Astronomy 141 - Life in the Universe - Autumn Quarter 2009

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.

What is the basic chemistry of living organisms? We introduce the requirements for metabolism (raw materials and energy), the ATP/ADP energy cycle in cells, auto- and heterotrophs, photosynthesis and chemosynthesis, and the role played by liquid water. The goal of today's lecture is to seek insights into the basic requirements for life from a consideration of the needs of the cells' chemistry. Recorded live on 2009 Oct 14 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.

How do we define life? This lecture reviews the six basic criteria for living systems described by biologists: order, reproduction, growth and development, energy utilization, reaction to environment, and evolution that characterize life. The last third of the lecture is an admittedly whirlwind review of natural selection (I got off my stride and got a little rushed for time at the end). The goal is not a complete survey of current biological thought, but to highlight those characteristics of "life" that may best inform us as to how to look for signs of life elsewhere in the Universe. Recorded live on 2009 Oct 12 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.

How have we pieced together the geological history of the Earth? This lecture reviews the different types of rocks and the cycle of transformation between them, with particular emphasis on stratigraphy. I will outline the 4 major Eons in Earth's history, and focus on the earliest Hadean Eon which proceeded from the formation of the Earth to the end of the epoch of Heavy Bombardment. The Hadean Eon saw the formation of the primordial atmosphere of the Earth and the formation of the Oceans. Recorded live on 2009 Oct 7 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.

What is the interior structure of the Earth and how does it drive the Earth's magnetic and geologic activity? We will review our current knowledge of the interior of the Earth, how we measure it using Seismology, the origins of the Earth's magnetic field, and discuss the workings of plate tectonics. the Earth is a dynamic, geologically active world, which has interesting implications later for understanding the past and future history of life on Earth. Recorded live on 2009 Oct 5 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.

What is the nature of life? In this lecture I will review the revolution in biological thinking that has dramatically changed how we view life. I will review such persistent ancient ideas as spontaneous generation and why it took so long to disprove this notion, the impact of the microscope on biology, and the discovery of the laws and agency of heredity. This is obviously a highly-selective view of a vast topic, and my goal is to highlight those episodes in the history of biology that inform us about the nature of science (its successes and failures), and which we will concern ourselves with in the rest of the course. Listeners will note that I do not introduce Evolution (more precisely, Natural Selection) since that is a huge other topic for another day. Recorded live on 2009 Oct 1 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.

What is the nature of matter, and how did we come to understand the chemical elements and atomic structure? This lecture is a brief and selective overview of the history of our understanding of the nature of matter and chemistry. We will also introduce spectroscopy and radioactivity, two very powerful tools that came out of the chemical revolution that are crucial for the inquiry in this class into the question of life on other worlds. Recorded live on 2009 Sep 29 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.

What is the cultural history of our imaginings of other worlds and their possible inhabitants? I will draw examples from history, philosophy, literature, cinema, and popular culture. In the end, our imaginings about other worlds inform us more about ourselves, our hopes and our fears, than about extraterrestrial life. The scientific inquiry we are undertaking must therefore approach the problem from a different direction. Recorded live on 2009 Sep 25 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.