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Gnomon Chronicles is a work of fiction and nonfiction by Karl Jones.

On This Day in History: September 27

1677: Mathematician, astronomer, and cartographer Johann Gabriel Doppelmayr born. He will publish works on mathematics and astronomy, including sundials, spherical trigonometry, and celestial maps and globes, along with biographical information on several hundred mathematicians and instrument makers.
1737: Physician, mathematician, and engineer Hubert Gautier dies. He authored the first book on bridge building, Traité des Ponts, in 1716, as well as books on roads, fortifications, antiquities, geology, and a first manual for watercolor practitioners.
1783: Mathematician Étienne Bézout dies. His Théorie générale des équations algébriques contained much new and valuable matter on the theory of elimination and symmetrical functions of the roots of an equation.
1879: Mathematician and philosopher Hans Hahn born. He will make contributions to functional analysis, topology, set theory, the calculus of variations, real analysis, and order theory.
1905: The physics journal Annalen der Physik received Albert Einstein's paper, "Does the Inertia of a Body Depend Upon Its Energy Content?", introducing the equation E=mc².
1928: Mathematician and academic Hans F. Weinberger born. He will contribute to variational methods for eigenvalue problems, partial differential equations, and fluid dynamics.
1962: Rachel Carson's book Silent Spring is published, inspiring an environmental movement and the creation of the U.S. Environmental Protection Agency.
2007: NASA launches the Dawn space probe. It is NASA's first purely exploratory mission to use ion propulsion. Dawn will study Vesta and Ceres, two of the three known protoplanets of the asteroid belt.