Astronomy 162 - Stars, Galaxies, & the Universe

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.