Harold Urey Harold Clayton Urey ( April 29 , 1893 – January 5 , 1981 ) was an American physical chemist whose pioneering work on isotopes earned him the Nobel Prize in Chemistry in 1934 for the discovery of deuterium . He played a significant role in the development of the atom bomb , but may be most prominent for his contribution to theories on the development of organic life from non - living matter . Born in Walkerton , Indiana , Urey studied thermodynamics under Gilbert N . Lewis at the University of California . After he received his PhD in 1923 , he was awarded a fellowship by the American - Scandinavian Foundation to study at the Niels Bohr Institute in Copenhagen . He was a research associate at Johns Hopkins University before becoming an associate professor of Chemistry at Columbia University . In 1931 , he began work with the separation of isotopes that resulted in the discovery of deuterium . During World War II Urey turned his knowledge of isotope separation to the problem of uranium enrichment . He headed the group located at Columbia University that developed isotope separation using gaseous diffusion . The method was successfully developed , becoming the sole method used in the early post - war period . After the war , Urey became professor of chemistry at the Institute for Nuclear Studies , and later Ryerson professor of chemistry at the University of Chicago . Urey speculated that the early terrestrial atmosphere was probably composed of ammonia , methane , and hydrogen . One of his Chicago graduate students , Stanley L . Miller , who showed in the " Miller - Urey experiment " that , if such a mixture be exposed to electric sparks and water , it can interact to produce amino acids , commonly considered the building blocks of life . Work with isotopes of oxygen led to pioneering the new field of paleoclimatic research . In 1958 , he accepted a post as a professor at large at the new University of California , San Diego ( UCSD ) , where he helped create the science faculty . He was one of the founding members of UCSD ' s school of chemistry , which was created in 1960 . He became increasingly interested in space science , and when Apollo 11 returned moon rock samples from the moon , Urey examined them at the Lunar Receiving Laboratory . Early life . Harold Clayton Urey was born on April 29 , 1893 , in Walkerton , Indiana , the son of Samuel Clayton Urey , a school teacher and a minister in the Church of the Brethren , and his wife Cora Rebecca née Reinoehl . He had a younger brother , Clarence , and a younger sister , Martha . The family moved to Glendora , California , but moved back to Indiana to live with Cora ' s widowed mother when Samuel became seriously ill with tuberculosis . He died when Urey was six years old . Urey was educated in an Amish grade school , which he graduated from at the age of 14 . He then attended high school in Kendallville , Indiana . After graduating in 1911 , he obtained a teacher ' s certificate from Earlham College , and taught in a small school house in Indiana . He later moved Montana , where his mother was then living , and he continued to teach there . Urey entered the University of Montana in 1914 , where he earned a Bachelor of Science ( BS ) degree in zoology in 1917 . After the United States entry into World War I that year , Urey took a wartime job with the Barrett Chemical Company in Philadelphia , Pennsylvania , making TNT . After the war ended , he returned to the University of Minnesota as an instructor in Chemistry . An academic career required a doctorate , so in 1921 Urey enrolled in a PhD program at the University of California , Berkeley , where he studied thermodynamics under Gilbert N . Lewis . His initial attempt at a thesis was on the ionization of cesium vapor . He ran into difficulties , and an Indian physicist published a better paper on the same subject . Urey then wrote his thesis on the ionization states of an ideal gas , which was subsequently published in the " Astrophysical Journal " . After he received his PhD in 1923 , Urey was awarded a fellowship by the American - Scandinavian Foundation to study at the Niels Bohr Institute in Copenhagen , where he met Werner Heisenberg , Hans Kramers , Wolfgang Pauli , Georg von Hevesy , and John Slater . At the conclusion of his stay , he traveled to Germany , where he met Albert Einstein and James Franck . On returning to the United States , Urey received an offer of a National Research Council fellowship to Harvard University , and also received an offer to be a research associate at Johns Hopkins University . He chose the latter . Before taking up the job , he traveled to Seattle , Washington , to visit his mother . On the way , he stopped by Everett , Washington , where he knew a woman called Kate Daum . Kate introduced Urey to her sister , Frieda . Urey and Frieda soon became engaged . They were married at her father ' s house in Lawrence , Kansas , in 1926 . The couple had four children : Gertrude Bessie ( Elisabeth ) , born in 1927 ; Frieda Rebecca , born in 1929 ; Mary Alice , born in 1934 ; and John Clayton Urey , born in 1939 . At Johns Hopkins , Urey and Arthur Ruark wrote " Atoms , Quanta and Molecules " ( 1930 ) , one of the first English texts on quantum mechanics and its applications to atomic and molecular systems . In 1929 , Urey became an associate professor of Chemistry at Columbia University , where his colleagues included Rudolph Schoenheimer , David Rittenberg , and T . I . Taylor . Deuterium . Around this time , William Giauque and Herrick Johnston at the University of California discovered the stable isotopes of oxygen . Isotopes were not well understood at the time ; James Chadwick would not discover the neutron until 1932 . Two systems were in use for classifying them , based on chemical and physical properties . The latter was determined using the mass spectrograph . Since it was known that the atomic weight of oxygen was almost exactly 16 times as heavy as hydrogen , Raymond Birge , and Donald Menzel hypothesized that hydrogen had more than one isotope as well . Based upon the difference between the results of the two methods , they predicted that only one hydrogen atom in 4 , 500 was of the heavy isotope . In 1931 , Urey set out to find it . Urey and George Murphy calculated from the Balmer series that the heavy isotope should have lines redshifted by 1 . 1 to 1 . 8 ångströms ( 1 . 1×10−10 to 1 . 8×10−10 metres ) . Urey had access to a grating spectrograph , a sensitive device that had been recently installed at Columbia and was capable of resolving the Balmer series . It had a resolution of 1 Å per millimetre , so on this machine , the difference was about 1 millimetre . However , since only one atom in 4 , 500 was heavy , the line on the spectrograph was very faint . Urey therefore decided to delay publishing their results until he had more conclusive evidence that it was heavy hydrogen . Urey and Murphy calculated from the Debye model that the heavy isotope would have a slightly higher boiling point than the light one . By carefully warming liquid hydrogen , 5 litres of liquid hydrogen could be distilled to 1 millilitre , which would be enriched in the heavy isotope by 100 to 200 times . To obtain five litres of liquid hydrogen , they traveled to the cryogenics laboratory at the National Bureau of Standards in Washington , D . C . , where they obtained the help of Ferdinand Brickwedde , whom Urey had known at Johns Hopkins . The first sample that Brickwedde sent was evaporated at 20 K ( −253 . 2 °C ; −423 . 7 °F ) at a pressure of 1 standard atmosphere ( 100 kPa ) . To their surprise , this showed no evidence of enrichment . Brickwedde then prepared a second sample evaporated at 14 K ( −259 . 1 °C ; −434 . 5 °F ) at a pressure of 53 mmHg ( 7 . 1 kPa ) . On this sample , the Balmer lines for heavy hydrogen were seven times as intense . The paper announcing the discovery of what we now call deuterium was jointly published by Urey , Murphy , and Brickwedde in 1932 . Urey was awarded the Nobel Prize in Chemistry in 1934 " for his discovery of heavy hydrogen " . He declined to attend the ceremony in Stockholm , so that he could be present at the birth of his daughter Mary Alice . Working with Edward W . Washburn from the Bureau of Standards , Urey subsequently discovered the reason for the anomalous sample . Brickwedde ' s hydrogen had been separated from water by electrolysis , resulting in depleted sample . Moreover , Francis William Aston now reported that his calculated value for the atomic weight of hydrogen was wrong , thereby invalidating Birge and Menzel ' s original reasoning . The discovery of deuterium stood , however . Urey and Washburn attempted to use electrolysis to create pure heavy water . Their technique was sound , but they were beaten to it in 1933 by Lewis , who had the resources of the University of California at his disposal . Using the Born – Oppenheimer approximation , Urey and David Rittenberg calculated the properties of gases containing hydrogen and deuterium . They extended this to enriching compounds of carbon , nitrogen , and oxygen . These could be used as tracers in biochemistry , resulting in a whole new way of examining chemical reactions . He founded the Journal of Chemical Physics in 1932 , and was its first editor , serving in that capacity until 1940 . Urey contributed a science article to " The Scientific Monthly " on Irving Langmuir , who invented atomic hydrogen welding in 1911 by utilizing 300 to 650 volts of electricity and tungsten filaments , and won the 1932 Nobel Prize in Chemistry for his work in surface chemistry . At Columbia , Urey chaired the University Federation for Democracy and Intellectual Freedom . He supported Atlanticist Clarence Streit ' s proposal for a federal union of the world ' s major democracies , and the republican cause during the Spanish Civil War . He was an early opponent of German Nazism and assisted refugee scientists , including Enrico Fermi , by helping them find work in the United States , and to adjust to life in a new country . Manhattan Project . By the time World War II broke out in Europe in 1939 , Urey was recognized as a world expert on isotope separation . Thus far , separation had involved only the light elements . In 1939 and 1940 , Urey published two papers on the separation of heavier isotopes in which he proposed centrifugal separation . This assumed great importance due to speculation by Niels Bohr that uranium 235 was fissile . Because it was considered " very doubtful whether a chain reaction can be established without separating 235 from the rest of the uranium , " Urey began intensive studies of how uranium enrichment might be achieved . Apart from centrifugal separation , George Kistiakowsky suggested that gaseous diffusion might be a possible method . A third possibility was thermal diffusion . Urey coordinated all isotope separation research efforts , including the effort to produce heavy water , which could be used as a neutron moderator in nuclear reactors . In May 1941 , Urey was appointed to the S - 1 Executive Committee , which oversaw the uranium project as part of the Office of Scientific Research and Development ( OSRD ) . In 1941 , Urey and George B . Pegram led a diplomatic mission to England to establish co - operation on development of the atomic bomb . The British were optimistic about gaseous diffusion , but it was clear that both gaseous and centrifugal methods faced formidable technical obstacles . In May 1943 , as the Manhattan Project gained momentum . Urey became head of the wartime Substitute Alloy Materials ( SAM ) Laboratory at Columbia , which was responsible for the heavy water and all the isotope enrichment processes except Ernest Lawrence ' s electromagnetic process . Early reports on the centrifugal method indicated that it was not as efficient as predicted . Urey suggested that a more efficient but technically more complicated countercurrent system be used instead of the previous flow - through method . By November 1941 , technical obstacles seemed formidable enough for the process to be abandoned . Countercurrent centrifuges were developed after the war , and today are the favored method in many countries . The gaseous diffusion process remained more encouraging , although it too had technical obstacles to overcome . By the end of 1943 , Urey had over 700 people working for him on gaseous diffusion . The process involved hundreds of cascades , in which corrosive uranium hexafluoride differed through gaseous barriers , becoming progressively more enriched at every stage . A major problem was finding proper seals for the pumps , but by far the greatest difficulty lay in constructing an appropriate diffusion barrier . Construction of the huge K - 25 gaseous diffusion plant was well under way before a suitable barrier became available in quantity in 1944 . As a backup , Urey championed thermal diffusion . Worn out by the effort , Urey left the project in February 1945 , handing over his responsibilities to John R . Dunning . The K - 25 plant commenced operation in March 1945 , and as the bugs were worked out , the plant operated with remarkable efficiency and economy . For a time , uranium was fed into the S50 liquid thermal diffusion plant , then the K - 25 gaseous , and finally the Y - 12 electromagnetic separation plant ; but soon after the war ended the thermal and electromagnetic separation plants were closed down , and separation was performed by K - 25 alone . Along with its twin , K - 27 , constructed in 1946 , it became the principal isotope separation plant in the early post - war period . For his work on the Manhattan Project , Urey was awarded the Medal for Merit by the Project director , Major General Leslie R . Groves , Jr . Post - war years . After the war , Urey became professor of chemistry at the Institute for Nuclear Studies , and then became Ryerson professor of chemistry at the University of Chicago in 1952 . He did not continue his pre - war research with isotopes . However , applying the knowledge gained with hydrogen to oxygen , he realized that the fractionation between carbonate and water for oxygen - 18 and oxygen - 16 would decrease by a factor of 1 . 04 between 0 and 25 °C ( 32 and 77 °F ) . The ratio of the isotopes could then be used to determine average temperatures , assuming that the measurement equipment was sufficiently sensitive . Examination of a 100 - million - year - old belemnite then indicated the summer and winter temperatures that it had lived through over a period of four years . For this pioneering paleoclimatic research , Urey was awarded the Arthur L . Day Medal by the Geological Society of America , and the Goldschmidt Medal of the Geochemical Society . Urey actively campaigned against the 1946 May - Johnson bill because he feared that it would lead to military control of nuclear energy , but supported and fought for the McMahon bill that replaced it , and ultimately created the Atomic Energy Commission . Urey ' s commitment to the ideal of world government dated from before the war , but the possibility of nuclear war made it only more urgent in his mind . He went on lecture tours against war , and became involved in Congressional debates regarding nuclear issues . He argued publicly on behalf of Ethel and Julius Rosenberg , and was even called before the House Un - American Activities Committee . Cosmochemistry and the Miller - Urey experiment . In later life , Urey helped develop the field of cosmochemistry and is credited with coining the term . His work on oxygen - 18 led him to develop theories about the abundance of the chemical elements on earth , and of their abundance and evolution in the stars . Urey summarized his work in " The Planets : Their Origin and Development " ( 1952 ) . Urey speculated that the early terrestrial atmosphere was probably composed of ammonia , methane , and hydrogen . One of his Chicago graduate students , Stanley L . Miller , showed in the " Miller - Urey experiment " that , if such a mixture be exposed to electric sparks and to water , it can interact to produce amino acids , commonly considered the building blocks of life . Urey spent a year as a visiting professor at Oxford University in England in 1956 and 1957 . In 1958 , he reached the University of Chicago ' s retirement age of 65 , but he accepted a post as a professor at large at the new University of California , San Diego ( UCSD ) , and moved to La Jolla , California . He was subsequently made a professor emeritus there from 1970 to 1981 . Urey helped build up the science faculty there . He was one of the founding members of UCSD ' s school of chemistry , which was created in 1960 , along with Stanley Miller , Hans Suess , and Jim Arnold . In the late 1950s and early 1960s , space science became a topical field of research in the wake of the launch of Sputnik I . Urey helped persuade NASA to make unmanned probes to a moon a priority . When Apollo 11 returned moon rock samples from the moon , Urey examined them at the Lunar Receiving Laboratory . The samples supported Urey ' s contention that the moon and the Earth shared a common origin . While at UCSD , Urey published 105 scientific papers , 47 of them about lunar topics . When asked why he continued to work so hard , he joked , " Well , you know I ’ m not on tenure anymore . " Death and legacy . Urey enjoyed gardening , and raising cattleya , cymbidium and other orchids . He died at La Jolla , California , and is buried in the Fairfield Cemetery in DeKalb County , Indiana . Apart from his Nobel Prize , he also won the Franklin Medal in 1943 , the J . Lawrence Smith Medal in 1962 , the Gold Medal of the Royal Astronomical Society in 1966 , and the Priestley Medal of the American Chemical Society in 1973 . In 1964 he received the National Medal of Science . He became a Fellow of the Royal Society in 1947 . Named after him are lunar impact crater Urey , asteroid 4716 Urey , and the H . C . Urey Prize , awarded for achievement in planetary science s by the American Astronomical Society . The Harold C . Urey Middle School in Walkerton , Indiana , is also named for him , as is Urey Hall , the chemistry building at Revelle College , UCSD , in La Jolla . UCSD has also established a Harold C . Urey chair whose first holder is Jim Arnold .