Bruno Rossi Bruno Benedetto Rossi ( 13 April 1905 – 21 November 1993 ) was an experimental physicist . He made major contributions to particle physics and the study of cosmic rays . A 1927 graduate of the University of Bologna , he became interested in cosmic rays . To study them , he invented an improved electronic coincidence circuit , and travelled to Eritrea to conduct experiments that showed that cosmic ray intensity from the West was significantly larger than that from the East . Forced to emigrate in October 1938 because of the Italian Racial Laws , Rossi moved to Denmark , where he worked with Niels Bohr , then to Britain , where he worked with Patrick Blackett at the University of Manchester , and finally to the United States , where he worked with Enrico Fermi at the University of Chicago , and later at Cornell University . Rossi stayed in the United States , and became an American Citizen . During World War II , Rossi worked on radar at the MIT Radiation Laboratory , and he played a pivotal role in the Manhattan Project , heading the group at the Los Alamos Laboratory that carried out the RaLa Experiment s . After the war , he was recruited by Jerrold Zacharias at MIT , where Rossi continued his pre - war research into cosmic rays . In the 1960s , he pioneered X - ray astronomy and space plasma physics . His instrumentation on Explorer 10 detected the magnetopause , and he initiated the rocket experiments that discovered Scorpius X - 1 , the first extra - solar source of X - rays . Italy . Rossi was born in Venice , Italy . He was the eldest of three sons of Rino Rossi and Lina Minerbi . His father was an electrical engineer , who participated in the electrification of Venice . Rossi was tutored at home until the age of fourteen , after which he attended the Ginnasio and the Liceo in Venice . After beginning his university studies at the University of Padua , he began advanced work at the University of Bologna , where he received a Laurea in Physics in 1927 . His thesis advisor was Quirino Majorana , who was a well - known experimentalist and uncle of the physicist Ettore Majorana . Florence . In 1928 , Rossi began his career at the University of Florence , as assistant to Antonio Garbasso , who founded the University ' s Physics Institute in 1920 . It was located in Arcetri , on a hill overlooking the city . When Rossi arrived , Garbasso was Podestà of Florence , appointed by Benito Mussolini ' s fascist government of Italy . However , he brought to the institute a group of brilliant physicists which included Enrico Fermi and Franco Rasetti before they moved to Rome , as well as Gilberto Bernardini , Enrico Persico , and Giulio Racah . In 1929 , Rossi ' s first graduate student , Giuseppe Occhialini , was awarded the doctoral degree . In search of pioneering research , Rossi turned his attention to cosmic rays , which had been discovered by Victor Hess in manned balloon flights in 1911 and 1912 . In 1929 , Rossi read the paper of Walther Bothe and Werner Kolhörster , which described their discovery of charged cosmic ray particles that penetrated of gold . This was astonishing , for the most penetrating charged particles known at the time were electrons from radioactive decay , which could penetrate less than a millimetre of gold . In Rossi ' s words it Rossi coincidence circuit . In 1954 , Bothe was awarded the Nobel Prize in Physics " for the coincidence method and his discoveries made therewith " . However , his implementation of this method was very cumbersome , for it involved visual correlation of photographed pulses . Within a few weeks of reading his paper with Kolhörster , Rossi invented an improved electronic coincidence circuit , which made use of triode vacuum tubes . The Rossi coincidence circuit has two major advantages : it offers very precise temporal resolution and it can detect coincidences among any number of pulse sources . These features make it possible to identify interesting events that produce coincident pulses in several counters . These rare events stand out even in the presence of high rates of unrelated background pulses in the individual counters . The circuit not only provided the basis for electronic instrumentation in nuclear and particle physics , but also implemented the first electronic AND circuit , which is a fundamental element of the digital logic that is ubiquitous in modern electronics . At the time , an improved tubular version of the original Geiger counter , invented by Hans Geiger in 1908 , had just been developed by his student Walther Müller . These Geiger – Müller tube s ( GM tubes or counters ) made possible Bothe ' s investigations . With Occhialini ' s help in the construction of GM tubes , and with the aid of a practical coincidence circuit , Rossi confirmed and extended the results of Bothe , who invited him to visit Berlin in the summer of 1930 . Here , with financial support arranged by Garbasso , Rossi collaborated on further investigations of cosmic ray penetration . He also studied Carl Størmer ' s mathematical description of the trajectories of charged particles in the Earth ' s magnetic field . On the basis of these studies , he realised that the intensity of cosmic rays coming from eastward directions might be different from that of westward ones . From Berlin , he submitted the first paper suggesting that observations of this East - West effect could not only confirm that cosmic rays are charged particles , but also determine the sign of their charge . Rome conference . In the fall of 1931 , Fermi and Orso Mario Corbino organized in Rome an international conference on nuclear physics , which was sponsored by the Royal Academy of Italy . Fermi invited Rossi to give an introductory talk on cosmic rays . In the audience were Robert Millikan and Arthur Compton , both of whom had won the Nobel prize in physics , in 1923 and 1927 , respectively . During the 1920s , Millikan , who is famous for his oil drop experiment , made extensive measurements of the mysterious radiation discovered by Hess . He coined the name " cosmic rays " and proposed that they were photons created by the fusion of hydrogen in interstellar space . He was not pleased by the presentation of evidence that most observed cosmic rays are energetic charged particles . Later , Rossi wrote : Compton , who is famous for the Compton effect , had a more positive reaction , for he told Rossi later that the talk had motivated him to begin his own research on cosmic rays . Rossi curve . Immediately after the Rome conference , Rossi carried out two experiments that led to a significant advance in the understanding of cosmic rays . Both involved triple coincidences of pulses from three Geiger counters ; but in the first , the counters were aligned and separated by blocks of lead , while in the second , they were placed in a triangular configuration such that all three could not be traversed by a single particle travelling in a straight line . Results from the first configuration demonstrated the existence of cosmic - ray particles capable of penetrating of lead . With the second configuration enclosed in a lead box , the results showed that some cosmic rays interact in lead to produce multiple secondary particles . In an extension of the second experiment , he measured the rate of triple coincidences as a function of the amount of the lead above the counters . A plot of this rate against thickness , which came to be known as the Rossi curve , showed a rapid rise as the lead layer was increased , followed by a slow decline . These experiments showed that ground - level cosmic rays consist of two components : a " soft " component which is capable of prolific generation of multiple particle events , and a " hard " component which is capable of traversing great thicknesses of lead . At the time , the physical nature of both was a mystery , for they did not yet fit into the growing body of knowledge about nuclear and particle physics . Late in 1931 , Rossi arranged for Occhialini to work in the Cavendish Laboratory at the University of Cambridge with Patrick Blackett , whom he had met in Berlin . With the aid of the new technique of electronic coincidence , Occhialini helped Blackett develop the first counter - controlled cloud chamber , with which they confirmed Carl Anderson ' s discovery of the positron and deduced that the positive electrons are produced in association with negative ones by pair production . Up to 23 positive and negative electrons were observed in some events , which were clearly related to the showers of Rossi ' s soft component . Padua . In 1932 , Rossi won a competition for an academic position in an Italian university , and was appointed professor of experimental physics at the University of Padua . Soon after Rossi arrived , the rector asked him to oversee the design and construction of Padua ' s new Physics Institute . Although this task diverted his attention from research and teaching , he complied willingly , and the institute opened in 1937 . East - West effect . In spite of this distraction , Rossi was able to complete , in 1933 , an experiment on the East - West effect that he had begun before leaving Aricetri . Because this effect is more prominent near the equator , he organised an expedition to Asmara in Eritrea , which was then an Italian colony on the Red Sea at a latitude of 15° N . With Sergio De Bennedetti , he set up a " cosmic ray telescope " , which consisted of two separated GM counters in coincidence , whose axis of maximum sensitivity could be pointed in any direction . It soon became apparent that cosmic ray intensity from the West was significantly larger than that from the East . This meant that there was a larger influx of positive primary particles than of negative ones . At the time , this result was surprising , because most investigators held the preconceived notion that the primaries would be negative electrons . Just as Rossi left Eritrea , he received news of two observations of a similar East - West effect . These were published in the " Physical Review " . One was by Thomas H . Johnson , and the other was by Compton and his student , Luis Alvarez , who reported observations at Mexico City , where the latitude is 19° N . Because others had carried out the first experimental exploitation of his important idea of 1930 , Rossi was disappointed , but published his results immediately after returning to Padua . Later , with Frederick C . Chromey , Alvarez and Rossi patented a " Vertical Determination Device " , which made use of cosmic ray telescopes . In Eritrea , Rossi discovered another phenomenon that would become a principal theme of his postwar cosmic ray research : extensive cosmic ray air showers . The discovery occurred during tests to determine the rate of accidental coincidences between the Geiger counters of his detector . To assure that no single particle could trigger the counters he spread them out in a horizontal plane . In this configuration , the frequency of coincidences was greater than that calculated on the basis of the individual rates and the resolving time of the coincidence circuit . Rossi concluded that : In 1937 , Rossi became acquainted with Nora Lombroso , the daughter of Ugo Lombroso , a professor of physiology at the University of Palermo , and Silvia Forti . Her grandfather was the renowned physician and criminologist Cesare Lombroso , and her aunts , Gina Lombroso and Paola Lombroso Carrara , were well known Italian writers and educators . In April 1938 , Bruno and Nora married and set up a household in Padua . Although Rossi avoided politics , some of Rossi ' s associates were active opponents of the fascist state . For example , he mentored Eugenio Curiel , who became a member of the communist party , while completing a degree at Padua . Later , in 1943 , Curiel joined the resistance in Milan , and in 1945 , was assassinated by soldiers of the Republic of Salò a German puppet state Similarly , Ettore Pancini , who received his PhD under Rossi in 1938 , spent the war years alternating between cosmic ray research and active participation in the Italian resistance movement s of Padua and Venice . Because of these associations , and because both Rossis were Jewish , they became apprehensive as Italy ' s antisemitism grew under the influence of Nazi Germany . Eventually , as a result of anti - Jewish laws resulting from the Manifesto of Race , Rossi was dismissed from his professorship . In his words : Exile . With this setback , Rossi began an important phase of his career . He summarised this period in a memoir : " The Decay of ' Mesotrons ' ( 1939 - 1943 ) : Experimental Particle Physics in the Age of Innocence " , which he presented in a symposium at Fermilab in 1980 . On 12 October 1938 , the Rossis left for Copenhagen , where the Danish physicist , Niels Bohr , had invited him to study . The couple had no intention of returning to Italy , and Bohr facilitated Rossi ' s search for a more secure position by sponsoring a conference attended by leading physicists . He hoped that one of them would find Rossi a job , and soon , Rossi received an invitation to come to the University of Manchester , where Blackett was developing a major center of cosmic ray research . After a pleasant two months in Denmark , Rossi and Nora arrived in Manchester . Manchester . Rossi ' s stay in Manchester was brief , but productive . At this time , a clear understanding of the soft component was available . In 1934 , Hans Bethe and Walter Heitler published a quantitative description not only of the production of electron - positron pairs by energetic photons , but also of the production of photons by energetic electrons and positrons . At Manchester , Rossi collaborated with Ludwig Jánossy on an experiment which demonstrated the correctness of the Bethe - Heitler theory of the second process , which had not yet been fully confirmed . This experiment also introduced the technique of anti - coincidence , which has become a ubiquitous feature of instruments for detecting and analyzing energetic particles . By this time , cloud chamber observations had clarified the nature of the hard component . In 1936 , Anderson and his student , Seth Neddermeyer , discovered cosmic ray particles with mass intermediate between those of the electron and the proton , which Anderson called " mesotrons " . The mesotron subsequently became the known as the " meson " , which was shortened to " muon " . Just before the Copenhagen conference , Blackett suggested that observed variations of cosmic ray intensity with atmospheric temperature could be an indication that mesotrons are unstable , and he held intense discussions with Rossi on this subject . As a result , Rossi left Manchester determined to confirm their decay and to measure the lifetime . Chicago . With war looming over Europe , Blackett and others advised Rossi to leave Britain . Consequently , he wrote to Compton , who invited him to attend a summer symposium in Chicago , and hinted that a job might become available . In June 1939 , the Rossis sailed for New York , where they were greeted by Fermi and his wife Laura , who had also left Italy because of the racial laws . After a brief reunion with the Fermis , the Rossis were offered a ride to Chicago by Bethe . They gratefully accepted , and arrived at the University of Chicago in mid - June 1939 . Mesotron decay . Immediately after a symposium session on mesotron instability reached a consensus that more definitive observations were needed , Rossi and Compton began to plan an experiment . Because the intensity of the hard component increases with altitude , while the density of air decreases , Compton suggested that the investigations should be carried out on Mount Evans in Colorado , where he had worked in the early 1930s , and where access to a research site at elevation is provided by the Mount Evans Scenic Byway , the highest paved road in North America . He urged Rossi to begin a series of experiments that summer , before snow blocked the road , and to help , enlisted two of his friends , Norman Hillberry and J . Barton Hoag , and a student , Winston Bostick . Rossi and his helpers hurriedly assembled equipment and loaded it onto a dilapidated bus that Compton borrowed from the Zoology department . By this time , it was known that the main process by which mesotrons lose energy is ionisation energy loss , which is described by the Bethe formula , and is proportional to the mass per unit area of the layer of material traversed . If this were the only process , the intensity of the hard component passing through a layer of solid material would decrease by the same amount as in an equivalent layer of air . Rossi and his collaborators found that the decrease was significantly larger in the atmosphere than in a corresponding layer of solid carbon . Because the distance traversed in air was much larger than that in carbon , they interpreted this result as evidence for decay of the mesotron , and taking into account the effect of relativistic time dilation , estimated its mean life at rest as roughly 2 microseconds . The next summer , Rossi returned to Mount Evans where he performed experiments near Echo Lake at an elevation . With the use of anti coincidence techniques , the apparatus made it possible to measure the mean free path before decay of two groups of mesotrons with different average momentum . The results , published with David B . Hall , not only confirmed the proportionality between particle momentum and the mean free path of mesotrons before decay that is expected on the basis of relativity theory , but also presented an improved estimate of the lifetime at rest : ( 2 . 4±0 . 3 ) microseconds . These results and those of the previous year were not only the first to show definitively that mesotrons are unstable , but also the first experimental confirmation of the time dilation of moving clocks predicted by relativity theory . Cornell . At Chicago , Rossi ' s position as research associate was not permanent , and Compton was unable to secure him a better one . Consequently , he began a job search , during which he gave a seminar at Cornell University , where coincidentally , death had created a vacancy in the Physics department . After Bethe suggested that Rossi should be invited to fill this position , he was appointed associate professor at Cornell . In the fall of 1940 , after returning to Chicago from Colorado , the Rossis left for Ithaca . At Cornell , Rossi met his first American graduate student , Kenneth Greisen , with whom he wrote an article , " Cosmic - Ray Theory " , which was published in the Reviews of Modern Physics and became known among cosmic - ray researchers as " The Bible " . During the summer of 1941 , Greisen and physicists from Denver and Boulder accompanied Rossi to Mount Evans , where they refined the knowledge of proportionality between mesotron momentum and lifetime before decay . Greisen and Rossi also carried out experiments , which showed , in terms of processes documented in the " Bible " , that not all particles of the soft component , could be produced by mesotrons of the hard component . They interpreted this as evidence for primary electrons or photons , but it became evident later that the soft excess arises from the decay of neutral pions . After the 1941 expedition to Colorado , Rossi decided that the question of whether mesotrons decay had been answered . However , he was not satisfied with the precision with which the lifetime had been determined , for existing estimates depended on mesotron mass , which was not accurately known . To perform a more direct measurement , he designed apparatus to measure the time interval between the arrival of a mesotron in an absorber , where it stopped , and the emission of an electron when the mesotron decayed . To assist , he obtained the help of graduate student Norris Nereson . At the heart of their experiment , was a " chronometer " , which was an electronic circuit that produced a pulse whose height was accurately proportional to the time interval , and which could be recorded by photographing an oscilloscope trace . This was the first time - to - amplitude converter , another of Rossi ' s contributions to electronic techniques of experimental physics . With absorbers of lead and brass , the number of decays was plotted against time . These decay curves had the same exponential form as those of ordinary radioactive substances , and gave a mean lifetime of 2 . 3±0 . 2 microseconds , which was later refined to 2 . 15±0 . 07 microseconds . After the war , Rossi deicovered that his Italian colleagues , Marcello Conversi and Oreste Piccioni , had performed experiments very similar to his and measured a lifetime consistent with his result . Looking back on what he called the " Age of Innocence " , Rossi wrote : Los Alamos . With the completion of his work on mesotrons , Rossi turned his attention toward the war effort . In 1942 , while commuting from Ithaca to Cambridge , Massachusetts , he became a consultant on radar development at the Radiation Laboratory of the Massachusetts Institute of Technology . Here , along with Greisen , he invented a " range tracking circuit " , which was patented after the war . In early July 1943 , Bethe invited Rossi to join the Manhattan Project . Within a month , he reported for duty at Los Alamos Laboratory . A few weeks later , Nora and their three - year - old daughter , Florence , joined Rossi in Los Alamos , New Mexico . The laboratory ' s director , Robert Oppenheimer , asked Rossi to form a group to develop diagnostic instruments needed to create the atomic bomb . He soon realized that there already existed a group with a similar mission headed by the Swiss physicist Hans H . Staub . The two decided to merge their efforts into a single " Detector Group " . They were assisted by approximately twenty young researchers , including Matthew Sands an " electronic wizard " , who later earned a PhD under Rossi , and David Nicodemus , whom Staub brought from Stanford University , who was an expert on particle detectors . Fast ionization chamber . Bomb development called for large detectors of ionising radiation , whose response is proportional to the energy released in the detector and follows rapid changes in radiation intensity . From the earliest research on radioactivity , radiation had been measured in terms of Ionisation , but existing Ionisation chamber s were slow to respond to changes . To address this problem , Rossi and Staub carried out a careful analysis of the pulses that result when individual charged particles create ions within an ionisation chamber . They realised that the high mobility of free electrons removed from ionised atoms means that the pulses produced by single particles can be very brief . With James S . Allen , Rossi found gas mixtures of high electron mobility and low electron attachment . On the basis of these investigations , Allen and Rossi invented the " fast ionisation chamber " , which they patented after the war . It was a crucial factor in the success of the Manhattan Project and became widely used in postwar research on particle physics . RaLa experiments . In April 1944 , the Manhattan project experienced a crisis , when Emilio Segrè ' s group discovered that plutonium made in reactors would not work in a gun - type plutonium weapon like the " Thin Man " . In response , Oppenheimer completely reorganised the laboratory to focus on development of an implosion - type weapon . Rossi was enlisted to implement a method to test various weapon designs to arrive at one that produced an accurately symmetrical spherical implosion . The tests measured changes of the absorption of gamma rays in a metal sphere as it underwent implosive compression . The gamma rays were emitted by a pellet of the short - lived radioisotope Lanthanum - 140 positioned in the center of the sphere . The term RaLa experiment is a contraction of Radioactive Lanthanum . As compression progressed , the rapid increase in absorption was detected as a decrease of gamma ray intensity recorded outside of the assembly . The RaLa experiments revealed many pitfalls on the way to a successful implosion . To understand problematic jets that plagued early implosion designs , other test methods were necessary , but the RaLa experiments played a primary role in the design of explosive lens es . In his history of the Los Alamos project , David Hawkins wrote : " RaLa became the most important single experiment affecting the final bomb design " . Trinity diagnostics . On 16 July 1945 , an implosion - type plutonium device was detonated at the Trinity site near Alamogordo , New Mexico . The code name for this device was " The gadget " , and its design was very similar to the Fat Man weapon that was dropped on Nagasaki twenty four days later . In preparation for Trinity , Rossi designed instrumentation to record gamma radiation during the chain reaction , whose duration was expected to be approximately 10 nanoseconds . Observations on this time scale were almost beyond the state of the art in 1945 , but Rossi designed and built a large cylindrical ionisation chamber whose speed of response was adequate because its coaxial electrodes were separated by a narrow gap of only . To record the signal , he installed a very fast oscilloscope , provided as a prototype by DuMont Laboratories , in an underground bunker several hundred feet from the Gadget , where it was photographed . To bring the signal to the oscilloscope , he devised an oversized coaxial transmission line , whose inner conductor was made smaller as it went from chamber to oscilloscope . Because this configuration enhanced the signal reaching the oscilloscope , there was no need for amplification . To confirm this surprising behaviour , Rossi consulted with Harvard professor Edward Purcell . A few days after the test , Rossi went into the darkroom with Fermi , and before the newly developed film was dry , they were able to compute the initial growth rate of nuclear activity , which was crucial information for future weapons development . Of three attempts to measure this rate at Trinity , Rossi ' s was the only one that was fully successful . MIT . With the success of the Manhattan Project and the Radiation Laboratory , MIT moved into a new era of " big science " funded by the US government . MIT ' s expansion in nuclear physics was spearheaded by Jerrold R . Zacharias , who went to Los Alamos late in the war , and recruited Viki Weisskopf and Rossi as MIT professors . Rossi left Los Alamos for Cambridge on 6 February 1946 . Within the new Laboratory for Nuclear Science , headed by Zacharias , Rossi was delegated to create a cosmic ray research group at MIT . To help , he recruited four young scientists who had been at Los Alamos as PhD candidates : Herbert Bridge , Matthew Sands , Robert Thompson and Robert Williams . Two who had been in the Radiation Laboratory also came to work with him : John Tinlot and Robert Hulsizer . All six were more mature than typical graduate students , for they had several years of wartime research experience . Consequently , they were paid a stipend similar to that of a postdoctoral research er , which was funded by the Office of Naval Research and enabled them to support families during their graduate studies . For this new phase of his activities , Rossi made a fundamental change of approach . In his words : Elementary Particles . With the discovery of the pion in 1947 , the search for new elementary particle s became a popular research topic . By operating fast ionization chambers within a cloud chamber , Herbert showed that the bursts of ionization they recorded were primarily produced by relatively low energy cosmic rays , whose nuclear interactions typically involve the ejection of several heavily ionising nuclear fragments . On the basis of this effect , he and Rossi demonstrated that the behaviour of these interactions is similarly to that of penetrating showers . Rossi ' s group focused on the use of cloud chambers to study their properties and interactions . In 1948 , with the aid of a multi - plate cloud chamber in which lead plates alternated with aluminium ones , Gregory , Rossi and Tinlot showed that the source of the electromagnetic component of cosmic ray interactions was predominantly energetic photons , rather than electrons . This result confirmed Oppenheimer ' s suggestion of 1947 , that neutral pions are produced in interactions , along with charged ones , and that this component arises from their rapid decay into photons . To study the new elementary particles , Bridge and Martin Annis operated a large rectangular multi plate cloud chamber at Echo Lake . This investigation provided the basis for a 1951 PhD thesis by Annis , supervised by Rossi . The next year , these authors , with another student of Rossi ' s , Stanislaw Olbert , showed how to derive information on particle energies from measurements of their multiple scattering . This added another way to use cloud chambers to measure the properties of elementary particles . In early 1953 , with Bridge , Richard Safford and Charles Peyrou , Rossi published results of a comprehensive cloud chamber study of the elementary particles that became known as kaons . Peyrou was a visitor from at the École Polytechnique , where he had obtained an accurate value of the muon mass in 1947 , and Safford was Rossi ' s student . Bagnères - de - Bigorre conference . By 1952 , a bewildering " zoo " of elementary particles had been reported , with various masses , decay schemes , nomenclature and reliability of identification . To deal with this situation , Blackett and Leprince - Ringuet organized an International Cosmic Ray Conference at Bagnères - de - Bigorre in 1953 . According to James Cronin , " this conference can be placed in importance in the same category as two other famous conferences , the Solvay congress of 1927 and the Shelter Island Conference of 1948 . " Leprince - Ringuet asked Rossi to give a summary of new information presented at the conference and to propose nomenclature for the new particles . Before the conference , in response to the latter assignment , Rossi circulated a suggestion that particles with mass smaller than that of a neutron be designated by small Greek letters and those with larger mass be designated by capital Greek letters . In his talk , on 11 July 1953 , he reported that conference results , which he had compiled with the aid of Powell and Fretter , were consistent with this scheme , which was commonly used afterwards . A highlight was Leprince - Ringuet ' s declaration in his closing talk that : " . . . in the future we must use particle accelerators . " With the 3 GeV Cosmotron already in operation at Brookhaven National Laboratory , this declaration reflected a consensus among the participants . As a result , Rossi ' s group began to wind down their cloud chamber experiments . However , in 1954 , Bridge , Hans Courant , Herbert DeStaebler , Jr . and Rossi reported on an unusual event in which a stopping singly charged particle decayed into three photons whose energies totaled more than the proton rest energy . This is the signature of an antiproton annihilation . The next year , a group led by Owen Chamberlain and Emilio Segrè detected antiprotons , for which they were awarded Nobel Prize in Physics in 1960 . Extensive air showers . By the time of the Bagnères - de - Bigorre conference , Rossi had already turned his attention toward the astrophysical implications of cosmic ray phenomena , particularly extensive air showers . After Rossi ' s recognition , in Eritrea , that these events exist , they were extensively studied by Pierre Auger , and by Williams . At this time , the extremely fast response of the newly developed scintillation counter s offered a new way to study the structure of air showers . To do this , Rossi enlisted his student , George W . Clark , who completed a PhD in 1952 , and Piero Bassi , who was a visitor from the University of Padua . Because solid scintillating material was unavailable , they decided to use terphenyl dissolved in benzine , which is an efficient liquid scintillator . With the aid of three counters deployed on the roof of the MIT Physics building during the winter of 1952 / 53 , they found that shower particles arrived within only one or two meters of a disk , which travels at nearly the speed of light in the direction of the shower axis . This result showed that scintillation counters can not only determine of the arrival times of shower disks at many detectors spread over a large area , but also to estimate the number of particles striking each detector . These capabilities combine the " fast - timing " method of determining shower arrival directions with the density sampling method of determining their size and the location of their axes . Agassiz experiment . With this progress , Rossi ' s group began a major experiment that could measure both primary energies and arrival directions of extensive air showers . Participating in this effort were : George Clark , William Kraushaar , John Linsley , James Earl , and Frank Scherb . Kraushaar came to MIT from Cornell in 1949 , after earning his PhD under Kenneth Greisen . With the support of Professor Donald Menzel who was director of the Harvard College Observatory , Rossi ' s group deployed fifteen liquid scintilators , of area on the wooded grounds of the observatory ' s Agassiz station . The signals were brought on cables to a Quonset hut , where they were displayed on fifteen oscillographs and recorded photographically . Shortly after the experiment began to record shower data , lightning ignited the flammable liquid of one of the counters . Local firemen quickly extinguished the resulting fire before it spread to nearby trees , which were soaked with rain water . Because the trees played an essential role in suppressing atmospheric convection that would degrade telescopic observations , Harvard and MIT carried out tense negotiations , until an elaborate system of fire protection was installed , and the experiment was allowed to resume . To eliminate the threat of fire , Clark , Frank Scherb and William B . Smith created a " factory " that made nonflammable plastic scintillator disks , whose thickness was and whose diameter was approximately . After a switch to plastic in the late spring of 1956 , the experiment ran continuously . Its findings were reported in Nature and the Physical Review . The most important results were summarized by Rossi as : As the Agassiz experiment came to an end , the group realized that observations near the equator and in the southern hemisphere were needed to extend their conclusion that air shower arrival directions are nearly isotropic . Consequently , Clark , in collaboration with Vikram Sarabhai , ran his smaller experiment at Kodaikanal , India , at a latitude of 10° N , and confirmed the absence of anisotropies . Later , at the suggestion of Ismael Escobar , the Agassiz equipment was moved to El Alto at 4200 meters on the Bolivian plateau at 16° S . Here , Clark , Escobar and Juan Hersil found no anisotropies , but they showed that the structure of air showers at their maximum development is different from that at sea level . Volcano Ranch experiment . The maximum energy of a particle recorded by Agassiz experiment , 10 electron volts , is close to energies beyond which charged particles can not be confined to the galactic disc by typical interstellar magnetic fields of 10 gauss . A detector array of very large dimensions is neded to detect showers of these energies . John Linsley agreed to take on responsibility for building such an array . He came to MIT in 1954 from the University of Minnesota , where he completed a PhD under Edward P . Ney . Soon , he was joined by Livio Scarsi , whom Rossi had recruited from Occhialini ' s group at the University of Milan . Because no large enough tract of open land was available near Boston , the array was constructed on a semi - desert property known as " Volcano Ranch " , about west of Albuquerque , New Mexico , at an altitude of . During 1957 and 1958 , Linsley and Scarsi deployed 19 scintillation counters , which used fluorescent plastic disks similar to those of the Agassiz detectors , except that each counter incorporated four disks viewed by four photomultipliers . Initially the area of the array was 2 . 5 * 10 m , which is to be compared with Agassiz ' s 10 m , but in 1960 , after Scarsi had returned to Milan , Linsley spread the detectors over an area of 10 m . Results from the Volcano Ranch experiment showed that the cosmic - ray intensity decreases smoothly with energy from 10 - 10 electron volts . and that primaries in this range arrive isotropically . Of particular significance was the detection of a single particle whose energy of 10 electron volts is larger than the maximum that could be contained in the galactic disc by galactic magnetic fields . Particles of these energies can only originate in the galactic halo or from beyond the galaxy , and their existence is not consistent with the Greisen - Zatsepin - Kuzmin limit . Space Plasma Research . On 4 October 1957 , the Soviet Union launched the first artificial Earth satellite , Sputnik 1 . This event created a " wave of near - hysteria " among a surprised American public . In response , the U . S . government increased funding for the National Science Foundation , and in 1958 , created both the National Aeronautics and Space Administration ( NASA ) and the Advanced Research Projects Agency , which was renamed the Defense Advanced Research Projects Agency ( DARPA ) in 1972 . On 4 June 1958 , two days after legislation creating NASA was introduced , Detlev W . Bronk , chairman of the National Academy of Sciences , met with the heads of these three agencies to create a new advisory body , the Space Science Board , to provide advice for the expansion of space research and to make sure that funding of fundamental science would be properly emphasized . The Board convened for its first meeting on 27 June 1958 . Only four members were already engaged in space research : Rossi , Leo Goldberg , John Simpson , and James Van Allen . Rossi formed a subcommittee which included Thomas Gold , Philip Morrison and biologist Salvador Luria , who agreed that investigations of plasma in interplanetary space would be desirable . Consequently , Rossi decided to turn his group ' s efforts towards its study . With Herbert Bridge , Rossi designed and tested a plasma probe based on the classical Faraday cup . However , to enhance the instrument ' s response to positively charged protons and to suppress its response to photoelectrons produced by sunlight , four grids were deployed within the cup . A key innovation was a modulating voltage applied to one of the grids , which converted the signal into an alternating current , proportional to the proton flux and uncontaminated by any contribution of photoelectrons . After intense lobbying of Homer Newell , NASA ' s deputy director of space flight programs , Rossi secured a flight opportunity on Explorer 10 , " Goddard ' s first home - grown satellite " . The unannounced goal was to hit the moon , but after launch on 25 March 1961 , the satellite went into a highly elongated orbit around Earth , whose apogee , at 70 % of the distance to the moon , was well short of this goal . Nevertheless , during 52 hours of data recorded by the MIT probe before battery power ran out , Rossi ' s group found a transition between two distinct regions around earth . Near earth . there were fairly strong and well organised magnetic fields , but no indication of interplanetary protons . At 22 earth radii , the spacecraft entered a region where magnetic fields were weaker and more irregular , and where a substantial flux of protons was observed coming from the general direction of the Sun . On several occasions during the rest of the flight , this flux disappeared and then reappeared again , which indicated that the spacecraft was flying close to the boundary between the two regions and that this boundary was moving irregularly . Eventually , this boundary became known as the magnetopause . Under Bridge and Rossi , the MIT space plasma group included Frank Scherb , Edwin Lyon , Alan Lazarus , Alberto Bonnetti , Alberto Egidi , John Belcher and Constance Dilworth , who was Ochialini ' s wife . Its Faraday cups have collected data on plasma throughout the solar system : near Earth on OGO - 1 , OGO 3 and IMP 8 , in interplanetary space on WIND , and in the Heliosphere and Heliosheath on Voyager 1 and Voyager 2 . X - Ray astronomy . As a consultant to American Science and Engineering , Inc . , Rossi initiated the rocket experiments that discovered the first extra - solar source of X - rays , Scorpius X - 1 . Rossi was made Institute Professor at MIT in 1966 . Retirement . Rossi retired from MIT in 1970 . From 1974 to 1980 he taught at the University of Palermo . In retirement he wrote a number of monographs , and a 1990 autobiography , " Moments in the Life of a Scientist " , which was published by Cambridge University Press . He died from a cardiac arrest at his home in Cambridge on 21 November 1993 . He was survived by his wife , Nora , daughters Florence and Linda and son Frank . He was cremated , and his ashes are in the graveyard of the church of San Miniato al Monte , which overlooks Florence and the hill of Arcetri . External links . city