Tuesday, December 20, 2011

Nerdy Fun for the Holidays!

Since I am not sure that I will be posting again before the end of the year (I hope so, but I also have the feeling that you will be busy with your own holiday events), I wanted to make this a fun post that will make you smile.

Happy Helium Holidays

The APS Physics Buzz Blog team performed this wonderful rendition of Carol of the Bells using helium or sulfur hexafluoride to modify their voices and a harmonious, hilarious way!  Many people are familiar with the fact that if you inhale helium your voice becomes much higher pitched.  This is because the helium gas is so much lighter than air, it allows your vocal cords to vibrate at a higher frequency producing the high pitch.  Sulfur hexafluoride is sometimes known as the anti-helium since it is so much heavier than helium, if causes your vocal cords to vibrate much slower producing a deep, low pitch.

The beginning of this video features Becky Thompson-Flagg who is the Head of Public Outreach for the APS and is also the model for the Spectra superhero character comic books (read here about that).  She explains the physics behind the voice changes and the mild peril involved in this performance.  Then the concert begins :)

Interactive Relativity Tutorial - Al's Relativistic Adventures

Al's Relativistic Adventures is an animated tutorial on special relativity.  While this is appropriate for middle school students, I found the lessons to be very accurate and the authors are talented at communicating complicated concepts in easy to understand ways (I even learned how to better communicate some concepts from working through this activity).  Once you are done, you are even awarded a certificate - I printed mine out and hung it in my office :)

Play the GRB Lottery

Gamma ray bursts (GRBs) are the most luminous events to be observed in the Universe and their origins, other than that they are produce from extraordinary energetic events), are still not certain.  They play a vital role to LIGO since whatever produces them could have produced gravitational waves and observe these gravitational waves may uncover the cause of these explosions.

There are several satellites currently in orbit around the Earth detecting these GRBs.  One of these is the Swift satellite and they have a fun GRB Lottery to play on their website (free to play, of course).  You are presented a map of the sky that has locations of past detected GRBs (notice that there is no area on the sky that is favored over another so any guess is really as good as another).  You then click on an area that you would like to select as your own and if you are the closest guess to a GRB within the two weeks, you win!  "What do you win?" you say...  Well, you get a nifty certificate commemorating your good fortune and the Swift outreach staff will send you a small gift (I got a nice package of education materials including a poster).

I played the GRB Lottery once and I won!  I decided that I would retire from my glorious reign so that the rest of you can have a chance!  :P  Below is the certificate I earned which is hanging proudly in my office:

Physics Carols

This webpage (www.PhysicsSongs.org) has an amazing collection of covers to well known songs with physics lyrics.  They even have a special page of physics related carols!  I have to admit to getting lost on the page and chuckling to myself (and feeling even more nerdy than usual)!

Monday, November 21, 2011

Bittersweet: The End of A Professional Service Term

I have mentioned many times on this blog that I feel that performing service to my profession is just as important as the research and public outreach that I do; in a way, this is a form of professional outreach.

I have had the uncommon honor to serve on the American Physical Society (APS) Council and then, half way into my four-year term, I was elected to serve on their Executive Board.  I have met many new colleagues whom I would have never met otherwise since we don't work in the same field of physics.  Even better, some of them have become friends (good enough friends that I will even discuss my Impostor Syndrome issue with them - I wrote a whole post about this).

As far as contributing to the profession, I have had the opportunity to work extensively on strategic planning for the next decade of the society and represented young physicists' concerns on many issues.  Even more than that, I am now able to better understand the workings of my professional society, understand the concerns of physicists who work in industry, outside of the United States, etc. and learn more about the politics (inside and outside of physics) that make research happen (or not).

My term comes to a close (on both the Council and the Executive Board) at the end of this year and I have just traveled back from my last meetings in Salt Lake City, UT.  I am sad about not getting to meet the new people who will be elected to replace all of us rotating off this year (I do recognize if we never left, there would be no new people!).  A big relief to me is that I won't have to travel so much - if you serve on the Council, that is 2 trips a year and then if you serve on the Executive Board that is an additional 3 trips (or 4 trips next year).  Since I HATE to travel, this will mean more nights in my own bed <contented sigh>.

The view from my hotel room in Salt Lake City.  This is facing Temple Square and the LDS temple is visible between the 2 red-orange buildings.
If you are reading this and are not a physicist (I hope some of you aren't since it is for you that I really write this blog), I hope that I have given you a little peek into the physics community outside of LIGO.  If you are a physicist, I urge you to consider expanding whatever service work you do to the APS, AAPT, OSA, etc.  It can be a lot of work, but I would definitely do it all over again.  Of course, service isn't all work (just mostly):

Wine tasting during the APS Executive Board Retreat, Santa Barbara, CA (Photo: Ken Cole)
Special thanks to Ken Cole for permission to use his picture of me (above).  Ken is the APS Special Assistant to the Executive Officer (and has done a great job a wrangling me these last years) and is also a gifted photographer.  You can view more of his photos here.

Friday, November 4, 2011

2 Questions: "Can there be a gravitational wave detection before Advanced LIGO?" & "What does it mean if gravitational waves aren't detected with aLIGO?"

Sorry for being away from the blog for as long as I have.  What has been keeping me away from you, you say?  Well, I got sick :(  The one thing that I am very susceptible to is sinus infections (ever since I was a kid) and autumn is prime time for me to catch one.  That kept me basically in bed for about 4 days with a few days before and after still feeling miserable but ambulatory.  My waterfall of post-nasal drip has begun to slow down but my coughing is starting to taste funny again.  I'm off to the after-hours clinic tonight to see if I need antibiotics to clear this up.

There was also a meeting at the LIGO Livingston Observatory where I work that brought astronomers and LIGO scientists together to discuss what data of ours they would like to have access to and what is the best way for them to get the data.  This is all in an effort to make the data the the American taxpayer has paid for available to other scientists.  This is an interesting topic because most of us here at LIGO have neuroses about making a detection claim that later turns out to be false.  Because of that, we tend to keep our data close to the vest until we are certain what is in it.  Anyway, I will talk about this more in a later blog post.

Now, back to answering reader questions!  Since I have been away so long I figured I would answer 2:


@AstroGuyz asked:

You know the question on every science bloggers' mind is the Big One; "When will LIGO discover gravity waves?"  Are the prospects for gravitational wave detection good before AdLIGO goes online?  Think we'll nab it before the Higgs?
First off, there is very little probability of detecting gravitational waves before Advanced LIGO is ready.  Notice I didn't say it was impossible.  There are 2 situations that could produce a pre-Advanced LIGO detection.

The first possibility is a joint run between two or more detectors outside of the United States.  This happened over this past summer when GEO and Virgo were both operational and while we are still looking at this data, we haven't seen anything yet.  Now that Virgo has commenced its upgrade efforts in earnest, there isn't really another chance for a joint run until Advanced LIGO is ready.  (FYI: you can see what gravitational wave detectors are operating right now on the GWIstat page, which is always displayed under my "Interesting Links" to the right.  Note that not all of these are interferometric (laser) detectors.)

The second chance for detection is going to rely on a single detector, mainly GEO, to be operating when a significant astronomical event is observed using other astronomy observations.  For example, if a supernova is detected in the sky at the same time a very strong event is detected in GEO, then chances are that these two events are related and there is a real gravitational wave detection.  That is why GEO is continually running while LIGO and Virgo undergo their upgrades - so that we don't miss something that is basically obvious.

So, unless one of these two situations happens, we will all need to wait for Advanced LIGO to be done.  And I wouldn't expect a detection as soon as we turn it on either...  It will take a while for us to get all of the new equipment "tuned-up" to the point that it is working to the best of its abilities.  Don't quote me on this, but I wouldn't expect anything until 2016-2017.

As far as detecting gravitational waves before the Higgs particle, I can't say but I am thinking about writing a post about what all the excitement over this particle is about in another post!


@EclipseMaps asked:

What are consequences for theory of gravity/relativity if null results for gravitational waves after extended observations?
From my last question, I mentioned not to expect a detection of gravitational waves until about 2016-2017.  Even if that time comes and goes, I still wouldn't get too worried.  However, if 2020 or so comes by (remember, this is just my opinion and not that of LIGO) and we firmly see no evidence of a detection, then this does have some implications.

The first thing most people would think is that LIGO has been a failure.  Actually, that is very far from the truth.  I, along with over 800 scientists in the LIGO Scientific Collaboration, have dedicated our careers to this as well as used taxpayer dollars to search for gravitational wave and we haven't done this on a hunch.  The 1993 Nobel Prize in Physics was awarded for proof that gravitational waves exist by observing their affects on an astronomical system.  We simply want to detect them affecting our own detectors so that we can do astronomy with them.

Not detecting gravitational waves after we have detectors that clearly should be detecting them tells us that there is something we don't understand about general relativity (the theory where gravitational waves originate) or that we don't understand enough about the composition of our universe, namely how many of those things we expect to produce detectable gravitational waves exist.  This would be extraordinarily interesting (although a bit disappointing to me).  So much so, that there would be whole conferences of physicists and astronomers debating the populations of gravitational wave sources to exotic interference such as gravitational waves leaking into separated universes (see my discussion about how gravitons behave in string theory here).


My "Lucky Yen"
This is my "Lucky Yen".  There really isn't anything special about it other than it was given to me by my first physics professor in college, Dr. Plitnik, who gave this to me on my birthday in 1997.  It was just after the Fall semester started.  I know it is kind of dumb, but it meant a lot to me and I have carried it in whatever bag I used through college, grad school and now.  It has even earned its own coin case (which has a higher market value than the coin).

Wednesday, October 5, 2011

Living LIGO 1 Year Anniversary!

Today is the one year anniversary of the Living LIGO blog!  Thank you to everyone who has ever read my blog and followed me on Twitter.  It has been an exciting year and I hope that the next one is even better for you.

I've learned many things through writing this blog.  The first thing I found was my voice.  Originally, I was targeting this blog to middle and high school teachers and students to give them an insight into the science of LIGO and what it is like to be a scientist.  While I think that this blog has served that role to a point, I also found an audience drawn from a great community of science enthusiasts and I've been able to engage them with all of the things that I love about my job.

By far, it is my readers who have made Living LIGO what it is (and I personally think it is great).  A high point for me came back in March when it was revealed that the "Big Dog" blind injection was not a real gravitational wave.  I wanted to share it on my blog since this was a rare peek into how science is done.  One of my readers shared it on his blog (here) which got the attention of a popular "Cosmic Variance" blog (here) and the story was then picked up by places like Discovery News (here) and various other blogs.  The number of readers went from a few a day to over 1000 on that particular day (and many of those reader have now become regulars).  This is something I never expected when I started writing my blog but it is very exciting for me and I hope that it has at least been interesting for you.

I usually like to post a picture with every post, but I didn't have anything particularly relevant to this so I decided to give you a peek into where I create my blog post and most of my other brilliant research - my office.  It's small but it's all mine!  I even have a window (which is great since fluorescent lights give me migraines) and a door:
If you look closely, you can see some of my collection of stuffed vampire/creepy things.
*Thank you again to every reader out there.*  As always, please let me know what kinds of things you would like to know about.  I'll answer almost anything - from science questions to how to become a physicist or whatever!  Ask in the comment section of any blog post or contact me on Twitter as @livingligo.

Monday, October 3, 2011

Night Life at the LIGO-Virgo Collaboration Meeting

I've talked before in this blog about what it is like being at various scientific conferences including the LIGO-Virgo Collaboration (LVC) Meetings.  At the March LVC Meeting, I was able to share the exciting news about the "Big Dog" blind injection (my blog about it | official LIGO release) and discuss the value of blind tests in science.  Last week I was at the September LVC Meeting in Gainesville, FL and, while there was much to talk about, nothing was truly exciting except to those of us in the business.  So, I decided that I would share with you what the night life is like at a meeting like this.

On the evening of Tuesday September 27th, A good friend of mine called me to ask if I had any plans.  Since I didn't I asked what she had in mind and she told me that she and a bunch of other LIGO people were going out to a trivia night.  I had to think about this for a minute since I am very much a homebody and was looking forward to finishing the book I was reading, but then I realized that I tend to have no life at all and should go out.  So, off I went!

We ended up going to The Laboratory which is a science themed pub/cafe.  Below is a picture of me standing in front of The Laboratory:

Me in front of The Laboratory
When I got inside, I saw that the place was definitely "no frills" and a little divey but the atmosphere was still fun and settled in for an evening of showing off my vast intellectual prowess (read: know a few of the answers and hope my other team mates know more than I do).  I grabbed one of the few menus and took pictures for your enjoyment:

Front of menu (FYI: the URL listed on this menu does not work)
Back of menu
All of the food has a science themed title.  I chose the Dr. Hawking chicken sandwich (the item on the left bottom corner on the back of the menu pictured above).  How could I possibly order any other sandwich since I specialize in relativity?  I was so hungry when it arrived that I dove right in and forgot to take a picture for you.  So, here what it looked like when I woke from my hunger craze and took a picture:

What was left of my Dr. Hawking when I remembered to take a picture
As I was eating, more and more people started showing up for the trivia event.  And the place ended up being nearly overrun by all of the usuals and the mass amounts of LIGO people who showed up as well (I didn't actually count, but there wer about 20 of us).  The lights went off, the black lights came on and the trivia started, hosted by none other than Doc (get it?).  We settled into teams of about 6 people and played the night away.  There were 20 questions.  After each question the DJ played a song and that song usually had some kind of hint to it.  Once the song was over, the team had to turn in the answer on a slip of paper and you got a seconds chance (for reduced points) if it was wrong.  I'm not sure exactly where our team finished (not first and not last) but we had a great time.  Below is a picture of the row of us LIGO people who invaded (and we stick together).  And this isn't even everyone since some stragglers ended up sitting at their own table to the right of the picture:

Just some of the LIGO people who showed up for trivia (yes, all the way to the back of the picture)
And what would a science themed cafe be without lab coats?  Here is one of us brilliant specimens modeling one (with a nice glow from the black lights):

A real scientist in a real lab coat at The Laboratory
After trivia fun was over, a few of my friends and I headed back to the hotel since there was another day of the meeting the next day, but I also had to pack since I left the meeting after lunch to head home (which was an adventure in itself since my plane from Atlanta to Baton Rouge was diverted to Jackson, MS just before we started our decent due to a really horrible storm.  As you can tell, after hours of sitting in a closed airport I did indeed make it home.  And I was glad for it since I was away on travel to Long Island, NY for an APS Executive Board Meeting just before this trip.  Remember how I said I was a homebody?  This body was very glad to be home!

Thursday, September 22, 2011

Q: How Does Einstein@Home Search for Gravitational Waves?

@umbonfo asked the following question:
What about the Citizen Science project Einstein@Home? I'm running it but I don't know which GW data it's analyzing.
This is a great question and there is so much I want to tell you all about that I am going to break this down into smaller questions:

What is Einstein@Home?

If you aren't familiar with Einstein@Home (read more, sign up), it is a screensaver that looks for gravitational waves in data collected by LIGO and other detectors like it.  Basically, users allow Einstein@Home to become part of a large supercomputer seeking gravitational waves but ONLY when the users are not using their computers.  How many times have you gone to bed at night and left your computer on?  If it doesn't have anything to do, it just sits there.  Einstein@Home gives it something productive to do that comes at no additional cost to the user.  Below is a screenshot of Einstein@Home as it is running on my computer.  It shows you where the two LIGO detectors are (the green and blue 'L' on the starsphere), where the GEO detector in Germany is (the red 'L') and where on the sky this program is looking for gravitaional waves right now (the orange cross-hairs).  To learn more about what you see on the screensaver, click here.

This is a screen shot of the Einstein@Home screensaver from my laptop just moments ago.
How does Einstein@Home get data?

Once you install the Einstein@Home screensaver, the central data servers (at the University of Wisconsin at Milwaukee) send a small portion of data to your computer for it to analyze.  Once your computer is done looking at that data, it sends a message back to the central computers telling them if there was a candidate gravitational wave in it.  Regardless of the result, 1 to 2 other computers also process the same data to make sure that they all get the same results (and we are sure that there isn't someone out tampering with the software to report false results).  If the same results are found and there is a candidate gravitational wave in the data, then it is looked at more closely by physicists who specialize in data analysis (like me - although I look for different kinds of gravitational waves than Einstein@Home looks for).

What kind of gravitational waves does Einstein@Home look for?

Einstein@Home looks for a very specific kind of gravitational wave call a continuous gravitational wave.  The are expected to be emitted by rapidly spinning, dense objects like neutron stars.  If there is even a small imperfection in the spherical shape of these stars, they will be constantly emitting a gravitational wave (if you were to put the signal of the gravitational wave through speakers, it would sound like a single tone).  We look for this kind of gravitational wave by breaking down the data collected from the detector into its different wave components.  Think of the data as the sum of a collection of many different waves each with a constant frequency.  We can then take a chunk of data and break it up into its component waves.  (This is called a Fourier transform.)  Since we know what a continuous wave should look like, Einstein@Home then inspects each of the component waves to see if it could be a gravitational wave.

Does Einstein@Home do anything else?

Why, that's insightful of you to ask!  :)  Einstein@Home also processes data from the Arecibo radio telescope looking for pulsars - a special kind of neutron star that emits radio waves from their magnetic poles.  Every time that the star spins its jet of radio waves across the Earth, radio telescopes can detect it.  The data analysis in not quite the same as when Einstein@Home looks for gravitational waves, but the basic process of breaking down the data into its component waves is the same.

Why is Enstein@Home interested in discovering pulsars?

Knowing more about where pulsars are in our universe lets us know better where to look for them in our gravitational wave data (notice that the screensaver has crosshairs that show you specifically were Einstein@Home is looking for gravitational waves) and, since pulsars are a special kind of neutron star, we can get a better sense of how many of them are out there in the Universe which give us more accurate measures of how often we should expect to detect gravitational waves from them.

What has Einstein@Home found?

Well, since there has been no direct detection of gravitational waves yet, it is obvious that Einstein@Home has not produced a real gravitational wave yet.  However, it has found over 10 previously unknown pulsars including the fastest known spinning pulsar!

All of this would not be possible without users like you!  When all of the computing power of Einstein@Home is combined, it is within the top 20 or so supercomputers in the world!   

I hope I answered at least most of your questions about Einstein@Home.  As always, feel free to ask me questions by leaving a comment on this blog or tweet me @livingligo.

Tuesday, September 13, 2011

About Time...

I know that I haven't been posting as much as I usually do (I like to post once a week) but life gets in my way.  For example, I had a tooth break that needed fixed and both my husband and I have come down with the cold that has been making its way around the observatory.  Basically, between life and getting work done, I haven't had a lot of time.

But today is an important day since we will reach GPS time 1,000,000,000.  This time is measured in seconds from Sunday January 6, 1980 at midnight UTC (this is the official time of the planet measured at the Prime Meridian passing through Greenwich, England) without any leap second corrections to match the rotation of the Earth (astronomers use a similar time keeping method called Julian Date which is the number of days since January 1, 4713 BC without any corrections for outright changes to the calendar [like to the Gregorian calendar - which is the calendar we use today]).  Here at LIGO, this is important to us since this is how we measure the official time for everything and this time needs to be very accurate since we will never believe a potential gravitational wave detection unless it is measured at different observatories within the time it would take a it to travel between the sites - for the two LIGO observatories, the maximum time is 10 milliseconds.

Other than it being cool to watch the time roll over to one billion (like watching your car odometer roll over to 100,000 miles) this event can cause issues with the data analysis programs that we write to search for gravitational waves.  For example, I wrote a software package while I was in grad school that we still use to produce simulations to test the efficiency of data analysis software.  My baby is called GravEn (for GRAVitational-wave ENgine) and uses the GPS time to determine where the simulations will be added to the real data (this data with fake signals is never saved together so that we don't trick ourselves into thinking we saw something real).  GravEn has specifications in its programing to return the time of the simulation in whole GPS seconds in one column of the log file and the nanoseconds after that time in another column.  I have made it so that the whole-second time is returned with 9 digits and this is now an issue since the time will be 10 digits.  It is easy enough to fix, but it must be fixed!

This new 1,000,000,000 time is not going to be of any serious concern like people feared the Y2K bug to be.  Instead, all of us code monkeys (as computer programers are lovingly referred to) need to go back and make sure that we allow enough (10) digits in the parts of our programs that use GPS time.

So, GPS 1,000,000,000 will happen today (September 14) at 1:46:25 UTC (or September 13 at 9:46:25 PM in Eastern Daylight Time).


My next blog post will be on Thursday and will answer the reader question on exactly what kind of gravitational waves Einstein@home seeks and how it looks for them.

Thursday, September 1, 2011

Free Books by Einstein on Kindle and a Request by "The Big Bang Theory"

I will get back to answering reader questions with my next post, but I wanted to mention some other things...

Free Books by Einstein on Kindle

I love to read (preferably books with vampires or other creatures that go bump in the night) and my Kindle has become something I am rarely far away from.  I am also frugal so I like to browse pages that list free or reduced cost ebooks (my favorite is eReaderIQ).  Today, I noticed that there are a number of books by Einstein that are free (if you don't have a Kindle, you can still download these books and read them on the Kindle app for your computer/smart phone):
I've only read all of "Out of My Later Years" but I have also read bits and pieces of most of the other titles.  I've always been impressed by Einstein's thoughts on a wide range of topics like religion and politics, even when I didn't agree with him.  I hope that you check these out to get a unique view of who Einstein was.

A Request by "The Big Bang Theory"

I recently received an email letting me know that the producers of "The Big Bang Theory" requested permission to use the "Gravitational Waves" poster I worked on with the APS.  The request went to the APS (as the publisher), they granted it, and forwarded the legal paperwork through channels to me.  By and large, the release is what you would expect but regarding how, when, and where the producers can use the poster it states:
"in any and all media whether now known or hereafter devised, in perpetuity, throughout the universe by Producer or its assignee."
"... Throughout the universe ..."  I suppose it makes sense to cover all your bases these days.  Evolving technology has made the wording of copyright notices ever more complicated and this kind of generalization seems to take care of that.  That's great, but I am not sure that the Earth laws this release is tailored to will hold up in Martian court :)

So, take a close look at the backgrounds on this season's "Big Bang Theory" and look for the "Gravitational Waves" poster.  It will be quite a thrill to see something that I worked on glimpsed on television and my favorite show to boot!


Thursday, August 25, 2011

Q: What are gravitons?

duhoc asked the following question in a comment to my post calling for reader questions:
I love cosmology and physics but understand very little about it.  What are gravitons, in simple terms? 
Gravitons can be complicated.  To that end, I want to state that I am no expert on the subject...  But maybe that's just right for a simple answer.  If my answer here doesn't do the job, let me know and I will track down a friend who researches quantum gravity or string theory to do a better job.

Gravity is one of the four fundamental forces, along with electromagnetism, strong force (which holds the nucleus of atoms together) and weak force (which is responsible for radioactive decay).  Every other fundamental force has a particle associated with it that communicates the force.  Electromagnetism has the photon, the strong force has gluons an the weak force has W and Z bosons (I know the least about these).  The only exception here is that gravity does not have a fundamental particle associated with it that has been observed.  However, it is safe to work on a theory that establishes the graviton as its communicating particle.  [Constructing theories by extending observations from similar situations to a new one that is not completely explained has proven effective before - the neutrino was a theoretical particle assumed to exist to account for the missing energy carried away in some forms of radioactivity and it was later proved to be true!]

One of the reasons that it is so difficult to directly detect the graviton is that gravity is the weakest of the fundamental forces (even though it holds the Universe together - that's because there is no negative mass and we don't know why that is either).  The weaker the force, the more effort there is needed to detect it.  For the graviton, it isn't a lack of motivation on scientists' part but a limit on technology... Just the contamination shielding for a detector the size of Jupiter, which would let us observe a gravitation once every 10 years, would be so massive that it would collapse into a back hole.

So, instead of observing the graviton directly, we can observe the effects of gravitons and gain knowledge about the its properties.  One of the most promising ways is by observing gravitational waves (and I know a lot about this!).  You may (or may not) have hear that we expect gravitational waves to travel at the speed of light.  The reason we expect it to is that we expect the graviton to be massless and massless particles cruise through the Universe at the speed of light.  But, if we detect a gravitational wave and it takes significantly longer the the time light would take to travel between the LIGO detectors and her international partners, then that would imply that the graviton has mass.  Think about that for a second...  Gravity exerts forces between masses and if the particle that communicated this force has mass itself, that can really complicate things.  There are theoretical physicists who spend their careers thinking about what if some detail of general relativity that hasn't been thoroughly verified is different than we think; what would be the consequences of that?  They know and they have more complicated theories worked out and the results of a massive graviton has been pondered by them as well.  Again, I am not a theoretical physicist but I do appreciate the complications involved.  However, one property of the Universe that has been shown time and time again is that the simple solution is usually the correct one which is why we say the we expect gravitational waves to travel at the speed of light.

There are some really interesting theories in cosmology that focus on the graviton.  For example, in string theory it is theorized that our Universe lives on a brane inside a higher dimensional bulk (where there are more dimensions than length, width, depth and time).  Here, gravitons are able to travel to other branes (universes).  If this theory is correct, then this could explain the missing mass in the Universe we call dark matter.

I like to include pictures with each of my blog post to help keep things interesting.  But, since the graviton has never been observed I haven't been able to find any strictly scientific images for this post.  However, if you would like a graviton of your very own to cuddle with, the Particle Zoo (which sells stuffed versions of elementary particles) has one you will be attracted to (ha, ha...  get it?):

I'm not endorsing or advertizing this product, I just thought it was interesting.
I hope this answers your question.  If not or if you anyone has more question, feel free to leave a comment below or ask me on Twitter @livingligo.

Friday, August 12, 2011

Q: What Was/Will Be the Detection Range of Initial/Advanced LIGO?

REMINDER: I DO NOT speak for the LIGO Scientific Collaboration or the Virgo Collaboration.  Therefore, these answers are mine alone as are any mistakes.

@vicnice137 asked the following question:
What's the effective range for LIGO? and for adv LIGO?  Will it include Virgo Cluster?  
The answer to this includes calibrations (which are fundamental to any experiment), astronomy, and General Relativity (I promise, no math).

First let's talk about calibration.  Any time you do an experiment, you use an instrument to measure something and before you can make statements with any confidence about your result, you need to know exactly how your instrument responds or works.  For LIGO, that means we need to understand how the light at the output of LIGO (where the interference pattern between the arms and gravitational waves are observed) changes when the mirror moves a known amount.  This is a bit more complicated than it sounds since there are feedback systems in LIGO that serve to keep the mirrors still (mostly to cancel vibrations of the mirror from our environment).  There are measurements that are made at the beginning and the end of each science data run that are used as reference characterizations of these feedback systems and there are measurements of small vibrations with a specific frequency that are purposefully and continually applied to the mirrors to characterize the calibration of LIGO at a given time.  (These calibration vibrations only affect our ability to detect gravitational waves at that specific frequency.)  Together, this information allows us to convert the intensity of the interference pattern LIGO produces into the change in length of LIGO's arms (which is what a passing gravitational wave will induce).

Now that we understand how LIGO responds to passing gravitational waves, we need to establish a reference gravitational wave that we will use to talk about how far out into space we would be able to detect that specific gravitational wave.  This reference source is known in traditional astronomy as a standard candle.  There are four main kinds of gravitational waves:
  • binary inspiral mergers (like 2 dense stars, 2 black holes or a dense star/black hole pair that orbit each other rapidly and then merge to become one), 
  • continuous gravitational waves (like from deformations on otherwise spherical rotating stars),  
  • stochastic gravitational waves (weak gravitational waves from many sources at once; perhaps the relic gravitational waves from the Big Bang), and 
  • burst gravitational waves (these are short gravitational waves from previously unknown sources or sources that are not well modeled - like what happens inside a star as it collapses right before the bright burst of light from a supernova).  
Since there is more than one kind of gravitational wave to choose from, we need to establish a priority and LIGO's priority is that:
  1. The gravitational wave should be from a source we theoretically know very much about.  That is, a simple system that produces a well characterized gravitational wave.
  2. The gravitational wave source should be abundant in the near Universe so that we can reasonably expect to detect it as one of the first direct gravitational wave measurements.
From these priorities the binary inspiral mergers stand out since bursts are inherently unknown, stochastic gravitational waves are inherently weak and the population of sources that produce continuous gravitational wave is not well established.

Now that we have settled on a source, we want to use a pair that is representative of the source but not exceptional in strength (otherwise, we would be overestimating how far out into space we can realistically expect to detect these gravitational waves).  LIGO chose a 1.4 solar mass neutron star paired with another 1.4 solar mass neutron star (FYI: 1.4 solar masses is on the lower limit of the expected mass of a neutron star so LIGO picked a very conservative measure for our detection distance measure).  Since General Relativity tells us how strong a gravitational wave this source will produce with respect to how far away the source is, we can combine this with our calibration (or current sensitivity) of LIGO to establish how far into the Universe we can expect to detect this representative gravitational wave.

This is such an important measure to us, that we constantly measure this value and project it on the wall at each of the control rooms in LIGO (there are 2 LIGOs: the one I work at in Louisiana and the other in Washington state).  By glancing at this and other figures-of-merit, we can quickly assess how the detector is working at that time.  Below is an example figure-of-merit that shows how far away we could detect two 1.4 solar mass neutron stars inspiraling:

The green line represents the detection range for the LIGO here in Livingston, Louisiana (known to us as L1) and the red line is other range of the LIGO detector in Hanford, Washington (known to us as H1).  The horizontal axis shows what time the measurement was taken (going back in time moving from right to left; the far right [Time = 0] was when this plot was produced) and the vertical axis measures the distance into space in Mpc (megaparsecs).  Parsecs are a somewhat odd unit of distance to anyone who doesn't study astronomy but it is equal to about 3.26 light years.

During the last data run with LIGO before the advanced LIGO upgrades began, you can see from the plot above that we were able to detect our neutron star pair out to about 20 Mpc or 65 million light years.  This did indeed encompass the Virgo Cluster of galaxies (which are between 53.5 and 54.1 million light years away).  However, LIGO was not able to maintain this detection distance all the time (you can see on the plot above that starting at about -1.5 hours the L1 range dropped from about 20 Mpc to about 15 Mpc - this was due to increased seismic activity in the region that was beyond our control).  Since the Virgo cluster is located at about 16.5 Mpc, you can see that it was not always within our detection range.

Advanced LIGO will increase our sensitivity, and therefore our detection range, by 10 times.  Once advanced LIGO reaches its design sensitivity, we will be able to detect our standard candle gravitational waves out to about 200-300 Mpc (or 650-978 million light years).  This will enable us to see 1000 times more of the Universe (since volume is proportional to the radius [distance] cubed and 10x10x10 = 1000):

Each dot in this illustration is an entire galaxy, not just a star!
It is also important to consider the limitations of this detection distance since we are limiting ourselves to thinking about only one particular kind of gravitational wave.  For example, I specialize in searching for burst gravitational waves.  These were not chosen as our standard candle because we don't know much about them (we like to call them the gravitational waves that go bump in the night).  But to apply the detection distance measured in our figure-of-merit based on a different class of gravitational waves would be short-sighted since bursts could very well be stronger (gamma ray bursts are some of the most energetic light signals astronomers have observed and, not only do we not know what causes them, many of them are VERY far away).  When we use a catalog of galaxies to target our burst searches (after all, a gravitational wave is much more likely to come from an area on the sky containing a galaxy unless we lucked out and had a nearby gravitational wave from our own galaxy), we include all known galaxies up to about 2.5 times the standard candle detection range (about 50 Mpc, or about 163 million light years).

I hope this answered this questions satisfactorily!  I know this is a bit long, but I wanted to be thorough and explain as much jargon as possible.

If you have questions about this or anything else, feel free to ask in a comment below or send it to me on Twitter @livingligo!

Thursday, August 11, 2011

Questions to be answered...

Wow... I can't believe the response that I got to my open call for questions!  I am so happy to see the interest in LIGO (and science in general) and I'm eager to start answering questions.  Here is the list of those that I have so far and who asked them (if you are unfamiliar with Twitter, the screen names listed after the @ sign are people who asked me questions through Twitter; otherwise the screen name is what was used to post a comment to my blog post):
duhoc - I love cosmology and physics but understand very little about it.  What are gravitons, in simple terms?  Answered on 25 August 2011

@AstroGuyz - You know the question on every science bloggers' mind is the Big One; "When will LIGO discover gravity waves?"  Are the prospects for gravitational wave detection good before AdLIGO goes online?  Think we'll nab it before the Higgs? Answered on 4 November 2011

@umbonfo - What about the Citizen Science project Einstein@Home? I'm running it but I don't know which GW data it's analyzing.  Answered on 22 September 2011

@HughScot - What do you hope to discover about gravitational waves that will help mankind in the future?  Answered on 26 January 2012

David Dickinson - Am curious if any "spin-off" discoveries are expected from the discovery of gravity waves... (i.e. exotic objects, new cosmological theories etc) 

@EclipseMaps - What are consequences for theory of gravity/relativity if null results for gravitational waves after extended observations?  Answered on 11 November 2011
@vicnice137 - What's the effective range for LIGO? and for adv LIGO?  Will it include Virgo Cluster?    Answered on 12 August 2011
ADDED 12 August 2011:
BDR - On the twitter feed it says LIGO/you look for space-time ripples; is that something that occurs naturally? If there was some kind of intentionally produced ripple effect (for time travel, maybe, or maybe just galaxy/universe disruption), would it be possible to tell that it was created by another being as opposed to a natural occurrence? Would it be possible to disrupt the universe with a big or chronic enough space-time ripple? I must know these things; tia.

I promise that I will address each of these questions in the coming weeks (and I will be sure to contact the inquirer when I answer their question so that they don't miss it).  As always, feel free to send me a question anytime and I will be happy to try and answer it on this blog!

Come back tomorrow and I will answer one of these questions (I haven't decided which one yet).  I may not answer them in order since I like to make sure I am giving you the clearest most accurate answer I can which may include consulting with colleagues.  

Today's picture - Advanced LIGO input beam tubes arriving on site at Livingston (yesterday):

These tubes replace ones that were a smaller diameter in Initial LIGO.  We now need bigger tubes to accommodate the new upgrades near the input of the laser into the detector and near the output.

This picture is from the new LIGO - Livingston Facebook page.  If you are interested in knowing more about what is happening, like us and you will see updates in your News Feed.

Tuesday, August 9, 2011

What Do You Want to Know About?

In all of my posts so far, I have talked about my day-to-day life as a LIGO scientist (which is the point of the blog after all).  That means I tell you about the things I think are interesting (otherwise I wouldn't be writing about them).

This time, I would love you hear from you!  What do you want to know about?  I can tell you more about becoming a scientist, answer questions about my research or general questions about LIGO and gravitational waves - whatever.  Let me know what you want know!

Post what your interested in as a comment below or tell me on Twitter @livingligo.

Below is a picture of me in my office not two seconds ago as seen from my laptop's webcam:


Friday, August 5, 2011

Using Astronomy to Teach Physics Workshop and AAPT Summer Meeting

I've just returned from a week long trip to Nebraska for 2 conferences, one in Lincoln and the other in Omaha.

Using Astronomy to Teach Physics Workshop:

The Lincoln trip was for a special workshop on Using Astronomy to Teach Physics (UATP).  The goal of this workshop is to bring educators in physics and astronomy together, share the information on the state-of-the-art science projects in their fields and then breakout into small groups to identify ways to bring this frontier science into the undergraduate physics curriculum.  I put together a professional poster (see my post on the different types of posters for more information on scientific posters) on the educational work done in the Science Education Center (SEC) at LIGO, both locally and nationally as part of the LIGO Scientific Collaboration's Education and Public Outreach (EPO) group [this group has just announced its partnership with the 2012 US Science & Engineering Festival].  (I will put a link to this post as soon as it becomes publicly viewable.) While I was making this poster, I found pictures of all of the SEC staff and myself engaging students and the public in some way.  For my picture, I found one that I adore (which is shocking since I hate nearly all pictures of myself) that shows me talking to school students while giving a tour of the LIGO control room:

I found this workshop particularly interesting for 2 reasons: 1) there were talks on the different frontier astronomy projects to make sure everyone in attendance at least had a working knowledge of what the state-of-the-art is and 2) there were breakout sessions where groups who were interested in similar goals met to discuss actionable ways to incorporate the new astronomy into the undergraduate physics curriculum.  My big project that I am now working on as a direct consequence of this is a document I intend to publish in the American Journal of Physics on connections between the basic physics concepts taught in the undergraduate physics courses and the technology that makes LIGO possible.  For example:
LIGO is looking for gravitational waves that will change the length of its 4 km arms less than 1/1000th the diameter of a proton (that's 0.000000000000000001 meters).  At this length scale, one must consider the effects of quantum mechanics.  So, here's the issue: the thermal vibration of the atoms in the mirrors used in LIGO is going to be much bigger than the "big" gravitational wave cited above.  How can LIGO possibly hope ever detect gravitational waves distinctly from this thermal mirror vibration?  (The 'no math' answer is at the end of this post.)  
After publication of this document, I am thinking about approaching LIGO's EPO group to propose that we create a web site to support this kind of effort.  Basically, I would like to take the document apart and use it to make a skeleton for the web site.  Then, any time a LIGO member has a homework question, activity, etc. that they use in their classroom, they can contribute that content to the site so that anyone who is interested can also use that content.

AAPT Summer Meeting:

After 3 days in Lincoln, I then went to the American Association of Physics Teachers (AAPT) Summer Meeting in Omaha.  There I got to make new friends in the Physics Instructional Resource Association (PIRA) and we did something together just about every night (which, if you know me, is remarkable since I am the type to hole up in my hotel room during down time).  I also co-presented an invited talk on LIGO outreach using demonstrations with my colleague Kathy Holt.  Demonstrations are really at the core of the outreach we so since we do demonstrations with teachers and give them the tools they need to take those demonstrations back to their classrooms, we do demonstrations during public open houses and there is often a demonstration or two when we work with student field trips.  It was great doing this talk with Kathy since the combination of our backgrounds (she was a teacher before working at LIGO) give different and useful perspectives on what we do in the SEC.

Then, besides going to other talks, I also had some academic service obligations.  I believe that I have mentioned that I am on the APS Forum on Education (FEd) Executive Committee.  Even though the AAPT is not affiliated with the APS, they work together closely since they both serve physicists but with different focus.  Because of this, the AAPT Executive Board meets with the APS FEd Exec. Comm. to coordinate efforts and we had a good lunch meeting this year.  I am also on the AAPT Committee on Graduate Education in Physics and this committee also met to make plan for the upcoming AAPT Meetings and to discuss the broader impact activities we are undertaking.

In past blog posts, I have included pictures of the city I happened to travel to as seen from my hotel window (see Long Beach, Milwaukee, Anaheim).  The view out of my window was a horrible view of a parking lot and another hotel.  Fortunately, the view from my colleague's room was much better (she got a room in the main hotel for the conference and I didn't since I waited too long to make my reservations).  So, here is the view of Omaha from the window:

OH!  One more thing...  When I was flying from Omaha (whose airport in actually in Iowa), the north terminal of airport of evacuated for a "suspicious package".  Luckily for me, I was flying out of the south terminal.  Once I got home, I found out that the hours long closing was due to someone's physics classroom apparatus that got TSA's panties in a bunch (it went through security as a carry-on).  I suppose it's good that they were awake enough to think something suspicious but what concerns me is that it is almost a certainty that the same thing was carried on the plane to get to the meeting at all.  I guess it wasn't as threatening then :) 

Answer to the quantum mechanics question posed above (highlight text below to uncover the answer):

The thermal vibration of the mirror's atoms would indeed make it impossible to measure a gravitational wave only if the laser was so well focused as to only shine on the area of a few of the mirror's surface atoms.  Fortunately, that is not the case in LIGO!  The beam spot on the mirror is about 10 cm (4 inches) in diameter.  In that area, there are MANY surface atoms that are vibrating.  By observing this large area, LIGO effectively averages over the vibration of all of the atoms that the light falls on yielding a zero net motion.  Thus, LIGO works just fine!

Tuesday, July 19, 2011

Academic Genealogy

I think that I have mentioned in other posts in this blog that one of my hobbies is genealogy.  I am planning to write more on my family history someday (it's always fun to find a great-grandfather in the state penitentiary when doing a census search) but I wanted to talk a little today about my academic genealogy. 

When earning an graduate degree in an academic field, one normally had an advisor that mentors the students in their research.  So, you can trace back through time who your advisor's advisor was and so on.  Normally, a modern student has only one advisor unless their research is interdisciplinary or other reasons.  Therefore, unlike a normal family tree where each child has a mother and a father, an academic genealogy doesn't branch as much.

I have done some research in the past on my academic genealogy.  My doctoral advisor was Lee Samuel Finn at Penn State and his advisor was Kip Thorne at Caltech.  On my own, I was able to trace my academic genealogy back about 10 'generations'.

Recently, I found the Mathematics Genealogy Project (MGP).  This work by North Dakota State University tracks the academic genealogy of mathematicians both their 'ancestors' and their 'descendants'.  Lucky for me, physics is closely related to mathematics (after all, Newton did pioneer calculus in order to do his physics) and my immediate academic family is documented in the MGP.  I found my advisor and started moving back through my ancestors.  It was amazing going back in time like this!  My academic genealogy goes back through 7 centuries to the High Middle Ages (essentially the founding of universities in Europe) and spans the fields of physics, astronomy, mathematics, chemistry, biology, medicine, philosophy and theology.  Before my academic great-grandfather all my 'ancestors' were educated in Europe, mostly in Germany, Austria, France and Italy.  And while this is not at all surprising, I am the only female in the tree (if you click on the poster sized image below, it will be a 6 MB JPEG; you can view the < 1 MB PDF here):

Warning: Clicking on this image will load a 6 MB JPEG.  Click here for the < 1 MB PDF.

Some of my academic ancestors of note (just the historically significant names I am familiar with):
  • Nicolas Copernicus - known for heliocentrism (a system where the Sun is the center of the solar system) which was in opposition the accepted geocentrism (a system where the Earth is stationary and the center of the Universe).
  • Christiaan Huygens - known as the first theoretical physicist, Huygens is also known for explaining Saturn's rings, wave theory and centrifugal force, among other things.
  • Jacob Bernoulli - known for discovering the mathematical constant e (2.71828...) among other mathematical contributions.
  • Johann Bernoulli - known for his development of infinitesimal calculus and other mathematical contributions
  • Leonhard Euler - mathematician and physicist who made contributions to many sub-fields including mathematical notation (e.g. using the Greek capital sigma as notation for summation), graphing and astronomy.
  • Joseph-Louis Lagrange - known for development of the calculus of variations and Lagrangian mechanics among other things.
  • Jean Baptiste Joseph Fourier - known for the series approximation for discontinuous functions and related transformation that are both named after him, he also was the first to discover the greenhouse effect.
  • Siméon Denis Poisson - known for the Poisson distribution which described the probability of a regular event that has no memory (dependency) on the events that happened before the present, among many other contributions to mathematics and physics.
  • Johann Peter Gustav Lejeune Dirichlet - mathematician credited with the modern formal definition of a function.
  • Jean-Baptiste le Rond d'Alembert - known for his contributions to fluid mechanics and testing for the convergence of a series, among other things.
  • Pierre-Simon Laplace - known for work in celestial mechanics (especially work concerning the stability of the orbits in the solar system), the dependence of the speed of sound on temperature, and was also the first to expound upon an object similar to a black hole, among many other things.
So, what does this illustrious heritage say about me?  NOTHING!  Even if you are mentored by the best, it is ultimately up to you to establish and prove yourself.  However, it is humbling to have any connection not only to history but to the science that I've been using for many years.

If you are interested in learning more about academic genealogies and why they are documented in the article "A Trace of Greatness" from the Times Higher Education (6 May 2010).

Monday, June 27, 2011

Slaying My Own Dragons

I haven't written in a while.  I've been working and traveling but that isn't why I haven't been writing.  I've stayed away because I have recently been dealing with my own personal demons (which surface for me at least on an annual basis)... 

When I first started this blog, I promised a look into my everyday life as a LIGO scientist.  Almost everything that I have shared has been positive and, truly, that is how the majority of my life passes - I am blessed beyond my dreams and I love my life and my work.  However, there are the other days where I feel like nothing I've done has amounted to anything other than keeping me busy.  Deep down, I know that isn't true but I have a horrible way of marginalizing everything I do.  Basically, if I did it then anyone could have or it wasn't meaningful.  This is a well known phenomenon called the Impostor Syndrome.  I've heard about this is various places; I think most recently it was in regard to women in physics but this is a widespread phenomenon in both genders. 

Honestly, I am hesitant to even write about this here.  Physics is a competitive profession.  I feel like a person's worth is usually judged on what you've done lately.  I am always afraid that I haven't accomplished enough to not be forgotten let alone respected.  And with my job being a temporary (I am a postdoctoral scholar - this is much like when a medical doctor goes through residencies after earning their medical degree) and on a yearly contract, not constantly earning respect means that I could lose my job all together.

It isn't something that I discuss with my co-workers; after all these are the people whose respect I am trying to earn and maintain.  I don't even bring it up to my friends because, since I really don't have much of a life outside of work, my friends are also physicists - sometimes even people I feel are my competition.  On my latest trip (to Santa Barbara, CA for the APS Executive Board retreat), I did bring this up in conversation over dinner (I felt more comfortable around these physicists since they are not in the same research circle as myself and I rarely see them).  As soon and I mentioned I'd been dealing with a bit of Impostor Syndrome the immediate response I got was, "We all feel that way."  At that, I didn't know how to respond since I was surprised at how open this person was with me.

So, how do I go about slaying this dragon?  Well, the first stage is messy and usually involves much anxiety and panic about the difference between what I feel I've accomplished and what I should have accomplished.  This then moves into a planning phase where I decide what I am going to do and is followed by a series of email feelers to people I need to collaborate with to perform the work.  By this time, I have usually exhausted myself (at least emotionally) and I wait for responses from collaborators.  If they are prompt, a new determined calm can begin to take root; otherwise, the anxiety increases again.  I start thinking, "Wow, I was right and everyone thinks so little of me that they don't want to work with me!"  (Note to self: next time check your spam filter before you flip out again.)  With a new plan of action intact, I get to start the cycle of the Impostor Syndrome again: "I have all this great work to do but I don't think that I am talented enough to complete it."  But, I plug away at it, complete tasks and rarely acknowledge what I've done.

The one good thing that comes from these episodes of mine is that it jump starts new projects for me.  It also reminds me of how lucky I am to have my husband since he is the only person with whom I share this insecurity.  The poor guy is my sounding board for all of the anxiety I've built up and there really isn't anything he can do for me.

A double rainbow taken from the LIGO Livingston Observatory parking lot on 30 June 2008.

This is a good article on the Impostor Syndrome: Laursen, Lucas, "No, You're Not an Impostor", Science Careers (15 February 2008).


Revised Erdös Number: 4

A friend of mine read my last blog post and showed that both of us (as members of the LIGO Scientific Collaboration) have a lower Erdös Number (4) than I noted in that post.  Here are the references establishing this network:

1: Paul Erdős & Mark Kac
    Erdös, P.; Kac, M. "The Gaussian law of errors in the theory of additive number theoretic functions",  Amer. J. Math.  62,  (1940). 738–742.
2: Mark Kac & Theodore A. Jacobson
    Gaveau B.; Jacobson T. ; Kac M.; Schulman L. S. "Relativistic extension of the analogy between quantum mechanics and Brownian motion", Phys. Rev. Lett. 53 (1984), no. 5, 419–422.
3. Theodore A. Jacobson & Bruce Allen
    Allen, Bruce; Jacobson, Theodore "Vector two-point functions in maximally symmetric spaces", Comm. Math. Phys. 103 (1986), no. 4, 669–692. 
4. Bruce Allen & Amber Stuver
    Abbott, B.; et al. "Detector description and performance for the first coincidence observations between LIGO and GEO," Nucl. Instrum. Methods A 517 (2004), 154 – 179.

Thursday, June 9, 2011

My Erdös Number

Many people have heard of the "6 Degrees of Kevin Bacon" game, introduced in 1994, where you try to connect a famous person to the actor Kevin Bacon within 6 connections, e.g. X acted in a movie with Y who acted in a move with Kevin Bacon gives a Bacon Number of 2 for actor X and 1 for actor Y.  The idea of six degrees of separation originated in the early 20th century (of course, not with Kevin Bacon) when Frigyes Karinthy conjectured that any 2 people could be connected through at most 5 people.  This was the basis of the Small World Experiment in 1967 by social psychologist Stanley Milgram.

Long before the Bacon Number in the entertainment industry was the Erdös Number (you can also view the Erdös Number Project page) in mathematics.  Paul Erdös was a prolific mathematician authoring the most academic papers in history, many of those in collaboration with others (at least 1,525).  It became a anecdotal measure of prominence in the field to have a low Erdös Number.  So much so, that the American Mathematical Society has a tool to calculate your Erdös Number based on their database of mathematical papers (click here to go to the tool and select the "Use Erdös" button, try "Einstein, A" and you should see his Erdös Number is 2).  Studies seem to show that, if a person has a finite Erdös Number (meaning, have you published a paper with another author that you can use to start your connection), that number is at most 15 with a median number of 5.  It turns out that my number is 5:

1: Paul Erdős & Mark Kac
    Erdös, P.; Kac, M. "The Gaussian law of errors in the theory of additive number theoretic functions",  Amer. J. Math.  62,  (1940). 738–742.
2: Mark Kac & Subrahmanyan Chandrasekhar
    Chandrasekhar, S., Kac, M., Smoluchowski, R., "Marian Smoluchowski: his life and scientific work. Chronological table and bibliography compiled by Alojzy Burnicki. Edited and with a preface by Roman Stanisław Ingarden", PWN---Polish Scientific Publishers, Warsaw, 2000. 141 pp. ISBN: 83-01-00671-4.
3: Subrahmanyan Chandrasekhar & James B. Hartle
    Chandrasekhar, S., Hartle, J. B., "On crossing the Cauchy horizon of a Reissner-Nordström black-hole",  Proc. Roy. Soc. London Ser. A  384  (1982), no. 1787, 301–315.
4: James B. Hartle & Kip S. Thorne
    Thorne, Kip S., Hartle, James B., "Laws of motion and precession for black holes and other bodies",  Phys. Rev. D (3) 31 (1985), no. 8, 1815–1837.
5: Kip S. Thorne & Amber L. Stuver
    B. Abbott, et al., "Detector description and performance for the first coincidence observations between LIGO and GEO," Nucl. Instrum. Methods A 517 (2004), 154 – 179. 

Special thanks to Nathan Urban for finding this low Erdös Number for me (using the tool listed above) - the best I was able to come up with was 8 with a manual search.

NOTE:  I have a revised Erdös Number of 4 - see my next blog post.

Do you have an Erdös Number?  Post it and your connections as a comment below!

Random picture for today's blog: an honest to goodness black widow spider I found dead behind the LIGO Science Education Center today (in Louisiana):