أفضل بودكاسات Life In The Universe (2024)

Course finale and summary. We look back over where we've been the lasteleven weeks, and bring together all of the main themes of this courseon Life in the Universe. Recorded live on 2009 Dec 4 in Room 1005 SmithLaboratory on the Columbus campus of The Ohio State University.بقلم Richard Pogge

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Lecture 45: The Future of Life in the Universe 44:04

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How will life, the Universe, and everything end? This lecture looks atthe evolution of our expanding Universe to project the prospects forlife into the distant cosmological future. Recent observations showthat we live in an infinite, accelerating universe. I will trace theevolution of the universe from the current age of stars into the future.The f…

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Lecture 44: The Future of Life in the Solar System 55:49

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What is the future of life on Earth and in our Solar System? The Sun isthe source of energy for life on the Earth, but it will not shineforever. This lecture looks at the impact of the various stages of theevolution of the Sun on the habitability of the Solar System, withparticular emphasis on the continued habitability of the Earth. I willrefer to…

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Lecture 43: Extraterrestrial Life 45:14

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What does extraterrestrial life look like? This lecture explorescurrent thinking about what extraterrestrial life might be like not byguessing their appearances, but instead applying lessons learned fromour growing understanding of how evolution and biochemistry work onEarth. I will discuss Universal versus Parochial characteristics,Convergent Evol…

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Lecture 42: The Fermi Paradox 44:58

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So, Where is Everybody? Interstellar colonization, in principle, is anexponential growth process that would fill the galaxy in a few millionyears even with a very modest star flight capability. This is a smallfraction of the lifetime of the Milky Way Galaxy, so the Galaxy shouldbe teaming with life. But, we so far have no compelling evidence ofextr…

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Lecture 41: Interstellar Travel and Colonization 45:36

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If we ever detect life elsewhere, how will we go visit? This lectureconsiders the challenges of interstellar travel and colonization. Theproblem is one of basic physics (the enormous energy requirements ofstar flight) coupled with the vast, irreducible distances between thestars. I will describe various starship concepts that use reasonableextrapol…

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Lecture 40: SETI - The Search for Extra-Terrestrial Intelligence 46:28

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Is anybody out there? This lecture reviews the ideas behind SETI, theSearch for Extra-Terrestrial Intelligence, an effort to find otherintelligent communicating civilizations by tuning in on their radio orother electromagnetic communications. I will discuss the basicapproaches being taken by various SETI efforts, and what we expect tofind. In addit…

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Lecture 39: The Drake Equation 45:31

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How many intelligent, communicating civilizations live in our Galaxy?We have no idea. One way to approach the question and come up withquasi-quantitative estimates is the Drake Equation, first introduced byradio astronomy Frank Drake in the 1960s. I will use the Drake equationas an illustration of the issues related to the question ofextraterrestri…

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Lecture 38: The Pale Blue Dot - Seeking Other Earths 44:09

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Are there other Earths out there? Do they have life on them? Thislecture looks at the search for ExoEarths - Earth-sized planets in thehabitable zones of their parent stars, and what we might learn frommeasuring them. The ultimate goal of all planet searches is to findother Earth's, what the late Carl Sagan so poetically calledthe "pale blue dot" a…

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Lecture 37: Strange New Worlds 46:50

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What are the properties of the 400+ exoplanets we have discovered sofar? This lecture reviews the properties of exoplanets, and finds acouple of surprises: Jupiter-mass planets orbiting close to their parentstars, and Jupiter-mass planets in very elliptical orbits. Both seem torequire some mechanism for migration: strong gravitational interactionsw…

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Lecture 36: Exoplanets - Planets Around Other Stars 47:10

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Are there planets around other stars? This lecture reviews the methodsused to hunt for exoplanets and the results thus far. I will describedirect imaging methods, indirect methods relying on the gravitationalinfluence of the planet on its parent star, planetary transits in whicha planet blocks part of its parent star's light, and gravitationalmicro…

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Lecture 35: The Solar Neighborhood 46:03

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What stars are near the Sun? Now that we have some idea of what we arelooking for - rocky planets in the habitable zones of low-massmain-sequence stars - what are the prospects near the Sun? This lectureexamines the hunting ground for planets, the nearby stars that make upthe Solar Neighborhood. I will describe our nearest neighbor, theProxima Cent…

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Lecture 34: Habitable Zones around Stars 47:29

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Which stars are the most hospitable for life? This lecture examines thefactors affecting the habitability of stars, with a goal ofunderstanding where we should search for life-bearing planets. We willdo this by generalizing the idea of a Habitable Zone developed for theSun back in Lecture 30. In this context, we find that the best placesto search f…

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Lecture 33: The Deaths of Stars 47:23

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What happens to a star when it runs out of hydrogen in its core? Thislecture describes the post main-sequence evolution of stars. Whathappens depends on the star's mass. Low mass stars swell up into RedGiants, and eventually shed their envelopes and end their lives as whitedwarf stars. High mass stars become Red Supergiants, and if largeenough, end…

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Lecture 32: The Lives of Stars 46:51

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Why do stars shine? How long do they shine? This lecture describes thephysics of stars on the main sequence, describes the mass-luminosityrelation of main sequence stars, introduces nuclear fusion power and thenuclear fusion lifetimes of stars. From this we gain an importantinsight into one of the criteria we might apply to the search for lifearoun…

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Lecture 31: The Properties of Stars 46:37

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What are the observed properties of stars? This lecture is a quickreview of the basic observational properties of stars, introducingluminosity, spectral classification, the luminosity-radius-temperaturerelation, and the Hertzsprung-Russell (H-R) diagram. This sets up theempirical basis of subsequent lectures on the lives and deaths of stars.Recorde…

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Lecture 30: Goldilocks and the Three Planets 46:19

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Why is the Earth habitable today but Venus and Mars not? This lectureexplores the question of planetary habitability from the perspective ofthe stability of liquid water on the surface of planetary bodies. Wewill see how the amount of sunlight and the greenhouse effect in theatmosphere combine to create a classic Goldilocks problem: whether ornot a…

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Lecture 29: The Children of Saturn 46:10

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Among the 61 known moons of Saturn, two stand out: Enceladus and Titan.Giant Titan is the only moon in our Solar System with a substantialatmosphere, composed of nitrogen and methane, dense enough to maintain aweather cycle with methane analogous to the water cycle on Earth, evenincluding great lakes of liquid methane and ethane at the poles.Encela…

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Lecture 28: The Galilean Moons of Jupiter 44:57

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The four large Galilean Moons of Jupiter seem unlikely places to lookfor life; at first glance they should be cold, dead, icy worlds.Instead we find tremendous geological diversity, and two big surprises:volcanically-active Io, and icy Europa. Io is the most volcanicallyactive world in the Solar System, heated by tides from Jupiter. Europais even m…

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Lecture 27: Is There Life on Mars? 47:04

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Is there life on Mars? We begin with a brief historical survey of the idea of inhabitable Mars, from Herschel to Lowell, and look at how the idea of Mars and Martians is deeply embedded in the popular culture. We then turn to spacecraft explorations of Mars, and how they have changed our view of the Red planet. We will discuss the on-going search o…

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Lecture 26: The Deserts of Mars 47:26

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For many, the most likely place in the Solar System to search for lifebeyond the Earth is Mars. This lecture describes the properties ofMars, a desert world with a thin, dry, cold carbon dioxide atmosphere.I will review evidence that has begun to point unequivocally to theconclusion that Mars had flowing and standing liquid water on itssurface in t…

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Lecture 25: The Requirements for Life in the Solar System 47:04

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Having completed our tour of the Solar System, we now turn to adiscussion of the requirements for life, and where those requirementsmight be satisfied elsewhere in the Solar System. Some - energy,complex chemistry, and liquid water - seem obvious, but they are not theonly possibilities or considerations. At the end, we will have a shortlist of poss…

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Lecture 24: The Jovian Planets 47:50

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We turn our attention to the Giant Planets of the outer Solar System: the gas giants Jupiter and Saturn, and the ice giants Uranus and Neptune. We will review their structure and properties, and then examine their systems of moons, with special attention to the giant moons. While the Jovian planets themselves seem unlikely places to hunt for life i…

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Lecture 23: Terrestrial Worlds in Comparison 46:41

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We follow our tour of our Solar System with an in-depth comparison ofthe Terrestrial Planets. In particular, we want to contrast and comparetheir geological and atmospheric histories. This will inform ourinquiry into whether or not we expect to find life on these worlds.Recorded live on 2009 Oct 27 in Room 1005 Smith Laboratory on theColumbus campu…

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Lecture 22: The Family of the Sun 46:22

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This first lecture of Unit 4 - Life in the Solar System - is a quicktour of our Solar System reviewing the planets, dwarf planets, moons,and small bodies that make up our celestial home. This lecture willintroduce many of the places we will be considering in detail over thenext two weeks, and which we'll find around other stars. Recorded liveon 200…

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Lecture 21: Impacts and Extinction 46:31

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We end our exploration of life on the Earth with a look at death in thefossil record. This lecture looks at the role asteroidal impacts haveplayed in the history of the Earth, and their possible role in massextinction events in the fossil record. We will discuss near-earthasteroids, historical impacts, and the K-T event in which a massiveasteroid i…

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Lecture 20: The History of Life on Earth 47:19

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In this lecture we step back and look at the history of life on Earthfrom the first signs of life at start of the Archaean Eon 3.5 billionyears ago to just up to the present day. We will review the appearanceof photosynthesis and the rise of oxygen in the atmosphere in theProterozoic, the appearance of the first eukaryotes and sexualreproduction, a…

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Lecture 19: The Origin of Life on Earth 46:08

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How did life arise from non-life? Frankly, we don't know, but currentexperimental work is aimed at trying to understand how it might work inbiochemical terms. This lecture sets out the problem of "abiogenesis",and describes our current thinking about the likely origins of life onEarth. We will review the classic Miller-Urey experiment, and look ati…

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Lecture 18: The First Living Things on Earth 46:08

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What are the first recognizable forms of life that we find in thegeological record? How far back can we go in geological time and stillfind life? This lecture reviews three lines of evidence that haveemerged in recent years to suggest that life may have emerged very earlyon the young Earth, perhaps within a few hundred million years of theend of th…

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Lecture 17: Life on the Edge 46:54

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Extremophiles are organisms that are adapted to survive in extreme environments. This lecture describes the challenges thatextremes of heat, cold, acidity, salinity, and radiation pose toorganisms, and show examples of how evolution has nonetheless allowedsome organisms to adapt to not just survive but thrive in such extremeconditions. Finally, we …

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Lecture 16: DNA and Heredity 46:53

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DNA and RNA are the key molecules of living cells. DNA plays a vital role in storing and transmitting the hereditary information that constitutesthe "operating instructions" of living cells; how to construct the functionaland structural proteins that perform vital cell functions, controldevelopmental pathways, and basically "build" the organism. RN…

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Lecture 15: The Chemistry of Life 45:04

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What is the basic chemistry of living organisms? We introduce the requirements for metabolism (rawmaterials and energy), the ATP/ADP energy cycle in cells, auto- andheterotrophs, photosynthesis and chemosynthesis, and the role played byliquid water. The goal of today's lecture is to seek insights into thebasic requirements for life from a considera…

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Lecture 14: Cells 45:32

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Cells are the basic structural and functional unit of all life on Earth.This lecture reviews the basic building blocks of cells, the mainchemical components, the two basic types of cells (Prokaryotes andEukaryotes), and introduces the Phylogenetic Tree of Life, the waybiologists order life by their biochemical and genetic relationships.Understandin…

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Lecture 13: What is Life? 46:16

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How do we define life? This lecture reviews the six basic criteriafor living systems described by biologists: order, reproduction, growth anddevelopment, energy utilization, reaction to environment, and evolutionthat characterize life. The last third of the lecture is an admittedlywhirlwind review of natural selection (I got off my stride and got a…

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Lecture 12: Climate Regulation and Climate Change 45:19

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What are the main mechanisms of climate regulation and climatechange that have operated through Earth's history? The Earth'sclimate is regulated by a Carbon Dioxide thermostat that is theinteraction between the Greenhouse Effect and the CO2 Cycle. I describethe CO2 cycle and its role in regulating global temperature. I willthen discuss other influe…

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Lecture 11: The History of the Earth 42:39

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How have we pieced together the geological history of the Earth?This lecture reviews the different types of rocks and the cycleof transformation between them, with particular emphasis on stratigraphy. I will outline the 4 major Eons in Earth's history, and focus on theearliest Hadean Eon which proceeded from the formation of the Earth to the end of…

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Lecture 10: The Earth's Atmosphere Erratum 1:17

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This lecture was to be about the Earth's atmosphere, its composition andstructure, the greenhouse effect, and the primordial atmosphere, butabout 2 seconds into the lecture, unbeknownst to me, the batterycompartment on my digital voice recorder came open in my pocket. At theend of lecture, I took it out of my pocket to turn it off and thebattery di…

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Lecture 9: Inside the Earth 42:47

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What is the interior structure of the Earth and how does it drive theEarth's magnetic and geologic activity? We will review our currentknowledge of the interior of the Earth, how we measure it usingSeismology, the origins of the Earth's magnetic field, and discuss theworkings of plate tectonics. the Earth is a dynamic, geologicallyactive world, whi…

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Lecture 8: The Cosmological Revolution - The Depths of Space and Time 46:29

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Cosmology is the study of the entire Universe as a physical system. Thepast century has witnessed a revolution in cosmological thought that has revealed the vastness of space and the depths of cosmic time, a revolutionthat is still playing out in the present day. The lecture will review the Earth's place in the Universe, the age of the Universe as …

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Lecture 7: The Biological Revolution - What is Life? 44:16

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What is the nature of life? In this lecture I will review the revolution in biological thinking that has dramatically changed how we view life. I will review such persistent ancient ideas as spontaneous generation and why it took so long to disprove this notion, the impact of the microscope on biology, and the discovery of the laws and agency of he…

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Lecture 6: The Geological Revolution - Deep Time and the Age of the Earth 46:11

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The geological revolution revealed that the Earth is of great antiquityand yet has a history we can read in the land. We will discuss ideas of cyclic and linear time, historical versus physical age estimates, the discovery of geological time, andradiometric dating methods that give us our present estimate of4.54+/-0.05 Gyr for the age of the Earth.…

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Lecture 5: The Chemical Revolution and the Nature of Matter 45:17

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What is the nature of matter, and how did we come to understand thechemical elements and atomic structure? This lecture is a brief andselective overview of the history of our understanding of the nature ofmatter and chemistry. We will also introduce spectroscopy andradioactivity, two very powerful tools that came out of the chemicalrevolution that …

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Lecture 4: The Copernican Revolution 43:56

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Modern science was borne of an effort over many centuries to understandthe motions of celestial bodies. The Copernican Revolution of the 16thand 17th centuries was the crucial moment in history when we finallyunderstood the nature of celestial motions, and opened the door to themodern world. This lecture reviews the problem of celestial motions,the…

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Lecture 3: Imagining Other Worlds 40:09

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What is the cultural history of our imaginings of other worlds and their possible inhabitants? I will draw examples from history, philosophy, literature, cinema, and popular culture. In the end, our imaginings about other worlds inform us more about ourselves, ourhopes and our fears, than about extraterrestrial life. The scientificinquiry we are un…

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Lecture 2: Astronomical Numbers 43:56

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An introduction and review of the basic notation and physical units we will beusing throughout this course. In particular, we will be using theMetric (SI) system for lengths, masses, times, and temperatures, andspecial astronomical units for distances (AU and Light Years) and masses(Earth Masses and Solar Masses) appropriate when discussinginterpla…

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Lecture 1: Introduction 19:24

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A brief overview of the topics we will cover inAstronomy 141, setting the stage for how we can make a seriousscientific inquiry out of the question of whether or not there is lifeelsewhere in the Universe. It is a short lecture, the first half was anoverview of course mechanics (tests, homework, office hours, etc.) thatI did not record. Recorded li…

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Welcome to Astronomy 141

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Welcome to the Astronomy 141 Lecture Podcasts. This is a brief messagefrom me explaining the podcasts, and welcoming new and old listeners.University. Lectures will begin on Wednesday, 2009 Sept 23, and runthrough Friday, 2009 Dec 4. New lectures will appear shortly before 6pmUS Eastern Time each day there is a regular class. Recorded live on 2009 …

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