By Richard Pogge
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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.
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...
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...
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...
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...
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...
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,...
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...
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. ...
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,...
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...
Having completed our tour of the terrestrial planets, we want to step back and compare their properties. In particular, we want to look at the processes that drive the evolution of their surfaces, their interiors, and their atmospheres. Recorded 2006 Nov...
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,...
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...
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...
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...
We start our exploration of the Solar System with a quick overview of its constituent parts. I will take as my starting point that Pluto, Eris, and Ceres are Dwarf Planets according to the 2006 IAU decision. This decision, which is not...
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...
What is the composition and structure of the Earth's atmosphere? Why is it as warm as it is, and how did it form? These are the questions for today's lecture. The Earth's atmosphere is a complex, dynamic, and evolving system....
What is the structure of the Earth? What better place to begin our exploration of the Solar System then with the best-studied planet, the Earth. This lecture discusses the interior structure of the Earth, introducing the idea of differentiation, how geologists...
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...
Telescopes, equipped with advanced electronic cameras and spectrographs, are the primary tools of the astronomer. This lecture reviews the types of telescopes and observatory sites, and discusses radio and space telescopes, and reviews briefy the observing facilities at Ohio State. Recorded 2006 Oct...
Why does each chemical element have its own unique spectral-line signature? How do emission- and absorption-line spectra work? This lecture is the second part of a two-part exploration of the interaction between matter and light, today discussing how the unique spectral-line signatures...
How do matter and light interact? This lecture is the first of a two-part lecture on the physical basis of spectroscopy. Today we will discuss the Kelvin Absolute Temperature scale, which provides a measure of the internal energy content of matter,...
What is Matter? This lecture reviews the nature of matter from subatomic to atomic scales, and introduces the ideas of atomic structure, atomic number (number of protons), the elements, isotopes, radioactivity, and half-life. We conclude with a brief overview of the four...
What is Light? This lecture reviews the basic properties of light, introducing the inverse square law of brightness and the Doppler Effect. Recorded 2006 Oct 23 in 100 Stillman Hall on the Columbus campus of The Ohio State University.
How do we prove physically that the Earth rotates on its axis and revolves around the Sun? Newtonian physics was so compelling that it was mostly accepted before there were ironclad physical demonstrations of the Earth's daily rotation about its axis and...
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...
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...
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. ...
The work of Copernicus, Kepler, and Galileo all contributed to a new way of looking at the motions in the heavens, but did not explain why they move that way. Enter Isaac Newton, who within a few years swept away the last...
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...
In the generation following Copernicus, the question of planetary motions was picked up by two remarkable astronomers: Tycho Brahe, the brilliant Danish astronomer whose precise measurements of the planets represented the highest expression of pre-telescope astronomy, and Johannes Kepler, the brilliant and tormented German...
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...
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...
How do the planets move across the sky? This lecture will review planetary motions, specifically the apparent motions of the five classical planets (Mercury, Venus, Mars, Jupiter, and Saturn) as seen from the Earth. We will discuss the classical division of...
Why are there leap years? This lecture explores the astronomical origins of the calendar. We will discuss lunar and solar calendars and their hybrids in history and tradition (for example, the Islamic Lunar Calendar and the Jewish Luni-Solar Calendar), and the...
What time is it? This lecture is the first part of a two-part exploration of the astronomical origins of our time-keeping and calendar conventions. Today we will discuss the division of the year into seasons by the motions of the Sun,...
Eclipses of the Sun and Moon are among the most glorious spectacles in the sky. This lectures looks at the causes and types of eclipses, and how often they occur. Recorded 2006 Oct 2 in 100 Stillman Hall on the Columbus...
How does the Moon appear to move through the night sky? This lecture introduces the Moon, and describes the monthly cycle of phases. Topics include synchronous rotation, apogee and perigee, the cycle of phases, and the sidereal and synodic month. ...
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....
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...
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...
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. ...
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...
Before we can begin our exploration of astronomy, we need to develop a common language for notating large numbers, and introduce the basic units of length, mass, and time that we will use throughout the quarter. We will first re-introduce the basic metric...
Welcome to the Astronomy 161 Lecture Podcasts. This is a brief message from me explaining the podcasts, and welcoming new and old listeners. University. Lectures will begin on Wednesday, 2006 Sept 20, and run through Friday, 2006 December 1. New...
