Mysterious rays capable of penetrating solid bodies. Produced in Cathode Ray Tube and detected by Scintillation Screen or Photographic Plates. Accidental and unforeseen discovery prompts a flood of research. Named “X” after the mathematical term for an unknown. Immediately applied to medicine. Astonishing photos pique public interest. Wilhelm Conrad Röntgen (1845-1923) read before the Würzburg Physical and Medical Society, 1895. Invisible rays discovered in Uranium acting similarly to X-rays. Penetrating rays capable of ionizing gases, but spontaneously emitted from Uranium, not mechanically generated. Photographic Plates exposed to potassium uranyl sulfate. Looking for X-rays in flourescent minerals. Process cannot be altered by any known chemical or physical process. Indicates that atoms have an internal structure. Extremely minute amounts of material giving off appreciable amounts of energy indicates undreamed of quantities of energy within the atom. Antoine Becquerel Nobel Lecture, December 11, 1903 Antoine Henri Becquerel (1852-1908) read before the French Academy of Science 24 Feb. 1896 Silvanus P. Thompson Phil. Mag. 42, 103 (1896)[1] X-rays and radioactivity cause ionization of gases. graduate student Ions produced in gases exposed to X-rays or radioactivity. Early Cloud Chamber of C.T.R. Wilson placed in electromagnetic field. X-rays cause gases that are normally insulators to become conductors of electric current. First observation of ionizing radiation The fundamental unit of electricity. First elementary particle. Applying electromagnetic fields to Cathode Rays causes rays to curve, enabling the measurement of the ratio between charge and mass. While atoms are uncharged on the whole, they contain negatively charged parts. J. J. Thomson Philosophical Magazine, 44, 293 (1897) J.J. Thomson, M.A., F.R.S. Philosophical Magazine, December 1899, Series 5, Vol. 48, No. 295, p. 547-567 J.J. Thomson, F.R.S. Philosophical Magazine, Series 6, Volume 7, Number 39, March 1904, p. 237-265 Prof J.J. Thomson, M.A., F.R.S. Philosophical Magazine, vol. 11, June 1906, p. 769-781 J.J. Thomson Nobel Lecture, December 11, 1906 Rays differentiated within radioactivity. Observing how radiation is absorbed by differing thicknesses of aluminum, distinguished a more intense radiation that is more easily absorbed, “Alpha”, and a less intense radiation but more penetrating, “Beta”. Beginning of Rutherford's many researches on the nature of radioactivity. E. Rutherford, M.A., B.SC. Philosophical Magazine for January 1899, ser. 5, xlvii, pp. 109-163 E. Rutherford, M.A., B.SC. Philosophical Magazine for January 1900, ser. 5, xlix, pp. 1-14 Ernest Rutherford (1871-1937) and T. Royds Phil. Mag. 17, 281-6 (1909) Ernest Rutherford Nobel Lecture, December 11, 1908 Naturally occurring elements discovered on the basis of their radioactivity. Called the first great woman scientist. Isolated from pitchblende, a Uranium ore. Detection with Electrometer invented by Pierre Curie using piezoelectricity. Birth of Radiochemistry. Quantities of elements too small to be detected otherwise found by their intense radioactivity. Marie Sklodowska Curie (1867-1934) note presented by M. Lippmann, Comptes Rendus 126, 1101-3 (1898) M. P. Curie and Mme. S. Curie note presented by M. Becquerel; Comptes Rendus 127, 175-8 (1898) M. P. Curie, Mme. P. Curie, and M. G. Bémont note presented by M. Becquerel; Comptes Rendus 127, 1215-7 (1898) Marie Curie Nobel Lecture, December 11, 1911 Pierre Curie Nobel Lecture, June 6, 1905 Marie Sklodowska Curie Century Magazine (January 1904), pp. 461-466 Marie Sklodowska Curie chapter five - Pierre Curie [1923] Marie Sklodowska Curie Ellen S. Richards Monographs No. 2 (Poughkeepsie: Vassar College, 1921), n.p. Naturally occurring element. Isolated from pitcheblende by means of its radioactivity. A third component discovered in radioactivity Electromagnetic deflection. Magnetic fields do not affect a part of the radioactivity but do cause both Alpha rays and Beta rays to be deflected. More penetrating that X-rays Brains considering Black Body Radiation Atoms emit energy in discreet units, and not continuously. Introduces a new universal constant “h”, called Planck's constant. Will play a key role in the development of a new language to describe the subatomic world. Max Planck Annalen der Physik, vol. 4, p. 553 ff (1901) Max Planck Nobel Lecture, June 2, 1920 Naturally occurring element. Demonstrated that Radium forms a gaseous element as it breaks down. A radioactive gas! that was something new. Every emission of radiation in radioactivity alters the emitting atom and turns it into an atom of another element. Radioactive decay series of Uranium, Thorium, and Actinium identified. “A magnificent combination of physical and chemical techniques.” Beginnings of Isotope concept. Radioactivity is atomic disintegration. Ernest Rutherford and Frederick Soddy Philosophical Magazine 4, 370-96 (1902) Elementary particle (still). The quantum of light energy. Brains considering the photoelectric effect and Planck's Quantum Hypothesis Metals exposed to ultraviolet light emit electrons. Light found behaving like particles, like discreet units of energy as opposed to continues waves. First of five revolutionary papers published in 1905, Einstein's Annus Mirabilis. A. Einstein Ann. Phys. 17, 132. Translation: American Journal of Physics, v. 33, n. 5, May 1965 [ http://spica.ihep.su/hist/owa/hw.part2?s_c=EINSTEIN+1905 ] A. Einstein Ann. Physik 17, 132 (1905). [ http://lorentz.phl.jhu.edu/AnnusMirabilis/#common ] Brains seeking conservation laws. Time and space relative to velocity. Equivalence of energy and matter. Speed of light is universal constant for any frame of reference. End of “luminiferous ether,” the hypothetical medium of light wave propogation. End of Newtons' absolute time and space. A. Einstein Annalen der Physik. 17:891, 1905 A. Einstein Annalen der Physik. 18:639, 1905 Albert Einstein New York: Henry Holt and Company, 1920. Translated by Robert W. Lawson. Albert Einstein (February 3, 1929) "presented to the general public"? Albert Einstein Nobel Lecture, July 11, 1923 perfected in 1928 working under Ernest Rutherford. Inert gas in a strong electrical field Capable of registering the influence of a single particle. Records single ionizing event. Most of the mass of an atom resides in an incredibly small and dense, positively charged center, which is surrounded by atomic electrons. In the light of the nuclear model of the atom it became clear that the origin of all radioactive radiations, including beta, was the nucleus of the atom, since only a change in the nucleus could transform one element into another. with experimental results of Hans Geiger and Ernest Marsden Alpha Particle Probe: scattering on a thin gold foil; the positively charged particle is deflected as it interacts electromagnetically with the positively charged nucleus; deflection angle depends on nearnesss of approach and amount of nuclear charge. Chemical properties of atoms are determined by the number of electrons, which is, in turn, determined by the amount of positive charge in the nucleus. Made possible determination of the value of Z of the scattering atom, which explained the regularity of the empirically derived periodic chart; provides a structural explanation for the regularities. Chemical characteristics being determined by the number of electrons surrounding the nucleus. Throws an experimental wrench into the works of classical mechanics. Leads Niels Bohr to apply the curious new quantum theory to describe the orbits of the electrons. “It was quite the most incredible events that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you. On consideration I realized that this scattering backwards must be the result of a single collision, and when I made calculations I saw that it was impossible to get anything of that order of magnitude unless you took a system in which the greatest part of the mass of the atom was concentrated in a minute nucleus” - Ernest Rutherford E. Rutherford, F.R.S. Philosophical Magazine, Series 6, vol. 21, May 1911, p. 669-688 Ernest Rutherford Philosophical Magazine, Series 6, Volume 27, March 1914, p. 488 - 498 H. GEIGER, Ph.D. Proceedings of the Royal Society, vol. A83, p. 492-504 By H. GEIGER,and E. MARSDEN Proc. Roy. Soc. 1909 A, vol. 82, p. 495-500 H. GEIGER and E. MARSDEN Philosophical Magazine, Series 6, Volume 25, Number 148, April 1913 penetrating radiation incident on the atmosphere from outer space. Carried an electroscope aloft up to 5,000 meters in a balloon and found that backgound ionization levels increased with altitude. Background ionization first imagined by C.T.R. Wilson as cause of unavoidable leaks of charge from electroscope. Range of energies has been found to be from a billion to ten quintillion electron volts. Victor F. Hess Nobel Lecture, December 12, 1936 proves electromagnetic nature of X-rays Diffraction by crystals Makes possible measurement of wavelengths of X-rays. Allows for determination of structure of crystals in terms of the arrangements of the atoms that compose them. Max von Laue Nobel Lecture, December 12, 1915 Paths of charged atomic particles made visible. In a supersaturated gas, the ions left in the trail of an ionizing event act as condensation nuclei for water droplets. From the width of the trail and it's shape (a straight or zigzag line) the type of particle could be deduced. Reactions between atomic particles may be “seen” and photographed. Very useful in the discovery of new particles. Useful in later years for studying the effects of electrical and magnetic fields on particle motion; measuring ratios of charge to mass ... C.T.R. Wilson Nobel Lecture, December 12, 1927 C.T.R. Wilson Stockholm, December 10, 1927 Atoms dentical in chemical properties (having same nuclear charge) and differing only in atomic mass. Established chemical identity of various decay change members. Radioactive Displacement Law: describes the resultant transformation of nuclei undergoing alpha and beta decay. Frederick Soddy Chemical News 107, 97-9 (1913) Frederick Soddy Nature 92, 399-400 (December 4, 1913) Frederick Soddy Chemical Society Annual Reports 10, 262-88 (1913) Frederick Soddy Nobel Lecture, December 12, 1922 Kasimir Fajans Berichte der Deutschen Chemischen Gesellschaft, Vol. 46, p. 422-439 (1913) Explains the Periodic Table of the elements on the basis of nuclear charge. Great promise for science was cut off when Moseley was killed at Gallipoli in World War One at the age of 28. X-ray diffraction Wavelengths of X-rays scattered off of different elements follow a simple law depending exactly on atomic number. Determined the number of positive charges in the nucleus. H. G. J. Moseley, M. A. Phil. Mag. (1913), p. 1024 Rutherford-Bohr Atom Model Central nucleus orbited by electrons (the 20th century atom icon familiar in popular culture). Brains considering Rutherford's nucleus, Quantum Theory, along with spectroscopic emissions and characteristic X-rays, as well as Isaac Newton's classical mechanics “One must assume that there are forces in nature of a kind completely different from the usual mechanical sort”
- Niels Bohr Correspondence principal. Awesome explanatory power, providing a theoretical ground for a multitude of chemical phenomena known empirically, e.g., the periodic table of the elements. Incorporates Quantum Theory into description of atomic electrons. Elaborated by Sommerfeld. Niels Bohr Philosophical Magazine, Series 6, Volume 26, July 1913, p. 1-25 Niels Bohr Nature, March 24, 1921 Niels Bohr Nobel Lecture, December 11, 1922 Irving Langmuir Proceedings of the National Academy of Science, Vol. V, 252 (1919) first use jointly with Frederic Paneth Uses radioactive isotopes to “see” physiological processes and chemical pathways. Used neutron activation to synthesize isotopes of biologically active elements, first: radiophosphorus. George de Hevesy Nobel Lecture, December 12, 1944 The nuclear carrier of positive charge; fundamental building block of all atoms. First human made nuclear transformation. Alpha particle bombardment converts Nitrogen into Oxygen and releases a Proton Between 1920 and 1925 alpha particle bombardment of boron, flourine, neon, sodium and other elements, in all cases caused release of a hydrogen nucleus; lead to conclusion that it was one of the fundamental building blocks of all other nuclei. Change of one type of atom into another: nuclear change. Beginning of many bombardment experiments probing internal structure of the nucleus. Leads to particle accelerator. Sir Ernest Rutherford The London, Edinburgh and Dublin Philosophical Magazine and Journal of Science, 6th series, 37, 581 (1919) Sir Ernest Rutherford Proc. Roy. Soc. A, 97, 374 (1920) Scattering of X-rays by electrons. Observed photons imparting energy to electrons as if by collision, wavelength decreases. Electromagnetic photons display both particle and wavelike behavior; photons have no mass, but do have momentum. Arthur H. Compton Nobel Lecture, December 12, 1927 Development and application of statistical mechanics to subatomic phenomena. Invented to describe the behavior of photons and ensembles of such as groups of electrons and molecules. for electrons The electron is a wave too! “Wavicles” very counter-intuitive, not actual physical quantity, rather it is a complex number. Accounts for N. Bohr's quantization of electron orbits. At subatomic dimensions, all particles have been shown to have wave properties/wave-nature, and vice versa; this explains the permissible states for electrons in the Bohr atom. Louis de Broglie presented by Jean Perrin (Translated from Comptes rendus, Vol. 177, 1923, pp. 507-510) Louis de Broglie Nobel Lecture, December 12, 1929 Brains and “pure” mathematics developed in 1800s Matrix algebra A purely mathematical representation/description of electrons. Leads to Heisenberg's famous “uncertainty principle,” saying that an electron's exact position and it's velocity cannot be determined at the same time, implying that in the subatomic world causality breaks down. No precise predictions possible of where an individual electron is, only statistical statements are possible, likeliness. Probability is introduced into the basic laws of nature permanently (?). “[In quantum mechanics] we free forces of their classical duty of determining directly the motion of particles and allow them instead to determine the probability of states.” - Max Born Werner Heisenberg Nobel Lecture, December 11, 1933 Max Born Stockholm, December 10, 1954 Max Born Nobel Lecture, December 11, 1954 Working independently. Invented to describe the behavior of protons, neutrons and electrons, particles now known as fermions Non-relativistic Quantum Mechanics Mathematical articulation of L. de Broglie waves for electrons and atoms. The Schrödinger Equation = Quantum Wave Equation Electrons considered as probability wave functions. Schrödinger later proves the equivalence with Quantum Mechanics of Heisenberg. Erwin Schrödinger Nobel Lecture, December 12, 1933 Observes cosmic ray particles with energies greatly exceeding those of natural radioactivity. First observation of cosmic ray showers. Cloud Chamber in magnetic field. Birth of High Energy Particle Physics. Discovered the nature of cosmic rays, i.e., heavy nuclei. Relativistic Wave Equation Antimatter Hypothesis Combines all the ideas of de Broglie, Schrodinger, Heisenberg and Born with Einstein's theory of relativity. “The crowning achievement of theoretical physics.” (?) “spin” Predicts positron, as well as anti-particles for every other charged particle. Predicts pair-production, positron and electron produced from photon with energy greater than 1.002 million electron volts (double the rest mass of the electron), which illustrates the equivalence of mass and energy! Provides the most precise conceptual tool for describing the physical world; the irony is that it is incomprehensible: any picture you can illustrate this theory with is incomplete and potentially misleading. Paul A.M. Dirac Nobel Lecture, December 12, 1933 Paul A.M. Dirac Stockholm, December 10, 1933 Cockcroft/Walton accelerator First high-voltage particle accelerater. High tension tube. Large electrical potenial difference. Transmutation experiments carried out. Accelerates hydrogen atoms to one to two million electron volts. Ernest T.S. Walton Nobel Lecture, December 11, 1951 John Cockcroft Nobel Lecture, December 11, 1951 John Cockcroft Stockholm, December 10, 1951 Brains considering the apparent violation of energy conservation in beta decay spectrum. Accelerates particles in successive pulses along a spiral trajectory. Opened the way to ever more powerful accelerators. Ernest Lawrence Nobel Lecture, December 11, 1951 Ernest Lawrence Berkeley, February 29, 1940 Uncharged particle of approximately same mass as a proton. Essential constituent of all atoms. following up on inconclusive experiments of 1930 by W. Bothe and H. Becker, and of 1932 by Irčne Curie and Frédéric Joliot Bombarding beryllium with alpha particles released neutrons whose mass was deduced from the amount of energy it imparted to other nuclei. No direct study of the electrically neutral particle possible. “The discovery of the neutron is a classical example of the way in which the addition of a new building block clarifies as if by magic many previously inexplicable facts.”(?) For example, the mass number, A, is just the total number of protons and neutrons in the nucleaus; explained the puzzle of atomic weights and numbers and solved the problem of isotopes. It seemed that the picture of the subatomic world was complete with photons, electrons, protons and neutrons. Different isotopes of an element are atoms with nuclei containing the same number of protons but different numbers of neutrons. Initially predicted by E. Rutherford in the 1920s. Replaces model where nucleus is made of of protons and electrons with a proton-neutron model. F. Soddy developed the isotope theory before neutrons were discovered! Brings up the question of what holds the nucleus together since charges of the same sign repel one another(Answer: a unique nuclear force: The Strong Force). James Chadwick Nature, p. 312 (Feb. 27, 1932) J. Chadwick, F.R.S. Proc. Roy. Soc., A, 136, p. 692-708 (Received May 10, 1932) James Chadwick Nobel Lecture, December 12, 1935 Another fundamental particle. The positive electron; the electron's anti-particle Source: secondary cosmic rays. Detector: cloud chamber in strong magnetic field. Curvature in magnetic field equal but opposite to that of electron. First predicted mathematically by P.A.M. Dirac (1928). Carl D. Anderson Nobel Lecture, December 12, 1936 Carl D. Anderson Stockholm, December 10, 1936 Carl D. Anderson interviewed by Harriett Lyle, 1979 Oral History Project, California Institute of Technology Archives, Pasadena, California. Positron/Electron pair produced from photon. Also observed cosmic ray showers, or cascades. Combining Occhialini's coincidence counters, developed by Rossi in Italy, with Blackett's cloud chambers for high altitude studies of cosmic rays. First predicted mathematically by P.A.M. Dirac (1928). Patrick M.S. Blackett Nobel Lecture, December 13, 1948 Patrick M.S. Blackett Stockholm, December 10, 1948 Walther Bothe Nobel Lecture [1954] Neutral charge allows neutron to easily penetrate nuclei without electrical repulsion from protons or electrons. Succeeded in making artificial radioactive isotopes of most known nuclei using slow neutrons. These isotopes become important as tracers in medicine and industry. Bombarding an element with the newly discovered subatomic particle often transforms the element into the element of the next higher atomic number. E. Fermi Nature, 133, p. 898-899 (1934) Enrico Fermi Nobel Lecture, December 12, 1938 Certain elements irradiated with alpha rays continued to emit radiation even after the irradiating source was removed. In earlier experiments conducted since 1919 the radioactivity ceased instantly when the inducing radiation was stopped. Artificial radioactive isotopes are now produced on a large scale in nuclear reactors for use in medicine and industry. Irčne Joliot-Curie Nobel Lecture, December 12, 1935 Frédéric Joliot Nobel Lecture, December 12, 1935 predicted mathematically. Brains considering what force is needed to hold together protons and neutrons in a nucleus. The quantum of the strong force: exchange boson carrier of the strong force. Hideki Yukawa Nobel Lecture, December 12, 1949 first called “mesotron” Cosmic ray observations with cloud chamber in powerful magnetic field. Range of penetration used to estimate energy; speed indicated by thickness of the tails of ions. At first, thought to be H. Yukawa's meson (1935). Bombarding heavy elements with neutrons. Produced elements heavier than any found naturally occurring. Splitting the atom. Explained later by Lise Meitner and Otto Frisch (1939) Irradiating uranium with slow neutrons splits nucleus into a number of light fragments. Barium found among the reaction products. Releases large amounts of energy. O. Hahn AND F. Strassman Die Naturwissenschaften 27, p. 11-15 (January 1939). [Transl. in American Journal of Physics, January 1964, p. 9-15] Otto Hahn and Fritz Strassmann Die Naturwissenschaften, Volume 27, No. 6, pp. 89-95 (10 February 1939) [Transl. from Journal of Chemical Education, May 1989, p. 363-363] Lise Meitner and O.R. Frisch Nature, 143, 239-240, (Feb. 11, 1939) 0. R. Frisch Nature (London), Volume 143, p. 276 (1939) Otto Frisch and John Wheeler Physics Today, p. 43, November 1937 the possibility Bombarding uranium with neutrons. Fission, splitting of atom with the release of more neutrons that can go on to induce more fission. uncontrolled = explosion; controlled = energy-producing pile. synthesized element Produced in cyclotron by neutron bombardment. First transuranic element produced. Controlled fission of uranium; sustained nuclear chain reaction. Atomic Pile: critical mass assembly of uranium -235 Ushers in the Atomic Age. Heat generated by fission can be used to produce steam to drive generators. Corbin Allardice and Edward R. Trapnell The U.S. Atomic Energy Commission, Washington, D.C., November 1949 synthesized transuranic element Produced in cyclotron bombardment. Extracted by radiochemical techniques. Edwin M. McMillan Nobel Lecture, December 12, 1951 Glenn T. Seaborg Nobel Lecture, December 12, 1951 Uncontrolled fission chain reaction. leading the Manhattan Project A massive feat of technology and scientific administration; organized effort of some 500,000 people costing a billion dollars per year. “represents another major leap forward in man's control of natural forces of the same order as, and possibly of greater ultimate importance than, those of fire, agriculture, and steam.” (?) Oppenheimer, Manley, Fermi, Bethe 15-24 April 1943 The Manhattan Engineer District June 29, 1946 Compiled and edited by Samuel Glasstone and Philip J. Dolan Third Edition, Prepared and published by the United States Department of Defense and the Energy Research and Development Administration, 1977. Henry De Wolf Smyth The Official Report on the Development of the Atomic Bomb Under the Auspices of the United States Government (July 1945) “Nuclear Research Emulsions” Refinement of emulsions gives more subtle measurement capability. with Giuseppe Occhialini, et al The atomic mass of particles passing through can be obtained by measuring the density of the small black dots which form the track, and from deviations caused by collisions with nuclei in the emulsion. The slower the particle, the more atoms ionized and the greater density of the dots; direction, energy and rate of energy loss can be estimated. “It was as if, suddenly, we had broken into a walled orchard, where protected trees had flourished and all kinds of exotic fruits had ripened in great profusion.” - C. Powell on the world of subatomic particles revealed in cosmic rays using the new emulsions. Cecil Powell Nobel Lecture, December 11, 1950 Cecil Powell Stockholm, December 10, 1950 The meson predicted by H. Yukawa in 1935. with Giuseppe Occhialini, et al Source: cosmic rays. Detector: Ilford Photographic Plates, new, more sensitive photographic emulsions that overcame problems of low ionization rate of high energy particles and allowed for identification of primary cosmic rays. with Louis Alvarez Sudden reduction of the pressure above a liquid close to its boiling point lowers the boiling point of the liquid and a situation of 'super-heating' is created where the temperature of the liquid is higher that its boiling point. If an ionizing particle passes now, bubbles of gas form around the ions, marking the path of the particle. Rumor: Glaser was inspired by a bottle of beer. Became most widely used detectors in the search for new particles. Great advantage: density of the liquid is greater than that of the gas in a cloud chamber, so particles are more often stopped within the chamber, permitting the entire path to be photographed. Donald A. Glaser Nobel Lecture, December 12, 1960 Luis Alvarez Nobel Lecture, December 11, 1968 Professor Anders Bárány Video of meeting of Nobel Prize Winners in Lindau, Germany, 2000. Hydrogen Bomb; Fusion Bomb et al J. Robert Oppenheimer, E. Fermi, I.I. Rabi, et al October 30, 1949 Hans Bethe Los Alamos Science, Fall 1982, Vol. 3, Num. 3