20th-century American physicists

Kenneth Marshall Watson (September 7, 1921 – August 18, 2023) was an American theoretical physicist and physical oceanographer.

Lloyd Viel Berkner (February 1, 1905 in Milwaukee, Wisconsin – June 4, 1967 in Washington, D.C.) was an American physicist and engineer. He was one of the inventors of the measuring device that since has become standard at ionospheric stations because it measures the height and electron density of the ionosphere. The data obtained in the worldwide net of such instruments were important for the developing theory of short wave radio propagation to which Berkner himself gave important contributions.
Berkner was elected to the United States National Academy of Sciences in 1948.Later he investigated the development of the Earth's atmosphere. Since he needed data from the whole world, he proposed the International Geophysical Year in 1950. At that time, the IGY was the largest cooperative study of the Earth ever undertaken.
Berkner was elected a Fellow of the American Academy of Arts and Sciences and a member of the American Philosophical Society in 1956. The IGY was carried out by the International Council of Scientific Unions while he was president in 1957–1959. He was also a member of the President's Scientific Advisory Committee in 1958 while he was president of Associated Universities Inc.
In 1963, Berkner, with L.C. Marshall, advanced a theory to describe the way in which the atmospheres of the Solar System's inner planets had evolved.
Beginning in 1926, as a naval officer, Berkner assisted in the development of radar and navigation systems, naval aircraft electronics engineering, and studies that led to the construction of the Distant Early Warning system, a chain of radar stations designed to give the United States advance warning in the event of a missile attack across the North Pole. In the 50s and 60s, Berkner held intelligence clearances in the Atomic Energy Commission and other agencies. He worked with the CIA in some capacity as well, but any activities are wholly classified as of 2015.Berkner worked with Dallas community leaders to establish the Graduate Research Center of the Southwest (later renamed the Southwest Center for Advanced Studies, which would eventually become The University of Texas at Dallas).He wrote more than 100 papers and several books, including Rockets and Satellites (1958), Science in Space (1961), and The Scientific Age (1964).
In 1961, Berkner was president of the Institute of Radio Engineers.

Trịnh Xuân Thuận (born August 20, 1948) is a Vietnamese-American astrophysicist.

Hartland Sweet Snyder (1913, Salt Lake City – 1962) was an American physicist who, together with Robert Oppenheimer, showed how large stars would collapse to form black holes. This work modeled the gravitational collapse of a pressure-free homogeneous fluid sphere and found that it would be unable to communicate with the rest of the universe.
This discovery was depicted in the movie Oppenheimer, where Snyder was portrayed by actor Rory Keane.Historian of physics David C. Cassidy assessed that this prediction of black holes might have won a Nobel Prize in Physics had the authors been alive in the 1990s when evidence was available.Some publications Snyder authored together with Ernest Courant laid the foundations for the field of accelerator physics. In particular, Snyder with Courant and Milton Stanley Livingston developed the principle of strong focusing that made modern particle accelerators possible. The Courant–Snyder parameters, a method of characterizing the distribution of particles in a beam, were an important part of that contribution.In 1954, Snyder bet against Maurice Goldhaber that antiprotons existed, and won.

Edward P. Tryon (September 4, 1940 – December 11, 2019) was an American scientist and a professor emeritus of physics at Hunter College of the City University of New York (CUNY). He was the first physicist to propose that our universe originated as a quantum fluctuation of the vacuum.

Peter Carruthers (1935 – August 3, 1997) was an American physicist best known for leading the theoretical division of Los Alamos National Laboratory from 1973 until 1980.

Fritz Reiche (July 4, 1883 – January 14, 1969) was a German physicist, a student of Max Planck and a colleague of Albert Einstein, who was active in, and made important contributions to the early development of quantum mechanics including co-authoring the Thomas-Reiche-Kuhn sum rule.Fritz Reiche was born in 1883 in Berlin, Germany. In 1901 and 1902, he attended the University of Munich and he attended the University of Berlin from 1902 to 1907, where he received his PhD. From 1913 to 1920 as privatdozent he worked and taught under Planck in Berlin. Reiche published more than 55 scientific papers and books including The Quantum Theory.He became a professor in 1921 at the University of Breslau and then was dismissed as a Jew from his academic position in 1933. Eventually, with the help of Ladenburg, Einstein, and the Emergency Committee in Aid of Displaced Foreign Scholars, Reiche emigrated with his family to the United States in 1941 and went on to work with NASA and the United States Navy on projects related to supersonic flow.

Arthur Robert von Hippel (November 19, 1898 – December 31, 2003) was a German American materials scientist and physicist. Von Hippel was a pioneer in the study of dielectrics, ferromagnetic and ferroelectric materials, and semiconductors and was a codeveloper of radar during World War II.

Franco Dino Rasetti (August 10, 1901 – December 5, 2001) was an Italian (later naturalized American) physicist, paleontologist and botanist. Together with Enrico Fermi, he discovered key processes leading to nuclear fission. Rasetti refused to work on the Manhattan Project on moral grounds.

Max Jakob (July 20, 1879 – January 4, 1955) was a German physicist known for his work in the field of thermal science.
Born in Ludwigshafen, Germany, Jakob studied engineering at Technical University Munich, from which he graduated in 1903. From 1903 to 1906, he was an assistant to O. Knoblauch at the Laboratory for Technical Physics. In 1910, Jakob embarked on a 25-year career at the Physikalisch-Technische Reichsanstalt in Charlottenburg, Berlin. During this time he founded and directed applied thermodynamics, heat transfer, and fluid flow laboratories.Fleeing Nazi persecution, Jakob left Germany in 1936 and immigrated to the United States, where he became a professor at Armour Institute of Technology (now Illinois Institute of Technology) and a consultant in heat transfer for Armour Research Foundation. There he conducted research, covering areas such as steam and air at high pressure, devices for measuring thermal conductivity, the mechanisms of boiling and condensation, and flow in pipes and nozzles.His many years of teaching, consulting, and writing resulted in contributions to the literature of the profession; nearly 500 books, articles, reviews and discussions have been published based on his research. He has published a number of books in thermal sciences including Elements of Heat Transfer and Insulation (1942) and Heat Transfer (1956).
He is credited with devising the Jakob dimensionless number, aka Jakob number, which is used in phase change heat transfer calculations:

J
a
=

c

p
,
f

(

T

w

−

T

s
a
t

)

h

f
g

{\displaystyle Ja={\frac {c_{p,f}(T_{w}-T_{sat})}{h_{fg}}}}

The Max Jakob Memorial Award, the highest honor in the field of heat transfer, was established in 1961 by the American Society of Mechanical Engineers (ASME) Heat Transfer Division in honor of Jakob.