SETI Institute Weekly Colloquium - Upcoming Speakers

Tuesday, April 28 2015 - 12:00 pm, PDT

Shape dynamics: a relational view of the Universe

Henrique Gomes
Perimeter Institute
Shape Dynamics is a new theory of gravity which removes the notion of local relativistic time from the guiding principles of gravity in the universe. It is a very promising approach which has been shown to be equivalent to Einstein's Theory of General Relativity, without being embedded in time. It is inspired by adherence to Mach's Principle, which is violated by Einstein's theory.
Shape Dynamics provides new tools in the quest for a theory that describes quantum gravity.
In the first part of the talk Dr. Gomes will review some of the Machian motivations for shape dynamics and sketch its construction. 
In the second half, Dr. Gomes will talk about recent developments on black holes in this formulation, and discuss some positive aspects of its ongoing quantization program.

Eventbrite - Shape dynamics: a relational view of the Universe

Tuesday, May 05 2015 - 12:00 pm, PDT

Brown Dwarf Variability and implications for Exoplanets

Tyler Robinson

Brown dwarfs are sub-stellar objects that occupy the region of parameter space between gas giant planets, like Jupiter, and the smallest bona fide stars.  Since brown dwarfs never achieve sustained core hydrogen fusion, they are destined to cool over cosmic timescales from thousands to hundreds of degrees Kelvin.  Observations and models of these strange worlds reveal hydrogen-dominated atmospheres with a variety of trace molecular species, as well as metal, dust, and salt condensates.

Recent surveys and targeted observations have revealed that a substantial fraction of brown dwarfs have a brightness that varies in time, with some variations as large as 30% at certain wavelengths.  In this presentation, Dr. Robinson will review the atmospheric physics of brown dwarfs and the current state of variability observations, and he will discuss the various processes that likely cause brown dwarf variability, which include dynamical effects, temporally- and spatially-varying clouds, and associated atmospheric temperature fluctuations.

Eventbrite - Brown Dwarf Variability and Implications for Exoplanets

Tuesday, May 12 2015 - 12:00 pm, PDT

Lakes, Fans, Deltas and Streams: Geomorphic Constraints on the Hydrologic History of Gale Crater, Mars

Marisa Palucis

It has been proposed that in Gale Crater, where the Curiosity rover landed in August 2012, lakes developed to various depths after the large central mound (informally referred to as Mt. Sharp) had evolved to a form close to its current topography. Using a combination of CTX and HiRISE imagery and CTX, HiRISE and HRSC topography, we have documented a sequence of rising and falling lake levels, thereby providing a possible relative timeline of the hydrologic events within Gale crater. Assuming that the entrance canyon deposits (the canyon which the Curiosity rover will ascend once it reaches Mt. Sharp) records a back-stepping sequence of fans and deltas, then a corresponding hydrologic sequence is suggested. After the formation of a gilbert-type delta exiting an 84-km long incised valley (Farah Vallis) that drains 270,000 km2 to the south of Gale, and a corresponding lake with an average depth of 700 meters, the inflow of water from Farah Vallis fell or ceased. The lake level dropped considerably, to an elevation at least below the entrance canyon deposits. At a later time, local precipitation drove gully erosion of the Gale rim, and amplified by renewed Farah Vallis runoff, caused a rising lake level that produced deltas on the western rim of Gale and the entrance canyon deposits on Mt. Sharp. This hydrologic system shut down sufficiently abruptly that the deltas did not cut down as the lake evaporated. The time gap between these two lake forming events, perhaps driven by different hydrologic systems, is not yet established. Fan deposition around Gale crater, including the Peace Vallis fan near the rover’s landing site, likely occurred after these large lakes disappeared. This has implications for understanding regional paleo-climates on Mars after the Noachian, as well as providing context for the geology and sedimentology along the Curiosity rover traverse.

Eventbrite - Lakes, Fans, Deltas and Streams: Geomorphic Constraints on the Hydrologic History of Gale Crater, Mars

Tuesday, May 19 2015 - 12:00 pm, PDT

Geology before Pluto: Pre-encounter considerations

Jeff Moore

Jeff Moore will give a pre-encounter view of our expectations for the New Horizons flyby of Pluto.

Eventbrite - Geology before Pluto: Pre-encounter considerations

Tuesday, May 26 2015 - 12:00 pm, PDT

Giant planet interiors studied with ab initio computer simulations

Burkhard Militzer

Dr. Militzer will briefly review the interior structure of different types of planets and discuss how it is affected by the miscibility of various planetary materials. Results from recent ab initiocomputer simulations will be presented that focus on the miscibility properties of four systems: hydrogen-helium mixtures in gas giant planets, hydrogen-water mixtures in ice giants, silicate-iron mixtures in the interiors of terrestrial planets.

Finally Dr. Militzer will discuss his recent model of Jupiter’s interior that he and his team are putting together before NASA’s Juno spacecraft inserts into orbit about this planet next year.

Eventbrite - Giant Planet Interiors Studied with ab initio computer simulations

Tuesday, June 02 2015 - 12:00 pm, PDT

Atmospheric Tides and the Diurnal Cycle on Earth and other Terrestrial Planets

Curt Covey