Brownian motion as both signal and noise
Logan Hillberry
JILA, CU-Boulder
Friday, November 22, 12:00 PM, C215 ESC
Abstract:
Strong evidence favoring the existence of atoms originated in the 1827 observation of persistent and random motion of microscopic particles in contact with a fluid bath, so-called Brownian motion. Since the invention of the laser and its enabling of optical trapping, the study of Brownian motion has become a precise science that affords fundamental tests of statistical mechanics and fluid dynamics. At the same time, Brownian motion is a ubiquitous source of noise in many measurements. In this talk, I will outline a few experiments performed by myself and others in the lab of Mark Raizen wherein Brownian motion is viewed as both signal and noise. Specific results include i) the first observation of a Brownian particle's instantaneous velocity and the corresponding direct measurement of a Maxwell Boltzmann distribution in both gas and liquid media, ii) weighing of an optically trapped microsphere, and iii) acoustic transduction using an optically trapped microsphere. I will end by discussing planned future experiments that promise access to new timescales and new physical insights on the origins of viscosity and the equipartition theorem.
Biographical Sketch:
Worlds Without Number, God's Infinite Creations
Denise Stephens
Brigham Young University
Friday, December 6, 12:00 PM, C215 ESC
Abstract:
Dr. Stephens recently participated in the creation of a 5-month display for the Washington DC Visitors Center focused on images taken with the James Webb Space Telescope (JWST) and our place in God's creation. She will share the presentation she gave at the visitor center on June 30, which combines the images and science we can do with JWST to our understanding of God's plan and our place in the creation. She will focus her ideas on the themes of discovery, filters, and perspective. Within these themes we will explore how JWST works, the wavelengths in which it observes, and how it has enhanced our scientific knowledge within the last few years and how we can relate that to our own lives.
Biographical Sketch:
Dr. Stephen's received her bachelors degree from BYU and her masters and PhD from New Mexico State University and then went on to work at the Space Telescope Science Institute and Johns Hopkins University before coming to BYU in 2007. Her research focuses on the study of brown dwarf atmospheres, objects that form like star but do not have enough mass to sustain hydrogen fusion. Her research group combines near- and mid-infrared photometry and spectroscopy with theoretical models to probe the depth of cloud layers as a function of wavelength and to examine how vertical mixing is driving key molecular species out of equilibrium. This work has direct application to understanding the atmospheres of directly imaged planets and interpreting the transmission spectra of exoplanets to determine the composition of their atmospheres. For fun, Dr. Stephens and a group of her students also use small telescopes to assist the TESS mission in the identification of stars with possible transiting planets.
We welcome anyone who wish to attend, and typically serve refreshments ten minutes before the colloquium begins. Speakers generally keep their presentation accessible to undergraduate physics students.