Kepler’s New Astronomy

This year (2009) is the 400th anniversary of the publication of Johannes Kepler’s book New Astronomy (Astronomia Nova) announcing the discovery of the elliptical orbit of Mars to the world. The discovery of the elliptical orbit of Mars and the mathematical rule of motion for Mars on its elliptical orbit by Johannes Kepler in 1605 is one of the most important advances in astronomy, physics, and science. This discovery transformed the unproven heliocentric theory of Copernicus into a rigorous predictive theory that outperformed the traditional geocentric theory of Claudius Ptolemy and his successors. The discovery paved the way for Newton’s theory of gravitation. It remains one of a small number of cases where a simple mathematical rule for seemingly complex and confusing data has been found. In many respects, the discovery of the elliptical orbit of Mars and other planets is more important than the better known work of Kepler’s contemporary Galileo. In honor of Kepler, NASA has named its recent mission to look for extra-solar planets, especially possible other Earths that might support life or even intelligence, the Kepler mission.

In Kepler’s time the reigning Ptolemaic theory could predict the position of Mars to within a few degrees, usually less than a one percent error. How important is such a small error? Space missions routinely depend on modern orbital dynamics, a lineal descendant of Kepler’s work, to make far more accurate calculations to succeed. The Mars Climate Orbiter mission in 1999 failed due to a tiny error. After traveling about 300 million miles, the Mars Climate Orbiter came in about 90 miles, a tiny fraction of 300 million miles, too low, burning up in the Martian atmosphere rather than aerobreaking successfully into orbit. Successful space missions, the Global Positioning System (GPS), and other modern applications depend on precision mathematical models similar to and sometimes directly descended from Kepler’s model of the orbit of Mars.

Kepler’s story is very different from the story of Galileo and it offers different lessons for today. Diverse fields ranging from astronomy and space physics to artificial intelligence are confronted with similarly complex and confusing data. A mathematical solution to an outstanding problem comparable to Kepler’s discovery could reveal long suspected connections between gravity and other forces, perhaps enabling new power or propulsion systems, enable computers to recognize objects and spoken words, or solve other problems. This article will discuss the discovery of the elliptical orbit of Mars in the context of Kepler’s time. It will also draw some lessons from Kepler and compare and contrast Kepler’s process of discovery to modern astronomy, physics, space science and engineering, including a detailed discussion of dark matter and dark energy.

Read the rest of Kepler’s New Astronomy on Scribd, where you’ll be able to download it in several formats including PDF, or click Fullscreen in the embedded document below.

PDF: Kepler’s New Astronomy.pdf


  1. Jack Waldbewohner December 18, 2009
  2. John F. McGowan December 28, 2009

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