Samuel Pierpont Langley (August 22, 1834 – February 27, 1906) was an American aviation pioneer, astronomer and physicist who invented the bolometer. He was the third secretary of the Smithsonian Institution and a professor of astronomy at the University of Pittsburgh, where he was the director of the Allegheny Observatory.
Life Langley was born in Roxbury, Boston, on August 22, 1834. Langley attended Boston Latin School and graduated from English High School of Boston, after which he became an assistant in the Harvard College Observatory. He then moved to a job at the United States Naval Academy, nominally as a professor of mathematics. However, he was actually sent there to restore the Academy's small observatory. In 1867, he became the director of the Allegheny Observatory and a professor of astronomy at the University of Pittsburgh (then known as the Western University of Pennsylvania), a post he kept until 1891 even while he became the third Secretary of the Smithsonian Institution in 1887. In same year (1887) the Manchester Literary and Philosophical Society awarded Langley honorary membership of the Society. Langley was the founder of the Smithsonian Astrophysical Observatory. In 1875, he was elected as a member to the American Philosophical Society. In 1888 Langley was elected a member of the American Antiquarian Society. In 1898, he received the Prix Jules Janssen, the highest award of the Société astronomique de France, the French astronomical society.
Allegheny Observatory Langley arrived in Pittsburgh in 1867 to become the first director of the Allegheny Observatory, after the institution had fallen into hard times and been given to the Western University of Pennsylvania. By then, the department was in disarray – equipment was broken, there was no library and the building needed repairs. Through the friendship and aid of William Thaw Sr., a Pittsburgh industrial leader, Langley was able to improve the observatory equipment and build additional apparatuses. One of the new instruments was a small transit telescope used to observe the position of the stars as they cross the celestial meridian. He raised money for the department in large part by distributing standard time to cities and railroads. Up until then, correct time had only occasionally been sent from American observatories for public use. Clocks were manually wound in those days and time tended to be imprecise. Exact time had not been especially necessary. It was enough to know that at noon the sun was at its highest elevation for the day. That changed with the arrival of railroads, which made the lack of standard time dangerous. Trains ran by a published schedule, but scheduling was chaotic. If the timepieces of an engineer and a switch operator differed by even a minute or two, trains could be on the same track at the same time and collide. Using astronomical observations obtained from the new telescope, Langley devised a precise time standard, including time zones, that became known as the Allegheny Time System. Initially he distributed time signals to Allegheny city businesses and the Pennsylvania Railroad. Eventually, twice a day, the Allegheny time signals gave the correct time via 4,713 miles of telegraph lines to all railroads in the US and Canada. Langley used the money from the railroads to finance the observatory. From about 1868 revenues from Allegheny Time continued to fund the observatory, until the US Naval Observatory provided the signals via taxpayer funding in 1883. Once funding was secure, Langley devoted his time at the Observatory initially in researching the sun. He used his draftsman skills—from his first job out of high school—to produce hundreds of drawings of solar phenomena, many of which were the first the world had seen. His remarkably detailed 1873 illustration of a sunspot, observed while using the observatory's 13-inch Fitz-Clark refractor, became a classic. It is featured on page 21 of his book, The New Astronomy, and was also widely reprinted in the Americas and Europe. In 1886, Langley received the inaugural Henry Draper Medal from the National Academy of Sciences for his contributions to solar physics. His publication in 1890 of infrared observations at the Allegheny Observatory in Pittsburgh together with Frank Washington Very along with the data he collected from his invention, the bolometer, was used by Svante Arrhenius to make the first calculations on the greenhouse effect. In 1898, Langley received the Prix Jules Janssen, the highest award of the Société astronomique de France (the French astronomical society).
Aviation work
Langley attempted to make a working piloted heavier-than-air aircraft. His models flew, but his two attempts at piloted flight were not successful. Langley began experimenting with rubber-band powered models and gliders in 1887. (According to one book, he was not able to reproduce Alphonse Pénaud's time aloft with rubber power but persisted anyway.) He built a rotating arm that functioned like a wind tunnel, and made larger flying models powered by miniature steam engines. Langley realised that sustained powered flight was possible when he found that a 1 lb. brass plate, suspended from the rotating arm by a spring, could be kept aloft by a spring tension of less than 1 oz. Langley understood that aircraft need thrust to overcome drag from forward speed, observed higher aspect ratio flat plates had higher lift and lower drag, and stated in 1902 "A plane of fixed size and weight would need less propulsive power the faster it flew", the counter-intuitive effect of induced drag. He met the writer Rudyard Kipling around this time, who described one of Langley's experiments in his autobiography:
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