The Pocono Conference of 30 March to 2 April 1948 was the second of three postwar conferences held to discuss quantum physics; arranged by Robert Oppenheimer

Robert Oppenheimer

Julius Robert Oppenheimer was an American theoretical physicist and professor of physics at the University of California, Berkeley. Along with Enrico Fermi, he is often called the "father of the atomic bomb" for his role in the Manhattan Project, the World War II project that developed the first...

 for the National Academy of Sciences

United States National Academy of Sciences

The National Academy of Sciences is a corporation in the United States whose members serve pro bono as "advisers to the nation on science, engineering, and medicine." As a national academy, new members of the organization are elected annually by current members, based on their distinguished and...

. It followed the Shelter Island Conference

Shelter Island Conference

The first Shelter Island Conference on the Foundations of Quantum Mechanics was held from June 2–4, 1947 at the Ram's Head Inn in Shelter Island, New York. Shelter Island was the first major opportunity since Pearl Harbor and the Manhattan Project for the leaders of the American physics community...

 of 1947 and preceded the Oldstone Conference

Oldstone Conference

The Oldstone Conference of 11 to 14 April 1949 was the third of three postwar conferences held to discuss quantum physics; arranged for the National Academy of Sciences by J. Robert Oppenheimer, who was again chairman. It followed the Shelter Island Conference of 1947 and the Pocono Conference of...

 of 1949.

Held at the Pocono Manor Inn in the Pocono Mountains of Pennsylvania, midway between Scranton, Pennsylvania

Scranton, Pennsylvania

Scranton is a city in the northeastern part of Pennsylvania, United States. It is the county seat of Lackawanna County and the largest principal city in the Scranton/Wilkes-Barre metropolitan area. Scranton had a population of 76,089 in 2010, according to the U.S...

 and the Delaware Water Gap

Delaware Water Gap

The Delaware Water Gap is on the border of New Jersey and Pennsylvania where the Delaware River cuts through a large ridge of the Appalachian Mountains...

, 28 physicists attended. New participants were Niels Bohr

Niels Bohr

Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...

, Aage Bohr, Paul Dirac

Paul Dirac

Paul Adrien Maurice Dirac, OM, FRS was an English theoretical physicist who made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics...

, Walter Heitler

Walter Heitler

Walter Heinrich Heitler was a German physicist who made contributions to quantum electrodynamics and quantum field theory...

, Eugene Wigner and Gregor Wentzel

Gregor Wentzel

Gregor Wentzel was a German physicist known for development of quantum mechanics. Wentzel, Hendrik Kramers, and Léon Brillouin developed the Wentzel–Kramers–Brillouin approximation in 1926...

; while Kramers

Hendrik Anthony Kramers

Hendrik Anthony "Hans" Kramers was a Dutch physicist.-Background and education:...

, MacInnes

Duncan MacInnes

Duncan MacInnes MBE, MC was an Anglican bishop in the 20th century.MacInnes was educated at Edinburgh Theological College and ordained in 1927. He began his ordained ministry with a curacy at St Columba's Clydebank, after which he was curate in charge of Knightswood. He was a chaplain to the...

, Nordsieck, Pauling

Linus Pauling

Linus Carl Pauling was an American chemist, biochemist, peace activist, author, and educator. He was one of the most influential chemists in history and ranks among the most important scientists of the 20th century...

 and Van Vleck

John Hasbrouck van Vleck

John Hasbrouck Van Vleck was an American physicist and mathematician, co-awarded the 1977 Nobel Prize in Physics, for his contributions to the understanding of the behavior of electrons in magnetic solids....

 who were at the Shelter Island Conference were absent.

Julian Schwinger

Julian Schwinger

Julian Seymour Schwinger was an American theoretical physicist. He is best known for his work on the theory of quantum electrodynamics, in particular for developing a relativistically invariant perturbation theory, and for renormalizing QED to one loop order.Schwinger is recognized as one of the...

 gave a day-long presentation of his developments in quantum electrodynamics

Quantum electrodynamics

Quantum electrodynamics is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and special relativity is achieved...

 (QED), the last great fling of the old way of doing quantum mechanics. Richard Feynman

Richard Feynman

Richard Phillips Feynman was an American physicist known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics...

 offered his version of quantum electrodynamics, introducing Feynman diagrams for the first time; it was unfamiliar and no-one followed it, so Feynman was motivated to go back to Cornell

Cornell University

Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...

 and write his work up for publication so others could see it in cold print. Schwinger and Feynman compared notes; and although neither could really understand the other’s approach, their arrival at the same answer helped to confirm the theory. And on his return to Princeton

Princeton University

Princeton University is a private research university located in Princeton, New Jersey, United States. The school is one of the eight universities of the Ivy League, and is one of the nine Colonial Colleges founded before the American Revolution....

, Oppenheimer received a third version by Sin-Itiro Tomonaga

Sin-Itiro Tomonaga

was a Japanese physicist, influential in the development of quantum electrodynamics, work for which he was jointly awarded the Nobel Prize in Physics in 1965 along with Richard Feynman and Julian Schwinger.-Biography:...

; his version of QED was somewhat simpler than Schwingers.