Most weeks during the semester, we host a scholar for a one-day visit. The visit culminates with a public talk on a topic of contemporary physics or astronomy. Students are welcome to these talks, and seniors are required to attend at least nine over the course of a year. Near the end of each semester, honors thesis students give public lectures on their work. We gather before the talks for tea, coffee, and cookies at 3:45, Ground Lobby of Science Center followed by the talk at 4:00 pm in A011.
Our Astronomy program is part of the Five College Astronomy Department, which hosts its own colloquium series Thursdays at 3:45 pm at UMass in LGRT 1033.
Tue, Mar 5, 2019
In the first billion years after the Big Bang, the universe's hydrogen gas became ionized, an event known as reionization. Reionization represents a fundamental transition in the universe's properties, and yet we know little about how it occurred. The most likely explanation is that ionizing, Lyman continuum (LyC) photons escaped into the intergalactic medium from early star-forming galaxies. However, most star-forming galaxies show no sign of LyC escape. If reionization was caused by galaxies, which galaxies were responsible? The recent discovery of escaping ionizing radiation from the unusual "Green Pea" galaxies has provided new clues to this puzzle. I will discuss what we are learning from the Green Peas about how ionizing radiation escapes galaxies and about the possible properties of the galaxies that reionized the universe.
Tue, Mar 19, 2019
"Biomechanics of Underwater Walking: Sea Stars, Crabs, Octopi": Talk by Olaf Ellers, Bowdoin College
The biomechanics of terrestrial legged locomotion has been extensively studied, but underwater legged locomotion is virtually unstudied. On land, animals change gaits as they increase in speed, e.g., from walking to running. These gaits are different in that step-by-step fluctuations in the kinetic and potential energy of the center of mass change from being out of phase in walking to being in phase during running. The transition from walking to running can be interpreted in terms of a dimensionless number, the Froude number, which is a ratio of inertial to gravitational forces. We have developed underwater versions of the Froude number to account for drag, fluid accelerations and buoyancy. We have discovered that sea stars use two gaits that are neither walking nor running, for two different speed ranges. And we have described how the multitude of legs work to develop effective steps. Octopi and crabs show similar oscillating patterns of motion as sea stars. A biomimetic approach based on sea stars is being used by engineers to design underwater soft-bodied robots.
Tue, Mar 26, 2019
Tina Shih, of the MIT Lincoln Laboratory, will discuss "Engineering Applications of Light-Matter Interactions."
Abstract: The study of how light interacts with materials serves to uncover phenomena that have led to the development of the sensors and technologies we readily use today. This talk will walk through a few examples of light-matter interactions that have demonstrable applications, including ultrafast material switches, aerial 3D mapping and laser communication to the moon and beyond.