ASTR 101. The Milky Way Galaxy. Not until the first half of the twentieth century did astronomers arrive at a reliable understanding of the enormity and overall structure of the Milky Way Galaxy. In more recent decades, observations of electromagnetic radiation across the spectrum from radio waves to gamma rays have revealed galactic features and phenomena that were not even imagined a century ago. This course explores the history of the discovery of our galaxy, from the invention of the telescope to the modern era of Earth-orbiting observatories. Enrollment limited to 64. [S] [L] [Q] Normally offered every year. E. Wollman. Concentrations.

ASTR 104. Cosmology in the Twentieth Century. The twentieth century saw the emergence of a coherent scientific understanding of the physical universe as a whole. According to this understanding, the universe has evolved from a hot, dense, and rapidly expanding soup of elementary particles into the system of galaxies we see today. But the picture is not complete, and topping the list of unresolved puzzles is the identity of the so-called dark matter. We cannot see the dark matter (hence its name), but we do measure its gravitational influences on matter we can see. The disconcerting conclusion is that there is much more dark matter than visible matter. This course examines the development of modern cosmology, with attention to both that which seems to be well-understood and that which is not yet understood. Enrollment limited to 64. [S] [Q] Normally offered every year. E. Wollman. Concentrations.

AT/GE 110. Lunar and Planetary Science. An introduction to the solar system using the methods of physics and geology. The historical development of our understanding of planetary motion leads to the contemporary view of celestial mechanics essential to exploration by spacecraft. The composition, formation, and age of the solar system are examined, together with the physical processes involved in the development of planetary interiors and surfaces. Basic algebra and geometry are used throughout. Laboratory work emphasizes the principles of remote sensing and exploration technology. Nighttime telescope work is expected. Enrollment limited to 56. [S] [L] [Q] Normally offered every year. G. Clough. Concentrations.

AT/GE 115. Impacts and Mass Extinctions. What happens when a ten-kilometer rock, traveling at forty kilometers per second, hits the Earth? As the dinosaurs discovered sixty-five million years ago, it is not a pretty picture. Scientists now believe that such catastrophically violent collisions, apparently common in the past, are inevitable in the future as well. But impacts alone may not explain the mass extinction events that have shaped the history of life on Earth; global-scale volcanism and climate change are examples of more familiar processes. This course examines the role of impacts in the Earth's history and the heated debate regarding the causes of mass extinctions. Enrollment limited to 64. [S] [Q] E. Wollman. Concentrations.