Colloquium Archives (before June 2017)

More recent colloquia are posted on the Physics & Astronomy Colloquia page.

Tom Giblin, Kenyon College

Title: Searching for the Secrets of the Non-Linear Universe  (Video)

Abstract: We have no evidence that general relativity is wrong; every precision test is a resounding confirmation of this elegant and powerful mathematical model.  Trouble is: the greatest cosmological problems of our time (likely require) us to abandon general relativity.  About 95% of the Universe remains a mystery whose solution evades our abilities.  I will talk about how there may still be places in general relativity that have, until now, gone unexplored.  Numerical simulations are a powerful tool that can model the complex non-linear issues of general relativity on cosmological scales.  I will present progress that we have made toward modeling the late Universe in its full splendor and outline where there’s hope that we can start to tackle these great questions.

Aaron Dotter, Harvard-Smithsonian

Title: Galactic Archaeology, Chemical Tagging, and Stellar Evolution  (Video)

Abstract: Galactic Archaeology describes the ongoing effort to understand the formation and subsequent evolution of the Milky Way galaxy through the analysis and interpretation of (very) old stars.  I will begin with an overview of Galactic Archaeology and then describe the new technique known as "Chemical Tagging", which seeks to identify the birth clouds of stars that are distributed throughout the Galaxy via the search for unique chemical signature(s) imprinted in those clouds of gas. Finally, I will show that our knowledge of stellar evolution theory raises a very important--but previously unaddressed--problem for these pursuits, and how we can proceed in light of it.

Heather Bloemhard, AAS

Title: Science Policy for Scientists (Video)

Abstract: Science policy is the interdisciplinary field where science and policy intersect. Science policy includes a wide array of topics where science and policy rely on each other. In this talk, we will focus on the ways that policy impacts science and how you, as individuals, can influence policy. This will include an overview of some of the relevant topics and a discussion of why you should and how you can get involved in science policy. This presentation is designed to be an interactive conversation, with an expectation that the audience will participate. Our goal will be gain a better understanding of how to utilize your leverage as scientists and constituents to help your members of Congress make policy decisions that will benefit you.

Michael J. Kurtz, Harvard-Smithsonian

Title: How a Student's Daydream About Stellar Spectra Became one of the World's Most Important Digital Libraries, the Smithsonian/NASA Astrophysics Data System (Video)

Abstract: In 1979 I was daydreaming out the window of the Kresge Library when I had a vision of stellar spectra as occupying points in an n-dimensional vector space, where n was the number of resolution elements in the spectra.  This led to my thesis work, where I used, for the first time, n-dimensional vector distances and Eigenvector techniques to classify astronomical spectra.

My thesis became well known enough that I was still talking about it five years later, at a meeting in Bavaria, where someone in the audience came to me and said that the exact same mathematical techniques could be used to classify documents.  I view the ADS as being born in that moment.

Alison Crocker, Reed College

Title:  Explaining the Diversity in the "end state" of Galactic Evolution  (Video)

Abstract: Early-type galaxies (elliptical and lenticular galaxies) are high-entropy stellar systems, all galaxies will eventually tend toward such states (perhaps sped up by interactions with other galaxies). Many early-type galaxies are also high-entropy gaseous systems, essentially with hot gas atmospheres maintained by energy input from their central super-massive black hole, not entirely differently than how central nuclear reactions support stars. However, some early-type galaxies still contain low-entropy, cold gas. In these cases, the galaxies are not quite in an ``end state”. I will discuss possible evolutionary pathways and physical processes that explain how some early-type galaxies still have cold gas reservoirs.

Ivan Deutsch, University of New Mexico

Title:  Controlling and Quantum World in Ultracold Atomic Spins  (Video) 

Abstract: The quantum information revolution has taught us that quantum mechanics is not a paler version of its classical counterpart, hindered by intrinsic uncertainty and random measurement outcomes.  Au contraire!  A machine whose operation takes full advantage of the laws of quantum mechanics has information processing capabilities well beyond those that are restricted to essentially classical laws.  To harness this power requires new methods for control and measurement, so that we can make quantum systems do our bidding, rather than what comes naturally.  In this colloquium, I will describe recent progress in this area.  In particular, I will describe a quantum information processing testbed, consisting of ensembles of spin in ultracold atoms gases at near absolute zero temperatures.  It’s a  Back to the Future vacuum-tube technology!

James Battat, Wellesley College

Title: Testing Fundamental Physics by Ranging to the Moon (Video)

Abstract: Lunar Laser Ranging has enabled comprehensive, precision tests of gravity for nearly 50 years.  I will discuss my work on the Apache Point Observatory Lunar Laser-ranging Operation (APOLLO), which achieves millimeter-precision measurements of the lunar orbit.  Such high-precision measurements, coupled with decades of archival data, provide exquisite constraints on gravitational physics. In fact, LLR currently provides the tightest bounds on the strong equivalence principle, the inverse square law of gravity at relevant scales, gravitomagnetic interactions, the time-rate of change of G and Lorentz symmetry in the gravitational sector.