# David Sattinger to visit Baylor April 21-24

**March 16, 2010**

David Sattinger will visit Baylor University on April 21-24 to deliver two special lectures on astronomy and mathematics. The titles of each lecture are *"Naked Histronomy: What Did Astronomers Know Before The Telescope And When Did They Know It?"*.

**David Sattinger**

Dr. Sattinger is a highly respected mathematician who is both nationally and internationally known. He has written more than 100 research papers in various areas of pure and applied mathematics, including ordinary and partial differential equations, differential geometry, dynamical systems, fluid mechanics, Lie groups, and operator theory. He spent most of his professional career at the University of Minnesota. He is most recently retired from Yale University and, between his positions at Minnesota and Yale, David was department head in mathematics at Utah State University.

David and his wife, Irene, are now living in Tucson, Arizona. For the past few years, he has worked as a docent at the Kitt Peak Observatory outside Tucson. Through this position, his varied scientific interests have lead him to a new passion of studying the origins of astronomy.

Prior to each lecture, there will be snacks and refreshments in SR 340. All faculty and students are welcome, and encouraged, to attend and meet Dr. Sattinger.

The abstract for each lecture is given below.

**Naked Histronomy: What Did Astronomers Know Before The Telescope And When Did They Know It?**

**Part I** (4 pm, Wednesday April 21, 344SR)

The foundations for modern astronomy, including the Equatorial and Ecliptic coordinate systems, the constellations and Zodiac, are laid by the Sumerians and Babylonians. In 499 BC a luni-solar calendar appears, based on the discovery that 235 synodic months = 19 solar years, accurate to 2 hours over the 19 year period!

The Greek astronomer Hipparchus introduces spherical trigonometry, discovers the precession of the Earth's axis, and develops the stereographic projection. Aristarchus proposes a heliocentric model of the universe, estimates the size of the Moon, and the distance from the Earth to the Sun.

**Part II** (3:30 pm, Friday April 23, 344SR)

Nicolaus Copernicus, a Church canon, puts forth the hypothesis that the Earth goes around the Sun, and dedicates the work to Pope Paul III. "The Copernican Hypothesis" quickly gets embroiled in the turmoil of the Reformation.

Tycho Brahe, a Danish nobleman, carries out extensive and accurate "Naked Eye" observations of the Sun and planets. He builds giant machines, compensates for refraction by the Earth's atmosphere, and aspires to a level of accuracy of 1 arcminute. After the death of Fredrick II of Denmark, he goes to Prague with the support of Rudolph II, the Holy Roman Emperor.

Johannes Kepler begins studies in Theology at Tübingen, but soon switches to astronomy and mathematics, defending the Copernican hypothesis in student debates. He obtains a teaching position at a seminary in Graz, but later leaves, rather than convert to Catholicism, and takes a position with Brahe. Examining Brahe's data for Mars, he concludes that its orbit is elliptical. His three fundamental laws of planetary motion, deduced from Brahe's data over many years, guide Newton to the inverse square law of gravity.

### More News ...