• Guest Blog: Justine Walker ’18

    Susan Lehman

    Summer Lovin’ – Falling in Love with Experimental Physics

    I remember the first hour of my research experience very clearly. I had always been horrible at keeping a good lab notebook and now I had been given an extremely fancy lab notebook with my name in silver and “Lehman Research Group” engraved in bold letters on the cover. I was so intimidated by this book that when I opened it to take notes on our readings, I wrote as neatly and as tiny as I could. That only lasted for a page though, because as soon as Dr. Lehman came in she told me that it would be best with my handwriting to write big and with lots of space. She reminded us to write everything we thought – questions, ideas, anything relevant to the experiment – and not to limit our writing and ourselves. With this advice, my writings in my notebook became more spontaneous and I had more fun recording my thoughts. As time passed, I began to feel more and more comfortable writing my thoughts down and expressing my ideas. That notebook became a home to my work, so that as I watched the pages fill I became prouder of and more confident with my ideas.
    This lab notebook is the embodiment of my experience this summer. I was so intimidated at the start – I was afraid to ask questions, speak my mind, and be anything but perfect. As the weeks flew by, I became more comfortable, started being more inquisitive, and learned that being imperfect is what makes me a good Physicist. Being willing to make mistakes is what leads to important questions and discoveries.

    BeadPilePlusMe

    Not only have I grown as a Physicist, but I’ve also grown as a person. The group of Physics researchers was very small this summer (just two students and two professors!) so it felt like a very friendly environment. I learned how to better collaborate with colleagues and how to be a more open-minded world citizen.
    I wouldn’t trade this experience for the world. The group this summer was amazing to work with. I never loved Physics more than I have now. Physics is not just an exciting area of study; it helps you feel like a part of something bigger than yourself.

    GroupPhoto

  • The Double Planet

    John F. Lindner

    Next week the New Horizons spacecraft falls through (or “flies by”) the Pluto-Charon binary system. This week New Horizons photos reveal dramatic differences between Pluto and Charon, despite their presumed common origin in an interplanetary collision. (By the way, some astronomers — and apparently the New Horizons science team — pronounce “Charon” more like “Charlene”, the name of the wife of Charon’s discoverer, and less like “Karen”).

    So close, yet so different: gray Charon (left) and beige Pluto (right) orbit the common center of mass between them forming a double planet. To fully appreciate the image, click on it for a larger version.
    So close, yet so different: beige Pluto (left) and gray Charon (right) orbit the common center of mass between them forming a double planet. UPDATED 2015 July 17; click image for a larger version.

    We already know spectroscopically that water H2O, methane CH4, nitrogen N2, and carbon monoxide CO ices cover Pluto’s surface (and form its tenuous and dynamic atmosphere). Ultraviolet or UV radiation probably converts nitrogen and methane into reddish, organic tholins CxHyNz. But what causes the patterns of bright ices and dark orangish tholins? By contrast, Charon’s darker surface appears to contain water crystals and ammonia hydrates (NH3)2H2O. Like Triton, the largest moon of Neptune, both Pluto and Charon may have active geysers, which may contribute to the distribution of their surface materials. Stay tuned!

  • Guest Blog: Avi Vajpeyi ’18

    Susan Lehman

    My first internship at Wooster has been a highly rewarding experience. Justine and I had the privilege to work with Dr. Lehman and Dr. Jacobs on a Wooster project that has been ongoing for over two decades – The Bead Pile Experiment.

    The essence of the project is the creation of a pile, using small metal beads that come from shotgun shells (yeah! pretty neat!). As additional beads are added, the pile topples. The avalanche characteristics are demonstrated when a critical point is reached or surpassed, changing in order to return to a stable point.

    The bead pile models critical systems – a few examples are avalanches, forest fires, stock markets (to a certain extent), and even dynamical synapses in neural networks! By studying the pile, the conclusions will be used to discern complex critical systems in the real world.
    When we commenced work, I didn’t completely understand what we were attempting to do. The thought of dropping one bead at a time to watch a pile build up and avalanche, wasn’t exactly exciting to me. Being a first year student, I was also a little anxious about being able to grasp the complexities, and make a significant contribution.

    After the final Examinations, Dr. Lehman briefed us in the intricacies of the project, allowing us to gain a better understanding of the work we would be doing. It was in the third week that I truly began understanding the specifics of our model, after Dr. Jacobs went over the theory of the Bead Pile Project with us, and even gave us a few classes on Criticality!

    During the course of the summer, we did a few more runs, but spent more time analyzing past data. Our focus was to recognize how changing the height the beads fall from and the stickiness of the beads changes the probability of getting avalanches of specific sizes.

    With Dr. Jacobs and Dr. Lehman’s help, we installed and programmed a high-speed camera to record videos of large avalanches. This enhanced our ability to analyze the variation of trends in the graphs of the large and small avalanches. The camera is mounted above the pile (next to the bead dropper) in order to be able to see the whole pile.

    BeadPileAvalanche_optimized
    A massive avalanche on the beadpile, viewed from above using the newly installed high speed camera. The perspective is slightly distorted because of the fish-eye lens and because the camera is not directly above the center of the pile. The pile center is slightly to the left of the visual center of the circle; you can tell because that’s the point the beads move away from.

    We were also very keen to study how the time between certain size avalanches changed as we varied the drop height and stickiness of the beads. We also wanted to set up particle tracking with the camera to trace the path of a bead in an avalanche. However, we didn’t have enough time to do this.

    In conclusion, I believe that I have gained a lot of knowledge this summer, and have thoroughly enjoyed my time working on The Bead Pile Experiment. While we learned a lot, and increased our understanding through our analysis, there is much left to be done. But isn’t that what science is all about?

  • 12th Annual Pie Festival

    Susan Lehman

    We held the 12th annual picnic and pie festival at my house just over a week ago.  (The tradition started the summer after my first year at the College, when one of the summer research students explained that, while she liked to bake pies, she didn’t really like to eat pies.  Dr. Lindner explained that he was the ideal complement — he liked to eat pies, but not to bake pies! The pie festival was born!)

    The pie festival is wonderful especially because of the participation of the students. Many start the summer daunted by the prospect of producing a pie, but by the time the pie festival rolls around, they rise to the challenge!  The rule of the pie party is that everyone brings a pie.  (Families are allowed to bring one pie for the family, and Dr. Lindner has a pass.)  I think our all time largest pie party had 15 pies for 17 people!

    Piiiiiie

    This year we had 10 pies for 12 adults (and 4 young kids). Delicious!  Pies included lemon meringue, peach, apple, pina colada, chocolate pecan, gooseberry, and one of the richest pies I’ve ever tasted – dark chocolate caramel Oreo!   At least three people managed to take at least a thin slice of all the pies (and also eat part of each slice!)!

    IMG_7105  IMG_7106

     

    I was a little worried about the weather earlier in the day — it rained most of the morning, but cleared up so that we could eat outside by 5 pm.  The weather did put a damper on our traditional games of badminton and croquet, but we played games inside instead.

  • BWISER and summer outreach

    Susan Lehman

    One of the Wooster summer traditions is the BWISER science camp for 7th and 8th grade girls.  The physics department has been responsible for an evening of demos for the campers since before I came to the College in 2003, and I’ve taken over responsibility for running our highly-choreographed rotation of nearly 100 girls through seven different demos over the course of two hours.  It’s quite an event!

    Usually we have at least six summer research students on campus who are the ones actually presenting the demos to the campers. This year, although we have a lot of students doing research for the summer, only two are on campus!  So, I had to put out a plea for volunteers and was so impressed with the awesome response from students who were near enough to Wooster to help.

    Popi and Carlos at the Sound demo
    Popi and Carlos at the Sound demo

    For one hour, the BWISER girls cycle through five shorter demos of about 12 minutes each — these are Sound, Polarization, Total Internal Reflection, Holography and Spectral Lines. For the other hour, the girls spend a half an hour building squeeze rockets and half an hour contemplating the vastness of the universe and communication at the speed of light watching Powers of 10 and the opening sequence to Contact.

    Building squeeze rockets
    Building squeeze rockets is best with lots of stickers and glitter tape.

    The squeeze rockets have turned out to be a great alternative to the Moon Cratering experiment that we used to do.  Moon Cratering was a lot of fun, but quite a mess, since it involved dropping different mass balls from different heights into a vat of flour with a fine coating of either tempera paint or cocoa powder. Squeeze rockets has pretty much all the fun of Moon Craters plus glitter tape, and none of the mess.

    2015-06-11 10.57.58 2015-06-10 10.56.55

    For the last two or three years, I’ve also been doing a session for the BWISER Alumnae camp (for 8th graders coming back a second time to camp). This year I had the alumnae for longer than previously, so I decided to do sessions on Light as a Wave, and Light as a Particle.  I’ve been doing optics and imaging for the camp already, so the Light as a Wave stuff mostly came from that, but the new Light as a Particle activities were a lot of fun!  The sun print paper in particular was really popular, with some very creative arrangements of leaves and flowers to make some beautiful prints.  I only have pictures here of the prints as they are being developed in the sun; after this step you develop the paper in water and the colors invert so that the paper turns dark blue wherever it was exposed to the sun and white wherever there was shadow.

    In addition to the BWISER outreach events, I also did a one-day special session for the West Holmes Summer Science Sessions.  Last year was the first year I did this program — I was worried that I didn’t have enough cool stuff and the night before the program, I built the GIANT kaleidoscope, which is now one of my favorite demos! All it takes are three full-length mirrors (like you would hang on a door) and a serious amount of duct tape.  What you get is awesome, especially when there are small children around to make crazy faces.

    Kaleidoscope crazy face
    Kaleidoscope crazy face
    Kaleidoscopic shirt and shorts
    Kaleidoscopic shirt and shorts

    The kaleidoscope was a hit again at the Summer Science Session, as were the Light as a Particle activities.  Besides the sun paper, I also talk about ultraviolet light, including why it’s more dangerous than visible light, since one photon has more energy and so can be more damaging.  And, we got some “secret message” pens that write with ink only visible under UV light.  Turns out, the pens can write not only on paper but also on skin.  I’m sure you can see where this is headed.

    UV temporary tattoos
    UV temporary tattoos

    Sooner or later, it had to happen — the combination of the kaleidoscope and the UV pens.

    IMG_7074

    In the interest of safety, I’ll just add that the students had previously tested this pair of sunglasses and found that they did in fact block UV.  Generally you should avoid shining a UV flashlight into someone’s eyes.

    Overall, these different outreach programs reached around 120 kids this summer!  Hopefully they all still remember my main take-home message: Physics is Awesome!

  • Criticality in Sandpiles and in the Brain

    Susan Lehman

    I’ve started following various science sites on Twitter as a way to keep up on the latest research, and last week an interesting article popped up on Phys.org with the title “Functioning brain follows famous sand pile model”.  Since my current research on avalanches on the beadpile is a essentially an experimental investigation of criticality and the sand pile model, I clicked on the link, interested to see how it connected to the brain.

    The article was about an article just published in Nature Physics on June 22, looking at the electrical activity (visual avalanches) in the brain and comparing to the sand pile model,  but it got really interesting in about the fourth paragraph when I discovered that the first author on the paper was Woodrow Shew, Wooster physics alum from 1998!  What a great way to bump into an alumnus!  Woodrow is now an assistant professor at the University of Arkansas, and clearly is doing some cool work.

     

  • Chaos in the Clockwork

    John F. Lindner

    The work of Newton and Laplace suggested to many that the solar system was like a giant clockwork, which was illustrated by beautiful mechanical models called orreries. The controversial Molchanov hypothesis avers that every oscillatory system evolves to a resonance governed by a family of integers, like the 3/2 resonance between the orbits of Pluto and Neptune, or the 2/1 resonance between Jupiter’s giant natural satellites Ganymede and Europa, and Europa and Io. (Europa orbits Jupiter once when Io orbits twice.) Yet my research this sabbatical suggests that the irrational golden ratio describes some variable stars. Indeed, overlapping resonances may account for evidence of chaos in the solar system.

    Saturn and two of its natural satellites, giant Titan and tiny Hyperion (left), and the Pluto-Charon binary system and one of its small satellites Nix. Hyperion and Nix appear to tumble chaotically in their orbits. The systems are not drawn to the same scale.
    Saturn and two of its natural satellites, giant Titan and tiny Hyperion (left), and the Pluto-Charon binary system and one of its small satellites Nix. Hyperion and Nix appear to tumble chaotically in their orbits. The systems are drawn to different scales.

    In the Saturn system, the 3/4 orbital resonance between tiny, irregularly-shaped Hyperion and planet-sized Titan causes Hyperion to tumble chaotically in its orbit. If you lived on Hyperion, the sun would appear to rise and set at irregular times. Last week, researchers announced that something similar occurs in the Pluto-Charon binary system. Using archival Hubble space telescope data ahead of the New Horizon’s July flyby, Mark Showalter and Doug Hamilton argued that the tiny moons are in orbital resonance but light curves of Nix and Hydra are not sinusoidal, suggesting chaotic tumbling. Nix’s small size implies an irregular shape. (We should know for sure next month.) Just as the dynamic gravity of Saturn and Titan chaotically tumble irregular Hyperion, the dynamic gravity of Pluto and Charon chaotically tumble irregular Nix. If you lived on Nix, the sun might one day rise in the east and set in the north.

  • Commencement

    Susan Lehman

    The class of 2015 graduated in style on May 11.  Those of us who have been around a while (that would be just me, this year!) were surprised to find that faculty and students were lining up in the Oak Grove on the north side of Kauke and that Commencement itself was on the quad (once called the Elm Grove, I hear) south of Kauke.  Apparently, the College was worried because the grass under the oaks was not growing, due to our late spring, and so there were concerns about Commencement being very muddy if we had it in the Oak Grove as usual.

    Thus we were set up on the south side, which I think made a nice perspective for some of the photos, but also meant that there was very little shade on this sunny and warm day.

    Lining Up for the Precession

    Here’s the faculty perspective as we line up in a double row so that the graduates can walk in.  Watching the new graduates file in between the rows of faculty while we clap for them is one of my favorite parts of Commencement.

    Elliot getting his degree

    Elliot Wainwright getting his diploma from President Cornwell.  Note Severance Hall in the background, instead of the Kauke Arch as usual.  The chemists must have especially appreciated this!

    Partial Group Picture

    As usual we attempted to get a group picture, but as usual, it is impossible to actually get everyone together at the same time.  Sorry to those of you not in the picture!

    Lehman and Hagedorn

    I especially like this photo of Evan Hagedorn and me — not only is it a nice picture of us, but you can also see Saul Propp and Ziyi Sang in the background.  I think the photos of Commencement turned out perhaps nicer than usual because of the trees in the background, since we were in the Oak Grove for this part.  Maybe the lesson is that the Oak Grove is the best spot for everything to do with Commencement. Once the elm trees south of Kauke get bigger, it will be nice there as well.

    Congratulations, Wooster Physics Class of 2015!

     

  • April is the busiest month

    Susan Lehman

    So many things happened in the department in April that I got totally behind. In fact, April was so busy that I’ve only barely caught up here at the end of May.
    But, some great things happened so I want to post about them even if it is a little behind times.
    MaggiePrague1

    First – junior Maggie Lankford, a Clare Boothe Luce Research Scholar who has been working with Dr. Cody Leary for two years, had the opportunity to go to Prague to report on her results at the SPIE Optics + Optoelectronics Conference.  Although we take a good-sized group of students to the APS March Meeting every spring, this is the first international conference for a student that I am aware of since I came to Wooster in 2003, other than the year that the APS March Meeting was in Montreal.

     

    MaggiePrague2

    Maggie is the first Physics Club Ambassador to the Czech Republic!

    Second – we had another great IS Symposium on April 24.  Alums who graduated before about 2008 may not know that the College now completely cancels classes on the Friday of the penultimate week of classes to allow a campus-wide celebration of Senior IS. There are posters all over campus, as well as oral presentations.

    Joey

    Joey Smith gave both a poster and an oral presentation on his research combining topology with a study of defects in liquid crystals.

    Jai

    Jai Ranchod explained his idea for an Archimedes Drill Propulsion system to Dr. Garg.

    Brian

    Brian Maddock was as cheerful as usual, explaining glueball trajectories to the general non-science public.

    Nicu

    Nicu Istrate looking snazzy in his bow tie. Bow ties are cool.

    Min

    Min explaining some nuclear physics to Dr. Lewis.

    Shawn

    The nuclei that Shawn studied are orders of magnitude larger than the nuclei studied by Min and Nicu!  Active galactic nuclei are unbelievably large and energetic, from our human perspective.

  • The Flight of the Dragon

    John F. Lindner

    Last week, SpaceX conducted a successful pad abort test of its innovative Crew Dragon spacecraft. Powered by hypergolic monomethylhydrazine CH3(NH)NH2 fuel and nitrogen tetroxide N2O2 oxidizer, which ignite on contact, the Super Draco engines accelerated Dragon from 0 to 100 mph in 1.2 seconds — that’s faster than a Tesla (the electric cars made by Elon Musk’s other company)! The Super Draco’s can be deeply throttled to modulate acceleration, including deceleration, and SpaceX intends to eventually use them for pinpoint propulsive landings on Earth and, in the Red Dragon version, on Mars.

    Rocket engines experience “fire and ice”, extreme temperatures separated by millimeters, and they must be manufactured to extreme precision. So SpaceX 3D printed (the combustion chambers of) the Super Dracos.

    When Crew Dragon separates from its trunk, it becomes unstable and flips over, as planned.
    When Crew Dragon separated from its trunk, it flipped over to deploy its parachute, just as planned. Click to zoom.

    Cool physics alert: Near apogee,  the Crew Dragon separated from its finned trunk and inverted for parachute deployment. I suspect the inversion was largely or completely passive. Stability depends on the relation between the CP and the CM: the CP is the Center of Pressure or effective application point of aerodynamic forces integrated over the vehicle; the CM is the Center of Mass, about which the vehicle rotates for observers translating with it. With the trunk attached, the Dragon’s CP was likely aft of its CM, like a dart, so the Dragon was stable with respect to small changes in angle of attack; however, without the trunk, the Dragon’s CP was likely forward of its CM, so it was unstable and inevitably and passively inverted — exactly as planned!

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