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Allegheny Observatory
The Allegheny Observatory is an American astronomical research institution, a part of the Department of Physics and Astronomy at the University of Pittsburgh. The facility is listed on the National Register of Historic Places (ref. # 79002157, added June 22, 1979) and is designated as a Pennsylvania state and Pittsburgh History and Landmarks Foundation historic landmark.
The observatory was founded on February 15, 1859, in the city of Allegheny, Pennsylvania (incorporated into the City of Pittsburgh in 1907) by a group of wealthy industrialists calling themselves the Allegheny Telescope Association. The observatory's initial purpose was for general public education as opposed to research, but by 1867 the revenues derived from this had receded. The facility was then donated to the Western University of Pennsylvania, today known as the University of Pittsburgh.
The University hired Samuel Pierpont Langley to be the first director. One of the research programs initiated under his leadership was of sunspots. He drew very detailed drawings of sunspots which are still used in astronomical textbooks to this day. He also had the building expanded to include dark rooms, class rooms, dormitories, and a lecture hall.
In 1869, Langley created income for the observatory by selling subscription service to time that was accurately determined by astronomical measurements and transmitted over telegraphs to customers. The Pennsylvania Railroad was the most influential subscriber to the "Allegheny Time" system. The Allegheny Observatory's service is believed to have been the first regular and systematic system of time distribution to railroads and cities as well as the origin of the modern standard time system. By 1870, the Allegheny Time service extended over 2,500 miles with 300 telegraph offices receiving time signals. On November 18, 1883, the first day of railroad standard time in North America, the Allegheny Observatory transmitted a signal on telegraph lines operated by railroads in Canada and the United States. The signal marked noon, Eastern Standard Time, and railroads across the continent synchronized their schedules based on this signal. The standard time that began on this day continues in North American use to this day.
The revenues from the sale of time signals covered Langley's salary and the bills. Allegheny Observatory continued to supply time signals until the US Naval Observatory started offering it for free in 1920.
In 1878, Langley invented the bolometer, which makes very sensitive detections of thermal radiation. He used it to measure the strong variation with wavelength of Earth’s atmospheric absorption, results used by Arrhenius in 1890 demonstrating the greenhouse effect. Langley also used it to discover new infrared atomic and molecular absorption lines and make the first accurate calculation of the solar constant. Bolometers are now essential physics instruments with applications extended to astronomy, particle physics, plasma physics, and thermal cameras.
In 1895, James Keeler (AO Director: 1891-1898) obtained spectroscopy of Saturn's rings with the 13-inch Fitz-Clark Refractor, proving that the rings were particles, not solid disks as thought since the 1650s and supporting James Clerk Maxwell's 1859 calculation which indicated that tidal forces necessitate rings composed of disconnected particles. Keeler's observations launched the detailed study of Saturn's rings, which today yield insights into less accessible disk systems.
John Brashear (Allegheny Observatory Committee Chairman: 1893-1920, Allegheny Observatory Director: 1898-1900, University of Pittsburgh Chancellor: 1901-1904) made many high-quality optics and precision instruments at his Allegheny-Observatory-affiliated shop, including the optical surfaces for the famous 1887 Michelson-Morley interferometer, which demonstrated the constant speed of light regardless of motion direction. This was a watershed moment in physics history, leading to Einstein’s theory of special relativity. Brashear also made the impressive 47-foot long 30-inch Thaw Refractor still in use at Allegheny Observatory.
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Allegheny Observatory
The Allegheny Observatory is an American astronomical research institution, a part of the Department of Physics and Astronomy at the University of Pittsburgh. The facility is listed on the National Register of Historic Places (ref. # 79002157, added June 22, 1979) and is designated as a Pennsylvania state and Pittsburgh History and Landmarks Foundation historic landmark.
The observatory was founded on February 15, 1859, in the city of Allegheny, Pennsylvania (incorporated into the City of Pittsburgh in 1907) by a group of wealthy industrialists calling themselves the Allegheny Telescope Association. The observatory's initial purpose was for general public education as opposed to research, but by 1867 the revenues derived from this had receded. The facility was then donated to the Western University of Pennsylvania, today known as the University of Pittsburgh.
The University hired Samuel Pierpont Langley to be the first director. One of the research programs initiated under his leadership was of sunspots. He drew very detailed drawings of sunspots which are still used in astronomical textbooks to this day. He also had the building expanded to include dark rooms, class rooms, dormitories, and a lecture hall.
In 1869, Langley created income for the observatory by selling subscription service to time that was accurately determined by astronomical measurements and transmitted over telegraphs to customers. The Pennsylvania Railroad was the most influential subscriber to the "Allegheny Time" system. The Allegheny Observatory's service is believed to have been the first regular and systematic system of time distribution to railroads and cities as well as the origin of the modern standard time system. By 1870, the Allegheny Time service extended over 2,500 miles with 300 telegraph offices receiving time signals. On November 18, 1883, the first day of railroad standard time in North America, the Allegheny Observatory transmitted a signal on telegraph lines operated by railroads in Canada and the United States. The signal marked noon, Eastern Standard Time, and railroads across the continent synchronized their schedules based on this signal. The standard time that began on this day continues in North American use to this day.
The revenues from the sale of time signals covered Langley's salary and the bills. Allegheny Observatory continued to supply time signals until the US Naval Observatory started offering it for free in 1920.
In 1878, Langley invented the bolometer, which makes very sensitive detections of thermal radiation. He used it to measure the strong variation with wavelength of Earth’s atmospheric absorption, results used by Arrhenius in 1890 demonstrating the greenhouse effect. Langley also used it to discover new infrared atomic and molecular absorption lines and make the first accurate calculation of the solar constant. Bolometers are now essential physics instruments with applications extended to astronomy, particle physics, plasma physics, and thermal cameras.
In 1895, James Keeler (AO Director: 1891-1898) obtained spectroscopy of Saturn's rings with the 13-inch Fitz-Clark Refractor, proving that the rings were particles, not solid disks as thought since the 1650s and supporting James Clerk Maxwell's 1859 calculation which indicated that tidal forces necessitate rings composed of disconnected particles. Keeler's observations launched the detailed study of Saturn's rings, which today yield insights into less accessible disk systems.
John Brashear (Allegheny Observatory Committee Chairman: 1893-1920, Allegheny Observatory Director: 1898-1900, University of Pittsburgh Chancellor: 1901-1904) made many high-quality optics and precision instruments at his Allegheny-Observatory-affiliated shop, including the optical surfaces for the famous 1887 Michelson-Morley interferometer, which demonstrated the constant speed of light regardless of motion direction. This was a watershed moment in physics history, leading to Einstein’s theory of special relativity. Brashear also made the impressive 47-foot long 30-inch Thaw Refractor still in use at Allegheny Observatory.
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