A new podcast, Astronomy 141, Life in the Universe, is availablefor those interested in continuing an exploration of topics inmodern astronomy.

A new podcast, Astronomy 141, Life in the Universe, is available for those interested in continuing an exploration of topics in modern astronomy.

Astronomy 141 Podcast Teaser

Are there planets around other stars?  Are there Earth-like planetsaround other stars?  Do any of those harbor life?  Intelligent life?We'd like to know the answers to all of these questions, and in recentyears we've made great progress towards at least answering the first.  To date, more than 200 planets have been found around other stars, most in theinterstellar neighborhood of the Sun, but a few at great distance.  Thislecture reviews the search for ExoPlanets, discussing the successfulDoppler Wobble, Transit, and Microlensing techniques.  What we havefound so far are very suprising systems, especially Jupiter-size orbigger planets orbiting very close (few hundredths of an AU) from theirparent stars.  The existance of a significant population of so-called"Hot Jupiters" may be telling us that planetary migration can be muchmore extreme that we saw in our own Solar System, or that theseplanetary system formed in a very different way than ours.  It seemsappropriate to end this class with more questions than answers, butthat's where the science becomes most exciting.  Recorded 2006 Dec 1 in100 Stillman Hall on the Columbus campus of The Ohio State University.

Are there planets around other stars? Are there Earth-like planets around other stars? Do any of those harbor life? Intelligent life? We'd like to know the answers to all of these questions, and in recent years we've made great progress towards at least answering the first. To date, more than 200 planets have been found around other stars, most in the interstellar neighborhood of the Sun, but a few at great distance. This lecture reviews the search for ExoPlanets, discussing the successful Doppler Wobble, Transit, and Microlensing techniques. What we have found so far are very suprising systems, especially Jupiter-size or bigger planets orbiting very close (few hundredths of an AU) from their parent stars. The existance of a significant population of so-called "Hot Jupiters" may be telling us that planetary migration can be much more extreme that we saw in our own Solar System, or that these planetary system formed in a very different way than ours. It seems appropriate to end this class with more questions than answers, but that's where the science becomes most exciting. Recorded 2006 Dec 1 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 46: ExoPlanets - Planets around Other Stars

What is a planet?  Is Pluto a planet?  This lecture traces the debate onthe nature of what it means to be a planet by taking an historical approach, looking at how the question has arisen with the discovery of the asteroids andlater Pluto and the Kuiper Belt.  Many of the issued raised at the 2006IAU General Assembly meeting were raised two centuries before after thediscovery of Ceres and Pallas.  We will end with the new definition of aplanet, and why Pluto is better understood as a Dwarf Planet, among thetwo largest objects of the class of small icy bodies of the outer solarsystem, than as the smallest of the planets.  Recorded 2006 Nov 30 in100 Stillman Hall on the Columbus campus of The Ohio State University.

What is a planet? Is Pluto a planet? This lecture traces the debate on the nature of what it means to be a planet by taking an historical approach, looking at how the question has arisen with the discovery of the asteroids and later Pluto and the Kuiper Belt. Many of the issued raised at the 2006 IAU General Assembly meeting were raised two centuries before after the discovery of Ceres and Pallas. We will end with the new definition of a planet, and why Pluto is better understood as a Dwarf Planet, among the two largest objects of the class of small icy bodies of the outer solar system, than as the smallest of the planets. Recorded 2006 Nov 30 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 45: Is Pluto a Planet?

Comets are occasional visitors from the icy reaches of the outer SolarSystem.  This lecture discusses the orbits, structure, and properties ofcomets, and introduces the "dirty snowball" model of a comet nucleus.The end of class was a demo where I created a model of a comet nucleusfrom common household and office materials.  Imagine a twistedcombination of Alton Brown and Emeril Lagasse with a PhD in Astrophysicsand you get the idea.  We were not able to arrange for a videographer tocome, but we did get some stills before the batteries died on thedigital camera.  The pictures are on the lecture webpage.  The lectureis slightly abbreviated because we did the student evaluation ofinstruction surveys before class started.  Recorded 2006 Nov 29 in 100Stillman Hall on the Columbus campus of The Ohio State University.

Comets are occasional visitors from the icy reaches of the outer Solar System. This lecture discusses the orbits, structure, and properties of comets, and introduces the "dirty snowball" model of a comet nucleus. The end of class was a demo where I created a model of a comet nucleus from common household and office materials. Imagine a twisted combination of Alton Brown and Emeril Lagasse with a PhD in Astrophysics and you get the idea. We were not able to arrange for a videographer to come, but we did get some stills before the batteries died on the digital camera. The pictures are on the lecture webpage. The lecture is slightly abbreviated because we did the student evaluation of instruction surveys before class started. Recorded 2006 Nov 29 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 44: Comets

Beyond the orbit of Neptune is the realm of the icy worlds, ranging insize from Triton, the giant moon of Neptune, and the dwarf planets Plutoand Eris, all the way down to the nuclei of comets.  This lecturediscussed the icy bodies of the Trans-Neptunian regions of the SolarSystem, discussing the basic properties of Triton (the best studied suchobject), Pluto, Eris, and the Kuiper Belt, introducing the dynamicalfamilies of Trans-Neptunian Objects that record in their orbits the slowmigration of Neptune outwards during the early history of the SolarSystem.  The Kuiper Belt is the icy analog of the main Asteroid Belt ofthe inner Solar System: both are shaped by their gravitationalinteraction with giant gas planets (Jupiter for the asteroids, Neptunefor the KBOs), and are composed of leftover raw materials from theformation of their respective regions of the Solar System.  Recorded2006 Nov 28 in 100 Stillman Hall on the Columbus campus of The OhioState University.

Beyond the orbit of Neptune is the realm of the icy worlds, ranging in size from Triton, the giant moon of Neptune, and the dwarf planets Pluto and Eris, all the way down to the nuclei of comets. This lecture discussed the icy bodies of the Trans-Neptunian regions of the Solar System, discussing the basic properties of Triton (the best studied such object), Pluto, Eris, and the Kuiper Belt, introducing the dynamical families of Trans-Neptunian Objects that record in their orbits the slow migration of Neptune outwards during the early history of the Solar System. The Kuiper Belt is the icy analog of the main Asteroid Belt of the inner Solar System: both are shaped by their gravitational interaction with giant gas planets (Jupiter for the asteroids, Neptune for the KBOs), and are composed of leftover raw materials from the formation of their respective regions of the Solar System. Recorded 2006 Nov 28 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 43: Icy Worlds of the Outer Solar System

Asteroids are the leftover rocky materials from the formation of theSolar System that reside mainly in a broad belt between the orbits ofMars and Jupiter.  Meteoroids are fragments of asteroids or bits ofdebris from passing comets that occasionally pass through our atmosphereas meteors, and even more rarely survive the fiery passage to reach theground as a meteorite.  This lecture reviews the physical and dynamical(orbital) properties of Asteroids and Meteoroids, and discusses the roleof Jupiter and orbital resonances in dynamically sculpting the MainBelt.  Recorded 2006 Nov 27 in 100 Stillman Hall on the Columbus campusof The Ohio State University.

Asteroids are the leftover rocky materials from the formation of the Solar System that reside mainly in a broad belt between the orbits of Mars and Jupiter. Meteoroids are fragments of asteroids or bits of debris from passing comets that occasionally pass through our atmosphere as meteors, and even more rarely survive the fiery passage to reach the ground as a meteorite. This lecture reviews the physical and dynamical (orbital) properties of Asteroids and Meteoroids, and discusses the role of Jupiter and orbital resonances in dynamically sculpting the Main Belt. Recorded 2006 Nov 27 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 42: Asteroids and Meteoroids

All Jovian planets have rings.  We are most familiar with the bright,spectacular rings of Saturn, but the other Jovian planets have ringssystems around them.  This lecture describes the different ring systemsand their properties, and discusses their origin, formation, and thephysics - resonances and shepherd moons - that govern their evolution.Recorded 2006 Nov 22 in 100 Stillman Hall on the Columbus campus of TheOhio State University.

All Jovian planets have rings. We are most familiar with the bright, spectacular rings of Saturn, but the other Jovian planets have rings systems around them. This lecture describes the different ring systems and their properties, and discusses their origin, formation, and the physics - resonances and shepherd moons - that govern their evolution. Recorded 2006 Nov 22 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 41: Planetary Rings

Saturn is attended by a system of 56 known moons and bright, beautifulrings.  The Moon system is the focus of our attention today.  Saturn hasone giant moon, Titan, which is the 2nd largest moon in the SolarSystem, and the only one with a heavy atmosphere.  On Titan, theatmosphere is mostly nitrogen and methane, but the temperature andpressure are such that methane plays the same role that water plays onthe Earth: it can be either a solid, gas, or liquid.  I will reviewtantalizing evidence from the Cassini and Huygens probes that there is,in fact, liquid methane and maybe even liquid methane lakes on Titan.Most of the other moons are ancient, icy, and heavily cratered -geologically dead worlds - but one, Enceladus, is a big surprise.  Theshiniest object in the Solar System, Enceladus has spectacular fountains- cryovolcanos - that spew water vapor from reservoirs created in itstidally-heated interior.  This ice repaves much of the surface ofEnceladus, giving it a young, shiny surface, and builds the E ring ofSaturn.  Recorded 2006 Nov 21 in 100 Stillman Hall on the Columbuscampus of The Ohio State University.

Saturn is attended by a system of 56 known moons and bright, beautiful rings. The Moon system is the focus of our attention today. Saturn has one giant moon, Titan, which is the 2nd largest moon in the Solar System, and the only one with a heavy atmosphere. On Titan, the atmosphere is mostly nitrogen and methane, but the temperature and pressure are such that methane plays the same role that water plays on the Earth: it can be either a solid, gas, or liquid. I will review tantalizing evidence from the Cassini and Huygens probes that there is, in fact, liquid methane and maybe even liquid methane lakes on Titan. Most of the other moons are ancient, icy, and heavily cratered - geologically dead worlds - but one, Enceladus, is a big surprise. The shiniest object in the Solar System, Enceladus has spectacular fountains - cryovolcanos - that spew water vapor from reservoirs created in its tidally-heated interior. This ice repaves much of the surface of Enceladus, giving it a young, shiny surface, and builds the E ring of Saturn. Recorded 2006 Nov 21 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 40: The Saturn System

Jupiter is surrounded by a solar system in miniature of 63 known moons.Most (59) are tiny, irregular bodies that are a combination of capturedasteroids and comets.  The 4 largest are the giant Galilean Moons: Io,Europa, Ganymede, and Callisto.  Each is a fascinating world of its own,with a unique history and properties: volcanically active Io, icy Europawhich may hide an ocean of liquid water beneath the surface, the groovedterrain of Ganymede, and frozen dirty Callisto with the most ancientsurface of the four.  Recorded 2006 Nov 20 in 100 Stillman Hall on theColumbus campus of The Ohio State University.

Jupiter is surrounded by a solar system in miniature of 63 known moons. Most (59) are tiny, irregular bodies that are a combination of captured asteroids and comets. The 4 largest are the giant Galilean Moons: Io, Europa, Ganymede, and Callisto. Each is a fascinating world of its own, with a unique history and properties: volcanically active Io, icy Europa which may hide an ocean of liquid water beneath the surface, the grooved terrain of Ganymede, and frozen dirty Callisto with the most ancient surface of the four. Recorded 2006 Nov 20 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 39: The Moons of Jupiter

Uranus and Neptune are the smallest and outermost of the 4 Jovianplanets.  While superficially similar to Jupiter and Saturn, there aresubstantial differences.  Uranus and Neptune have smaller rocky coressurrounded by deep, slushy ice mantles and relatively thinner hydrogenatmospheres, quite different from the massive cores and deep metallichydrogen mantles of Jupiter and Saturn.  We will also ask why theyappear blue, look at their internal energy and weather, and then reviewthe properties of the Jovian planets as a group.  Recorded 2006 Nov 16in 100 Stillman Hall on the Columbus campus of The Ohio StateUniversity.

Uranus and Neptune are the smallest and outermost of the 4 Jovian planets. While superficially similar to Jupiter and Saturn, there are substantial differences. Uranus and Neptune have smaller rocky cores surrounded by deep, slushy ice mantles and relatively thinner hydrogen atmospheres, quite different from the massive cores and deep metallic hydrogen mantles of Jupiter and Saturn. We will also ask why they appear blue, look at their internal energy and weather, and then review the properties of the Jovian planets as a group. Recorded 2006 Nov 16 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 38: Uranus and Neptune

Astronomy 161, Introduction to the Solar System, is the first quarter ofa 2-quarter introductory Astronomy for non-science majors taught at TheOhio State University.  This podcast presents audio recordings ofProfessor Richard Pogge's lectures from his Autumn Quarter 2006 class.All of the lectures were recorded live in 100 Stillman Hall on the OSUMain Campus in Columbus, Ohio.

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Astronomy 161, Introduction to the Solar System, is the first quarter of a 2-quarter introductory Astronomy for non-science majors taught at The Ohio State University. This podcast presents audio recordings of Professor Richard Pogge's lectures from his Autumn Quarter 2006 class. All of the lectures were recorded live in 100 Stillman Hall on the OSU Main Campus in Columbus, Ohio.

Astronomy 161 - Introduction to Solar System Astronomy

What are the constellations, and how have they be named and used by manydifferent cultures throughout human history?  We will review the mostbasic feature of the night sky, the 6000 visible stars sprinkled aboutthe sky, and introduce the idea of constellations, reviewing theirhistory and uses.  We'll end with a brief discussion of where stars gettheir names.  Recorded 2006 Sep 22 in 100 Stillman Hall on the Columbuscampus of The Ohio State University.

What are the constellations, and how have they be named and used by many different cultures throughout human history? We will review the most basic feature of the night sky, the 6000 visible stars sprinkled about the sky, and introduce the idea of constellations, reviewing their history and uses. We'll end with a brief discussion of where stars get their names. Recorded 2006 Sep 22 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 3: The Starry Night

What is the shape and size of the Earth?  This lecture traces historicalideas about the shape of the Earth, from ancient flat-Earth models tothe compelling demonstrations by Aristotle in the 3rd century BC thatthe Earth was a sphere.  We then discuss ways people measured the sizeof the Earth, describing the results of Eratosthenes of Cyrene in the2nd century BC and Claudius Ptolemy in the 2nd century AD, and theirimpact.  Recorded 2006 Sep 25 in 100 Stillman Hall on the Columbuscampus of The Ohio State University.

What is the shape and size of the Earth? This lecture traces historical ideas about the shape of the Earth, from ancient flat-Earth models to the compelling demonstrations by Aristotle in the 3rd century BC that the Earth was a sphere. We then discuss ways people measured the size of the Earth, describing the results of Eratosthenes of Cyrene in the 2nd century BC and Claudius Ptolemy in the 2nd century AD, and their impact. Recorded 2006 Sep 25 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 4: Measuring the Earth

How did the Solar System form?  This lecture examines the clues in thepresent-day dynamics (orbital and rotation motions) of the planets andplanetary composition to the formation of the solar system.  We willthen describe the accretion model, where grains condense out of theprimordial solar nebula, grains aggregate by collisions intoplanetesimals, then gravity begins to work and planetesimals grow intoprotoplanets.  What kind of planet grows depends on where theprotoplanets are in the primordial solar nebula: close to the Sun onlyrocky planets form, beyond the Frost Line ices and volatiles cancondense out, allowing the growth of the gas giants.  The whole processtook about 100 million years, and we as we explore the solar system wewill look for traces of this process on the various worlds we visit.Recorded 2006 Nov 7 in 100 Stillman Hall on the Columbus campus of TheOhio State University.

How did the Solar System form? This lecture examines the clues in the present-day dynamics (orbital and rotation motions) of the planets and planetary composition to the formation of the solar system. We will then describe the accretion model, where grains condense out of the primordial solar nebula, grains aggregate by collisions into planetesimals, then gravity begins to work and planetesimals grow into protoplanets. What kind of planet grows depends on where the protoplanets are in the primordial solar nebula: close to the Sun only rocky planets form, beyond the Frost Line ices and volatiles can condense out, allowing the growth of the gas giants. The whole process took about 100 million years, and we as we explore the solar system we will look for traces of this process on the various worlds we visit. Recorded 2006 Nov 7 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 32: The Origin of the Solar System

Where are we?  Where is someplace else?  How do I get from here tothere?  These are questions we need to answer both on the Earth and inthe Sky to assign a location to a place or celestial object on thesurface of a sphere.  We start by introducing angular units, and usethem to describe the terrestrial system of latitude and longitude on thespherical Earth.  We then define the Celestial Sphere, with itsCelestial Equator and Poles, and begin to define an analogous coordinatesystem on the sky.  An important wrinkle is that what part of the sky wesee at any given time depends on both where we are on the Earth, andwhat date/time it is.  This gives us the start of the coordinate systemwe need to begin our exploration of motions in the sky in the nextlectures.  Recorded 2006 Sep 26 in 100 Stillman Hall on the Columbuscampus of The Ohio State University.

Where are we? Where is someplace else? How do I get from here to there? These are questions we need to answer both on the Earth and in the Sky to assign a location to a place or celestial object on the surface of a sphere. We start by introducing angular units, and use them to describe the terrestrial system of latitude and longitude on the spherical Earth. We then define the Celestial Sphere, with its Celestial Equator and Poles, and begin to define an analogous coordinate system on the sky. An important wrinkle is that what part of the sky we see at any given time depends on both where we are on the Earth, and what date/time it is. This gives us the start of the coordinate system we need to begin our exploration of motions in the sky in the next lectures. Recorded 2006 Sep 26 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 5: Mapping Earth and Sky

Jupiter and Saturn are the largest planets in the Solar System,and the prototype of the Jovian Gas Giant planets.  This lecturefocusses on the planets themselves, looking at their composition,atmospheres, and internal structures.  We will leave discussionof their fascinating systems of rings and moons for next week.Recorded 2006 Nov 15 in 100 Stillman Hall on the Columbus campusof The Ohio State University.

Jupiter and Saturn are the largest planets in the Solar System, and the prototype of the Jovian Gas Giant planets. This lecture focusses on the planets themselves, looking at their composition, atmospheres, and internal structures. We will leave discussion of their fascinating systems of rings and moons for next week. Recorded 2006 Nov 15 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 37: Jupiter and Saturn

Venus, the second planet from the Sun, is perpetually veiled behindopaque clouds of sulfuric acid droplets atop a hot, heavy, mostly carbondioxide atmosphere.  In size and apparent composition, however, it is anear twin-sister of the Earth.  Why is it do different?  This lecturereviews the basic properties of Venus, and examines the similarties anddifferences with the Earth.  Recorded 2006 Nov 9 in 100 Stillman Hall onthe Columbus campus of The Ohio State University.

Venus, the second planet from the Sun, is perpetually veiled behind opaque clouds of sulfuric acid droplets atop a hot, heavy, mostly carbon dioxide atmosphere. In size and apparent composition, however, it is a near twin-sister of the Earth. Why is it do different? This lecture reviews the basic properties of Venus, and examines the similarties and differences with the Earth. Recorded 2006 Nov 9 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 34: Venus Unveiled

Why do celestial objects appear to rise in the East and set in the West?How does this depend on where you are on the Earth, or the time of year?Today we set the heavens into motion, and look at the two most basictypes of celestial motions.  Apparent daily motions are a reflection ofthe daily rotation of the Earth about its axis.  The apparent annualmotions are a reflection of the Earth's orbit around the Sun.  Todescribe the Sun's apparent annual motion, we introduce the Ecliptic,the Obliquity of the Ecliptic, and four special locations along theEcliptic: the Solstices and Equinoxes.  This will set the stage for muchof our discussions in rest of this section.  Recorded 2006 Sep 27 in 100Stillman Hall on the Columbus campus of The Ohio State University.

Why do celestial objects appear to rise in the East and set in the West? How does this depend on where you are on the Earth, or the time of year? Today we set the heavens into motion, and look at the two most basic types of celestial motions. Apparent daily motions are a reflection of the daily rotation of the Earth about its axis. The apparent annual motions are a reflection of the Earth's orbit around the Sun. To describe the Sun's apparent annual motion, we introduce the Ecliptic, the Obliquity of the Ecliptic, and four special locations along the Ecliptic: the Solstices and Equinoxes. This will set the stage for much of our discussions in rest of this section. Recorded 2006 Sep 27 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 6: Daily and Annual Motions

What is the structure of the Moon, and what physical processes haveshaped its surface?  In this lecture we turn to our nearest celestialneighbor, the Moon, to see a world quite different than the dynamicEarth.  We will discuss the surface features of the Moon (the Mariaand cratered highlands), see how crater density tells us the relativeages of terrain, and look at the composition of Moon rocks returnedby astronauts and robotic probes.  We also discuss the interiorof the Moon, and review what we know about lunar history and formation.Recorded 2006 Nov  2 in 100 Stillman Hall on the Columbus campusof The Ohio State University.

What is the structure of the Moon, and what physical processes have shaped its surface? In this lecture we turn to our nearest celestial neighbor, the Moon, to see a world quite different than the dynamic Earth. We will discuss the surface features of the Moon (the Maria and cratered highlands), see how crater density tells us the relative ages of terrain, and look at the composition of Moon rocks returned by astronauts and robotic probes. We also discuss the interior of the Moon, and review what we know about lunar history and formation. Recorded 2006 Nov 2 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 30: The Moon

How old is the Earth?  This lecture reviews the idea of cyclic andlinear time, since how you view time determines whether the question ofthe age of the Earth is even meaningful.  We then review various wayspeople have estimated the age of the Earth, starting with historicalages that equate human history with the history of the Earth proper, andthen see how various physical estimates, which do not make an appeal tohuman history, were made.  This brings us to the technique ofradioactive age dating of the oldest rocks, leading to our current bestestimate of 4.5+/-0.1 Billion years for the age of our planet.  Recorded2006 Oct 30 in 100 Stillman Hall on the Columbus campus of The OhioState University.

How old is the Earth? This lecture reviews the idea of cyclic and linear time, since how you view time determines whether the question of the age of the Earth is even meaningful. We then review various ways people have estimated the age of the Earth, starting with historical ages that equate human history with the history of the Earth proper, and then see how various physical estimates, which do not make an appeal to human history, were made. This brings us to the technique of radioactive age dating of the oldest rocks, leading to our current best estimate of 4.5+/-0.1 Billion years for the age of our planet. Recorded 2006 Oct 30 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 27: Deep Time - The Age of the Earth

Why are there two high tides a day?  This lecture examines another ofthe consequences of gravity, the twice-daily tides raised on the Earthby the Moon.  Tides are a consequence of differences in the gravityforce of the Moon from one side to the other of the Earth (stronger onthe side nearest the Moon, weaker on the side farthest from the Moon).The Sun raises tides on the Earth as well, about half as strong as Moontides, giving rise to the effect of Spring and Neap tides that stronglycorrelate with Lunar Phase.  We also look at body tides raised on theMoon by the Earth, and how that has led to Tidal Locking of the Moon'srotation, which is why the Moon always keeps the same face towards theEarth.  We then explore the combined effects of tidal braking of theEarth, which slows the Earth's rotation and increases the length of theday by about 23 milliseconds per century, and causes the steadyRecession of the Moon, which moves 3.8cm away from Earth every year.Tidal effects are extremely important to understanding the DynamicalEvolution of many bodies in the Solar System, as we'll see time andagain in the second half of the class.  Recorded 2006 Oct 18 in 100Stillman Hall on the Columbus campus of The Ohio State University.

Why are there two high tides a day? This lecture examines another of the consequences of gravity, the twice-daily tides raised on the Earth by the Moon. Tides are a consequence of differences in the gravity force of the Moon from one side to the other of the Earth (stronger on the side nearest the Moon, weaker on the side farthest from the Moon). The Sun raises tides on the Earth as well, about half as strong as Moon tides, giving rise to the effect of Spring and Neap tides that strongly correlate with Lunar Phase. We also look at body tides raised on the Moon by the Earth, and how that has led to Tidal Locking of the Moon's rotation, which is why the Moon always keeps the same face towards the Earth. We then explore the combined effects of tidal braking of the Earth, which slows the Earth's rotation and increases the length of the day by about 23 milliseconds per century, and causes the steady Recession of the Moon, which moves 3.8cm away from Earth every year. Tidal effects are extremely important to understanding the Dynamical Evolution of many bodies in the Solar System, as we'll see time and again in the second half of the class. Recorded 2006 Oct 18 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 20: Tides

Mercury is the innermost of the planets, a hot, dead world that has beenheavily battered by impacts.  This lecture reviews the basic propertiesof Mercury, particularly its surface and interior.  Recorded 2006 Nov 8in 100 Stillman Hall on the Columbus campus of The Ohio StateUniversity.

Mercury is the innermost of the planets, a hot, dead world that has been heavily battered by impacts. This lecture reviews the basic properties of Mercury, particularly its surface and interior. Recorded 2006 Nov 8 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 33: Battered Mercury

Why do Kepler's Laws work?  This lecture discusses how Newton appliedhis Three Laws of Motion and the Law of Universal Gravitation to theproblem of orbits.  Newton generalized Kepler's laws to apply to any twomassive bodies orbiting around their common center of mass.  We discussthese new, generalized laws of orbital motion, introducing the familiesof open and closed orbits, circular and escape velocity, center-of-mass,conservation of angular momentum, and how orbital mechanics is used tomeasure the masses of astronomical objects.  Recorded 2006 Oct 17 in 100Stillman Hall on the Columbus campus of The Ohio State University.

Why do Kepler's Laws work? This lecture discusses how Newton applied his Three Laws of Motion and the Law of Universal Gravitation to the problem of orbits. Newton generalized Kepler's laws to apply to any two massive bodies orbiting around their common center of mass. We discuss these new, generalized laws of orbital motion, introducing the families of open and closed orbits, circular and escape velocity, center-of-mass, conservation of angular momentum, and how orbital mechanics is used to measure the masses of astronomical objects. Recorded 2006 Oct 17 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 19: Orbits

Nicolaus Copernicus

In 1543, Nicolaus Copernicus re-introduced the Heliocentric idea ofAristarchus of Samos in an attempt to purge Ptolemy's geocentric systemof the un-Aristotelian idea of the Equant.  His goal was to derive amodel that, in his words, pleased the mind as well as preservedappearances.  What he started, without intending, was a profoundrevolution in thought that was to overturn both Ptolemy and Aristotlewithin two centuries, and help give birth the the modern world.  Thislecture looks at the Copernican system, and sets the stage for thescientific revolution of the following generations.  Recorded 2006 Oct10 in 100 Stillman Hall on the Columbus campus of The Ohio StateUniversity.

In 1543, Nicolaus Copernicus re-introduced the Heliocentric idea of Aristarchus of Samos in an attempt to purge Ptolemy's geocentric system of the un-Aristotelian idea of the Equant. His goal was to derive a model that, in his words, pleased the mind as well as preserved appearances. What he started, without intending, was a profound revolution in thought that was to overturn both Ptolemy and Aristotle within two centuries, and help give birth the the modern world. This lecture looks at the Copernican system, and sets the stage for the scientific revolution of the following generations. Recorded 2006 Oct 10 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 14: The Revolutions of Nicolaus Copernicus

Mars, fourth planet from the Sun, is a cold desert planet with a thin,dry carbon-dioxide atmosphere.  The geology of Mars, however, showssigns of an active past, with hot-spot volcanism, and tantalizing signsof ancient water flows.  While a cold, dead desert planet today, Mars'past may have been warmer and wetter, with liquid water during the firstthird of its history.  This lecture will review the properties of Mars,and discuss the evidences of its active past.  Recorded 2006 Nov 13 in100 Stillman Hall on the Columbus campus of The Ohio State University.

Mars, fourth planet from the Sun, is a cold desert planet with a thin, dry carbon-dioxide atmosphere. The geology of Mars, however, shows signs of an active past, with hot-spot volcanism, and tantalizing signs of ancient water flows. While a cold, dead desert planet today, Mars' past may have been warmer and wetter, with liquid water during the first third of its history. This lecture will review the properties of Mars, and discuss the evidences of its active past. Recorded 2006 Nov 13 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 35: The Deserts of Mars

What is Gravity?  This lecture reviews the law of falling bodies firstdescribed by Galileo, and then Newton's explanation in terms of his Lawof Universal Gravitation.  Gravity is a mutually attractive force thatacts between any two massive bodies.  Its strength is proportional tothe product of the two masses, and inversely proportional to the squareof the distance between their centers.  We then compare the fall of anapple on the Earth to the orbit of the Moon, and show that the Moon isheld in its orbit by the same gravity that works on the surface of theEarth.  In effect, the Moon is perpetually "falling" around the Earth.Recorded 2006 Oct 16 in 100 Stillman Hall on the Columbus campus of TheOhio State University.

What is Gravity? This lecture reviews the law of falling bodies first described by Galileo, and then Newton's explanation in terms of his Law of Universal Gravitation. Gravity is a mutually attractive force that acts between any two massive bodies. Its strength is proportional to the product of the two masses, and inversely proportional to the square of the distance between their centers. We then compare the fall of an apple on the Earth to the orbit of the Moon, and show that the Moon is held in its orbit by the same gravity that works on the surface of the Earth. In effect, the Moon is perpetually "falling" around the Earth. Recorded 2006 Oct 16 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 18: The Apple and the Moon - Newtonian Gravity

What are the origins of the Geocentric and Heliocentric modelsput foward to explain planetary motion?  This lecture begins a newunit that will chart the rise of our modern view of the solar system byreviewing the highly influential work by Greek and Roman philosopherswho elaborated the first geocentric and heliocentric models ofthe Solar System.  We discuss the various geocentric systems fromthe simple crystaline spheres of Anaximander, Eudoxus, and Aristotlethrough the Epicyclic systems of Hipparchus and Ptolemy.  We willalso briefly discuss what is known of Aristarchus' mostly-lost heliocentricsystem, which was to so strongly influence the work of Copernicus.  Theultimate expression of an epicyclic Geocentric system was that described by Claudius Ptolemy in the middle of the 2nd Century AD, andwas to prevail virtually unchallenged for nearly 14 centuries.Recorded 2006 Oct  9 in 100 Stillman Hall on the Columbus campusof The Ohio State University.

What are the origins of the Geocentric and Heliocentric models put foward to explain planetary motion? This lecture begins a new unit that will chart the rise of our modern view of the solar system by reviewing the highly influential work by Greek and Roman philosophers who elaborated the first geocentric and heliocentric models of the Solar System. We discuss the various geocentric systems from the simple crystaline spheres of Anaximander, Eudoxus, and Aristotle through the Epicyclic systems of Hipparchus and Ptolemy. We will also briefly discuss what is known of Aristarchus' mostly-lost heliocentric system, which was to so strongly influence the work of Copernicus. The ultimate expression of an epicyclic Geocentric system was that described by Claudius Ptolemy in the middle of the 2nd Century AD, and was to prevail virtually unchallenged for nearly 14 centuries. Recorded 2006 Oct 9 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 13: Greek Astronomy

Tycho did as much as could be done with the naked eye, a new technologywas required to extend our vision, the telescope.  This lectureintroduces Galileo Galilei, the contemporary of Kepler who was in manyways the first modern astronomer, and his discoveries with thetelescope.  These observations were to electify Europe in the early 17thcentury, and begin the final intellectual dismantling of theAristotelian view of the world.  Galileo's claims that they constitutedproof of the Copernican Heliocentric System, however, were to bring himinto conflict with the Roman Catholic Church.  Recorded 2006 Oct 12 in100 Stillman Hall on the Columbus campus of The Ohio State University.

Tycho did as much as could be done with the naked eye, a new technology was required to extend our vision, the telescope. This lecture introduces Galileo Galilei, the contemporary of Kepler who was in many ways the first modern astronomer, and his discoveries with the telescope. These observations were to electify Europe in the early 17th century, and begin the final intellectual dismantling of the Aristotelian view of the world. Galileo's claims that they constituted proof of the Copernican Heliocentric System, however, were to bring him into conflict with the Roman Catholic Church. Recorded 2006 Oct 12 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 16: Galileo and the Telescope

Why do we have different seasons?  This lecture looks at theconsequences of the tilt of the Earth's rotation axis relative to itsorbital plane (the Obliquity of the Ecliptic) combined with the apparentannual motions of the Sun around the Ecliptic.  The important factordetermining whether it is hot or cold at a given location at differenttimes in the year is "insolation": how much sunlight is spread out onthe ground.  This, combined with the different length of the day whenthe Sun as at different declinations, determines to total amount ofsolar heating per day, and drives the general weather.  It has nothing,however, to do with how far away we are from the Sun at different timesof the year.  Finally, the direction of the Earth's rotation axis slowlydrifts westward, taking 26,000 years to go around the sky.  This"Precession of the Equinoxes" represents a tiny change that is stillmeasureable by pre-telescopic observations, and means that at differentepochs in human history there is a different north pole star, or none atall!  Recorded 2006 Sep 28 in 100 Stillman Hall on the Columbus campusof The Ohio State University.

Why do we have different seasons? This lecture looks at the consequences of the tilt of the Earth's rotation axis relative to its orbital plane (the Obliquity of the Ecliptic) combined with the apparent annual motions of the Sun around the Ecliptic. The important factor determining whether it is hot or cold at a given location at different times in the year is "insolation": how much sunlight is spread out on the ground. This, combined with the different length of the day when the Sun as at different declinations, determines to total amount of solar heating per day, and drives the general weather. It has nothing, however, to do with how far away we are from the Sun at different times of the year. Finally, the direction of the Earth's rotation axis slowly drifts westward, taking 26,000 years to go around the sky. This "Precession of the Equinoxes" represents a tiny change that is still measureable by pre-telescopic observations, and means that at different epochs in human history there is a different north pole star, or none at all! Recorded 2006 Sep 28 in 100 Stillman Hall on the Columbus campus of The Ohio State University.

Lecture 7: The Four Seasons

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