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A nontechnical talk by Dr. Robert Kirshner, Jan 28, 2026. One hundred years ago, Edwin Hubble showed that the universe is expanding. In the 1990s, astronomers found that the expansion is not slowing down, as expected, but speeding up. This led to a Nobel Prize in Physics (for our speaker's students) and a consensus that we live in a universe that is made up of invisible dark matter, mysterious dark energy, and only a pinch of the atoms we, and everything we can see in the Universe, are made of. Dr. Kirshner explains this history in everyday language and reviews recent observations indicate that even this picture may be too simple to account for all the evidence. He also discusses the status of building the largest telescopes ever planned in Earth's Northern and Southern hemispheres.  Robert Kirshner is Emeritus Professor of astronomy at Harvard and Research Professor at the California Institute of Technology. He was the Head of Science at the Gordon and Betty Moore Foundation, and now serves as the Executive Director of the Thirty-Meter Telescope International Observatory.  

Dr. Alfonso Davila (NASA Ames Research Center) Nov. 24, 2025 In 2005, NASA's Cassini spacecraft made a groundbreaking discovery—it found massive plumes of ice and gas erupting from the south pole of Enceladus, a small but geologically-active moon of Saturn. These plumes are now believed to originate from a subsurface ocean of liquid water beneath the moon’s icy crust, with conditions compatible with life, as we know it. The talk focuses on our current understanding of Enceladus' plume and subsurface ocean, and on past and future strategies to search in them for possible evidence of life.    Alfonso Davila is a Research Scientist in the Exobiology branch at NASA Ames Research Center, where he helps develop strategies to search for evidence of life beyond Earth.

A Nontechnical talk by Dr. Steven Kahn (University of California, Berkeley) Oct. 8, 2025 The amazing Vera Rubin Observatory is a unique astronomy facility just built in Chile, with the largest digital camera in the world, designed to provide a time-lapse “movie” of the entire sky from the Earth’s southern hemisphere.  Over its planned ten years of operation, the Rubin Observatory will obtain nearly 1,000 images of every part of that sky.  By comparing the various images, we will be able to detect everything that varies in brightness and everything that moves across the sky. By adding together all of the images, we will be able to catalog nearly 20 billion galaxies and a comparable number of stars.  After 20 years of development, this facility has just come on-line and will soon begin its nightly operations.  Prof. Kahn, who was Director of the Observatory during its construction phase, reviews the design, development, and construction of Rubin, and describes the exciting science that lies ahead.

A Talk by Dr. Oliver White (SETI Institute) May 28, 2025 Ten years ago, the New Horizons spacecraft flew by the Pluto system and revealed an unexpectedly diverse range of landscapes on that dwarf planet and its largest moon Charon -- implying much more complex geological histories for these distant worlds than anyone expected. Dr. White leads a vivid tour of their often bizarre terrains, some of which are still evolving, and explains what processes scientists think molded them into their present appearances. After a brief stop at Pluto's four small moons, Dr. White extends the tour 2 billion km farther out into space, to show us Arrokoth, the tiny "planetesimal" that New Horizons flew past three and a half years after visiting Pluto.  It is the most primitive object in the Solar System ever visited by a spacecraft.

Non-technical Talk by Prof. Jonathan Fortney (U. of California, Santa Cruz)  Apr. 9, 2025 Over 6000 planets have now been found around other stars, but we only have information about what their atmospheres are like for a few dozen.  NASA's powerful James Webb Space Telescope (JWST), which features a 20-foot mirror in space, is currently being used to understand planetary atmospheres.  Prof. Fortney explains how we can look for atmospheres around rocky planets the size of the Earth, and how his group and others are already measuring the abundances of molecules like water, methane, ammonia, and carbon dioxide in the atmospheres of larger planets, of sizes similar to Neptune and Jupiter.  And he tells us what astronomers are looking forward to in the next year or two with JWST.

 Mar. 5, 2025  Dr. Simon Steel (SETI Institute) Dr. Steel discusses the Copernican revolution and how it changed humanity's view of its place in the universe. He then talked about other "Copernican" discoveries that displaced us from a central perch, including the revision of our place in the Galaxy, the discovery of other galaxies, and now our finding a remarkable number of planets (including Earth-like planets) orbiting other stars.  He explains how such discoveries give context for, and have prepared us for, the next potential Copernican revolution, the discover of intelligent life elsewhere in the cosmos. He concludes by describing some of the most exciting experiments now underway to find evidence of such life among the nearest stars and busiest galaxies.  Dr. Steel is  Deputy Director of the Carl Sagan Center for Research at the SETI Institute.

Jan. 29, 2025 Dr. Darlene Lim (NASA Ames Research Center) NASA's Volatiles Investigating Polar Exploration Rover (VIPER) is a planned mission to go to the South Pole of the Moon and get a close-up view of the locations that can sustain water ice – ice that could eventually be harvested to support human exploration on the Moon, on Mars — and beyond. Dr. Lim discusses how, for the first time in NASA’s history, the science team would be fully integrated into the mission operations team and will provide near real-time input on where to explore on the Moon.  While the fate of the mission is now in some doubt, Dr. Lim discusses the lessons learned, and the remarkable techniques the team developed to make real-time, almost instant decisions about what the rover does next at each point in its journey.  She also tells about how her earlier experience exploring deep lakes on Earth with robotic and crewed vehicles taught her valuable lessons that she could apply to designing lunar exploration protocols.

Nov. 13, 2024 Dr. Dan Coe (Space Telescope Science Institute) The Webb Telescope was designed to look back in time, to study the first generation of stars, and reveal our cosmic origins. Now in its second year of operation, JWST has already brought us tantalizingly close to our dream of seeing those first stars. Dr. Coe takes us on a tour of some of the  latest results from the telescope, and tells us about his and others' observations of the most distant stars and galaxies astronomers have ever seen, providing a view of the universe as it was 13 billion years ago. Dan Coe is an Astronomer at the Space Telescope Science Institute (STScI) and Johns Hopkins University in Baltimore. STScI is home to JWST mission control and science operations, where staff scientists like Dan support other astronomers using Hubble and JWST. Dan has also led the Hubble RELICS and JWST Cosmic Spring science teams in discovering and studying some of the most distant galaxies known in the early universe. 

Recorded Oct. 9, 2024 Astronomers have now discovered thousands of planets in orbit around other stars. Dr. Weintraub discusses those discoveries, and predicts the progress astronomers are likely to make in their more detailed studies of these planets over the next fifty years. Then he considers the consequences of those potential discoveries for Roman Catholicism, Mainline Protestantism, Christian Creationism, Seventh Day Adventism, Judaism, Islam, and Hinduism -- for all of which the discovery of a planet with life on it may be profound. These thoughts are based on the writings of key religious leaders on this topic -- in the past and in our times. Dr. David A. Weintraub is Professor of Astronomy Emeritus at Vanderbilt University where he founded and directed the Communication of Science and Technology program, and conducted research on the formation of stars and planets. His most recent book is The Sky is for Everyone: Women Astronomers in Their Own Words (2022; with Virginia Trimble). Previous books include Religions and Extraterrestrial Life: How Will We Deal With It? (2014), Life on Mars: What to Know Before We Go (2018), How Old is the Universe? (2010), and Is Pluto a Planet? (2006). He also created the Who Me? series of inspirational scientific autobiographies for fifth-grade level readers (from World Scientific Publishing), which helps young people see themselves as scientists.

With Prof. Caleb Scharf (Columbia University) Is humanity on Earth special or unexceptional?  Extraordinary discoveries in astronomy and biology have revealed a universe filled with endlessly diverse planetary systems, and a picture of life as a phenomenon intimately linked with the most fundamental aspects of physics. But just where these discoveries will lead us is not yet clear.  We may need to find a way to see past the mediocre status that Copernicus assigned to us 500 years ago.  Dr. Scharf helps us to come to grips with the implications of some of the latest scientific research, from the microscopic to the cosmic. Caleb Scharf is Director of Astrobiology at Columbia University in New York and is considered one of the leading scholars at the interface of astronomy and biology.  He is the author of the popular book Gravity’s Engines, which was the basis of the BBC/Science Channel documentary, Swallowed by a Black Hole.  His textbook, Extrasolar Planets and Astrobiology won the 2011 Chambliss Prize.   His book, The Copernicus Complex, was published by Scientific American/Farrar, Straus and Giroux;  Recorded October 2014

With Dr. Roger Romani (Stanford University): NASA's Fermi Gamma-ray Space Telescope has revealed a violent high-energy universe full of stellar explosions, black hole jets, and pulsing stars.  These cosmic objects are often faint when observed with visible light, but glow bright with gamma rays.   Dr. Romani describes the quest to discover the true nature of the most puzzling of these gamma-ray sources.  Several turn out to be a kind of bizarre star corpse called a 'black widow' pulsar -- where a dead star has a companion that it is slowly destroying. This is a talk from 2014, but it is still relevant today.

Presenter is the Project Scientist, Dr. Robert Pappalardo (JPL) May 22, 2024 Jupiter's moon Europa may be a habitable world, containing the “ingredients” necessary for life within its ocean. Data from NASA’s earlier Galileo mission suggest that a global, salty ocean exists beneath the icy surface. Tides have broken that floating ice shell to create impressive ridges, bands, and chaotic terrains. The Europa Clipper mission will explore Europa with a suite of instruments, through multiple close flybys from Jupiter orbit, examining the moon’s ice shell, ocean, and geology.  And it will search for current activity –including plumes that emerge from surface cracks. Dr. Pappalardo, the mission's Project Scientist, summarizes our understanding of Europa and the and status and promise of the Europa Clipper.

Apr. 17, 2024 In this talk, physicist and popular author Paul Halpern (St. Joseph's College) examines the history of the concept of a multiverse in science, and discusses the ideas by Einstein and other noted physicists that have led scientist today to take the notion of multiple universes seriously.  He also contrasts the scientific view of a multiverse to the picture we get in popular culture (think Marvel movies) and notes how significantly the two differ.  Dr. Halpern is the author of a new popular-level book also called "The Allure of the Multiverse" and many other nontechnical science books.

With Dr. Leonard Susskind (Stanford University) Black holes, the collapsed remnants of the largest stars, provide a remarkable laboratory where the frontier concepts of our understanding of nature are tested at their extreme limits. For more than two decades, Professor Susskind and a Dutch colleague had a running battle with Stephen Hawking about the implications of black hole theory for our understanding of reality — a battle that he has described in his well-reviewed book The Black Hole Wars. In this talk Dr. Susskind tells the story of these wars and explains the ideas that underlie the conflict. What's at stake is nothing less than our understanding of space, time, matter and information! Recorded: October 1, 2008         Although this was taped some years ago, this was the most popular talk in the 24-year history of our series.  So we wanted to make it available as a podcast, so new audiences could also hear it.

A Non-technical Talk by Dr. Jessica Lu (University of California, Berkeley) on March 13, 2024 The population of black holes, objects left over from dead stars,  is almost entirely unexplored. Only about two dozen black holes are confidently known in our Galaxy. As a result, some of the most basic properties of black holes remain unknown, including the true number of black holes in the Galaxy, their masses and sizes, and how the black holes were formed.  Dr. Lu discusses how she and other astronomers are using "gravitational lensing" -- something predicted by Einstein’s work -- to open a new window onto black holes, and how the first free-floating black holes are now being discovered.  She explains, in everyday language, why astronomers expect that the number of known black holes will increase by a factor of 100 over the next decade.