April 8: David Rittenhouse

David Rittenhouse
April 8, 1732 – June 26, 1796

David Rittenhouse was a renowned American astronomer, inventor, clockmaker, mathematician, surveyor, scientific instrument craftsman, and public official. Rittenhouse was a member of the American Philosophical Society and the first director of the United States Mint.

Rittenhouse was born near Germantown, Philadelphia, Pennsylvania. He was self-taught and from a young age showed great ability in science and mathematics. At nineteen years old, he started a scientific instrument shop at his father's farm in West Norriton Township, Pennsylvania. His skill with instruments, particularly clocks, led him to construct two orreries, one of which is currently in the library of the University of Pennsylvania and the other is at Peyton Hall of Princeton University. Rittenhouse was one of the first to build a telescope used in the United States.

His telescope, which utilized natural spider silk to form the reticle, was used to observe and record part of the transit of Venus across the sun on 1769-06-03, as well as the planet's atmosphere.

In 1785, Rittenhouse made perhaps the first diffraction grating using 50 hairs between two finely threaded screws, with an approximate spacing of about 100 lines per inch. This was roughly the same technique that Joseph von Fraunhofer used in 1821 for his wire diffraction grating.

At a young age Rittenhouse showed a high level of intelligence by creating a working scale model of his grandfather's paper mill. His uncle was a carpenter in Philadelphia, who died at a young age. When he died, he left young Rittenhouse a set of tools and instructional books. It was with these tools that Rittenhouse became an inventor and carved out a career. Sparked by the making of his first clock as a young boy, he later impacted the United States in many ways, from creating the first observatory in the country to founding the United States Mint.

After Galileo saw the first sign of Earth's neighbor, Venus, in 1610, astronomers who had been studying the planet, chose Rittenhouse as the person to study the transit path of Venus and its atmosphere. Rittenhouse was the perfect person to study the mysterious planet, as he had a personal observatory on his family farm. "His telescope, which he made himself, utilized grating intervals and spider threads on the focus of the telescope." His telescope is very similar to some modern day telescopes. Rittenhouse served on the American Astronomical Society, and this was another factor in being chosen to study Venus . Throughout his life, he had the honour to serve in many different clubs, committees, and much more. One example is the American Philological Society, he began as a librarian, became secretary, and after Benjamin Franklin's death, he became Vice President. Another one of his interests was the Royal Society of London; this was very rare to see a foreign member of this exclusive society.

When Rittenhousee was thirteen years of age, he had mastered Isaac Newton's Laws of Motion and Gravity. As a young boy he loved to build scale models, such as a working waterwheel and a paper mill. Rittenhouse never went to elementary school and was completely self-educated from family books. With his love of tools and his amazing ability to create things he crafted two orreries for Rutgers University in New Jersey. In return for the gift, the college gave him a scholarship to attend the college enabling him to obtain a degree in philosophy. At the age of twenty-eight, he published his first mathematical paper, one of many papers published throughout his life.

His great excitement at observing the infrequently-occurring transit of Venus (for which he had prepared for a year) resulted in his fainting during the observation. In addition to the work involved in the preparations, Rittenhouse had also been ill the week before the transit. Lying on his back beneath the telescope, trained at the afternoon sun, he regained consciousness after a few minutes and continued his observations. His account of the transit, published in the Transactions of the American Philosophical Society, does not mention his fainting, though it is otherwise meticulous in its record.

The Lunar crater Rittenhouse is named in his honor.