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Astronomy 162 - Stars, Galaxies, & the Universe

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Rank #159 in Courses category

Education
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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.

Read more

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.

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126 Ratings
Average Ratings
110
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5
3

Wonderful

By KD9CWX - Jan 20 2020
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You can tell this professor really loves this topics. Highly detailed, and well explained.

Happy

By Derrick_Fields - Mar 27 2015
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A great set of lectures for anyone interested.

iTunes Ratings

126 Ratings
Average Ratings
110
5
3
5
3

Wonderful

By KD9CWX - Jan 20 2020
Read more
You can tell this professor really loves this topics. Highly detailed, and well explained.

Happy

By Derrick_Fields - Mar 27 2015
Read more
A great set of lectures for anyone interested.
Cover image of Astronomy 162 - Stars, Galaxies, & the Universe

Astronomy 162 - Stars, Galaxies, & the Universe

Latest release on Dec 06, 2009

Read more

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.

Rank #1: Lecture 32: Space, Time, & Gravity: General Relativity

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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.

Feb 21 2006

Play

Rank #2: Lecture 20: Black Holes

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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.

Feb 01 2006

Play

Rank #3: Lecture 41: Dark Matter & Dark Energy

Podcast cover
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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.

Mar 07 2006

Play

Rank #4: Lecture 11: The Internal Structure of Stars

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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.

Jan 18 2006

Play

Rank #5: Lecture 18: Supernovae

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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.

Jan 30 2006

Play

Rank #6: Lecture 19: Extreme Stars: White Dwarfs & Neutron Stars

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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.

Jan 31 2006

Play

Rank #7: Lecture 31: A Tale of Two World Views: Special Relativity

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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.

Feb 20 2006

Play

Rank #8: Lecture 42: Time Travel

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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.

Mar 08 2006

Play

Rank #9: Lecture 33: Einstein's Universe

Podcast cover
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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.

Feb 22 2006

Play

Rank #10: Lecture 36: The Big Bang

Podcast cover
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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.

Feb 27 2006

Play

Rank #11: Lecture 14: Star Formation

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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.

Jan 24 2006

Play

Rank #12: Lecture 23: The Milky Way

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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.

Feb 07 2006

Play

Rank #13: Lecture 30: Active Galaxies & Quasars

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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.

Feb 16 2006

Play

Rank #14: Lecture 17: The Evolution of High-Mass Stars

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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.

Jan 27 2006

Play

Rank #15: Lecture 38: The First Three Minutes

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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.

Mar 01 2006

Play

Rank #16: Lecture 34: The Expanding Universe

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How did we discover that the Universe is Expanding? What does
it mean that it is expanding? This lecture introduces Hubble's Law,
the observational evidence that the Universe is systematically
expanding. As galaxies get more distant from us, the apparent speed
of recession gets larger in proportion. The proportionality is the
rate of expansion, called the Hubble Parameter (H0). This leads us
to the idea of expanding space, and the Cosmological Redshift, which
combined with the Hubble Law allows us a way to estimate very large
cosmic distances. We will take up the more thorny issue of the
Cosmic Distance Scale in tomorrow's lecture.
Recorded 2006 February 23 in 1008 Evans Laboratory on the Columbus campus
of The Ohio State University.

Feb 23 2006

Play

Rank #17: Lecture 12: As Long as the Sun Shines

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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.

Jan 19 2006

Play

Rank #18: Lecture 07: Stellar Brightness

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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.

Jan 11 2006

Play

Rank #19: Lecture 39: The Fate of the Universe

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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.

Mar 02 2006

Play

Rank #20: Lecture 22: The Cosmic Distance Problem

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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.

Feb 06 2006

Play

Astronomy 141 Podcast Teaser

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

Dec 06 2009

Play

Lectures 1-4: An Explanation

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Where are Lectures 1-4? This is a good question, and one I've gotten
from many listeners. Here's the answer. Recorded 2006 Nov 27 on the
Columbus campus of The Ohio State University.

Nov 27 2006

Play

Welcome to Astronomy 162

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Welcome to the Astronomy 162 Lecture Podcasts! This is a brief message
from me explaining the podcasts, and welcoming new and old listeners.
Recorded 2006 Mar 10 on the Columbus campus of The Ohio State
University.

Mar 10 2006

Play

Lecture 44: Life, the Universe, and Everything (Life Part II)

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How can we search for extraterrestrial intelligence, and what are we
looking for? This second part of a 2-part lecture picks up where we
left off yesterday by examining SETI, the Search for ExtraTerrestrial
Intelligence, and reviews what we might look for and how. We will use
this as a point of departure to then briefly review where we have come
and what we have learned in Astronomy 162, bringing this course to a
close for Winter Quarter 2006. Recorded 2006 Mar 10 in 1008 Evans
Laboratory on the Columbus campus of The Ohio State University.

Mar 10 2006

Play

Lecture 43: Life in the Universe, Part I

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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.

Mar 09 2006

Play

Lecture 42: Time Travel

Podcast cover
Read more
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.

Mar 08 2006

Play

Lecture 41: Dark Matter & Dark Energy

Podcast cover
Read more
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.

Mar 07 2006

Play

Lecture 40: The Once and Future Sun

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How will the Sun evolve? The Sun is now a middle-aged, low-mass, Main
Sequence star in a state of hydrostatic and thermal equilibrium that has
consumed about half of the Hydrogen available for fusion in its core.
What will its subsequent evolution be as its core runs out of Hydrogen?
This lecture describes our current state of understanding of the
expected evolution of the Sun, informed by a combination of
state-of-the-art solar models and stellar evolution codes, and data
gathered from observations of nearby stars in our Galaxy. We will trace
the future history of the Sun from the present until it begins its final
phase as a fading White Dwarf some 8 Billion years in the future. Along
the way, we'll also ask what will become of Earth.
Recorded 2006 March 6 in 1008 Evans Laboratory on the Columbus campus of
The Ohio State University.

Mar 06 2006

Play

Lecture 39: The Fate of the Universe

Podcast cover
Read more
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.

Mar 02 2006

Play

Lecture 38: The First Three Minutes

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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.

Mar 01 2006

Play

Lecture 37: The Whispers of Creation

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Is there any evidence that the Universe was very hot and dense
in the distant past as predicted by the Big Bang model of the
expanding Universe? This lecture examines observational tests
of the Big Bang Model. We have already covered expansion in the
previous lecture. Today we look at Primordial Nucleosynthesis, the creation
of light elements from fusion during the first 3-4 minutes of the
hot phases of the Big Bang, and the Cosmic Background Radiation, the relic
blackbody radiation remaining from when the Universe became transparent
to light 300,000 years after the Big Bang. Both predictions of the Big
Bang Model have been spectacularly confirmed by observations of the
present-day Universe. These give us confidence that the Big Bang, in
broad outline, is the correct physical model of our expanding Universe.
Recorded 2006 February 28 in 1008 Evans Laboratory on the Columbus campus
of The Ohio State University.

Feb 28 2006

Play

Lecture 36: The Big Bang

Podcast cover
Read more
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.

Feb 27 2006

Play

Lecture 35: The Cosmic Distance Scale

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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.

Feb 24 2006

Play

Lecture 34: The Expanding Universe

Podcast cover
Read more
How did we discover that the Universe is Expanding? What does
it mean that it is expanding? This lecture introduces Hubble's Law,
the observational evidence that the Universe is systematically
expanding. As galaxies get more distant from us, the apparent speed
of recession gets larger in proportion. The proportionality is the
rate of expansion, called the Hubble Parameter (H0). This leads us
to the idea of expanding space, and the Cosmological Redshift, which
combined with the Hubble Law allows us a way to estimate very large
cosmic distances. We will take up the more thorny issue of the
Cosmic Distance Scale in tomorrow's lecture.
Recorded 2006 February 23 in 1008 Evans Laboratory on the Columbus campus
of The Ohio State University.

Feb 23 2006

Play

Lecture 33: Einstein's Universe

Podcast cover
Read more
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.

Feb 22 2006

Play

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

Podcast cover
Read more
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.

Feb 21 2006

Play

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

Podcast cover
Read more
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.

Feb 20 2006

Play

Lecture 30: Active Galaxies & Quasars

Podcast cover
Read more
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.

Feb 16 2006

Play

Lecture 29: When Galaxies Collide

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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.

Feb 15 2006

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Lecture 28: Groups & Clusters of Galaxies

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Galaxies are found in groups and clusters, and these are only the
start of a hierarchy of cosmic structures up to the largest scales
observed. This lecture introduces the properties of groups and
clusters of galaxies, superclusters (clusters of clusters), and
large scale structure with filaments of superclusters surrouning
vast voids. We start with our Local Group, and then expand our
view to encompass the depths of intergalactic space.
Recorded 2006 February 14 in 1008 Evans Laboratory on the Columbus campus
of The Ohio State University.

Feb 14 2006

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Wonderful

By KD9CWX - Jan 20 2020
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You can tell this professor really loves this topics. Highly detailed, and well explained.

Happy

By Derrick_Fields - Mar 27 2015
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A great set of lectures for anyone interested.