For the Love of Spectra

by Kara Mattioli

Almost a year ago my research advisor and I decided to start a project that I initially thought was an exciting, but difficult, task. We had been discussing a research project that I was about to start working on, and my to-do list initially looked something like this:

  1. Help grow a material called graphene
  2. Study the graphene using a technique called Raman spectroscopy
  3. Figure out a way to make hydrogen atoms bond to the graphene (this is called “hydrogenating” the graphene)

The goal of my project was to learn how to study graphene using Raman spectroscopy, and then to use what I had learned to find out whether my graphene hydrogenations would work. At first, I didn’t know how to do any of the things on my to-do list. But I also had no idea of what was in store for me: working with awesome people, discovering a new subject that would fascinate me, and realizing that I love doing research.

I didn’t accomplish step #1 by myself. Instead, I found myself working with several other undergraduate students to learn how to grow graphene by a process called chemical vapor deposition. Two important questions had to be addressed: first, what is graphene? And second, what is chemical vapor deposition?

Graphene is a single layer of carbon atoms – it is incredibly thin, so thin that scientists call it a two-dimensional material because it barely has any thickness to it! The carbon atoms are bonded together and form little hexagon shapes. Chemical vapor deposition is a process where you start with a metal, typically copper or nickel, place it in a furnace, and then flow hydrogen, methane, and nitrogen gases over the metal surface while the metal is being heated. With the right amounts of gases and with the metal in a certain temperature range, you can actually grow a layer of graphene on top of the metal! It is a very cool process.

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Graphene is a single layer of carbon atoms bonded in a hexagonal arrangement.

The group of students that I was a part of was called the Graphene Factory, which is a research group formed in the Physics Department at The Ohio State University to give students an opportunity to create graphene for other researchers to study. We first made graphene on copper, but it’s hard to study graphene when it is on copper because the chemical properties of copper sometimes obscure the properties of the graphene. So we transferred the graphene onto silicon dioxide. Each student in the group had a different specialty, and mine was Raman spectroscopy. So to complete step #2 on my to-do list, I had to learn about Raman and what it actually measures.

There are many different types of spectroscopy – it is the study of light emitted from or absorbed by atoms and molecules. For Raman spectroscopy, you shine light from a laser at whatever material you want to study, and you study the light reflected from the sample. Light from a laser is at one wavelength and one frequency, but materials can reflect light at many different frequencies. Atoms in a material will absorb light at specific energies and then re-emit some of the energy. A detector collects the re-emitted light and a computer plots the intensity of light emitted at each frequency, creating a plot called a spectrum.

Raman spectroscopy measures the difference in frequency between the frequency of the laser light and the frequency of light emitted by the material. This difference is called the Raman shift.

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Raman spectroscopy measures a “Raman shift,” which is the difference between the frequency of the laser light (red) and the frequency of light emitted from the sample (black).

I took Raman spectra on our graphene samples and learned what the spectra were telling me about our graphene. That’s right – spectra are not just a display of different peaks! You can get a lot of information from them, and that is one reason why I think spectra, and especially graphene Raman spectra, are so beautiful.

Graphene Raman spectrum

This is a Raman spectrum of graphene. The Raman shift is measured in units called wavenumbers, or cm^-1, which is proportional to frequency.

The presence of the two big peaks, and the fact that the peak on the right is larger than the peak on the left, tells me that the material is graphene. The coolest part is that the peaks appear due to the vibration of carbon atoms in graphene that are bonded together. The carbon atoms vibrate side to side as well as up and down.

The width of the peaks tells me something about how many layers of graphene I’m looking at, and the fact that I don’t see a third peak before the first one tells me that our graphene is not damaged. Sometimes if carbon atoms are missing or if other molecules are bonded to the graphene surface, the graphene can have many defects and be unusable. And those are just a few of the pieces of information I get from looking at a single spectrum!

Modern art graphene Raman spectra

Sometimes just for fun I like to make what I call “modern art” versions of my spectra!

I studied lots of graphene Raman spectra to learn as much about our graphene as I could. Then came step #3 – trying to hydrogenate graphene. To do this, I place a graphene sample in a vacuum chamber, then heat the graphene and expose it to hydrogen. I’m still fine-tuning the hydrogenation details, but I did get to build my own vacuum chamber for this project, which was really fun!

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This is a picture of the vacuum chamber I built, which is circled in purple.

I take Raman spectra of the graphene before and after my hydrogenations to see if the “normal” Raman spectrum of graphene changed. Remember the extra peak I mentioned earlier that only shows up if the graphene is damaged? Well, when I try to hydrogenate graphene, I want that peak to appear! It means that the graphene structure would be “damaged” because it would not consist of just carbon atoms anymore – a lot of the carbon atoms would be bonded to hydrogen.

hydrogenated graphene image (Image from Science magazine)

When graphene has been hydrogenated, hydrogen atoms are bonded to one or both sides of the graphene. Source: Science

I really enjoy interpreting spectra and finding out what does and doesn’t work in an experiment. In many ways, my job is kind of like constantly solving puzzles, and I love it. I like viewing research projects as puzzles to be solved, and with that view the things on my to-do list are more like putting a few of the pieces together. I’m so glad that I have the opportunity to learn how to become a scientist, and to discover new things that I never suspected I would love so much.

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About Kara Mattioli

Kara Mattioli pictureWhile I have always loved science, I never imagined that I would become a physicist. I initially came to Ohio State as a pre-medicine biochemistry major and had my heart set on becoming a surgeon. I decided that I wanted to learn more physics, so I changed my major to physics and ended up loving it. My career interests changed from medicine towards pursuing a full-time career as a scientist. I’m now entering my senior year as an undergraduate at Ohio State, and I plan on applying to physics graduate school. In my free time, I enjoy reading, hiking, and visiting art museums.

Atom-smashing and Femtoscopy

by Christopher Plumberg

Hi! My name is Christopher Plumberg, and I’m a sixth-year graduate student in nuclear physics at The Ohio State University, studying relativistic heavy-ion collisions. Those last four words may be a bit unfamiliar, so let me break it down:

“Relativistic” = wicked fast. Like, 99%-the-speed-of-light fast. Let’s just say, don’t get caught doing that on the freeway.

“Heavy ion” = large atomic nuclei. You might have heard that everything around us—water, air, kitty cats—is made up of atoms. And if you’ve ever thought about what atoms are made of, you might know they have a big part in the middle (the “nucleus”) and an outer part (the “electrons”), and the whole thing looks a little bit like honeybees buzzing around their hive. The “ion” part is basically just another name for the nucleus after its electrons have been stripped away, and the “heavy” part means we’re looking at relatively big nuclei (like gold and lead), rather than “light” nuclei (like hydrogen and helium).

“Collisions” = smashing things together. But you probably already knew that.

So there you have it. My job is taking large atomic nuclei, and smashing them together, wicked fast. Sounds pretty cool, right? Well, to tell you the truth, my job isn’t quite that glamorous. I don’t actually get to do the “smashing” myself: there are labs that do this for me, like the Relativistic Heavy Ion Collider (RHIC) in Brookhaven, NY, or CERN in Switzerland. My real job, however, is slightly different: I try to understand how these atom-crunching collisions actually work.

Of course, this is what physics really is: trying to figure out how things work. And knowing this helps us to understand why physicists went to all the trouble of smashing these atomic nuclei together in the first place. If you want to understand how a toaster works, one way to do it is to simply take the toaster apart (after it’s unplugged!) and peek inside. It turns out, if you want to understand how the atomic nucleus works, you just take it apart and look inside it!

The only catch is that, in the nuclear case, the object of study is way too small for a screwdriver to pry it apart, so we have to settle for smashing the nuclei together. How does that help? Well, the physical theories that we use to describe how the atomic nucleus works can also tell us what should happen when we smash two of those nuclei together at nearly the speed of light. If what we see in the laboratory matches what our theories predict, we know we’re probably on the right track.

Of course, this doesn’t happen automatically: there’s plenty of math that goes into making the connection between a physical theory (like the theory for an atomic nucleus) and the results of an experiment (like smashing two nuclei together). Working to make that connection between theory and experiment is a large part of the job of a theoretical physicist…in fact, that’s what my job is: I use the theories of nuclear physics to try to predict what experimental physicists (the folks who help run the atom-smashing machines) will measure in their laboratories. Working out exactly what those predictions are requires a good deal of intense math, but fortunately, we have computers to help us do most of it (phew!).

A friendly sidenote: you may be thinking about a career in science, but find the “math” part to be a bit scary at times. And that’s totally okay: most scientists are not math geniuses. In fact, I used to be somewhat terrified by really difficult math myself. The thing I have found is, if you tell yourself that the math will be too hard for you, then you will probably find it overwhelming. But, if you pretend instead that math is like a secret message—written in a coded language, to teach you something about the world that no one else has ever figured out before—then math becomes much more exciting, and it actually becomes a bit easier, too. Of course, like any code or language, math has rules, and it often takes some practice to get really good at using them. Nevertheless, if you are willing to do some hard work, chances are that you will surprise yourself with how much you are capable of doing. So keep at it.

The special focus of my research has to do with ‘taking pictures’ of heavy-ion collisions (via a technique known as “femtoscopy”). Here’s how it works: when two nuclei smash together, they are actually travelling so fast that they crash right on through each other. In the process, some of their energy gets converted into new particles that fly away from the collision—particles that we can measure. These particles can fly away in any direction, but the rules of quantum mechanics tell us that these particles prefer to ‘clump’ together in a way that depends on how far apart they were when they were created. If we can measure the ‘clumpy-ness’ of the emitted particles, we can learn something about the size and shape of the collision.

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A rough picture of two atomic nuclei smashing through each other, and the leftover energy which converts to particles that fly away from the collision.

And now comes the really cool part: using femtoscopy has allowed me to explain some puzzling triangular patterns that experimentalists have noticed in their data. Some folks thoughts that these patterns only showed up because the collisions themselves were triangular in shape. However, I was able to show that these “triangles” are actually due to the way that the collision itself expands, giving us some important clues about the behavior of an exotic form of matter—known as the quark-gluon plasma—which is formed during the collisions, and which is one of the hottest topics in nuclear physics today.

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Some femtoscopic measurements of size and shape for some typical heavy-ion collisions. The “double-hump” curves on the top (in red) represent a kind of “elliptical” structure in the collisions; the “triple-hump” curves on the bottom (in blue) show that some “triangular” structure is present as well.

But there is still more work to be done, and the next big step might be made by a bright young scientist like you. Nuclear physics is still an active field of research with much to teach us about nature. So what will your contribution be?

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About Christopher Plumberg

ChrisAndAllysonMy name is Christopher Plumberg and I am a year or two from completing my PhD in nuclear physics at Ohio State. My undergraduate work was done at Eastern University in astronomy and astrophysics, in cooperation with Villanova University. When I’m not working on my research or learning something new about math or physics, I’m probably reading books on theology and philosophy of science, practicing the piano, or hanging out with my awesome fiancée, Allyson (who is pictured with me to the left).

Exploring Science Communication and Science Policy: My Trip to the AAAS Annual Meeting

by Rebecca Reesman

Upon beginning grad school people often have aspirations of being a professor at a university or being a researcher at a national lab. In the long run, less than half of physicists with PhDs will still be in academia, though many will be at national labs or working in industry. However, during my 3rd year of grad school I decided that physics research is not what I want to do long term.

After I complete my PhD, I plan to promote science and reasoning skills through a combination of policy development, education, and communication. My love for physics and mathematics has taught me a great deal about using data to make decisions. This is true whether it is about astrophysics or life. My dream is to help people understand and appreciate the world in which we live using science, data, and evidence-based reasoning. Being able to make sense of numbers, such as statistics, is important for thinking critically. Our country remains low in science education and high in innumeracy. Making learning and understanding science more accessible and desirable for the general public is a key component of my aspirations.

Consequently, I have been looking into many of the fellowships that are available for scientists to transition into policy. The big one is the AAAS Science & Technology Policy Fellowship. This fellowship takes PhD scientists and puts them in Washington DC to influence policy. There are two general tracks, the executive and the congressional track. The former offers you the chance to work in a national agency such as the National Science Foundation (NSF) or the Department of Energy (DOE), for example. The latter gives you the opportunity to work in a congressional office, assisting with science related issues. As a result I have decided I should familiarize myself with AAAS — which is the American Association for the Advancement of Science. AAAS is an international non-profit organization that, according to their website, seeks to “advance science, engineering, and innovation throughout the world for the benefit of all people.” AAAS is also the publisher of the prestigious journal Science. They are in the unique position of supporting all scientific fields whether it concerns policy issues, education, or enhancing communication between scientists, the public, and the government.  A short video about the fellowship program is included below.

Back in February I was able to attend the AAAS Annual Meeting in Chicago, Illinois. I was even fortunate enough to win the Joshua E. Neimark Memorial Travel Assistance Award from AAAS to present a poster on my research at the conference. The research I presented dealt with looking at gamma rays, or high-energy photons, interacting with ambient light from stars. This allows one to understand the history of when stars formed. Through this interaction I can also look for new particles interacting with gamma rays as they travel to detectors on/near Earth.

Chicago! The meeting was held at the Hyatt Regency hotel.

Given the size and scope of the conference, and the fact that the poster sessions were open to the public, I got to talk about my research with a wide array of people. This included talking to a high school biology teacher, something that doesn’t get to happen at a physics conference. It was very cool to share my research with people of such diverse backgrounds; the range of attendees allowed me to practice explaining my research at a multitude of levels.

Prior to this meeting I had only attended conferences and workshops that pertained to my subfield, astroparticle physics, and the differences were substantial. Workshops typically consist of 30-50 graduate students and post-docs. Conferences focusing on a particular subfield are likely to have a couple hundred attendees and consist of many technical talks. However, the AAAS Annual Meeting consisted of thousands of people from a wide array of backgrounds. It was far and away the biggest and most exciting scientific meeting that I have ever been to! There were technical talks in all sorts of fields from mathematics to biology, talks discussing getting more women in STEM fields, talks about the math of elections, and talks about the science of science fiction. A talk titled “Where’s my flying car? Science, science fiction, and a changing vision of the future” included Lawrence Krauss, a well known astrophysicist.

There were many talks about science communication, and in fact the first day of the conference was dedicated entirely to science communication! Session titles included “Engaging with Journalists,” “Engaging with Social Media,” (see video below!) and “Engaging with Public Programs.” The speakers have impressive resumes, including Paula Apsell who is the Senior Executive Producer of NOVA and NOVA scienceNOW on PBS, Danielle Lee who writes the Urban Scientist blog on Scientific American, and Ben Lillie who is the Director of The Story Collider.

I was particularly excited to see Danielle Lee there, as I have heard about her efforts of getting underrepresented minorities in STEM fields. In fact I spoke with her, one-on-one, afterwards and discussed some ways to improve the Society For Women in Physics group at OSU! She suggested we get in contact with STEM minority groups already established on campus, such as the National Society of Black Engineers (NSBE), and get involved with their activities. Here’s a link to watch all of the talks about science communication.

One evening I attended a mixer for past/current/future AAAS Science & Technology Policy fellows. This was an amazing opportunity that allowed me to learn about the exciting projects that fellows get to do. I made many connections through this event — this included meeting an alum of the Ohio State Physics Department, Gregory Mack, who is a current fellow working at the National Science Foundation. Greg gets to work on STEM outreach initiatives such as finding ways to convey new scientific findings to the public.

This conference got me excited for my future. I got to learn about more ways I can get involved in both science policy and science communication. I learned about companies that focus on bringing together scientists, policy-makers, and other stakeholders to facilitate dialogue on science-related policy issues. For example, a company called COMPASS holds workshops and training sessions for groups of scientists to develop these skills. Based on my experience attending this conference, I am excited about one day applying to the AAAS fellowship program, but I also learned about other opportunities to pursue a career that embraces science policy and science communication.

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About Rebecca Reesman

becca becca2My name is Becca Reesman and I am wrapping up my PhD in Physics at Ohio State! In 2009 I received my undergraduate degree from Carnegie Mellon University where I double majored in physics and statistics. I have a horse (Dandy) who has moved with me throughout my collegiate career; being able to ride on a regular basis has been an important part of my life.

A Night on the Mountain

by Kate Grier

My name is Kate Grier and I’m part postdoc and part Planetarium Director in the Department of Astronomy at OSU. That means I get to play two different roles in the department: In my role as a postdoctoral researcher, I spend my time measuring the masses of black holes at the centers of galaxies, and in my role as the planetarium director, I oversee all of the activity of our awesome, newly-renovated planetarium on campus. This week, I am putting on my research hat and escaping the cold Columbus weather with OSU graduate student Jamie Tayar to the sunny desert mountains of Arizona to collect data.

Desert mountains, like those found in Arizona, are perfect places for astronomers to put telescopes for a number of reasons: First, there aren’t many people around, so the skies are very dark. Second, deserts are known for being very dry, and we like dry climates because water molecules in the air interfere with our observations. Third, desert mountains are at high elevations, which means there is less atmosphere between us and outer space, which also helps us to get more accurate information about the stars and galaxies we’re looking at!

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MDM Observatory at sunset.

This brings me to the top of Kitt Peak, a mountain in Arizona that has a large number of telescopes at its top. OSU co-owns two telescopes on Kitt Peak at an observatory called MDM, which stands for “Michigan-Dartmouth-MIT” — the original owners of the observatory. One of these telescopes has a mirror that is 1.3m in diameter, and the other has a mirror that is 2.4m in diameter. Even the 1.3m, which is fairly small when compared with the largest telescopes in the world, weighs over 1000 pounds, and the entire telescope structure dwarfs us humans!

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The 1.3m McGraw-Hill telescope, with OSU Graduate student Jamie Tayar standing below

Now, follow me as I take you through a night of observing at the 1.3m telescope at MDM in March, on a beautiful, clear (but cold), early-spring night.

The Night Begins

5:oo PM — Before it even gets dark out, we must start taking “calibration data” in the afternoon. Astronomers don’t look through telescopes by eye anymore—we use CCD cameras (basically really expensive digital cameras) to take pictures of galaxies and stars and then save the pictures to analyze later. Because these CCD cameras are not perfect, we take many calibration images before the observing even starts so that we can account for any imperfections in the cameras.

6:oo PM The first thing we have to do is to make sure the CCD camera that we’re using stays cool. Warm cameras radiate their own light that interferes with the light coming down from the sky, so we cool the cameras down to about -165°F with liquid nitrogen (using liquid nitrogen as a coolant is also a really, really fun way to make ice cream). The liquid nitrogen itself is actually much colder than this—liquid nitrogen is about -321°F, but the insulation of the camera isn’t perfect, so it’s generally warmer than the liquid nitrogen itself. We have to make sure the camera never warms up much more than this, or we could have problems with our observations.

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Jamie filling up the instrument with liquid nitrogen to cool down the camera.

6:45 PM It’s sunset time! Watching the sun set from a beautiful desert mountain in Arizona is one of my favorite parts of observing. Sunsets in Arizona are spectacular, and sunsets at MDM observatory never disappoint.

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Me watching the sunset on a clear evening from MDM Observatory in March.

It takes nearly an hour after sunset before it is dark enough for us to take data, but after watching the sunset, we start getting the telescope ready to observe. We call this period after the sun sets “evening twilight,” when there’s still some ambient light in the sky.

7:45 PM It is now dark enough for us to observe! We start with a star to use for calibrations—we use a star that has had very detailed brightness measurements taken previously. Since we know how bright it should be, we can see how bright it looks to us, and use that to calibrate the brightness of all of our data.

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Me hard at work in the telescope control room

8:15 PM It’s time to observe our first galaxy! Tonight, we are looking at galaxies that are hundreds of millions of light-years away—specifically, we are looking at the centers of these galaxies. Each galaxy has a supermassive black hole that is millions or billions of times as massive as our sun. We watch the gas and other material falling into the black holes in these galaxies to learn about the black holes—specifically, by watching the gas move around the black hole, we can calculate how strong the gravity of the black hole is, which gives us a measurement of the black hole’s mass. Because these galaxies are so far away, they are faint and we have to take really long exposures to collect enough light, so we take three 20-minute-long exposures on each target. Throughout the night, we move to a new galaxy every hour.

10:00 PM Time for some star gazing. It’s important that we go outside and look at the sky often to make sure there are no clouds interfering with our observations, and on a beautiful, clear night like this, I am happy to go out and check out the sky! Out here, we can see the Milky Way up in the sky, and so many stars! It’s a beautiful night.

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The Milky Way galaxy, as seen from MDM. Photo taken by Matthias Dietrich.

12:30 AM Dinnertime! Since we’re on an observing schedule, our mealtimes are a bit mixed up. I woke up and had breakfast at about 3:00PM and had lunch right after sunset, so now it’s time for dinner! The dorm at the telescope has a mini kitchen that we use to cook food in, so we bring groceries up with us when we come up the mountain. We have to eat quickly, though—we can go eat food while the telescope is taking a 20-minute long exposure, but we can’t leave it for longer than that.

3:00 AM — It’s time for a 3AM dance party! This time of night, even after I’ve been observing for a few days, I tend to get pretty tired—it’s hard work staying up all night long. What better way to wake myself back up then by staging my own dance party inside the control room?

5:15 AM — It’s about an hour before the sun rises this morning, which means it will start getting light out soon. Sunlight will start interfering with our observations, so it’s about time for us to stop observing and pack up for the night. We return the telescope to its home position (pointing straight up), close the dome, cover up the mirrors, and once again, refill the container of liquid nitrogen so the camera doesn’t warm up during the day. Time to head in and go to sleep – successful night of observing!

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About Kate Grier

IMGP1046My name is Kate Grier and I am a recent PhD graduate from The Ohio State University (OSU). I grew up in the suburbs of Chicago and received my undergraduate degrees in both physics and astronomy from the University of Illinois at Urbana-Champaign. Having completed my PhD in Astronomy last summer, I am currently serving as the Director of the OSU Planetarium as well as carrying out postdoctoral research on supermassive black holes. I also love teaching and public outreach, and in my spare time I like to read, hike, and travel the world!

Science Stuck in the Middle: Lasers, Diamonds, and DNA, Oh My!

by Richelle Teeling-Smith

What does it mean to do ‘interdisciplinary’ research? Sometimes in research, you might find that your path to solving a specific problem leads you outside the traditional boundaries of the field you set out to study. That’s how my graduate school experience has gone and I’m not the only one!

I’m a fifth year graduate student at the Ohio State University and I am studying physics. However, unlike most graduate students, I work for three different advisors with three different specialties. All of us are technically in physics, but our work takes us outside of physics on a daily basis. I study the dynamics of single biomolecules, like DNA. I look at how DNA moves using a tool called nitrogen-vacancy (or NV) diamond. My work involves lasers, DNA, diamonds, gold, and magnetic resonance. I use physics, biology, chemistry, and engineering on a daily basis. Yes, it is as cool as it sounds!

Why are scientists so interested in studying the dynamics of single biomolecules? Who cares how a single molecule (like DNA) moves? Single-molecule measurements are becoming more and more popular in biophysics, biology, and biochemical and biomedical engineering because they allow us to clarify and better understand important biochemical processes such as protein-DNA interactions (transcription and translation), protein folding, and the functions of membrane proteins – and much more!

It’s important to look at a single molecule because so much information can be lost in measuring a large number of molecules together. If you take a pipette and suck up some small volume of your sample, you have moles of molecules! We’re talking 1023 molecules. That’s 23 zeros! When you measure a large ensemble you are averaging over the whole group and you lose important information. Imagine you are an alien studying the planet Earth. You want to understand the life forms that live on Earth and you take one snapshot that averages over all humans on Earth. What do you see? First off, this human is half male and half female. Weird right? Now what do they look like on the outside? Do they have hair? What color?  How tall are they? You get my point? One averaged human does not do a great job of representing us accurately.  Single-molecule measurements of these complex biological systems have allowed us to get a much more accurate and detailed view of what is going on in our bodies!

So why diamond?  And what do lasers have to do with this?

NV diamond is really a great tool. Have you ever heard of colored diamonds? Diamonds can be blue, yellow, or pink. These colors are caused by impurities in the diamond crystal. Normally, diamond is composed of carbon atoms arranged in a tetrahedral lattice structure. However, if you replace or remove some of these carbon atoms in a specific way, you can change the optical and electrical properties of diamond.

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Pink Nitrogen-Vacancy Diamond (image by Young Woo Jung)

NV diamond involves just that. One carbon atom is replaced by a nitrogen atom. Adjacent to that, one carbon atom is removed altogether to leave a gap in the lattice. These atoms form the NV center. This is what makes the NV diamond pink!

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Nitrogen-vacancy centers in the carbon diamond lattice. Nitrogen atoms are yellow, the vacancies are transparent, and the bond between the N-V is highlighted in pink. (Image by Young Woo Jung)

NV diamond has the unique electrical property that if you shine a laser on it, it will fluoresce. This means that it emits red photons. It glows red. No really… And NV diamond is a good measurement tool because this fluorescence can be controlled by external magnetic fields and microwaves. This is called magnetic resonance. We apply energy (in the form of microwaves) to the NV diamond sample. I use gold waveguides to do this.

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Gold waveguide (fabricated on a glass slide) and soldered to a copper mount to create a microwave circuit. 8 flow channels are placed across the microwave channel. This is where the DNA experiment is housed. (Design and image by Richelle Teeling-Smith)

I design a very intricate pattern in gold that controls the path and intensity of the traveling microwaves. At very specific frequencies, the diamond absorbs the microwave energy. This causes the electrons in the diamond to change their quantum state and ‘go dark’. You control the ‘dark’ frequencies of the diamond by applying magnetic fields to the sample. People have used this to measure small magnetic fields, or even measure a single electron and nuclear spin. This is the tool that allows us to track the dynamics of a single biomolecule in a magnetic field.

In the process of conducting this interdisciplinary experiment, I have had to become a jack-of-all-trades. I engineered and built my own microscope for imaging this diamond-DNA sample. This required learning how to design and utilize both the hardware and software needed to take this measurement. I’ve learned electrical engineering, mechanical engineering, and coding through trial and error.   I also design and fabricate my own waveguides (to supply the microwaves to the sample).   I’ve even become a bit of a biologist and a chemist. Biophysics is an inherently interdisciplinary field, as Morgan Bernier pointed out in her post.  To create my sample, I had to learn the chemistry and biology necessary to attach a single molecule of DNA to a piece of glass on the microscope objective, and also to attach a single nanometer-sized diamond to the other end of the DNA molecule.

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Schematic of the NV-nanodiamond attached to the end of a single DNA molecule. This experiment is conducted in a ‘flow channel’ where we house the DNA in solution and apply magnetic and microwave fields. (Design and image by Richelle Teeling-Smith)

This project is highly interdisciplinary. I regularly pull from the expertise of each of my three advisors (magnetic resonance measurements, optics and lasers, and biophysics) and I have had to teach myself a wide array of new skills to conduct this experiment. But as scientists move forward and push the boundaries of the incredibly small, incredibly large, and imperceptibly fast, research is by necessity becoming more and more interdisciplinary. More and more often, the solutions to our problems are beyond the scope of a single discipline and require specialized knowledge from multiple fields. Thinking across boundaries, and a willingness to take on any new challenge to solve a problem, are two important skills that will allow us to develop innovative solutions to our research problems.

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About Richelle Teeling-Smith

BlogPost_biophotoI grew up in Akron, Ohio.  I am the first woman in my family to earn a bachelor’s degree in any field.  I went to college at Kent State University in Kent, OH, and didn’t decide to go into physics until my sophomore year.  I graduated in 2009 with my B.S. and now attend The Ohio State University.  In 2011 I earned my M.S. in physics and I am now working on finishing my Ph.D.  I do research in experimental condensed matter physics and biophysics.  I study the dynamics of bio-molecules, like DNA, using impurity centers in diamonds. I am also a mother to a beautiful little girl.

The Only Woman in the Room

by the “A Day in the Life” Editorial Board

Most people probably suspect that physicists tend to be male.  The most well-known personalities in physics, both past and present, with the exception of Marie Curie, are men, from Albert Einstein and Richard Feynman to Carl Sagan to today’s Neil deGrasse Tyson.  Most of the physicists portrayed on the popular television show “The Big Bang Theory” are men.  But is this an accurate portrayal?  Is physics still mostly male?

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The famous 1927 Fifth Solvay International Conference on Electrons and Photons.
A message to Marie Curie – the only woman in the photo – you go girl!

Yes, it is.  While many other STEM fields have seen an improvement in gender balance in recent decades, the number of women entering physics has been rising much more slowly.

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Source: “Women, Minorities, and Persons with Disabilities in Science and Engineering,” National Science Foundation.

The OSU Physics Department is not atypical in this regard.  Here, there were four women out of 48 students who graduated with physics bachelor degrees in 2013.  The entering class of 48 physics graduate students included 12 women last year.  Out of approximately 55 professors, five are women.  Three of those were only hired in the past four years, and Prof. Connolly is the first female professor in experimental physics in the history of the department.

With such a small female-to-male ratio, at some point on a typical day a woman in physics often sees herself alone in a room full of men.  The first time that this happens in a young woman’s educational path, it can have a tremendous effect on how she views herself, physics, and her place in it, often very unexpectedly.  We would like to share our memories of the first time we were the only woman in the room along our physics path and the effect that it had on us.

Amy Connolly

I went to Purdue University for college knowing that I liked math and unsure what I would do once I graduated.  I took physics classes because I had done well in physics in high school and enjoyed it.  However, I just didn’t see myself as a scientist.  I had watched a lot of Bill Nye The Science Guy and Julius Sumner Miller (“Physics is my business!”), but I didn’t feel like one of them.

I was a sophomore in college the first time that I was the only woman in a class, and it was an Intro to Electricity and Magnetism (E&M) course with only about eight students.  I looked around and saw that I was the only woman, and it was such a mix of emotions.  I nearly panicked, while being really surprised at my response.  All kinds of questions went through my mind.  How on earth did I get here?   Can I possibly pass this class?  Do these guys already know everything about E&M while I know nothing?  If I take the class and don’t do well, am I doing a disservice to women everywhere?  Again, how did I get here?

I was very upset when I went home that day.  Now it seems so silly that I could have possibly thought that the guys in that class knew more about E&M than me.  That’s why we were all taking the class!  I think it even seemed silly to me then, but I couldn’t help but think it.

But I told myself I couldn’t quit then, I had to give it a shot.  So I studied hard for that class, learning the subject backwards and forwards, working every problem in the book.  I think I was overcompensating for this feeling that I had some sort of disadvantage.  As a result I got the highest grade in the class, and in the process I became hooked on physics.  I saw the math that I loved in a new light, as it so beautifully guides our understanding of the fundamental laws of nature.

But could I be a scientist?  The professor for that class encouraged me and helped me find a research position at Argonne National Lab that summer, where I got to participate in a beam test to calibrate a detector component for the ZEUS experiment.  I traveled to Brookhaven Lab and worked all-night shifts with my co-workers from Argonne, using the relativity equations that I had just learned that year, and changing the beam energy myself.  It was really fun.

After that summer I decided to go after the goal of becoming a physicist, and here I am.  At times when I am the only woman in the room I still have that question popping into my head “How did I get here?” but now I know that I got here by working hard at doing what I love, having luck on my side at pivotal moments in my career, and continuing on during those times when I felt very out of place.

Megan Harberts

The first time I remember being the only woman in the room came early in my science career.  As I have written previously, I was very active in science activities in elementary and middle school.  One of the things I enjoyed the most in middle school was Science Olympiad.  When I got to high school, I found out there was a team and started going to the after school practices.

However, I was the only girl and the only freshmen who was interested in the Science Olympiad team at the time.   No one excluded me directly, but it wasn’t as much as fun as when I was middle school. This was the first time I felt like I didn’t fit in with a group other people interested in science.

Since I was just starting out a new school, I was trying out lots of new things, including the swim team, which it turns out practiced after school at the same time as Science Olympiad.  I considered doing both, but since I didn’t really like going to Science Olympiad I just joined the swim team, which I did for four years and led me into my favorite sport, water polo.

I don’t feel like there has been a negative impact on my career because I didn’t join my high school Science Olympiad team.  I still took 5 different science classes in high school and decided to become a physics major in my junior year.  I do feel like because I encountered this experience so early it didn’t faze me much when I got to college where there were only a couple of girls in my physics classes of 30 people. I also came from a family where science was heavily emphasized.  My sisters and I have all ended up majoring in science in college, but I can see how somebody who doesn’t come from such supportive background might encounter a similar experience to me and let that feeling of not fitting in turn them away from science.

Personally this is something that I have been thinking about a lot recently: there are advantages I had growing up that helped me become a scientist and not everybody has those same opportunities.  Therefore all scientists should really consider how we can include people who don’t come from the same background as us and how we can encourage people of different genders, races, and economic status to become a part of the science community.

Meredith Meyer

I am still in high school at Columbus School for Girls, and so far the only certainty I have about college is that it will be co-ed. I have always been in classes with only women in the room, so I am a little anxious to experience a classroom with a majority male or all-male population.

Since I’ve grown up in an all-girl community, the first time I was the only girl in the room was pretty recently. During my summer research project, which I loved and which didn’t expose me to any discouragement, I saw, first-hand, that the statistics hadn’t lied. I was the only woman working in the physics group that summer.

I knew that women had worked in that group in the past, but that summer when we gathered for our weekly meetings, I was the only female. I wondered where all the girls were and why I was alone. I was having a lot of fun, and I thought, “Why wouldn’t more women want to be a part of this research?” At first, I was a little angry at my gender: why weren’t they there? However, I later thought about my fellow females, and that they haven’t been as lucky as I have.

I know that I am an irregularity: for the most part I’ve never really any negative experiences when it comes to math or science.  Looking around the room and seeing only men made me feel lucky that I’ve never had to face the underestimation and discouragement that I know a lot of women face every day, a factor that probably caused me to be the only woman in the room that summer.

My experience as the only woman in the room was eye opening for me, and I am glad that I experienced it amongst a group of really encouraging people who believed in me. I know that the next time I may not be so lucky, and I hope that when that next time does come around, I won’t give up; I’ll only try harder.

Nancy Santagata

My story must first begin with a confession: I am actually a chemist that masquerades around as a physicist.  Often my physicist colleagues express surprise upon learning of my true identity, to which I respond with a joke about stealthily sneaking in through an unlocked back door of the department so that I could play with the cool kids.  In my defense, my attempt to major in physics as an undergrad was foiled by the fact that the small private university at which I was a student did not actually offer a physics major.  I instead chose the next best thing, chemistry.

My class of budding chemists at the aforementioned small private university was 83% female, and if I remember correctly, the class after mine was 100% female.  We became a close-knit group, struggling through difficult homework sets and seemingly incomprehensible physical chemistry exams together.  Because the Chemistry Department was so small, I also came to know the female faculty quite well.  Both my professors and my classmates were supportive as I set off to participate in a summer research program hosted by the Chemistry Department at Penn State.  There, my primary mentor was a female graduate student.  I purposely highlight this strong female presence because, surrounded by so many intelligent women, never once in four years did I believe that I was incapable of academic success simply because I was female.

Over the course of my studies, my scientific interests quickly gravitated toward a branch of chemistry (surface chemistry) that is entangled with physics.  As graduation neared, my hunt for potential graduate schools narrowed its focus to a few specific surface chemistry groups whose research was insanely fascinating to me.  In browsing the website of one particular experimental lab, I couldn’t help but notice that every. single. person. was male.  However, in place of feelings of insecurity, intimidation, or doubt, I perceived a challenge.  I wanted to join the group, and I did, because I knew that I could be just as successful as my male peers.

Upon arrival at my new school, I learned that another female had joined the group at the same time, and over the years several others followed.  Graduate school certainly isn’t easy, but we stuck together and each of us achieved our ultimate goal, a PhD.

Fast forward to today.  As a postdoc, my lab mates (all physicists!) informally refer to me as Second-in-Command (only our faculty advisor ranks higher), and in the general chemistry course that I teach, students respectfully address me as Dr. S.  In both environments, I’m completely in my element, and hey, would you look at that, I just happen to be woman.  And so I help manage this blog and lecture on the physics of sports GRASP because I want to show young women that gender isn’t an obstacle to accomplishing your goals.  If I can do it, then you certainly can too!

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We leave you with an awesome selfie! From left to right: Nancy, Megan, Amy, and Meredith.

Beaming with Electrons

by Meredith Meyer

Research used to intimidate me. I’m still in high school, and I didn’t think that I could run experiments like the revolutionary ones I had read about. However, this summer, I ignored the daunting feelings that I linked with research, and I worked with graduate student James Perkins at The Ohio State University (OSU) in the Center for Emergent Materials (CEM) in Professor Brillson’s physics laboratory.

Before my research work began, I had no idea what to expect. I came across the opportunity through my high school, so I asked the student that worked in Professor Brillson’s lab last year, Jasneet Singh, who was the previous high-school board member on this blog and a year ahead of me in school, how she felt about her experience. She told me how fun and easy-going everyone was, but I still had trouble believing her, which I later found out was ridiculous of me.

I was extremely nervous my first day; all I knew was that I would be in a physics lab, and I was pretty sure we wouldn’t be dealing with mechanics—the only course I had ever taken in the subject. However, after weeks of freaking myself out, I walked into the Physics Research Building at OSU and met a few members of Prof. Brillson’s group. Unlike what I had feared, all the students were kind and understanding when I explained that I was clueless about their research. So, for my first few days, a couple of different graduate students taught me about the work they did. In the morning I read scholarly articles, and in the afternoon I clarified what I had read with the graduate students. (Coincidentally, now around six months after my research experience, my AP Chemistry class just began covering a few of the ideas I had to learn for my summer research project.)

I first learned about semiconductors, which have both conducting and insulating properties. I discovered that semiconductors have a band gap, which is the energy difference between the electrons held by the atom (valence band) and the electrons free to move within the material (conduction band).

I worked with zinc oxide (ZnO), which is a semiconductor used in computer equipment and detectors. The graduate student I worked with, James, had samples of ZnO doped with varying levels of magnesium (Mg) to create a new semiconductor with different conductive properties called magnesium zinc oxide (MgZnO). (Doping is a process in which you add another substance to a semiconductor to change its electrical properties.) Zinc oxide has a smaller band gap than magnesium zinc oxide (MgO), so when they were combined into MgZnO, one could theoretically control the band gap depending on the level of magnesium doping. Our purpose was to see how the levels of Mg affected the band gap in order to understand a way for future band gap control and widen its uses.

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The samples of MgZnO that I tested.

For the six weeks that I spent at OSU, a day in my life started with taking data. After a week of learning and training, I was responsible for running the experimentation on the MgZnO samples. Through a process known as depth-resolved catholdoluminescence spectroscopy (DRCLS), I could characterize the electrical properties of the samples of MgZnO with varying levels of Mg content. (DRCLS is a method in which an electron beam is shot at a sample to excite the sample’s electrons at varying depths into the sample, which depend on the beam energy because at higher beam energies, one tested deeper into the sample. The excited electrons would then emit energy in the form of light, and we looked at this light energy to characterize the sample.)

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The equipment I used to run DRCLS. On the left is what the equipment I used looked like with the lights on, and on the right is what it looked like with the lights off, which is how I ran the experiment.

Every morning I spent my days in a dark lab (since we were looking at the light released, we couldn’t have any outside light interfering), and I took data on at least two spots on each sample at 25 different beam energies. The equipment I got to use to run DRCLS looked like it was straight out of Star Trek: The Original Series, and when I messed with the dials to change beam energies, I felt like I was the star of a science fiction movie.

After I collected data in the morning, I returning to the office and looked through the data for James. I found the spots of the data that represented major defects or the band gap energies. Then I shared my findings with James and eventually Professor Brillson, who was thrilled to see that we found that as we increased the level of Mg, the band gap widened, but the number of electrical defects decreased and then increased once we had more than 50% Mg.

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An example graph of the data I took on a sample of MgZnO with DRCLS.

At the end of my research project, I presented these findings to a group of graduate students, OSU professors, and  students and teachers from my high school, and my mentors are submitting my research to the scientific journal Applied Physics Letters in a paper that will list me as co-author.

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A group picture of the OSU professors and the students from my high school that participated in summer research. That’s me with the long black hair! Source: Columbus School for Girls

At first, I was extremely apprehensive about research. I thought I would mess something up and ruin the entire study, or I wouldn’t be smart enough to actively participate. However, I discovered that my fears were irrational. Everyone I met was encouraging and understanding: they were patient as I struggled for a few days to understand band gaps and DRCLS, and even though I began my research with knowing only a simple definition of what a semiconductor was, I ended up feeling confident in the background information of all my work. I think I learned more about physics in the six weeks I spent at OSU than the full year class I took at my high school. After this summer, I know that I want to participate in some kind of research during my undergraduate years, for example, biological research related to neuroscience to coordinate with my passion for medicine. My experience with physics taught me that I love to experiment, and, more importantly, I am no longer intimidated by research one bit.

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About Meredith Meyer

BioPictureI am a senior at Columbus School for Girls (CSG). I was born and raised in Columbus, Ohio, but I am excited to leave my hometown for college next year! I love to read, watch TV (too much according to my parents), play field hockey, and work on my school’s FIRST Robotics Team, which I am a captain of this year. I’ve always wanted to become a doctor, but I am keeping my options open for my future college major—maybe I will choose physics!

Physics Education Research: The Science of Teaching Science

by Brendon Mikula

Physics is, to a first order approximation, the math of how the physical world works. It is a class that many struggle with. Those of you who have taken physics may have found yourselves sitting in class confused, wishing this whole physics thing made more sense. Well, your wishes are being answered by Physics Education Research (PER).

In PER, researchers use scientific principles to test and make conclusions about how students learn physics, as well as how physics is best taught. Given how scientific physicists generally are, you’d be surprised how long it took them to start applying the scientific process to their own teaching! PER research comes in many flavors and is conducted with students anywhere from middle school to graduate school.

This research is where I come in. I have always had a passion for figuring out how the world works, so I got my bachelors degree in physics. Many of the teachers in my own education were an inspiration to me and my learning, and I would love to do the same for others, so PER seemed like a perfect place for me.

To give you an idea of what Physics Education researchers do, I’ll walk you through one of my favorite projects. One of the benefits of education research is the ability to collaborate with people in other fields, and this project is focused on engineering students.

The first step of any education research is to find a research question to ask or to choose a student difficulty to address. Research by a previous student in my group had discovered—much to the surprise and dismay of professors in engineering—that introductory engineering students struggle with basic skills that are essential to becoming an engineer. An example of the skills mentioned is being able to read values off of a logarithmic scale. Logarithmic scales are a lot like linear scales with one big difference: instead of each step up the number line adding a constant amount (i.e., 1, 2, 3, 4…), each step up the number line multiplies by a constant amount (i.e., 1, 10, 100, 1000…). Logarithmic scales are useful for many reasons, one of which is being able to represent a wide range of numbers on the same scale and still be able to see what’s happening. This turns out to be especially important for engineers.

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Log scales comic courtesy of xkcd.

By looking at assessments students had taken, we were able to deduce some of the reasons they were struggling. Namely, students were treating logarithmic scales as though they were linear. The question then became how to best go about correcting these errors. To that end, the Essential Skills Quizzes (ESQ) were developed.

The making of the ESQ began with a tedious process that involved playing in MS Paint and making images for problems to test students on their knowledge of logarithmic scales.

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This is a simple picture of a log scale image I made using MS Paint.

Once the images were finished, the quizzes themselves were constructed. But we didn’t just make up things we thought would help, we based our training quizzes on the theory of mastery learning, which is supported by years of education research. Mastery learning means letting students take as much—or as little—time as they needed to learn the skills, but requiring each student to “master” the subject before moving on. For the ESQ, students could take the quizzes as many times as they wanted, but needed to score 80% or better for full credit. After each attempt, students were shown the correct answers to the questions so they could self-correct their errors. Each quiz covered a different set of topics and, once the quizzes were created, we began giving them to engineering students as part of their class.

But simply assigning the quizzes is no guarantee that they will help the students understand, nor is it good science. We need some way to measure what, if anything, the students are learning. We designed an assessment to test the knowledge contained in the ESQ, and gave this to the students both before (pretest) and after (posttest) the ESQ. If there was a change in scores between these two identical tests, it is most likely a result of the training.

Once the data had been collected, it was my turn to code it. This involved looking through all of the student responses (both to training, as well as the pretest and posttest) and recording various things about the students’ answers. We are interested not only in whether the students were right or wrong, but exactly how students were wrong. In this sense and others, coding data is much more than just “grading a test.”

After coding, we then analyzed the data using the powers of statistics. As it turns out, students performed drastically better on questions interpreting and reading logarithmic scales! We believe this success has come from 1) forcing students to repeat the test until they “master” the material before obtaining full credit and 2) allowing students to correct their own errors, rather than just telling them the right way to do things.

“Success! Case closed! Time for a new project!” you may say. But this is science, and the process never truly concludes, but rather it begins anew. Conclusions from the last round of research will raise new questions that had not been considered before, and new studies must be designed to answer these new questions and continue to improve what is already known. The life of a scientist is nothing if not cyclical, and there is always more to discover.

After the term ended, we met once again with engineering professors to discuss how the quizzes could be improved and what new knowledge we could include. This process is best shown by student responses to a survey about the ESQ. The blue graphs show the results from the first term of the ESQ, and the green/red graphs are the following two terms. The left column shows how much students enjoyed the ESQ, the middle column shows how much students thought they learned from the ESQ, and the right column shows how strongly the students recommend keeping the ESQ as part of the course. These graphs shows that the ESQ have 1) become more enjoyable for the students, 2) taught the students more, and 3) become a valuable piece of the engineering curriculum, all as a result of continued improvements.

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Success!

I’m happy to say that the ESQ are as effective as ever, and they continue to improve. It brings me joy to know that I’ve helped students to understand things in the same way my teachers helped me. I may not see the students directly, but the things they learned from the ESQ will be useful for the rest of their careers.

If you are looking for more information, you can check out the American Association of Physics Teachers, which is our primary research conference/organization, or Physical Review Special Topics – Physics Education Research, which is the part of the American Physical Society that publishes PER findings.

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About Brendon Mikula

BioPhotoI graduated from Michigan State University in 2010 with a BS in Lyman Briggs Physics. While in Lyman Briggs, I worked as an Learning Assistant (undergraduate TA) for the laboratory portion of the Lyman Briggs physics course. I received the “Outstanding LA Award” for Physics in Fall 2009. I now work in Physics Education Research under Dr. Andrew Heckler, primarily studying the use of computers as learning tools. In addition to studying student understanding of vector algebra in Physics students, I also participate in two interdisciplinary projects: investigating student understanding of log plot interpretation (and other “essential skills”) in Materials Science Engineering students, and using a computer-based farming game to help Geography students better understand the Green Revolution.  My hobbies and interests include skiing, billiards, disc golf, darts and other games. I love spending time outdoors and with friends, family, and my girlfriend. Oh, and I’m a die-hard, bleed-green Michigan State fan (sorry, Buckeyes).

Happy New Year!

by Megan Harberts and Nancy Santagata

Colourful 2014 in fiery sparklers

Happy New Year from A Day in the Life in Physics at OSU!

2013 has been a busy year for us at A Day in the Life (ADitL): we’ve added a new member of the editorial board, continued to build our following in the US and all over the world, and expanded our use of social media. We would never have been so successful without the support of our readers, so we would like to extend a great big Thank You!

After starting ADitL in July 2012, we (Professor Amy Connolly, postdoc Nancy Santagata, and graduate student Megan Harberts) were joined by high school student Jasneet Singh. We were excited for Jasneet as she left the board almost a year later upon graduating from Columbus School for Girls and enrolling as a freshmen at THE Ohio State University. We are very happy to be joined by Jasneet’s former schoolmate, Meredith Meyer, who excels at ensuring that our posts are understandable for a high school audience.

Since our last New Year’s post, we have published 25 new blogs written by a diverse group of female and male contributors that address a variety of topics.  Our most popular post to date is Archana Anandakrishnan’s account of the three role models who inspired her to become the scientist that she is today.  Achana’s story has also helped us develop a large following in her home country of India and we are excited to see so much more color on our “Top Views by Country” statistics map.  As Helena Reichlova appropriately wrote, Physics Works Best if International, and we couldn’t agree more!

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Hello World!

Other popular posts for the past year have been Tori Boggs’ exuberant connection between the amazing sport of jump rope and the science behind it, Andy Berger’s explanation of the sizes of things that are smaller than microscopic, and Calen Henderson’s account of his adventures searching for exoplanets in South Korea.  Calen’s post was also shared on the news site of the National Science Foundation!

We have also been expanding our social media presence.  We have almost 200 followers on our Facebook page and have also tackled Twitter.  There we not only share our blog posts, but other cool science stories that we think may be of interest to our readers. Twitter is such a great tool for sharing science, which is one of the things Megan learned when she attended a conference on communicating science, ComSciCon, in Boston in June. Megan enjoyed meeting other graduate students who run websites that help make science accessible, like Astrobites, among others, and received tons of positive feedback on ADitL blog.  Please visit us on Facebook and Twitter if you haven’t already!

In closing 2013, we want to thank all of our contributors and readers for making this past year so much fun.  We look forward to sharing more great stories with you in 2014!  To help ensure that our posts remain relevant and fun, we would love for you take a few minutes to answer three questions and provide some feedback for us.  We encourage you to share your thoughts in the comments as well!

Thanks again everyone!  Happy New Year!

Across the World for ~80 Days

by Calen Henderson

The plan was two weeks. But two became three and weeks stretched to months as I toiled to tailor my application to the requirements of the NSF Graduate Research Opportunities Worldwide (GROW) fellowship. Then in April of this year, several months after submitting the final version, I received the congratulatory email informing me that I’d been awarded the fellowship and would be spending the summer working with a team of my collaborators in Cheongju, South Korea. My name is Calen Henderson, I’m a senior-level PhD student who studies exoplanets, or planets that orbit other stars, and below I’m going to describe an extraordinary summer in the life of an astrophysicist.

First, some background. Prior to 1989, humans knew about the existence of nine planets. They all resided in our Solar System, and Pluto had not yet been demoted. Then, in 1989, our knowledge of other worlds, and with it our own worldview, began to change. To date, astronomers have discovered over one thousand exoplanets that collectively provide insight into how planets form, how common it is for a star to have one or more planets orbiting it (extremely common, it turns out, with our Milky Way Galaxy alone estimated to harbor over 100 billion planets, or one planet per star, on average), and specifically what kinds of planets and planetary architectures are out there. Such findings are the result of using a variety of exoplanet discovery techniques, including transit, radial velocity, and pulsar timing. I specialize in one known as gravitational microlensing, and this method forms the backbone of my PhD research.

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The number of known exoplanets has increased dramatically, especially over the past few years due to the launch of the Kepler satellite. These are indeed exciting times to be an astronomer and to study exoplanets!

Normally when you look at a star, whether with your naked eyes or through a telescope, its brightness remains relatively constant as time marches forward. But, all objects in space are moving, with stars passing in front of and behind other stars, and every so often the alignment of the Earth and two distant stars will be so nearly collinear (all three in a straight line) that the gravity of the middle star will bend some of the light rays emitted from the background star so that they reach Earth rather than continuing to traverse through empty space. We see the manifestation of this alignment as a brightening of the background star, and if the intervening star has a planet in orbit around it, it is possible to see additional amplification of the light of the background star due to the gravity of the planet.

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The brightness as a function of time for the first microlensing event in which a planet was discovered. The circle in the upper panel shows the star being microlensed, though you can’t see the intervening star whose gravity is actually bending the light. When the circle turns red it denotes the anomaly caused by the additional gravity of planet orbiting the intervening star. This animation was created by Dr. Andrzej Udalski of the OGLE collaboration and was borrowed from Dr. David Bennett’s webpage.

Such an occurrence is rare and unpredictable, and so requires monitoring tens of millions of stars to detect a few thousand microlensing events per year. A single microlensing event refers to a star that has been magnified by the gravity of an intervening star that may or may not host one or more planets. Ultimately this process leads to the discovery of just a handful of planets each year. But wait! There’s less! Not only is detecting a possible planetary signature in a microlensing event an unlikely situation, but sifting through the mountains of data taken by the dozens of telescopes around the world to accurately and precisely determine the physical parameters of the planetary system—how massive the planet is, how far away it is from its host star, et cetera—can often take years. Furthermore, only a small number of people have both the knowledge and the access to the vast amounts of computing power necessary to do so.

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Astronomers overcome the extreme rarity of detecting a microlensing event by pointing their telescopes where the density of stars is the highest—toward the central Bulge of our Milky Way Galaxy, marked by the red line.

So far we’ve learned that microlensing is infrequent, difficult, and not very popular. These factors, coupled with the fact that microlensing has not yet discovered as many planets as certain other techniques, often leads to other astronomers viewing microlensing as the “Whose Line Is It Anyway” of exoplanets—the science is made up and the planets don’t really matter. In fact, such an assessment couldn’t be further from the truth. Microlensing is unique in that is has unparalleled sensitivity to low-mass planets orbiting their host stars at large distances. Whereas other discovery techniques can easily find a Jupiter-mass planet orbiting a star at the distance at which Mercury orbits the Sun, only microlensing can easily find planets with the mass of Earth at the distance of Earth. This is integral for our understanding of how common architectures like our own Solar System are as well as how planets are formed.

Re-enter our hero. One of the premier teams of astronomers in the world with the expertise and ability to analyze microlensing events and look for planets is based at Chungbuk National University in Cheongju, South Korea. They are led by Dr. Cheongho Han, who obtained his PhD in astronomy from OSU and with whom I have closely collaborated for the past two years. Through the NSF GROW fellowship, I was able to spend the summer working with Dr. Han and his group to learn how to analyze microlensing events.

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Many consider the entire Korean peninsula to resemble a rabbit. Others, a tiger. I fall in the latter group, and so spent my summer nestled, ferociously, in Korea’s hindquarters.

The primary office in which Dr. Han, his graduate students, and I worked is probably the closest thing to Hollywood’s portrayal of science that I’ve ever witnessed. In this “War Room” there are computers lining two of the walls, with a third hosting a bank of clocks to help keep track of the current time for telescopes at a variety of longitudes. The center of the room is dominated by four huge monitors—the kind measured in feet, not inches—each connected to a different computing cluster, all of which are housed in a separate building due to the loud whirring of the fans that cool them as they radiate extreme amounts of heat while performing billions and billions of calculations.

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Several of Dr. Han’s graduate students and I in the “War Room.”

What makes his group’s approach so unique and powerful is its comprehensiveness. Every day we would analyze all ongoing microlensing events in search of anomalies in the magnified brightness of the microlensed star due to the existence of a planet orbiting the intervening star. We would subsequently circulate our findings to the teams of astronomers in charge of the telescopes to encourage more or fewer observations, depending on our estimation of the likelihood of the existence of a planet. Any spare time was spent reanalyzing older microlensing events—perhaps there were additional or improved data, or maybe someone had insight into a different solution that would better describe the data.

In order to competently perform these tasks, there were several skills I needed to learn. To efficaciously utilize the computing clusters, Dr. Han’s team helped me become proficient in what is called parallel computation. Rather than using a single computer to solve a problem you use several in concert, farming out different tasks to each machine to most efficiently complete the computational task. I also brushed up on my complex analysis background. It turns out that microlensing equations can be more readily solved if you use imaginary numbers, a formalism that is the foundation of the best analysis codes in the world. Most importantly, however, was being able to analyze a multitude of microlensing events and the experience gained from it. When a star becomes microlensed by another, intervening star, there is a myriad of ways that the resulting magnification the light of that background star experiences can change as a function of time. In many cases, knowing a lot of math and having a lot of computers at your disposal can only get you so far—being able to intuit a good guess at the solution right off the bat is your most valuable skill.

near_peak_daecheongbong_lowres

I was able to do some exploring as well! Here is a view near the peak of Daecheongbong, the tallest peak in Seoraksan National Park.

While Dr. Han and his graduate students imparted a wealth of astrophysics, computer science, and higher-level math to me, some of the most meaningful things I took away had nothing to do with microlensing. They were unremitting in their hospitality and eagerness to help me explore Korean cuisine and culture. Their patience was admirable, particularly since I was the visitor who was able to speak only a few phrases of Korean here and there. And their desire to teach was paralleled only by the vast trove of knowledge, both within and external to science, upon which they were able to draw. I find it appropriate and comforting that my search for other worlds comes hand in hand with learning more about my own.

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About Calen Henderson

calen_oryeon_falls_lowresHey! I enjoy playing classical piano music, running, and traveling. I spend my spare time working on a PhD in astronomy at The Ohio State University, trying to discover and characterize exoplanets and gain insight into planet formation. As an Eagle Scout, outreach is also a big component of my life, and I love giving shows at our newly-renovated digital planetarium!