Department of Physics & Astronomy
University of New Mexico

Physics and Astronomy Colloquium

From Maxwell's Demon to Einstein's Speed Demon

Presented by Mark Raizen, University of Texas

In this talk, I will describe two historical thought experiments in statistical mechanics and their experimental realization. Maxwell’s Demon was proposed by James Clerk Maxwell in 1871 as a way to reduce the entropy of gas-phase particles by means of an “intelligent creature with deft hands.” We have realized this thought experiment with a self-acting one-way wall for atoms, as originally suggested by Maxwell. This construction has been used to cool atoms, and for efficient isotope separation which will have important medical applications. In 1907, Albert Einstein predicted that Brownian motion should be ballistic on very short time scales, rather than diffusive. Einstein concluded that this instantaneous velocity would be impossible to measure in practice, a prediction that held for over 100 years. We have realized such a ‘speed demon’ by measuring the motion of micrometer beads held in optical tweezers, and have resolved the instantaneous velocity of a Brownian particle in air and in liquid. This system can be used to study the onset of irreversibility, the “arrow of time,” and may have surprising real-life applications.

3:30 pm, Friday, February 16, 2018
Room 125, Dane Smith Hall
Southwest corner of Las Lomas and Yale, Albuquerque, New Mexico

Refreshments will be available before the colloquium, at 3:15 pm, in the lobby of Dane Smith Hall.

Disability NoticeIndividuals with disabilities who need an auxiliary aid or service to attend or participate in P&A events should contact Sandra Ortiz (phone: 505-277-5900, email: well in advance to ensure your needs are accomodated. Event handouts can be provided in alternative accessible formats upon request. Please contact Mrs. Ortiz if you need written information in an alternative format.

A schedule of talks within the Department of Physics and Astronomy is available on the P&A web site at