Black holes are regions of space where gravity is so strong that nothing, not even light, can escape! No longer confined to the imaginations of science-fiction writers and theoretical physicists, black holes have recently been discovered in large numbers by observational astronomers. Learn about the remarkable properties of these bizarre objects from Dr. Alex Filippenko (University of California, Berkeley), one of the finest explainers in the field of astronomy. Recorded May 19, 2010.

Many people have heard the rumors that the world will end in 2012 -- and that some astronomical event or alignment is to blame. Dr. David Morrison of the NASA Lunar Science Institute and SETI Institute discusses the public fears and how they have been enflamed by the media. He sets our minds at ease, showing why there is no reason to worry more in 2012 than any other year. Recorded April 21, 2010.

Antimatter is just like matter with all its properties reversed. Scientists think there may have been equal amount of matter and antimatter in the early universe, and yet today we have lots of matter and very little antimatter. How and when that imbalance developed is one of the great mysteries in understanding the underlying properties of the universe. Dr. Helen Quinn, Professor of Physics at the Stanford Linear Accelerator and co-author of a popular book on antimatter, discusses the history of our understanding of antimatter and how we use the little bit of antimatter around today to study some of the highest energy processes among the stars and galaxies. (This talk is a bit more technical than our usual lectures, but well worth exploring if you are interested in some of the most exciting frontiers of physics.) Recorded March 10, 2010.

A half-century ago, astronomers began trying to "eavesdrop" for radio messages from nearby star systems. However, today, SETI researchers continue to point their telescopes at individual stars, on the assumption that technically advanced societies will inhabit a watery world like our own. Dr. Seth Shostak of the SETI Institute describes these searches, but then discusses some novel ideas for how we might pursue the hunt for "cosmic company" and why it's possible that we might find evidence of sophisticated intelligence out there within only a few decades. Seth Shostak is Senior Astronomer at the SETI Institute, in Mountain View, California and hosts the syndicated radio show called "Are We Alone?" Recorded January 20, 2010.

Astrobiologist Dr. Lynn Rothschild of the NASA Ames Research Center has gone from the Bolivian Andes to the Rift Valley of Kenya searching for the hardiest of organisms in the most extreme environments for life. By getting to know life forms on Earth that can occupy the most hostile niches, we can begin to understand the survival requirements for life in general. She describes her quest for "life at the edge" and how such discoveries will shape our search for life in the Solar System and beyond. Recorded November 11, 2009.

Paul Kalas was the leader of the team who managed the long-sought feat of actually taking a photograph of a planet orbiting another star. Before this, all the planets outside our solar system were found by indirect means. He describes how they achieved the breakthrough, using the Hubble Space Telescope, and discusses the wide range of planets out there that astronomers are discovering. Recorded October 7, 2009.

In the last decade or so, astronomers have been forced to accept two mysterious observations. About a quarter of the universe is made of "dark matter," which attracts things with its gravity, but is otherwise invisible. And roughly two-thirds of the universe is composed of "dark energy," which causes space itself to expand at an ever-increasing rate. That means only a small fraction of the universe is made of ordinary matter -- the stuff we understand! In this non-technical presentation, Dr. Patricia Burchat of Stanford University explores the evidence for the dark side of the cosmos, and the experiments that are being developed to investigate it further. Recorded May 20, 2009.

Scientists searching for life elsewhere have to worry about avoiding harmful cross contamination during the exploration of planets and their moons. We don't want to take Earth microbes to Mars or bring back alien microbes to Earth. In this timely talk, Dr. Margaret Race of the SETI Institute gives a behind-the-scenes view of "environmental management" planning for solar system missions, and explains the role of the Outer Space Treaty and other related national and international policies in planning our hunt for life-forms out there. Recorded April 22, 2009.

All the great islands of stars got their start in the first billion years after the beginning of time, the Big Bang. Every deep picture of the sky reveals thousands of these galaxies, each made up of billions of stars like the Sun. Modern instruments like the Hubble Space Telescope have made it possible to look back to a time when the universe looked very different that it does today. Dr. Stephen Beckwith of the University of California discusses some of the deepest images of the universe ever taken and shares recent discoveries about the early days of the cosmos. Recorded March 4, 2009.

In 2009, NASA will purposely crash two spacecraft into one of the Moon's polar regions. The impacts should raise huge plumes of material, visible even to smaller telescopes on Earth. Dr. Anthony Colaprete (NASA Ames Research Center), the Principal Investigator for this intriguing mission, fills us in on why scientists believe there is water in deep craters at the Moon's poles and how the LCROSS mission plans to look for it in the plumes. Recorded January 21, 2009.

NASA's Cassini spacecraft has entered its fifth year exploring the planet Saturn, its rings, and its moons. Dr. Mark Showalter (SETI Institute), a key member of the Cassini science team, shares some of the marvelous results from Saturn and recent discoveries from the mission. His special focus is Saturn's complex and beautiful ring system (which shows a variety of surprising phenomena, including "jets", "propellers", "wisps", "spokes", and "braids") and the remarkable interactions between Saturn's rings and moons. Recorded November 12, 2008.

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 Leonard Susskind of Stanford University and a Dutch colleague have 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.

Dr. Jill Tarter of the SETI Institute is the leader of the main project looking for radio signals from alien civilizations (she was also the model for the character Jodie Foster played in the movie "Contact.") She updates us on the latest tools and plans in this quest, as digital technologies make possible huge improvements in our search systems. The Allen Telescope Array, being constructed in Northern California, will be the most powerful tool for finding SETI signals ever built. It is an innovative radio telescope assembled from a large number of small dishes, using consumer off-the-shelf technologies whenever possible to minimize costs. In the next decade, this new instrument will enable exploration that is 1000 to 10,000 times more sensitive than in the previous decades. This may just be enough! Recorded April 23, 2008.

Astronomers have now discovered more than 250 planets orbiting other stars. Hear the scientist who has discovered more planets than anyone else in the history of the world discuss what kinds of planets we have found so far, and what a new generation of telescopes might find in the future. Could discoveries of planets that resemble the Earth spark a new era when we could someday begin communication with alien life? Dr. Geoff Marcy won the Shaw Prize (one of the highest honors in science) in 2005 and was Discover Magazine's Space Scientist of the Year. He and his co-workers pioneered the technique for finding planets around other stars without seeing light from the planet (by looking for wiggles in the motion of the star each planet orbits.) Recorded March 5, 2008.

In February, NASA's New Horizons spacecraft swung by the giant planet Jupiter on its way to Pluto. Its instruments recorded winderful images and other data about Jupiter's wild weather, its ring, and its giant moons. Dr. Jeff Moore, who was Leader of the Imaging Node for the encounter, shows the new photos of the Jupiter system and discusses some of the discoveries made by New Horizons. He also talk about one of the most exciting discoveries of the Cassini mission around Saturn -- the new understanding and exploration of water geysers on the moon Enceladus. Recorded November 13, 2007.

Asteroids have hit the Earth many time in the past, and they will continue to hit in the future, whether we are prepared or not. Collisions with our planet over 4.5 billion years have profoundly influenced the evolution of life. (In fact, were it not for the impact of a 15-km wide asteroid 65 million years ago, it is likely humanity would not be here.) Dr. David Morrison, one of the world's experts on the study of asteroid impacts, discusses the past and the future of these catastrophic hits, and explains how, in the last two decades, we have learned (in principle) how to defend ourselves. Unlike other natural hazards, we now have the capability of removing most of the impact risk within the next generation. However, the government still does not have a plan of action for when an asteroid is discovered heading our way or when an impact happens without any warning. (We recommend you listen to this podcast holding hands with someone you love.) Recorded October 3, 2007.

Astronomers have discovered dusty "doughnuts" of cosmic raw material around many younger stars. In some cases, astronomers can see tantalizing hints in the rings that planets may be forming or may already have formed from this material. Dr. Dana Backman explains how new kinds of telescopes and observations are making it possible for us to detect the birth process of planets around nearby stars. He concludes by previewing future observations of these intriguing dusty rings with upcoming telescopes, particularly the SOFIA (Stratospheric Observatory for Infrared Astronomy) Project in which NASA has outfitted a 747 plane with a telescope that can observe heat-rays from distant objects. Recorded May 23, 2007.

Take an entertaining and enlightening journey with astronomer and popular author Dr. David Grinspoon through the history of our solar system, discovering runaway greenhouses and snowball planets. Compare the evolution of Venus, Earth, and Mars over the years. And learn how studying the evolution of other planets can help us understand and predict climate change on Earth. Recorded April 11, 2007.

Dr. Nathalie Cabrol is a planetary geologist who is a member of the Science Team for the Mars Exploration Rover mission. She specializes in exploring regions of Earth that resemble Mars (including Licancabur, the highest lake on our planet). She was instrumental in the selection of one of the landing sites for the Mars rovers and is busily analyzing images and data from the mission. In this 2005 lecture, she gave an early progress report on the work of the Spirit and Opportunity rovers, and some of their discoveries about the red planet. Recorded May 19, 2005.

In 1961, Dr. Frank Drake (SETI Institute, University of California, Santa Cruz) proposed an intriguing method of estimating the number of intelligent life-forms out there that we might communicate with, now called the Drake Equation. In this talk, Dr. Drake provides a modern update on estimates for the existence of "E.T." He draws on new ideas and new observations (including the discovery of surprising planets around other stars), which have helped astronomers refine both the targets where they search for life and the methods they use. Recorded April 20, 2005.

Dr. Janice Voss of NASA Ames Research Center, who has logged 49 days in space (traveling almost 19 million miles in 779 Earth orbits) discusses her work in space and what it's like flying on the Shuttle as a scientist. She then talks about NASA's upcoming Kepler mission, which will use a telescope in space to search for "transits" -- when a planet orbiting another star moves in front of its star and blocks its light. Although a planet might only block a tiny fraction of the light from a star, that decrease in brightness is enough to give a clear signal that the planet is there. With this mission, scientists hope to be able to find not only Jupiter and Saturn-sized planets, but also those as small as Earth. At the end, Dr. Voss answers a number of audience questions about both aspects of her work. Recorded March 7, 2007

The Hubble Space Telescope has circled the Earth 15 times every day for more than 16 years. Dr. Bruce Margon (University of California, Santa Cruz), who was until recently the Associate Director for Science for the Hubble, describes the most important discoveries made with the telescope and how it can show us new details of the universe from the solar system to the most distant reaches of space. In addition, he briefly discusses the future of the Hubble and some interesting public reactions to it. Recorded January 24, 2007

In 1998, observations of very distant exploding stars provided intriguing evidence that the expansion of the Universe is speeding up with time, rather than slowing down due to gravity as expected. Today, new and completely independent observations strongly support this amazing conclusion. Over the largest scales of space, our Universe seems to be dominated by a repulsive "dark energy," stretching the very fabric of space itself. Dr. Filippenko, who is a leader in the group that has made some of these remarkable observations, gives us a progress report on our "runaway universe" and then answers a host of audience questions about the overall behavior of the universe. Recorded October 4, 2006

Dr. Dale Cruikshank reviews what we knew about Pluto (including its atmosphere, of which he was the co-discoverer), why Pluto was re-classified as a dwarf planet in the fall of 2006, and what the New Horizons spacecraft may reveal about this distant world in the next decade. Recorded November 8, 2006.