Arnold Johannes wilhelm sommerfeld 1868-1951.(Courtesy of the AIP Niels Bohr Library) had separated a rays, stoppable by metal foil or paper sheets, from the In1900 Rutherford had identified the Bs as high-speed electrons: deflected in a magnetic field they showed the cor ratio. A third component of the uranium rays undeviable and highly penetrating, was discovered by Paul villard at the Hermann Haga and Cornelius Werd, Ecole Normale Superieur in Paris announced that X rays could be dif- Rutherford named these y rays. In WE WANT TOKNOW fracted. and a privatdozent at got her 1903 thesis Marie Curie made tingen named Arnold Sommerfeld these comparisons: y rays to X rays If thhe Roentgen rays, that are way ahead, carried out a mathematical analy- Brays to cathode rays, and a rays to will show us in simple note, sis of diffraction to show that their canal rays (Canal rays were streams How, when we ask our best gir/ to wed results could be explained in terms of positively charged molecules. That lump will look in our throat of aperiodic impulses. In 1904, A few years later another story Charles glover barkla. a student of came out. The British scientist If the cathode rays, that we hear all about, both Stokes and Thomson at Cam- William Henry bragg announced in When the burglar threatens to shoot, vill they show us the picture without any doubt bridge, showed that X rays were 1907 that X rays and y rays were not Of the heart that we feel in our boot. plane polarizable while experiment- in fact ether waves, but rather par- ing with secondary and tertiary ticles, a neutral pair at that: electron If the new x-rays, that the papers do laud X rays. (These were produced by plus positively charged particle When the ghosts do walk at night, directing X rays against solids. Braggs serious research began at a Will show neath our hat to the world abroad As X rays began to show, more and late age, 41, after twenty pleasant How our hair stands on end in our fright. more, the properties of light, urani- years at the University of Adelaide If the wonderful new, electric rays, um rays provided new mysteries. Australia, where he played golf and Will do all the people have said, They themselves were composed of hobnobbed with government of And show us quite plainly, before many days three sorts of distinct rays: a, B, and ficials. He announced his new in- Those wheels that we have in our head physics, which had seemed to some Address to the Australian Associa If the Roentgen, cathode, electric x-light. to be coming to a conclusion, was tion for the Advancement of Science Invisible/ Think of that/ faced with unexplainable, qualita- during which he made a critical Can ever be turned on the Congressman brightI tive discoveries. They were not"in review of Rutherfords work, ques- And show him just where he is at the sixth place of the decimals, as tioning the law of exponential Oh, ifthese rays should strike you and me Michelson had predicted. At the decrease for the absorption of arays Going through us without any pai international congress on physics, For two and a half years he published Oh what a fright they would give us to see staged in Paris in 1900 by the French a paper every few months, work that The mess which our stomachs contain/ Physical Society, fully nine percent led him to make the radical state- -Homer C. Bennett. of the papers delivered were on the ment that X rays were particles. His X-ray Journal, 1897 new ray physics idea was based on two facts: (i)Xrays In 1899 Ernest Rutherford, another excite fewer gas molecules in their student of Thomsons and the man path than would be expected from who would become his successor as a wave-like disturbance, and (ii)the 16 SUMMER 199516 SUMMER 1995 Hermann Haga and Cornelius Werd, announced that X rays could be dif￾fracted, and a Privatdozent at Göt￾tingen named Arnold Sommerfeld carried out a mathematical analy￾sis of diffraction to show that their results could be explained in terms of aperiodic impulses. In 1904, Charles Glover Barkla, a student of both Stokes and Thomson at Cam￾bridge, showed that X rays were plane polarizable while experiment￾ing with secondary and tertiary X rays. (These were produced by directing X rays against solids.) As X rays began to show, more and more, the properties of light, urani￾um rays provided new mysteries. They themselves were composed of three sorts of distinct rays: α, β, and γ rays. What were these? Suddenly physics, which had seemed to some to be coming to a conclusion, was faced with unexplainable, qualita￾tive discoveries. They were not “in the sixth place of the decimals,” as Michelson had predicted. At the international congress on physics, staged in Paris in 1900 by the French Physical Society, fully nine percent of the papers delivered were on the new ray physics. In 1899 Ernest Rutherford, another student of Thomson’s and the man who would become his successor as WE WANT TO KNOW If the Roentgen rays, that are way ahead, Will show us in simple note, How, when we ask our best girl to wed, That lump will look in our throat. If the cathode rays, that we hear all about, When the burglar threatens to shoot, Will they show us the picture without any doubt, Of the heart that we feel in our boot. If the new x-rays, that the papers do laud, When the ghosts do walk at night, Will show ’neath our hat to the world abroad How our hair stands on end in our fright. If the wonderful, new, electric rays, Will do all the people have said, And show us quite plainly, before many days, Those wheels that we have in our head. If the Roentgen, cathode, electric, x-light, Invisible! Think of that! Can ever be turned on the Congressman bright And show him just where he is at. Oh, if these rays should strike you and me, Going through us without any pain, Oh, what a fright they would give us to see The mess which our stomachs contain! —Homer C. Bennett, American X-ray Journal, 1897 director of the Cavendish Laboratory, had separated α rays, stoppable by metal foil or paper sheets, from the more penetrating β rays. In 1900, Rutherford had identified the βs as high-speed electrons: deflected in a magnetic field they showed the cor￾rect charge-to-mass ratio. A third component of the uranium rays, undeviable and highly penetrating, was discovered by Paul Villard at the Ecole Normale Superieur in Paris. Rutherford named these γ rays. In her 1903 thesis Marie Curie made these comparisons: γ rays to X rays; β rays to cathode rays; and α rays to canal rays. (Canal rays were streams of positively charged molecules.) A few years later another story came out. The British scientist William Henry Bragg announced in 1907 that X rays and γ rays were not in fact ether waves, but rather par￾ticles, a neutral pair at that: electron plus positively charged particle. Bragg’s serious research began at a late age, 41, after twenty pleasant years at the University of Adelaide, Australia, where he played golf and hobnobbed with government of￾ficials. He announced his new in￾tellectual work in a Presidential Address to the Australian Associa￾tion for the Advancement of Science during which he made a critical review of Rutherford’s work, ques￾tioning the law of exponential decrease for the absorption of α rays. For two and a half years he published a paper every few months, work that led him to make the radical state￾ment that X rays were particles. His idea was based on two facts: (i) X rays excite fewer gas molecules in their path than would be expected from a wave-like disturbance, and (ii) the Arnold Johannes Wilhelm Sommerfeld, 1868–1951. (Courtesy of the AIP Niels Bohr Library)