Edward Mills Purcell

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Edward Mills Purcell
Edward Mills Purcell.jpg
Edward Mills Purcell (1912–1997)
Born(1912-08-30)August 30, 1912
Taylorville, Illinois, United States
DiedMarch 7, 1997(1997-03-07) (aged 84)
Cambridge, Massachusetts, United States
NationalityUnited States
Alma mater Purdue University (BSEE)
Harvard University (M.A.)
Harvard University (Ph.D)
Known for Nuclear magnetic resonance (NMR)
Smith-Purcell effect
21 cm line
Scallop theorem
Awards Nobel Prize for Physics (1952)
Oersted Medal (1967)
National Medal of Science (1979)
Max Delbruck Prize (1984)
Beatrice M. Tinsley Prize (1988)
Scientific career
Fields Physics
Institutions Harvard University
Doctoral advisor Kenneth Bainbridge
Other academic advisors John Van Vleck
Doctoral students George Pake
George Benedek
Charles Pence Slichter
Other notable students Nicolaas Bloembergen
Horn antenna used by Harold I. Ewen and Edward M. Purcell at the Lyman Laboratory of Physics at Harvard University in 1951 for the first detection of radio radiation from nuclear atomic hydrogen gas in the Milky Way at a wavelength of 21 cm. Now at National Radio Astronomy Observatory in Green Bank, WV. Green Banks - Ewen-Purcell Horn Antenna.jpg
Horn antenna used by Harold I. Ewen and Edward M. Purcell at the Lyman Laboratory of Physics at Harvard University in 1951 for the first detection of radio radiation from nuclear atomic hydrogen gas in the Milky Way at a wavelength of 21 cm. Now at National Radio Astronomy Observatory in Green Bank, WV.

Edward Mills Purcell (August 30, 1912 – March 7, 1997) was an American physicist who shared the 1952 Nobel Prize for Physics for his independent discovery (published 1946) of nuclear magnetic resonance in liquids and in solids. [2] Nuclear magnetic resonance (NMR) has become widely used to study the molecular structure of pure materials and the composition of mixtures.

United States Federal republic in North America

The United States of America (USA), commonly known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, and various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is slightly smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U.S. is the third most populous country. The capital is Washington, D.C., and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico. The State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean. The U.S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The extremely diverse geography, climate, and wildlife of the United States make it one of the world's 17 megadiverse countries.

Nuclear magnetic resonance spectroscopic technique relying on the energy difference between the quantum spin states of electrons when exposed to an external magnetic field

Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong static magnetic field are perturbed by a weak oscillating magnetic field and respond by producing an electromagnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved; in practical applications with static magnetic fields up to ca. 20 tesla, the frequency is similar to VHF and UHF television broadcasts (60–1000 MHz). NMR results from specific magnetic properties of certain atomic nuclei. Nuclear magnetic resonance spectroscopy is widely used to determine the structure of organic molecules in solution and study molecular physics, crystals as well as non-crystalline materials. NMR is also routinely used in advanced medical imaging techniques, such as in magnetic resonance imaging (MRI).

Molecule Electrically neutral entity consisting of more than one atom (n > 1); rigorously, a molecule, in which n > 1 must correspond to a depression on the potential energy surface that is deep enough to confine at least one vibrational state

A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge. However, in quantum physics, organic chemistry, and biochemistry, the term molecule is often used less strictly, also being applied to polyatomic ions.



Born and raised in Taylorville, Illinois, Purcell received his BSEE in electrical engineering from Purdue University, followed by his M.A. and Ph.D. in physics from Harvard University. He was a member of the Alpha Xi chapter of the Phi Kappa Sigma Fraternity while at Purdue. [3] After spending the years of World War II working at the MIT Radiation Laboratory on the development of microwave radar, Purcell returned to Harvard to do research. In December 1946, he discovered nuclear magnetic resonance (NMR) with his colleagues Robert Pound and Henry Torrey. [4] NMR provides scientists with an elegant and precise way of determining chemical structure and properties of materials, and is widely used in physics and chemistry. It also is the basis of magnetic resonance imaging (MRI), one of the most important medical advances of the 20th century. For his discovery of NMR, Purcell shared the 1952 Nobel Prize in physics with Felix Bloch of Stanford University.

Taylorville, Illinois City and County seat in Illinois, United States

Taylorville is a city in and the county seat of Christian County, Illinois, United States. The population was 11,427 at the 2000 census, making it the county's largest city.

A Bachelor of Engineering is a first professional undergraduate academic degree awarded to a student after three to five years of studying engineering at an accredited university. In the UK, a B.Eng. degree will be accredited by one of the Engineering Council's professional engineering institutions as suitable for registration as a incorporated engineer or chartered engineer with further study to masters level. In Canada, the degree from a Canadian university can be accredited by the Canadian Engineering Accreditation Board (CEAB). Alternatively, it might be accredited directly by another professional engineering institution, such as the US-based Institute of Electrical and Electronics Engineers (IEEE). The B.Eng. contributes to the route to chartered engineer (UK), registered engineer or licensed professional engineer and has been approved by representatives of the profession.

Electrical engineering field of engineering that deals with electricity

Electrical engineering is a professional engineering discipline that generally deals with the study and application of electricity, electronics, and electromagnetism. This field first became an identifiable occupation in the later half of the 19th century after commercialization of the electric telegraph, the telephone, and electric power distribution and use. Subsequently, broadcasting and recording media made electronics part of daily life. The invention of the transistor, and later the integrated circuit, brought down the cost of electronics to the point they can be used in almost any household object.

Purcell also made contributions to astronomy as the first to detect radio emissions from neutral galactic hydrogen (the famous 21 cm line due to hyperfine splitting), affording the first views of the spiral arms of the Milky Way. [5] This observation helped launch the field of radio astronomy, and measurements of the 21 cm line are still an important technique in modern astronomy. He has also made seminal contributions to solid state physics, with studies of spin-echo relaxation, nuclear magnetic relaxation, and negative spin temperature (important in the development of the laser). With Norman F. Ramsey, he was the first to question the CP symmetry of particle physics.

Astronomy natural science that deals with the study of celestial objects

Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, and comets; the phenomena also includes supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, all phenomena that originate outside Earth's atmosphere are within the purview of astronomy. A related but distinct subject is physical cosmology, which is the study of the Universe as a whole.

Hydrogen line Spectral line of hydrogen state transitions

The hydrogen line, 21-centimeter line or H I line refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation is at the precise frequency of 1420405751.7667±0.0009 Hz, which is equivalent to the vacuum wavelength of 21.1061140542 cm in free space. This wavelength falls within the microwave region of the electromagnetic spectrum, and it is observed frequently in radio astronomy, since those radio waves can penetrate the large clouds of interstellar cosmic dust that are opaque to visible light.

Milky Way spiral galaxy containing our Solar System

The Milky Way is the galaxy that contains our Solar System. The name describes the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. The term Milky Way is a translation of the Latin via lactea, from the Greek γαλαξίας κύκλος. From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies. The Milky Way is a barred spiral galaxy with a diameter between 150,000 and 200,000 light-years (ly). It is estimated to contain 100–400 billion stars and more than 100 billion planets. The Solar System is located at a radius of 26,490 light-years from the Galactic Center, on the inner edge of the Orion Arm, one of the spiral-shaped concentrations of gas and dust. The stars in the innermost 10,000 light-years form a bulge and one or more bars that radiate from the bulge. The galactic center is an intense radio source known as Sagittarius A*, assumed to be a supermassive black hole of 4.100 million solar masses.

Purcell was the recipient of many awards for his scientific, educational, and civic work. He served as science advisor to Presidents Dwight D. Eisenhower, John F. Kennedy, and Lyndon B. Johnson. He was president of the American Physical Society, and a member of the American Philosophical Society, the National Academy of Sciences, and the American Academy of Arts and Sciences. He was awarded the National Medal of Science in 1979, and the Jansky Lectureship before the National Radio Astronomy Observatory. Purcell was also inducted into his Fraternity's (Phi Kappa Sigma) Hall of Fame as the first Phi Kap ever to receive a Nobel Prize.

Dwight D. Eisenhower 34th president of the United States

Dwight David "Ike" Eisenhower was an American army general and statesman who served as the 34th president of the United States from 1953 to 1961. During World War II, he was a five-star general in the United States Army and served as supreme commander of the Allied Expeditionary Forces in Europe. He was responsible for planning and supervising the invasion of North Africa in Operation Torch in 1942–43 and the successful invasion of France and Germany in 1944–45 from the Western Front.

John F. Kennedy 35th president of the United States

John Fitzgerald "Jack" Kennedy, commonly referred to by his initials JFK, was an American politician and journalist who served as the 35th president of the United States from January 1961 until his assassination in November 1963. He served at the height of the Cold War, and the majority of his presidency dealt with managing relations with the Soviet Union. A member of the Democratic Party, Kennedy represented Massachusetts in the U.S. House of Representatives and Senate prior to becoming president.

Lyndon B. Johnson 36th president of the United States

Lyndon Baines Johnson, often referred to as LBJ, was an American politician who served as the 36th president of the United States from 1963 to 1969. Formerly the 37th vice president of the United States from 1961 to 1963, he assumed the presidency following the assassination of President John F. Kennedy. A Democrat from Texas, Johnson also served as a United States Representative and as the Majority Leader in the United States Senate. Johnson is one of only four people who have served in all four federal elected positions.

Purcell was the author of the innovative introductory text Electricity and Magnetism. [6] The book, a Sputnik-era project funded by an NSF grant, was influential for its use of relativity in the presentation of the subject at this level. The 1965 edition, now freely available due to a condition of the federal grant, was originally published as a volume of the Berkeley Physics Course . Half a century later, the book is also in print as a commercial third edition, as Purcell and Morin. Purcell is also remembered by biologists for his famous lecture "Life at Low Reynolds Number", [7] in which he explained a principle referred to as the Scallop theorem.

Relativistic electromagnetism

Relativistic electromagnetism is a physical phenomenon explained in electromagnetic field theory due to Coulomb's law and Lorentz transformations.

The Berkeley Physics Course is a series of college-level physics textbooks written mostly by UC Berkeley professors.

The Scallop theorem states that to achieve propulsion at low Reynolds number in Newtonian fluids a swimmer must deform in a way that is not invariant under time-reversal. Edward Mills Purcell stated this theorem in his 1977 paper Life at Low Reynolds Number explaining physical principles of aquatic locomotion. The theorem is named for the motion of a scallop - an opening and closing of a simple hinge - which is not sufficient to create migration at low Reynolds numbers.

See also

The Purcell effect is the enhancement of a quantum system's spontaneous emission rate by its environment. In the 1940s Edward Mills Purcell discovered the enhancement of spontaneous emission rates of atoms when they are incorporated into a resonant cavity. The magnitude of the enhancement is given by the Purcell factor

Magnetic resonance imaging non-destructive technique for imaging internal structures of objects or organisms

Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body in both health and disease. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to generate images of the organs in the body. MRI does not involve X-rays or the use of ionizing radiation, which distinguishes it from CT or CAT scans and PET scans. Magnetic resonance imaging is a medical application of nuclear magnetic resonance (NMR). NMR can also be used for imaging in other NMR applications such as NMR spectroscopy.

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  1. "E. M. Purcell - Biography". The Nobel Prize in Physics 1952 Felix Bloch, E. M. Purcell. The Nobel Foundation. 1952. Retrieved 22 May 2012.
  2. Bleaney, B. (1999). "Edward Mills Purcell. 30 August 1912 -- 7 March 1997: Elected For.Mem.R.S. 1989". Biographical Memoirs of Fellows of the Royal Society . 45: 437–447. doi:10.1098/rsbm.1999.0029.
  3. "Famous Phi Kappa Sigma's - Famous Fraternity & Sorority Greeks - Greek 101". greek101.com.
  4. Purcell, E.; Torrey, H.; Pound, R. (1946). "Resonance Absorption by Nuclear Magnetic Moments in a Solid". Physical Review. 69: 37. Bibcode:1946PhRv...69...37P. doi:10.1103/PhysRev.69.37.
  5. Ewen, H. I.; Purcell, E. M. (1951). "Observation of a Line in the Galactic Radio Spectrum: Radiation from Galactic Hydrogen at 1,420 Mc./sec". Nature. 168 (4270): 356. Bibcode:1951Natur.168..356E. doi:10.1038/168356a0.
  6. "Electricity and Magnetism". google.com.
  7. Purcell, E. M. (1977). "Life at low Reynolds number". American Journal of Physics. 45: 3–11. Bibcode:1977AmJPh..45....3P. doi:10.1119/1.10903.