Wooster Physicists – Page 21

Guest Blog: Avi Vajpeyi ’18

Susan Lehman

July 9, 2015

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.

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

July 8, 2015

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!

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!)!

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

June 29, 2015

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

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 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.

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

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

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

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

June 29, 2015

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

June 9, 2015

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 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

May 31, 2015

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.

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 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!

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!

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

May 31, 2015

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.

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.

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

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

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

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

Min explaining some nuclear physics to Dr. Lewis.

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

May 13, 2015

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 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!
The Unveiling of Pluto

John F. Lindner

May 2, 2015

As a kid, I poured over diagrams in Popular Science magazine describing possible Grand Tours of the outer solar system (Jupiter, Saturn, Uranus, Neptune, and Pluto) made possible by a rare alignment of the planets. Unfortunately, budget cuts reduced the Grand Tour to the Voyager missions to Jupiter and Saturn. While Voyager 2’s mission was ultimately extended to fly by Uranus and Neptune, Voyager 1 was deflected out of the ecliptic (plane of the solar system) by close fly-bys of Saturn and its planet-size moon Titan to obtain breathtaking and unprecedented photographs of Saturn’s rings from above, but thereby sacrificing its opportunity to visit Pluto.

After an intense public relations campaign, of which I was a small part, NASA launched New Horizons in 2006 with the highest launch speed of any spacecraft, crossing the moon’s orbit in under half a day. Powered by the radioactive decay of 11 kg of Pu-238 and carrying an ounce of Pluto discoverer Clyde Tombaugh’s ashes, New Horizons will fly by Pluto and its large moon Charon this July. I expect both Pluto and Charon to be complex worlds, possibly including phenomena like exotic snows and cyrovolcanism.

New Horizons mid April 2015 views of dwarf double planet Pluto and Charon orbiting their barycenter. Click for a larger view.

New Horizons will transmit a few highly-compressed closeup images of Pluto and Charon just after the fly-by but will transmit most of the fly-by data over the next year. (For fixed spacecraft transmission power, Earth reception power decreases like the inverse square of the distance, which is about 4.5 light-hours at Pluto. The spacecraft compensates by reducing the data rate to allow the receiver to integrate the incoming signal, thereby increasing the signal-to-noise ratio.)

This week, images from New Horizons will exceed the resolution of the Hubble Space Telescope. Already images from April suggest surface features, including a polar cap. The long awaited unveiling of Pluto has begun.
Strange Nonchaotic Stars

John F. Lindner

April 15, 2015

On the second day of my University of Hawai’i sabbatical, I began to work with space telescope data that would invigorate the study of variable stars and justify my NASA T-shirts.

While the brightness of stars like the sun is nearly constant, the brightness of other stars changes with time. Exploiting the unprecedented capabilities of the planet-hunting Kepler space telescope, which stared at 150 000 stars for four years, my colleagues and I discovered evidence that certain stars dim and brighten in complex patterns with fractal features. Such stars pulsate at primary and secondary frequencies whose ratios are near the famous golden mean, the most irrational number. A nonlinear system driven by an irrational ratio of frequencies is generically attracted toward a “strange” behavior that is geometrically fractal without displaying the “butterfly effect” of chaos. Strange nonchaotic attractors have been observed in laboratory experiments and may be useful in describing brain activity and climate, but a bluish white star 16 000 light years from Earth in the constellation Lyra may manifest, in the scale-free distribution of its frequency components, the first strange nonchaotic attractor observed in the wild. The recognition of stellar strange nonchaotic dynamics may improve the classification of these stars and refine the physical modeling of their interiors.

We sampled the KIC 5520878 light curve at its primary period and decomposed the resulting time series into sine waves of different amplitudes and frequencies. The number of amplitudes varied with a negative power of the detection threshold. Specifically, if the threshold increased four-fold the number decreased eight-fold, for a wide range of thresholds. Similarly, in a famous example of spatial scaling, the length of the rugged, fractal Norwegian coast depends on the length of the measuring stick. In fact, the measured coast length decreases with increasing stick length, just like our frequency amplitudes: if the stick length increases four-fold, the measured coast length decreases eight-fold, for a wide range of stick lengths.

Using stellar luminosity data from the Kepler spacecraft (left), we reconstructed a star’s dynamical attractor (left center), modeled it phenomenologically (right center), and found that the spectral scaling of the star’s secondary frequencies is similar to the spatial scaling of the coast of Norway (right).

Fractal self-similarity can describe processes in time as well as patterns in space, and a music analogy elucidates our analysis of the variable starlight: From the stellar pulsation, we removed the backbeat to discover a subtle melody.

My colleague John Learned and others had earlier proposed that sufficiently advanced extra-terrestrial civilizations may “tickle” variable stars with neutrino beams to jog their otherwise very regular expansions and contractions and thereby transmit information throughout the galaxy and beyond. A team including many of us tested this hypothesis on the Kepler’s space telescope’s unprecedented photometric data for star KIC 5520878. Although we found some oddities in the KIC 5520878 light curve, we ultimately concluded that they are likely of natural origin. Nevertheless, we encourage testing of archival and future time series photometry for evidence of artificially modulated variable stars. Bill Ditto subsequently recognized the possibility of strange nonchaotic behavior in KIC 5520878 based on his 1990 experience obtaining the first laboratory observation of such behavior in a magnetoelastic ribbon experiment. We subsequently applied the diagnostic analysis used on the ribbon to the star.

We are currently creating phenomenological models of strange nonchaotic stars and are attempting to expand our results to multi-frequency variable stars outside the Kepler database. Can we connect their frequency ratios to the golden ratio or to the distribution of other hard-to-approximate irrational frequency ratios? Some natural dynamical patterns result from universal features that are common to even simple models. However, other patterns are peculiar to particular physical details. We don’t yet know if the frequency distribution of all variable stars is universal or particular. We are currently organizing an international conference for August to explore these issues.

Recent Comments

John F. Lindner on Venus’s Supercritical OceanMarch 1, 2024
Thanks, Mark! I enjoy reading your posts as well.
Mark Wilson on Venus’s Supercritical OceanMarch 1, 2024
Nice post, John! Thanks for writing these. I always enjoy them.
John F. Lindner on Ein SteinMay 6, 2023
David Smith’s ein stein is an awesome shape!

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