Astronomy 141 - Life in the Universe - Autumn Quarter 2009

We turn our attention to the Giant Planets of the outer Solar System: the gas giants Jupiter and Saturn, and the ice giants Uranus and Neptune. We will review their structure and properties, and then examine their systems of moons, with special attention to the giant moons. While the Jovian planets themselves seem unlikely places to hunt for life in our Solar System, a few of their largest moons may be more promising than appears at first sight. We'll explore this further in subsequent lectures in this unit. Recorded live on 2009 Oct 28 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.

This first lecture of Unit 4 - Life in the Solar System - is a quick tour of our Solar System reviewing the planets, dwarf planets, moons, and small bodies that make up our celestial home. This lecture will introduce many of the places we will be considering in detail over the next two weeks, and which we'll find around other stars. Recorded live on 2009 Oct 26 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.

In this lecture we step back and look at the history of life on Earth from the first signs of life at start of the Archaean Eon 3.5 billion years ago to just up to the present day. We will review the appearance of photosynthesis and the rise of oxygen in the atmosphere in the Proterozoic, the appearance of the first eukaryotes and sexual reproduction, and the Cambrian explosion of plant and animal species at the start of the Phanerozoic Eon, and briefly review the changes in life to the present day from the Cambrian Explosion to the colonization of land by plants and then animals. Most of the lecture will be where most of the time was spent, in the early, microbiological Earth. Recorded live on 2009 Oct 21 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.

What are the first recognizable forms of life that we find in the geological record? How far back can we go in geological time and still find life? This lecture reviews three lines of evidence that have emerged in recent years to suggest that life may have emerged very early on the young Earth, perhaps within a few hundred million years of the end of the epoch of heavy bombardment. I will describe fossil stromatolites, microfossils, and carbon isotope data that are used to explore these questions. Recorded live on 2009 Oct 19 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.

DNA and RNA are the key molecules of living cells. DNA plays a vital role in storing and transmitting the hereditary information that constitutes the "operating instructions" of living cells; how to construct the functional and structural proteins that perform vital cell functions, control developmental pathways, and basically "build" the organism. RNA is the crucial actor in protein synthesis and other cell functions. Mutations, changes in the DNA coding, are the molecular basis for evolution, providing the genetic variation required by natural selection. Understanding the molecular basis of heredity and evolution gives us important insights into the functional requirements for life. Recorded live on 2009 Oct 15 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.

Cells are the basic structural and functional unit of all life on Earth. This lecture reviews the basic building blocks of cells, the main chemical components, the two basic types of cells (Prokaryotes and Eukaryotes), and introduces the Phylogenetic Tree of Life, the way biologists order life by their biochemical and genetic relationships. Understanding life at the cellular level gives us important insights into the nature and history of life on Earth, and clues as to what we might look for elsewhere. Recorded live on 2009 Oct 13 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.

What are the main mechanisms of climate regulation and climate change that have operated through Earth's history? The Earth's climate is regulated by a Carbon Dioxide thermostat that is the interaction between the Greenhouse Effect and the CO2 Cycle. I describe the CO2 cycle and its role in regulating global temperature. I will then discuss other influences on climate, and periods of glaciation (ice ages) in the recent and distant past, including the possible Snowball Earth events in the early and late Proterozoic Eon. Recorded live on 2009 Oct 8 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.

This lecture was to be about the Earth's atmosphere, its composition and structure, the greenhouse effect, and the primordial atmosphere, but about 2 seconds into the lecture, unbeknownst to me, the battery compartment on my digital voice recorder came open in my pocket. At the end of lecture, I took it out of my pocket to turn it off and the battery didn't come with it. Oops! Fail. My apologies, I'll put in some work to prevent a recurrence in future lectures. Recorded live on 2009 Oct 6 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.

Cosmology is the study of the entire Universe as a physical system. The past century has witnessed a revolution in cosmological thought that has revealed the vastness of space and the depths of cosmic time, a revolution that is still playing out in the present day. The lecture will review the Earth's place in the Universe, the age of the Universe as reckoned by the time since the Big Bang, and the origin of the elements. We will return to many of these topics later in the course, but this presents the big picture. Recorded live on 2009 Oct 2 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.

The geological revolution revealed that the Earth is of great antiquity and yet has a history we can read in the land. We will discuss ideas of cyclic and linear time, historical versus physical age estimates, the discovery of geological time, and radiometric dating methods that give us our present estimate of 4.54+/-0.05 Gyr for the age of the Earth. Recorded live on 2009 Sep 30 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.

Modern science was borne of an effort over many centuries to understand the motions of celestial bodies. The Copernican Revolution of the 16th and 17th centuries was the crucial moment in history when we finally understood the nature of celestial motions, and opened the door to the modern world. This lecture reviews the problem of celestial motions, the two competing models for explaining them, and the final revolution in thought starting with Copernicus and ending with Newton. Mid-lecture my classroom AV system lost power, and the recovery slowed things down a bit. These are recorded live, after all. This lecture was conducted on 2009 Sep 28 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.

An introduction and review of the basic notation and physical units we will be using throughout this course. In particular, we will be using the Metric (SI) system for lengths, masses, times, and temperatures, and special astronomical units for distances (AU and Light Years) and masses (Earth Masses and Solar Masses) appropriate when discussing interplanetary and interstellar scales. Recorded live on 2009 Sep 24 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.

Welcome to the Astronomy 141 Lecture Podcasts. This is a brief message from me explaining the podcasts, and welcoming new and old listeners. University. Lectures will begin on Wednesday, 2009 Sept 23, and run through Friday, 2009 Dec 4. New lectures will appear shortly before 6pm US Eastern Time each day there is a regular class. Recorded live on 2009 Sep 23 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.