Carroll Overton Alley, Jr. (June 13, 1927 – February 24, 2016) was an American

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

. He served as the Principal Investigator on the

Apollo Program The Apollo program, also known as Project Apollo, was the United States human spaceflight program led by NASA, which Moon landing, landed the first humans on the Moon in 1969. Apollo followed Project Mercury that put the first Americans in sp ...

Lunar Laser Ranging Experiment Lunar Laser Ranging (LLR) is the practice of measuring Lunar distance (astronomy), the distance between the surfaces of the Earth and the Moon using Lidar, laser ranging. The distance can be calculated from the Round-trip delay, round-trip time ...

, which significantly restricted the possible range of spatial variation of the strength of the gravitational interaction. Alley was a PhD student of Robert Henry Dicke. Alley’s goal was to understand

quantum mechanics Quantum mechanics is the fundamental physical Scientific theory, theory that describes the behavior of matter and of light; its unusual characteristics typically occur at and below the scale of atoms. Reprinted, Addison-Wesley, 1989, It is ...

gravitation In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...

, and relativity. His lifelong research interests included experimental and theoretical questions about the foundations of gravitational and quantum physics. Alley developed some of the earliest important laboratory tests of

Albert Einstein Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence f ...

's theories of relativity. In recent years he became known for alternative theories of

. He was a Physics professor at

University of Maryland, College Park The University of Maryland, College Park (University of Maryland, UMD, or simply Maryland) is a public university, public Land-grant university, land-grant research university in College Park, Maryland, United States. Founded in 1856, UMD i ...

, emeritus since 2008, until his death on 24 February 2016.

Career details

Professor C. O. Alley served as the first chairman of the Lunar Ranging Experiment team. He was the Principal Investigator (PI) for the

Apollo 11 Apollo 11 was a spaceflight conducted from July 16 to 24, 1969, by the United States and launched by NASA. It marked the first time that humans Moon landing, landed on the Moon. Commander Neil Armstrong and Lunar Module pilot Buzz Aldrin l ...

laser ranging retro-reflector (LR³) experiment, deployed on the moon by

Neil Armstrong Neil Alden Armstrong (August 5, 1930 – August 25, 2012) was an American astronaut and aerospace engineering, aeronautical engineer who, in 1969, became the Apollo 11#Lunar surface operations, first person to walk on the Moon. He was al ...

and

Buzz Aldrin Buzz Aldrin ( ; born Edwin Eugene Aldrin Jr.; January 20, 1930) is an American former astronaut, engineer and fighter pilot. He made three extravehicular activity, spacewalks as pilot of the 1966 Gemini 12 mission, and was the Lunar Module Eag ...

in 1969. In addition to the gravitational interaction results mentioned above, the experiment measured the orbit of the moon to centimeter accuracy—and still produces data to this day. For this work he was awarded the NASA Exceptional Scientific Achievement Award in 1973; was designated by the Maryland Academy of Sciences, for their 1976 Bicentennial Exhibit, as one of two outstanding 20th Century Scientists; and received an honorary Doctor of Science degree from the University of Richmond in 1978.Alley, C. O., Brief Curriculum Vitae of C. O. Alley Some additional accomplishments of Professor Alley, his graduate students, the Quantum Electronics Research and Lunar Ranging Experiment Teams, support staff, and numerous collaborators include: *

Surveyor 7 Surveyor 7 was sent to the Moon in 1968 on a scientific and photographic mission as the seventh and last lunar lander of the American uncrewed Surveyor program. With two previous unsuccessful missions in the Surveyor series, and with Surveyor 7's ...

laser beam pointing tests in preparation for the Apollo 11 experiment and visual detection of laser beams from Earth, as well as subsequent lunar laser ranging on later Apollo missions * Role in the commissioning of the

Global Positioning System The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide ge ...

by contributing to the calculations that correct for time dilation in gravitational fields * Conducting relativistic proper time experiments by flying

caesium Caesium (IUPAC spelling; also spelled cesium in American English) is a chemical element; it has Symbol (chemistry), symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only f ...

and

rubidium Rubidium is a chemical element; it has Symbol (chemistry), symbol Rb and atomic number 37. It is a very soft, whitish-grey solid in the alkali metal group, similar to potassium and caesium. Rubidium is the first alkali metal in the group to have ...

atomic clocks in a Navy P3C aircraft over the Chesapeake Bay, to measure the effects of gravitational potential difference on their recorded proper times and comparing those times to ground clocks using short laser pulses * Experiments in fundamental quantum mechanics with light quanta, including the first delayed-choice experiment in quantum mechanics * First use of spontaneous parametric down conversion in quantum optics to exhibit entangled polarization quantum states of the Einstein-Podolsky-Rosen-Bohm type (thesis of Alley’s PhD student Yan Hua Shih) * Direct measurements of possible difference in the

one-way speed of light When using the term "speed of light, the speed of light" it is sometimes necessary to make the distinction between its one-way speed and its two-way speed. The "one-way" speed of light, from a source to a detector, cannot be measurement, measured ...

between the east-west and west-east directions on the rotating Earth, by flying atomic clocks between Christchurch, New Zealand, and Thule, Greenland In later years Alley collaborated in the study, development, and application of a new formulation of gravity as curved spacetimeBaden, Drew, University of Maryland Department of Physics Newsletter, March 4, 2016 found by Professor Huseyin Yilmaz. They postulated that the correct understanding of the lunar laser ranging measurements, the behavior of clocks in a global positioning system, and many strong gravity field astrophysical phenomena—such as gravitational radiation—require the interactive N-body solutions of th
Yilmaz Theory (or "New Theory")
which are not present in Einstein’s General Relativity field equations. Alley maintained the validity of the Yilmaz Theoryand remained active in the study of gravitation until his death.

Biography

Carroll O. Alley, Jr. was born in Richmond, VA to Carroll Overton Alley, Sr. and Mittie Points Alley on June 13, 1927. Alley attended John Marshall High School, where he was a swimmer, choir member, and Cadet Corps First Captain and Regimental Commander of A Company. He earned a B.S. in mathematics and physics from the

University of Richmond The University of Richmond (UR or U of R) is a Private college, private Liberal arts colleges in the United States, liberal arts college in Richmond, Virginia, United States. It is a primarily undergraduate, residential institution with approxim ...

in 1948, and returned there in 1951-’52 as a physics instructor.Alley, C.O., Some Biographical Information about Carroll Alley Alley attended

Princeton University Princeton University is a private university, private Ivy League research university in Princeton, New Jersey, United States. Founded in 1746 in Elizabeth, New Jersey, Elizabeth as the College of New Jersey, Princeton is the List of Colonial ...

, earning a master's degree (1952) and PhD (1962) in Physics. From 1954 to 1960, he was an instructor and lecturer in both

Electrical Engineering Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems that use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...

and Physics at Princeton, where he met and married his late wife, Elizabeth (Slack) Delany Alley. His daughter Frances Alley Kruger was born in Princeton in 1955. At Princeton, Alley studied electrical engineering as well as theoretical and experimental physics. He was greatly influenced by the work of

Eugene Wigner Eugene Paul Wigner (, ; November 17, 1902 – January 1, 1995) was a Hungarian-American theoretical physicist who also contributed to mathematical physics. He received the Nobel Prize in Physics in 1963 "for his contributions to the theory of th ...

and

John Archibald Wheeler John Archibald Wheeler (July 9, 1911April 13, 2008) was an American theoretical physicist. He was largely responsible for reviving interest in general relativity in the United States after World War II. Wheeler also worked with Niels Bohr to e ...

. His PhD dissertation developed new methods of detecting the ground state hyperfine transition in optically-pumped rubidium vapor for the type of atomic clock invented by Princeton professors Robert Henry Dicke—Alley’s thesis advisor—and Thomas R. Carver. This type of

atomic clock An atomic clock is a clock that measures time by monitoring the resonant frequency of atoms. It is based on atoms having different energy levels. Electron states in an atom are associated with different energy levels, and in transitions betwee ...

was later used in the U.S.

and the European Union’s Galileo Global Positioning System. Alley initiated laser physics research at the Institute of Optics and the Physics Department of the

University of Rochester The University of Rochester is a private university, private research university in Rochester, New York, United States. It was founded in 1850 and moved into its current campus, next to the Genesee River in 1930. With approximately 30,000 full ...

, where he was an assistant professor of physics and optics from 1960 to 1963. His daughter Margaret Alley Seymour was born in Rochester in 1961. In 1963 Alley was recruited to the University of Maryland, College Park Campus, by John S. Toll, then-chair of the Department of Physics and Astronomy. For most of his career—more than 40 years—Alley served as professor of Physics and director of the Quantum Electronics Research Group at the University of Maryland. He taught and conducted research at Maryland from 1963 to 2008, at which time he was granted

Professor Emeritus ''Emeritus/Emerita'' () is an honorary title granted to someone who retirement, retires from a position of distinction, most commonly an academic faculty position, but is allowed to continue using the previous title, as in "professor emeritus". ...

status—a post he held until his death on February 24, 2016.

References

External links

Carroll Alley's University of Maryland page

Oral History interview transcript with Carroll O. Alley on 19 May 2006, American Institute of Physics, Niels Bohr Library and Archives

* http://www.lpi.usra.edu/lunar/missions/apollo/apollo_11/experiments/lrr/ * http://www.jpl.nasa.gov/news/news.php?feature=605 * http://ilrs.gsfc.nasa.gov/science/scienceContributions/lunar.html
https://umdphysics.umd.edu/about-us/news/department-news/1128-carroll-alley-june-13-1927-february-24-2016.html#!Alley_Lunar_Laser_Ranging_Retroreflector_1.
* https://umdphysics.umd.edu/images/alley-memorial/AlleyRemembrances.pdf * https://www.nasa.gov/feature/pioneering-physicist-carroll-alley-dies {{DEFAULTSORT:Alley, Carroll American physicists University of Maryland, College Park faculty 2016 deaths 1927 births