, but not enough to be sensitive to objects in our Solar System.

So, what frequency would be the gravitational waves from Sun?  The Earth orbits the Sun once every year (365.25 days or 31,556,926 seconds).  This gives a frequency (f=1/year) of 3.1689x10-8 Hz or 0.000000031689 Hz.  This is WAAAAY too low of a frequency for LIGO or for any proposed space based detector (like the recently canceled LISA which only goes down to about 10-4 Hz or 0.0001 Hz):

Plot comparing the sensitivity curves of Initial LIGO and LISA.

Therefore, since nothing with great mass moves in our Universal neighborhood with high frequencies, we must look deeper for things like stars exploding an black holes colliding.  These are much more interesting that just observing the gravitational waves from the Solar System; they really wouldn't tell us much new information about the Universe.  At LIGO we are not just seeking to make the first direct detections of gravitational waves, but we are trying to use these gravitational waves as a new way to do astronomy!

Thursday, May 3, 2012

More on LISA/NGO and What Would You Ask a Scientist?


On May 2nd, the ESA officially decided to accept their Science Programme Committee's recommendation to choose the JUICE (JUpiter ICy moons Explorer) mission for the 2020ish launch opportunity.  While this is unexpected, it is still a disappointment.  A thoughtful article on possible factors contributing to why LISA/NGO was passed over can be found here.

While this is disappointing, all isn't lost.  The scuttlebutt is that LISA may have a good shot at being the next mission chosen when the next mission selection takes place in 2015. (I know...  That's still a long while off.)  The science case for LISA/NGO has always been strong and by then the results of the LISA Pathfinder mission will be in (it appears that it will fly in 2014, not in June like I cited from the NASA website on my last LISA post).  Assuming success, many of the technical concerns should be resolved.

As LISA/NGO detects lower frequency gravitational waves than LIGO ever can (since seismic vibrations create too much noise for LIGO to be sensitive there), it is a beautifully complimentary observatory.  Who wouldn't love a detector where your main noise source is detecting too many gravitational waves at the same time (which is exactly the case for LISA/NGO)?

I'm looking forward to it!

What Would You Ask A Scientist (or Engineer, etc.)?

One of the reasons that I started this blog is that I wanted to show people that scientists are real people.  I've been told too many times to count that I look too young, normal, etc. to be a "real" scientist.  I know that they are trying to compliment me, but the subtext of this is that they thought I wouldn't be human like them.  So, since not all of you can come to visit me, I figured I would share some of my experience and life with you.

Well, it turns out that I am not as interesting as I thought I was (actually, I never thought that - I like vampire books, I have migraines, and I love my job at LIGO - that is me in a nutshell).  But the LIGO Scientific Collaboration is made up of over 800 scientists from across the country and around the world and I am guessing that you may like to find out more about them.

Here is what I am thinking...  I have a few basic questions I would like anyone profiled here to answer:
  • What is it that you do for a living?
  • What motivated you to choose this career?
  • What kind of education do you have/need to do your work?
  • Where are you from?
  • Please tell us something unique about yourself.
I also have a list of questions that I would like the person being profiled to pick and choose from (not all are appropriate for everyone or would produce interesting answers).  Of these, I would love to know that you think is most interesting.  This may help guide the person being profiled in choosing what they wish to answer (or I can ask that your favorites be answered).

So, what would you like to ask someone who works on LIGO?  I have a survey you can click below and there is also a link just below the blog banner called "Survey" where you can respond.  Please note that the last option is where you can put your pressing question that isn't already listed.  Also, feel free to let me know if there is anyone in particular from LIGO that you would like me to profile!  Hope to hear from you!!!