Can we travel through time?  This is not a frivilous, science-fictionkind of question.  Certain restricted kinds of time travel are in factallowed by classical General Relativity.  This lectures takes up thisquestion, and looks at some of the surprising answers that have beenfound. Recorded 2006 March 8 in 1008 Evans Laboratory on the Columbuscampus of The Ohio State University.

Can we travel through time? This is not a frivilous, science-fiction kind of question. Certain restricted kinds of time travel are in fact allowed by classical General Relativity. This lectures takes up this question, and looks at some of the surprising answers that have been found. Recorded 2006 March 8 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 42: Time Travel

What is the ultimate fate of the Universe?  The ultimate fate ofthe Big Bang is either expansion to a maximum size followedby re-collapse (the Big Crunch) or eternal expansion into a cold,dark, disordered state (the Big Chill).  Which of these is ourfuture depends on the current density of matter and energy in theUniverse, Omega0.  This lecture examines our current knowledge ofthe matter and energy content of the Universe, which leads to thesurprising discovery that we live in a Universe thatis Flat (Omega0=1), Infinite, and Accelerating!  We will end the lectureby exploring the possible fate of an infinite accelerating Universe.Recorded 2006 March 2 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

What is the ultimate fate of the Universe? The ultimate fate of the Big Bang is either expansion to a maximum size followed by re-collapse (the Big Crunch) or eternal expansion into a cold, dark, disordered state (the Big Chill). Which of these is our future depends on the current density of matter and energy in the Universe, Omega0. This lecture examines our current knowledge of the matter and energy content of the Universe, which leads to the surprising discovery that we live in a Universe that is Flat (Omega0=1), Infinite, and Accelerating! We will end the lecture by exploring the possible fate of an infinite accelerating Universe. Recorded 2006 March 2 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 39: The Fate of the Universe

What are the properties of stars on the Main Sequence?  This lecturediscusses what happens to a star after it alights onto the MainSequence, burning H to He in its core, and maintaining a stateof Hydrostatic and Thermal Equilibrium.  We will see how the massof a star determines its location along the Main Sequence andinfluences its energy generation and internal structure.  We finallyintroduce the nuclear timescale and derive the Main-Sequence Lifetimefor stars, and discuss its consequences.Recorded 2006 January 25 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

What are the properties of stars on the Main Sequence? This lecture discusses what happens to a star after it alights onto the Main Sequence, burning H to He in its core, and maintaining a state of Hydrostatic and Thermal Equilibrium. We will see how the mass of a star determines its location along the Main Sequence and influences its energy generation and internal structure. We finally introduce the nuclear timescale and derive the Main-Sequence Lifetime for stars, and discuss its consequences. Recorded 2006 January 25 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 15: The Main Sequence

How do we measure distances on cosmic scales?  This lecture describesthe rungs in the cosmic distance ladder from measuring the AU in ourown Solar System out into the Hubble expansion of the universe.  Thesedistances form the basis of the measurements that let us piece togetherthe present, past, and future history of the expanding Universe, settingthe stage for next week's lectures.Recorded 2006 February 24 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

How do we measure distances on cosmic scales? This lecture describes the rungs in the cosmic distance ladder from measuring the AU in our own Solar System out into the Hubble expansion of the universe. These distances form the basis of the measurements that let us piece together the present, past, and future history of the expanding Universe, setting the stage for next week's lectures. Recorded 2006 February 24 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 35: The Cosmic Distance Scale

What do the spectra of stars look like, and what can they tell usabout stellar properties?  This lecture introduces the idea of stellarcolor, gives a brief overview of the history of stellar spectroscopy,and introduces spectral classification and the main stellar spectraltypes OBAFGKMLT.  Recorded 2006 January 13 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

What do the spectra of stars look like, and what can they tell us about stellar properties? This lecture introduces the idea of stellar color, gives a brief overview of the history of stellar spectroscopy, and introduces spectral classification and the main stellar spectral types OBAFGKMLT. Recorded 2006 January 13 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 09: Stellar Spectra

What happens if two galaxies collide?  The average distance betweenbright galaxies is only about 20 times their size, so over the historyof the Universe (14 Billion years), we expect that most bright galaxieswill have had at least one close gravitational encounter with aneighboring galaxy.  This lecture explores what happens when twogalaxies undergo interactions ranging from passing tidal interactions tohead-on collisions, all the way to multiple collisions and galaxy"cannibalism" in the centers of large clusters.  While at first glancegalaxy interactions explain rare "peculiar" galaxies, on closerexamination we find that galaxy interactions and mergers are central tounderstanding the assembly and evolution of galaxies.  At the end, wetake a speculative look at the distant future 3-4 Billions years henceif in fact Andromeda and the Milky Way are on a collision course.  Recorded 2006 February 15 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

What happens if two galaxies collide? The average distance between bright galaxies is only about 20 times their size, so over the history of the Universe (14 Billion years), we expect that most bright galaxies will have had at least one close gravitational encounter with a neighboring galaxy. This lecture explores what happens when two galaxies undergo interactions ranging from passing tidal interactions to head-on collisions, all the way to multiple collisions and galaxy "cannibalism" in the centers of large clusters. While at first glance galaxy interactions explain rare "peculiar" galaxies, on closer examination we find that galaxy interactions and mergers are central to understanding the assembly and evolution of galaxies. At the end, we take a speculative look at the distant future 3-4 Billions years hence if in fact Andromeda and the Milky Way are on a collision course. Recorded 2006 February 15 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 29: When Galaxies Collide

Are we alone in the Universe?  This is the first part of a 2-partlecture that will explore the question of life and the Universe.  Wewill look at the conditions needed for life, and address the question ofhow often we expect those conditions to be satisfied in our own Galaxy.In this part, we introduce the Drake Equation and make some basicestimates.  To be honest, it was supposed to be one lecture, but I ranover time and ran into the bell.  Oops!  Very embarrasing.  Tomorrow'slecture will finish up our discussion of life in the Universe, and thenwrap up Astronomy 162 for the quarter.  Recorded 2006 March 9 in 1008Evans Laboratory on the Columbus campus of The Ohio State University.

Are we alone in the Universe? This is the first part of a 2-part lecture that will explore the question of life and the Universe. We will look at the conditions needed for life, and address the question of how often we expect those conditions to be satisfied in our own Galaxy. In this part, we introduce the Drake Equation and make some basic estimates. To be honest, it was supposed to be one lecture, but I ran over time and ran into the bell. Oops! Very embarrasing. Tomorrow's lecture will finish up our discussion of life in the Universe, and then wrap up Astronomy 162 for the quarter. Recorded 2006 March 9 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 43: Life in the Universe, Part I

What are Active Galaxies and Quasars?  We have good reason to think that buried deep in the hearts of nearly every (?) bright galaxy is a supermassive black hole with masses of millions or even billions oftimes the mass of the Sun.  Most, like the one in our Milky Way, are quiescent, but in about 1% of galaxies, they are fed enough matter(up to about a sun's worth per year), and light up as an Active GalacticNucleus (AGN) that can outshine an entire galaxy full of billions of stars.This lecture reviews the observed properties of Active Galaxies, theriddle of the Quasars, and the recognition that they are powered bythe accretion of matter onto supermassive black holes.  The lecture endswith some open questions in this active area of current research.Recorded 2006 February 16 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

What are Active Galaxies and Quasars? We have good reason to think that buried deep in the hearts of nearly every (?) bright galaxy is a supermassive black hole with masses of millions or even billions of times the mass of the Sun. Most, like the one in our Milky Way, are quiescent, but in about 1% of galaxies, they are fed enough matter (up to about a sun's worth per year), and light up as an Active Galactic Nucleus (AGN) that can outshine an entire galaxy full of billions of stars. This lecture reviews the observed properties of Active Galaxies, the riddle of the Quasars, and the recognition that they are powered by the accretion of matter onto supermassive black holes. The lecture ends with some open questions in this active area of current research. Recorded 2006 February 16 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 30: Active Galaxies & Quasars

How long can the Sun continue to shine, and what source of energydoes it tap to keep shining?  This lecture answers this question byintroducing two important energy sources for stars: GravitationalContraction otherwise known as the Kelvin-Helmholz Mechanism, andNuclear Fusion.  We will show that fusion of 4 Hydrogen nuclei intoa Helium nucleus via the proton-proton chain liberates enough energyto provide for the Sun's Luminosity needs for about 10 Billion Years.Recorded 2006 January 19 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.  Note: the recording mistakenly saysJanuary 18th.  Oops.

How long can the Sun continue to shine, and what source of energy does it tap to keep shining? This lecture answers this question by introducing two important energy sources for stars: Gravitational Contraction otherwise known as the Kelvin-Helmholz Mechanism, and Nuclear Fusion. We will show that fusion of 4 Hydrogen nuclei into a Helium nucleus via the proton-proton chain liberates enough energy to provide for the Sun's Luminosity needs for about 10 Billion Years. Recorded 2006 January 19 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Note: the recording mistakenly says January 18th. Oops.

Lecture 12: As Long as the Sun Shines

How do we measure the distances to the stars?  This lectureintroduces the method of trigonometric parallaxes and theunits of the Parsec and Light Year.  Recorded 2006 January 9in 1008 Evans Laboratory on the Columbus campus of TheOhio State University.

How do we measure the distances to the stars? This lecture introduces the method of trigonometric parallaxes and the units of the Parsec and Light Year. Recorded 2006 January 9 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 05: Distances of the Stars

Astronomy 162, Stars, Galaxies, and the Universe, is part 2 of a2-quarter introductory Astronomy for non-science majors taught at TheOhio State University.  This podcast presents lecture audio fromProfessor Richard Pogge's Winter Quarter 2006 class.  All of thelectures were recorded live in 1008 Evans Laboratory on the OSU MainCampus in Columbus, Ohio.

You can tell this professor really loves this topics.  Highly detailed, and well explained.

Wonderful

A great set of lectures for anyone interested.

Happy

Astronomy 162, Stars, Galaxies, and the Universe, is part 2 of a 2-quarter introductory Astronomy for non-science majors taught at The Ohio State University. This podcast presents lecture audio from Professor Richard Pogge's Winter Quarter 2006 class. All of the lectures were recorded live in 1008 Evans Laboratory on the OSU Main Campus in Columbus, Ohio.

Astronomy 162 - Stars, Galaxies, & the Universe

Relativity

What is gravity?  Newton left that question unanswered when he formulatedhis inverse square law of the gravitational force, framing no hypothesisfor what agency transmits gravity, only asserting it was an actionat a distance.  Einstein brought gravity into relativity by answeringNewton's unanswered question with his General Relativity, our moderntheory of gravity.  In Einstein's formulation, Matter tells spacetime howto curve, and curved spacetime tells matter how to move.  This lecturepresents the basic picture of General Relativity, and introduces someof its observational consequences.  The surprising conclusion is thatinstead of space and time being a backdrop for physics in Newton's view,united into spacetime by Relativity they are understood to be physicaland dynamic.  This is important for understanding how the Universe asa whole works.Recorded 2006 February 21 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

What is gravity? Newton left that question unanswered when he formulated his inverse square law of the gravitational force, framing no hypothesis for what agency transmits gravity, only asserting it was an action at a distance. Einstein brought gravity into relativity by answering Newton's unanswered question with his General Relativity, our modern theory of gravity. In Einstein's formulation, Matter tells spacetime how to curve, and curved spacetime tells matter how to move. This lecture presents the basic picture of General Relativity, and introduces some of its observational consequences. The surprising conclusion is that instead of space and time being a backdrop for physics in Newton's view, united into spacetime by Relativity they are understood to be physical and dynamic. This is important for understanding how the Universe as a whole works. Recorded 2006 February 21 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 32: Space, Time, & Gravity: General Relativity

What happens if even Neutron Degeneracy pressure is insufficient tohalt the collapse of gravity?  In that case, the object simply collapsesin upon itself, approaching a state of infinite density.  Such an objecthas such strong gravity that nothing, not even light can escape from it.We call these Black Holes.  This lecture describes the basic propertiesof black holes, takes an imaginary journey through the event horizon,and discusses observational evidence that stellar-mass black holes(the remnants of the evolution of very massive stars) actually exist,and ends with the suggestion that if Steven Hawking and othersare right, black holes may not be so black after all.  One Erratum:during the lecture while commenting on the fate of Karl Schwarzschild,for whom the Schwarzschild Radius is named, I incorrectly identify Henry Moseley (killed by a sniper during the Galipoli Campaign of WWI) as one of the discoverers of the neutron.  Moseley was the person who discovered that "atomic number" corresponded to nuclear charge, and hence the number of protons in the nucleus.  The discoverer of the neutron was James Chadwick, who died in 1974.Recorded 2006 February 1 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

What happens if even Neutron Degeneracy pressure is insufficient to halt the collapse of gravity? In that case, the object simply collapses in upon itself, approaching a state of infinite density. Such an object has such strong gravity that nothing, not even light can escape from it. We call these Black Holes. This lecture describes the basic properties of black holes, takes an imaginary journey through the event horizon, and discusses observational evidence that stellar-mass black holes (the remnants of the evolution of very massive stars) actually exist, and ends with the suggestion that if Steven Hawking and others are right, black holes may not be so black after all. One Erratum: during the lecture while commenting on the fate of Karl Schwarzschild, for whom the Schwarzschild Radius is named, I incorrectly identify Henry Moseley (killed by a sniper during the Galipoli Campaign of WWI) as one of the discoverers of the neutron. Moseley was the person who discovered that "atomic number" corresponded to nuclear charge, and hence the number of protons in the nucleus. The discoverer of the neutron was James Chadwick, who died in 1974. Recorded 2006 February 1 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 20: Black Holes

We are not made of the same matter as most of the Universe!  Thissurprising conclusion, that the ordinary matter we are made of (protons,neutrons, and electrons) constitute only 13% or so of the total matterin the Universe, the rest being in the form of Dark Matter.  Further,this dark matter is only about 30% of the combined matter and energydensity of the Universe, the remaining 70% of which appears to be a formof Dark Energy that fills the vacuum of space and acts in the presentday to accelerate the expansion of the Universe.  This lecture willsummarize the state of our understanding of Dark Matter and Dark Energy,and look at the questions remaining to be answered in this active areaof current research.  Recorded 2006 March 7 in 1008 Evans Laboratory onthe Columbus campus of The Ohio State University.

We are not made of the same matter as most of the Universe! This surprising conclusion, that the ordinary matter we are made of (protons, neutrons, and electrons) constitute only 13% or so of the total matter in the Universe, the rest being in the form of Dark Matter. Further, this dark matter is only about 30% of the combined matter and energy density of the Universe, the remaining 70% of which appears to be a form of Dark Energy that fills the vacuum of space and acts in the present day to accelerate the expansion of the Universe. This lecture will summarize the state of our understanding of Dark Matter and Dark Energy, and look at the questions remaining to be answered in this active area of current research. Recorded 2006 March 7 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 41: Dark Matter & Dark Energy

What are space and time?  To begin our exploration of the evolvingUniverse, we must first understand what we mean by space and time.This lecture contrasts the Newtonian view of the World, with itsabsolute space and absolute time, with that of Einstein, who showedthat space and time were not absolute but relative constructs, andthat only spacetime, unified by light, was independent of the observer.This requires such non-intuitive notions as the speed of light beingthe same for all observers regardless of their motion, and thatobservers moving relative to each other will agree on the same physicallaws and speed of light, but disagree on lengths, times, masses, etc.measured by applying those laws.  This sets the stage for Einstein'srevision of the Law of Gravity, General Relativity, which we willreview in the following lecture.Recorded 2006 February 20 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

What are space and time? To begin our exploration of the evolving Universe, we must first understand what we mean by space and time. This lecture contrasts the Newtonian view of the World, with its absolute space and absolute time, with that of Einstein, who showed that space and time were not absolute but relative constructs, and that only spacetime, unified by light, was independent of the observer. This requires such non-intuitive notions as the speed of light being the same for all observers regardless of their motion, and that observers moving relative to each other will agree on the same physical laws and speed of light, but disagree on lengths, times, masses, etc. measured by applying those laws. This sets the stage for Einstein's revision of the Law of Gravity, General Relativity, which we will review in the following lecture. Recorded 2006 February 20 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 31: A Tale of Two World Views: Special Relativity

Once a massive star builds a massive Iron/Nickel core at the end ofthe Silicon Burning day, it is doomed.  A catastrophic core collapseis followed by explosive ejection of the envelope in a Supernova.This lecture describes the stages of a core-bounce supernova explosion,and the subsequent seeding of the interstellar medium with heavymetals by the explosion debris.  The fate of the collapsing core isthe subject of the next lecture in this series.Recorded 2006 January 30 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

Once a massive star builds a massive Iron/Nickel core at the end of the Silicon Burning day, it is doomed. A catastrophic core collapse is followed by explosive ejection of the envelope in a Supernova. This lecture describes the stages of a core-bounce supernova explosion, and the subsequent seeding of the interstellar medium with heavy metals by the explosion debris. The fate of the collapsing core is the subject of the next lecture in this series. Recorded 2006 January 30 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 18: Supernovae

What happens to the cores left behind at the end of a star's life?This lecture introduces these stellar remnants: White Dwarfs(remnants of low-mass stars held up by Electron Degeneracy Pressure),and Neutron Stars (remnant cores of core-bounce supernovae held upby Neutron Degeneracy Pressure).  We also the Chandrasekhar Mass forWhite Dwarfs, Type Ia Supernovae resulting from a white dwarf gettingtipped over the Chandrasekhar Mass, Pulsars (rapidly rotating magnetizedneutrons stars), and ask what happens when a neutron star gets tippedover its mass limit.Recorded 2006 January 31 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

What happens to the cores left behind at the end of a star's life? This lecture introduces these stellar remnants: White Dwarfs (remnants of low-mass stars held up by Electron Degeneracy Pressure), and Neutron Stars (remnant cores of core-bounce supernovae held up by Neutron Degeneracy Pressure). We also the Chandrasekhar Mass for White Dwarfs, Type Ia Supernovae resulting from a white dwarf getting tipped over the Chandrasekhar Mass, Pulsars (rapidly rotating magnetized neutrons stars), and ask what happens when a neutron star gets tipped over its mass limit. Recorded 2006 January 31 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 19: Extreme Stars: White Dwarfs & Neutron Stars

What are the implications of Relativity for the Universe?  This lectureintroduces the Cosmological Principle, which states that the Universe isHomogeneous and Isotropic on Large Scales.  Applying this to histhen-new General Relativyt, Einstein got a surprise: the Universe musteither expand or contract in response to all the matter/energy thatfills it, something not observed in 1917.  To attempt to stabilize theUniverse, he introduced a Cosmological Constant (Lambda), that was toprove his greatest blunder.  Subsequent theoretical and observationalwork was to establish that the Universe is indeed expandingsystematically, if you look on scales large enough (the scale ofgalaxies).  We will review observational evidence for the large-scaleHomogeneity and Isotropy of the Universe, Einstein's brilliant conjecture,and see how the Cosmological Constant maybe wasn't such a blunder afterall, as it has recently made a comeback of sorts.  We'll explore thesethemes in greater detail in subsequent lectures.Recorded 2006 February 22 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

What are the implications of Relativity for the Universe? This lecture introduces the Cosmological Principle, which states that the Universe is Homogeneous and Isotropic on Large Scales. Applying this to his then-new General Relativyt, Einstein got a surprise: the Universe must either expand or contract in response to all the matter/energy that fills it, something not observed in 1917. To attempt to stabilize the Universe, he introduced a Cosmological Constant (Lambda), that was to prove his greatest blunder. Subsequent theoretical and observational work was to establish that the Universe is indeed expanding systematically, if you look on scales large enough (the scale of galaxies). We will review observational evidence for the large-scale Homogeneity and Isotropy of the Universe, Einstein's brilliant conjecture, and see how the Cosmological Constant maybe wasn't such a blunder after all, as it has recently made a comeback of sorts. We'll explore these themes in greater detail in subsequent lectures. Recorded 2006 February 22 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 33: Einstein's Universe

What are the physical laws that determine the internal structureof stars?  We first introduce the Mass-Luminosity Relation forMain Sequence stars, as well as seeing how the mean density of starsdiffers for stars on different parts of the H-R diagram.  We thenintroduce the Ideal Gas Law, which relates pressure, density, and temperature,and show how the internal structure of a star is determined bya continuous tug-of-war between internal pressure trying to blowthe star apart, and self-gravity trying to make it collapse.  Thebalance between the two is the state of Hydrostatic Equilibrium.  Howthe balance is maintained, and what happens when it is tipped infavor of either will determine the appearance and subsequent evolutionof the star.  Recorded 2006 January 18 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

What are the physical laws that determine the internal structure of stars? We first introduce the Mass-Luminosity Relation for Main Sequence stars, as well as seeing how the mean density of stars differs for stars on different parts of the H-R diagram. We then introduce the Ideal Gas Law, which relates pressure, density, and temperature, and show how the internal structure of a star is determined by a continuous tug-of-war between internal pressure trying to blow the star apart, and self-gravity trying to make it collapse. The balance between the two is the state of Hydrostatic Equilibrium. How the balance is maintained, and what happens when it is tipped in favor of either will determine the appearance and subsequent evolution of the star. Recorded 2006 January 18 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 11: The Internal Structure of Stars

The Universe today is old, cold, low-density, and expanding.  If we runthe expansion backwards, we will eventually find a Universe where allthe matter was in one place where the density and temperature are nearlyinfinite.  We call this hot, dense initial state of the Universe the BigBang.  This lecture introduces the Big Bang model of the expandinguniverse, and how the history of the Universe depends on two numbers:the curretn expansion rate (H0), and the relative density of matter andenergy (Omega0).  Combined with observations, these give us an estimateof the age of the Universe of 14.0 +/- 1.4 Gyr.  Recorded 2006 February 27 in1008 Evans Laboratory on the Columbus campus of The Ohio StateUniversity.

The Universe today is old, cold, low-density, and expanding. If we run the expansion backwards, we will eventually find a Universe where all the matter was in one place where the density and temperature are nearly infinite. We call this hot, dense initial state of the Universe the Big Bang. This lecture introduces the Big Bang model of the expanding universe, and how the history of the Universe depends on two numbers: the curretn expansion rate (H0), and the relative density of matter and energy (Omega0). Combined with observations, these give us an estimate of the age of the Universe of 14.0 +/- 1.4 Gyr. Recorded 2006 February 27 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 36: The Big Bang

What happens when a high-mass (more than 4 solar masses) Main Sequencestars runs out of Hydrogen in its core.  At first the internal evolutionlooks like that of a low-mass star, but now we get first a Red Supergiantthen a sucession of blue and red supergiant phases as different nuclearfuels are tapped by the star for its energy.  This lecture describesthe evolution of high-mass stars from the Main Sequence until theireventual ends.Recorded 2006 January 27 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

What happens when a high-mass (more than 4 solar masses) Main Sequence stars runs out of Hydrogen in its core. At first the internal evolution looks like that of a low-mass star, but now we get first a Red Supergiant then a sucession of blue and red supergiant phases as different nuclear fuels are tapped by the star for its energy. This lecture describes the evolution of high-mass stars from the Main Sequence until their eventual ends. Recorded 2006 January 27 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 17: The Evolution of High-Mass Stars

What is the Milky Way, and what is our place within it?  This lectureintroduces the Milky Way, the bright band of light that crosses thesky, and describes how we came to our present understanding of the sizeand shape of the Milky Way Galaxy, and our location in it.Recorded 2006 February 7 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

What is the Milky Way, and what is our place within it? This lecture introduces the Milky Way, the bright band of light that crosses the sky, and describes how we came to our present understanding of the size and shape of the Milky Way Galaxy, and our location in it. Recorded 2006 February 7 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 23: The Milky Way

How do stars form?  The Sun is old and in Hydrostatic andThermal equilibrium.  How did it get that way?  This lecturepresents the basic steps of star formation as a progress fromcold interstellar Giant Molecular Clouds to Protostars inHydrostatic Equilibrium, and then Pre-Main Sequence evolution which ends in ignition of core Hydrogen fusion and establishingThermal Equilibrium on the Zero-Age Main Sequence.Recorded 2006 January 24 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

How do stars form? The Sun is old and in Hydrostatic and Thermal equilibrium. How did it get that way? This lecture presents the basic steps of star formation as a progress from cold interstellar Giant Molecular Clouds to Protostars in Hydrostatic Equilibrium, and then Pre-Main Sequence evolution which ends in ignition of core Hydrogen fusion and establishing Thermal Equilibrium on the Zero-Age Main Sequence. Recorded 2006 January 24 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 14: Star Formation

How do we quantify stellar brightness?  This lecture introducesthe inverse square-law of apparent brightness, the relation betweenLuminosity and Apparent Brightness, introduces the stellar magnitude system, and discusses photometry and the how we measure apparent brightness in practice.  Recorded2006 January 11 in 1008 Evans Laboratory on the Columbus campus ofThe Ohio State University.

How do we quantify stellar brightness? This lecture introduces the inverse square-law of apparent brightness, the relation between Luminosity and Apparent Brightness, introduces the stellar magnitude system, and discusses photometry and the how we measure apparent brightness in practice. Recorded 2006 January 11 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 07: Stellar Brightness

What was the Universe like from the earliest phases immediately afterthe Big Bang to the present day?  This lecture reviews the physics ofmatter, and follows the evolution of the expanding Universe from thefirst instants after the Big Bang, when all 4 forces of nature wereunified in a single grand-unified superforce until the emergence of thevisible Universe we see around us today.  Recorded 2006 March 1 in 1008Evans Laboratory on the Columbus campus of The Ohio State University.

What was the Universe like from the earliest phases immediately after the Big Bang to the present day? This lecture reviews the physics of matter, and follows the evolution of the expanding Universe from the first instants after the Big Bang, when all 4 forces of nature were unified in a single grand-unified superforce until the emergence of the visible Universe we see around us today. Recorded 2006 March 1 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 38: The First Three Minutes

How do we measure distances to astronomical objects that are too faraway to use Trigonometric Parallaxes?  This first lecture of Unit 4reviews geometric methods like trigonometric parallaxes, and thenintroduces the idea of Standard Candles, and how they are used todevelop methods for deriving Luminosity Distances based on the InverseSquare Law of Brightness.  We will explore three luminosity-baseddistance methods useful for studying our Galaxy and nearby galaxies:Spectroscopic Parallaxes, Cepheid Variable Period-Luminosity Relation,and the RR Lyrae P-L Relation.  Recorded 2006 February 6 in 1008 EvansLaboratory on the Columbus campus of The Ohio State University.

How do we measure distances to astronomical objects that are too far away to use Trigonometric Parallaxes? This first lecture of Unit 4 reviews geometric methods like trigonometric parallaxes, and then introduces the idea of Standard Candles, and how they are used to develop methods for deriving Luminosity Distances based on the Inverse Square Law of Brightness. We will explore three luminosity-based distance methods useful for studying our Galaxy and nearby galaxies: Spectroscopic Parallaxes, Cepheid Variable Period-Luminosity Relation, and the RR Lyrae P-L Relation. Recorded 2006 February 6 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 22: The Cosmic Distance Problem

What happens to a low-mass star (less than 4 solar masses) whenit runs out of core Hydrogen and must leave the Main Sequence.This lecture describes the changes inside a low-mass star afterHydrogen exhaustion through the Red Giant, Horizontal Branch,Asymtotic Giant, and Planetary Nebula phases.  In the end, we willsee the star's envelope and core go their separate ways, theenvelope gently puffed off into space, briefly flowering as aPlanetary Nebula, and the Carbon-Oxygen core collapsing intoa White Dwarf.Recorded 2006 January 26 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

What happens to a low-mass star (less than 4 solar masses) when it runs out of core Hydrogen and must leave the Main Sequence. This lecture describes the changes inside a low-mass star after Hydrogen exhaustion through the Red Giant, Horizontal Branch, Asymtotic Giant, and Planetary Nebula phases. In the end, we will see the star's envelope and core go their separate ways, the envelope gently puffed off into space, briefly flowering as a Planetary Nebula, and the Carbon-Oxygen core collapsing into a White Dwarf. Recorded 2006 January 26 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 16: The Evolution of Low-Mass Stars

How do we measure the masses and radii of stars?  This lecturedescribes the three basic types of binary stars, and how each are used to measure the masses of stars.  Details of how to measurestellar radii are beyond the scope of this class, but we brieflydescribe the direct measurements of stellar radii.Recorded 2006 January 12 in 1008 Evans Laboratory on the Columbus campusof The Ohio State University.

How do we measure the masses and radii of stars? This lecture describes the three basic types of binary stars, and how each are used to measure the masses of stars. Details of how to measure stellar radii are beyond the scope of this class, but we briefly describe the direct measurements of stellar radii. Recorded 2006 January 12 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University.

Lecture 08: Stellar Masses & Radii

The Best Multi-Part Documentaries, with documentaries on Obama, Federer vs Nadal, the making of Star Wars, Netflix vs Blockbuster and more. Add episodes you're interested into your queue below!

Best Multi-Part Documentaries

The best podcast episodes on global issues affecting everyone. Covering topics such as the #metoo movement, climate change, the impact of technology and some of the biggest global issues facing us right now. For anyone interested in learning more about the world, and some of the issues we're facing, pick an episode below and start listening! Add episodes you're interested into your queue below!