Colloquium Archive

Thursday, September 13th
Welcome Back Physics Majors

Come and learn about the departmental expectations for its Physics Majors. Get to know everyone in the department. Ask questions.

Noon
Tome 115
Lunch provided

Thursday, September 20th
Paul Baker, West Virginia University
"Detecting Gravitational Waves with a Pulsar Timing Array"

The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) expects to directly detect a stochastic gravitational wave background (GWB) from super massive black hole binaries in the near future.  This will be accomplished by monitoring many stable millisecond radio pulsars and looking differences in the expected and actual time of arrival of pulses.  We will review the sources of nanohertz gravitational waves that are detectable with pulsar timing arrays, like NANOGrav.  Then we will discuss the fundamental techniques used by pulsar timing arrays to time pulsars and identify the GWB signature in data.

Noon
Tome 115
Lunch provided

Thursday, September 27th
Dr. Rajmal Jain, Indian Space Research Organization
"The Dynamic Sun"

The Sun is most important for us on the Earth. Without the energy from the Sun: heat and light, the Earth would be a lifeless ball of ice-coated rock. The Sun warms our seas, stirs our atmosphere, generates our weather patterns, and gives energy to the growing green plants that provide the food and oxygen for life on the Earth. Thus study of the Sun is extremely important. In my presentation I will try to address important question such as: why and how the Sun shines, is the rotation of the San similar to earth, what are the dark spots, how they form, and what is the ingredient of the spots? I will also discuss the explosions taking place in the sunspot regions known as flares and coronal mass ejection (CME), and explore the possible influence of the sunspots, flares and CMEs on the Earth as well as on the other planets. Currently the Sun is heading to low solar activity and I will present what would be future because it is related to Earth’s weather and climate. The exploration of the Sun from the ground and space over the globe will also be presented along with motivation to students why the solar astronomy is very important for future prospects.

Noon
Tome 115
Lunch provided

Thursday, October 11th
Mikael Rechtsman, Penn State
"Topological Photonics"

Topological insulators are solid-state materials whose transport properties are remarkably immune to defects and disorder due to underlying topological order. Perhaps the first such phenomenon was the quantum Hall effect, wherein the Hall conductivity is quantized and hence extremely robust. In this talk, I will present the experimental observation of the topological protection of the transport of photons (rather than electrons in the solid state) in a complex dielectric structure. I will then present the observation of optical Weyl points in the context of three-dimensional photonic crystals. Applications of topological photonic devices include robust photonic networks and delay lines, and potentially high-power single-mode lasing.

Noon
Tome 115
Lunch provided

Thursday, October 18th
James Puckett, Gettysburg College
"Mechanics of Collective Animal Behaviour"

Collective behavior is ubiquitous in living systems (e.g. bacteria, fish schools, bird flocks and humans.) While there are several current models that successfully describe qualitative features of collective structures in animal behavior, the dynamical behavior of these systems in response to perturbation is not well understood. I show results of two recent experiments to better understand collective behaviour from a physicist point of view. Using midges, I study a disorganized aggregation (a swarm), and compare its natural fluctuations with the group-level response to an external stimulus. I quantify the swarm’s frequency-dependent linear response and its spectrum of intrinsic fluctuations, and show that the ratio of these two quantities has a simple scaling with frequency. In my second set of experiments, I explore the thermodynamics of fish schools. Leveraging the fish’s innate negative phototactic behavior, I employ both static light fields and dynamic light fields which apply a stress on the school increasing the density. Our results highlight how a materials and thermodynamic approach can give insights to current models.

Noon
Tome 115
Lunch provided

Thursday, November 15th
Sigma Pi Sigma Induction Ceremony & Keynote Speaker
Giles Howlett '08; M.S. Mechanical Engineering, Penn State University; Test Engineer, NAVAIR
"What comes after graduation? Sleep? A job? Graduate school? Where do you go, what do you study? How can you take full advantage of the opportunities you are given?"

I will share from my experiences after graduation, including the process switching areas of study to mechanical engineering; applying to and selecting a graduate program; obtaining my masters while studying lithium ion battery materials; and my current position working for NAVAIR as a flight test engineer. In the ten years since graduating, I have found that my Dickinson education prepared me not just for a career in physics, but for several careers. I have studied or worked in the fields of fluid mechanics, nanostructured battery materials, systems engineering for electronic systems, additive manufacturing and 3-D printing, and flight test engineering. And in every case I was able to build upon the foundation of my Dickinson education to enable me to quickly adapt to the technical and professional challenges that were presented to me.

4:30pm
Tome 115
Dinner will follow in HUB Social Hall East (for those Physics/Astronomy students who sign up in advance)

Thursday, November 29th
Dr. Ravi Sankrit, Space Telescope Science Institure/AURA
"V*R Aquarii: the Astronomy and the Physics"

R Aquarii (R Aqr) is the pre-eminent member of a small subset of interacting binaries — the symbiotic Miras, in which the highly evolved, pulsating, cool red giant star loses material via a wind to its even more evolved hot white dwarf companion.  The radiation from the white dwarf, and the energy released in the accretion flow, heat and ionize the circumstellar material, thereby completing the symbiosis.  The next periastron passage of R Aqr in its 44 year binary orbit will occur circa 2022, during which time we expect to observe dramatic changes due to enhanced accretion.   Anticipating the excitement, we have initiated a program to monitor the mid-infrared emission from the circumstellar dust in R Aqr, using the airborne Stratospheric Observatory for Infrared Astronomy (SOFIA).  

In this talk I will present the preliminary results of our study, which is designed to trace the evolution of the dust emission.  I will place these results in the context of the rich history of observations of R Aqr that date back to the early 20th century, when the system was first determined to be symbiotic, and even earlier to its discovery as a variable star.  Through the talk, I will describe the basic physical processes underlying the phenomena, and their connection to the observations, and to the interpretation of the data.

Noon
Tome 115
Lunch provided