bluuebunny/crossref_metadata_2025_split huggingface dataset:
Max von Laue – The Nature of X Rays and the Atomic Structure of Crystals (1912)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
The nature of the X rays discovered by Röntgen in 1895 was not known. Röntgen himself conjectured that they might be longitudinal ether waves as opposed to the transverse ones, the electromagnetic waves found by Hertz. Since in Röntgen’s original experiment the X rays originated from the point where cathode rays, i.e., electrons, hit matter, Wiechert and also Stokes suggested already in 1896 that X rays were emitted by electrons while the latter were decelerated. In Maxwell’s theory an electric charge with a velocity, which is not constant, emits electromagnetic waves. In the Hertzian dipole antenna the charges oscillate to and fro. In a Röntgen tube electrons lose their velocity hitting a piece of matter. The fact that interference effects, characteristic of all waves, in particular, light and Hertzian waves, were not observed for X rays, did not preclude that they were electromagnetic waves. Their wavelength might be too small for the detection of interference.
J. J. Thomson Identifies Isotopes (1912)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
The idea of atoms as final constituents goes back to antiquity. In 1803 Dalton formulated it in a precise scientific form and thus, at the same time, created the framework of modern chemistry. One of his five postulates reads: Atoms of the same element are similar to one another and equal in weight. This statement could be taken as a definition of an element. But the name element was, and is, used for a substance that cannot be decomposed into others by chemical means. Prout noted the fact that the atomic mass numbers of those elements for which these numbers had been determined with some accuracy were multiples of the atomic mass number of hydrogen. (The latter can be taken to be equal to one.) Therefore, in 1815, he pronounced the hypothesis that the atoms of all elements were made up of hydrogen atoms. In the course of the nineteenth century atomic mass numbers were obtained with increasing accuracy and many elements were found for which that number was far from an integer (i.e., far from a whole number). Prout’s hypothesis was therefore rejected but there was no reason to doubt Dalton’s postulate. In the twentieth century the situation was reversed: The second half of Dalton’s postulate was shown to be wrong and Prout’s hypothesis was shown to carry some truth.
Moseley and the Periodic Table of Elements (1913)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
In 1913 and 1914, respectively, Moseley [1] published two papers which, once and for all, established a firm connection of the Periodic Table, which was based on empirical chemistry, to the physical structure of atoms. In 1915 at the age of 27, he was killed in the ill-fated campaign of the British against the Turkish army on the Gallipoli peninsula.
Nitrogen is Turned into Oxygen (1919)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
In June 1919, a paper by Rutherford was published in which he announces another of his great discoveries, the transmutation of an element in a planned experiment. He had already discovered the spontaneous transmutation of radioactive elements (see Episode 9), which could not be influenced by man. Now he showed that transmutation could be achieved, more or less, at will.
Astronomers Verify General Relativity (1919)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
In 1704 Newton published his book Opticks. In his foreword to a reprint of 1931 Einstein wrote [1]: Fortunate Newton, happy childhood of science! He who has time and tranquillity can by reading this book live the wonderful events which the great Newton experienced in his young days. Nature to him was an open book, whose letters he could read without effort … In one person he combined the experimenter, the theorist, the mechanic and, not least, the artist in exposition. He stands before us strong, certain and alone; his joy in creation and his minute precision are evident in every word and in every figure.
Bose and Einstein – A New Way of Counting (1924)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
There are two rather different phenomena that furthered the development of quantum theory: blackbody radiation and atomic spectra. In fact quantum theory began in 1900 with Planck’s radiation law and his introduction of the quantum of action h (Episode 7). His derivation of the law was by no means stringent. He assumed the existence of many resonators (atoms or molecules) of different but fixed frequencies ν, which could emit or absorb radiation only in quanta of energy E = hν. Einstein, in his light-quantum hypothesis of 1905, postulated that the energy quantization is a property of the radiation field itself and not due to the material resonators. He found a similarity between a cavity filled with radiation consisting of quanta and a vessel filled with gas consisting of atoms. However, he could not obtain Planck’s law but only Wien’s (Episode 10).
Pauli’s Exclusion Principle (1925)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
The exclusion principle is one of the most far-reaching theorems in physics. In a telegram to the Nobel committee, quoted in [1], Einstein wrote: ‘Nominate Wolfgang Pauli for physics prize stop his contributions to modern quantum theory consisting of so-called Pauli or exclusion principle became fundamental part of modern physics being independent from other basic axioms of that theory stop Albert Einstein.’ It is interesting to note that quantum mechanics, the theory Einstein alluded to, was formulated a little after the Pauli principle.
Hubble Finds that the Universe is Expanding (1929)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
In 1929, through the work of Hubble [1,2], our present picture of the expanding universe, consisting of galaxies moving away from one another, was established. Hubble is considered by many to be the greatest astronomer of the twentieth century. Certainly he made good use of the fact that, nearly from the outset of his career, he worked with the world’s largest telescope and concentrated on work that could be done with this instrument only.
Chadwick Discovers the Neutron (1932)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
In June 1920, Rutherford presented his Bakerian Lecture on the Nuclear Constitution of Atoms. Among experimental facts and the assertion, that the atomic nucleus is composed of protons and electrons, it contains the following speculation [1]: Under some circumstances, however, it may be possible for an electron to combine much more closely with the H nucleus [the hydrogen nucleus, i.e., the proton], forming a kind of neutral doublet. Such an atom would have novel properties. Its external [electric] field would be practically zero, and in consequence it should be able to move freely through matter. Its presence would probably be difficult to detect by the spectroscope, and it may be impossible to contain it in a sealed vessel. On the other hand it should enter readily the structure of atoms, and may either unite with the nucleus or be disintegrated by its intense field, resulting possibly in the escape of a charged H atom or an electron or both.
Fermi’s Theory of Beta Rays (1933)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
In 1926, not long after Fermi had published the work on his new statistics (Episode 41), Corbino, his mentor, succeeded to have a chair for theoretical physics established at the University of Rome. The customary competition was won by Fermi who thus, in 1927, at the age of only 26 years, became professor in Rome. As a result of the same competition Persico, his friend from school days in Rome, became professor in Florence. Fermi’s chair was attached to the Institute of Physics headed by Corbino and the two men decided to thoroughly modernize physics in Rome in both theory and experiment. As a first step Rasetti , a young experimentalist with wide interests whom Fermi knew from Florence, was hired as Corbino’s assistant. He began with important work on optical spectroscopy, some together with Fermi. There were only very few young people studying physics. But additional students were won over from electrical engineering, the first two being Segrè and Amaldi .
Irène and Frédéric Joliot–Curie – Artificial Radioactivity (1934)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
In Episode 48, we told the story how, early in 1932, the Joliot–Curies barely missed the discovery of the neutron but made observations which helped Chadwick find it. In 1935, the year in which Chadwick was awarded the Nobel Prize in physics, the young couple received the same honour in chemistry. They had produced radioactive elements not normally existing on earth.
A New Kind of Liquid: Superfluid Helium (1937)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
Early in January 1938, two letters to the editor appeared on adjacent pages of Nature, describing a hitherto unknown state of matter, superfluidity of helium. Author of the first letter [1], dated 3 December 1937, was Kapitza who worked in an institute in Moscow which had specially been erected for him. The second letter [2], dated 22 December, was signed by Allen and Misener who did their research in Cambridge, also in an institute planned and built for Kapitza.
Fermi Builds a Nuclear Reactor (1942)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
The discovery of nuclear fission (Episode 60) had two important aspects: one scientific, the other technical. A nucleus could be split in two and in the process an enormous amount of energy was liberated. Lise Meitner had quite accurately estimated 200 MeV to be the energy set free in one fission process. The typical chemical binding energy of one molecule, gained, for instance, by burning one atom of carbon with two atoms of oxygen to one molecule of carbon dioxide, is on the order of 1 eV. The two numbers differ by eight orders of magnitude! A hectic activity began in many laboratories on both sides of the Atlantic. A review article [1] reports on nearly a hundred papers about fission published within less than a year after its discovery. In Europe Joliot [2], in independent work, saw fission products only days after Frisch. In the United States the news was spread by Bohr, who came on 16 January 1939 to participate in a conference and to stay on for several months at the Institute for Advanced Studies in Princeton. Only two weeks earlier, Fermi, the world expert on neutrons, had arrived in New York to work at Columbia University. Under his leadership the first nuclear reactor would be built and made to operate within less than four years. Although its construction was motivated by military reasons, we relate the story here
The Lamb Shift (1947)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
In 1947, Lamb and Retherford performed an experiment on hydrogen atoms demonstrating a deviation from Dirac’s relativistic theory of the electron of 1928. Although until then this theory described the observed hydrogen spectrum within the high precision achieved by experiment, it was known to be plagued by fundamental difficulties. Still more accurate data were needed to test and stimulate theoretical ideas. The measurements of Lamb and Retherford led, within a few years, to the completion of quantum electrodynamics (QED) as we now know it.
Glaser’s Bubble Chamber (1953)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
For at least a decade, the late 1950s and all through the 1960s, most discoveries in particle physics were made with a new kind of detector, the bubble chamber, exposed to beams of particles produced by accelerators. The bubble chamber was invented by Donald Glaser who was searching for a track detector adapted to the needs of high-energy particle physics and, only a little later, forged by Luis Alvarez and his group into an indispensable tool.
Antimatter (1955)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
In Episode 64 we described the invention of a new type of particle accelerator, the synchrotron, and mentioned that the US Atomic Energy Commission, in 1948, approved funds to build two large synchrotrons, one accelerating protons to an energy of 3 GeV (the Cosmotron) at Brookhaven and one of 6 GeV (the Bevatron) at Berkeley. The latter energy was chosen because that would suffice for the production of antiprotons if such particles existed. It was generally expected there would be an antiproton, i.e., a particle with the proton mass but of opposite (negative) charge as partner of the proton in the same way as there was the positron as antiparticle of the electron (Episode 49). (That expectation was, however, by no means a certainty. Because it had an anomalous magnetic moment the proton was assumed to have a substructure; it might not be an elementary particle in the same sense as the electron was.)
Superconductivity Explained by Bardeen, Cooper, and Schrieffer (1957)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
In May 1950, Bardeen received a phone call from Bernard Serin from Rutgers University in New Brunswick which alerted him to a new experimental development in superconductivity. Bardeen was still working at the Bell Laboratories, where, a little more than two years ago, he and Brattain had invented the first transistor (Episode 69). Since Shockley, the leader of their research group, was pursuing the development of the next type of transistor on his own, Bardeen was looking for a new research topic. The phone call made him return to superconductivity, a field on which he had tried his hand nearly ten years earlier at Harvard. Before we can discuss the work of Bardeen and his group [1,2] we have to mention at least a few of the advances in superconductivity since its discovery in 1911 (Episode 18).
The Mössbauer Effect (1958)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
A simple and most instructive experiment, shown in many lectures for beginners in physics, is the demonstration of resonant absorption and resonant fluorescence (also called resonant scattering) with yellow sodium light. A beam of light produced by a lamp, in which a glow discharge is maintained in sodium vapour, is directed through an evacuated glass globe containing some metallic sodium. The beam falls on a screen behind the globe, producing a bright yellow patch. As the globe is heated and thus fills with sodium vapour, the yellow patch loses intensity and at the same time the incident beam becomes visible as a yellow glow within the glass globe. Excited sodium atoms in the lamp perform a transition to the ground state by emitting light quanta of energy E 0. These, in turn, can excite atoms in the globe and thus be absorbed from the beam. The excited atoms return to their ground state, again by emitting quanta of the energy E 0 and causing a visible glow where the incident light beam passes.
A Fourth Quark – Charm (1974)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
At noon on 11 November 1974, in a seminar at the Stanford Linear Accelerator Center (SLAC), a discovery was announced which strongly influenced particle physics; for some time one even spoke of the November Revolution . Not only was the discovery important but it had been made independently by two groups, working on either coast of the United States, and not till that very morning had they heard of each other’s success. These were the groups of Ting from MIT, experimenting with the proton synchrotron at Brookhaven, and a collaboration between Stanford and Berkeley and initiated by Richter, working at an electron–positron collider at Stanford. A meeting of a SLAC advisory committee, of which Ting was an external member, had been scheduled for the morning of 11 November. As Richter remembers [1], Ting said to him before the meeting: ‘Burt, I have some interesting physics to tell you about.’ His response was: ‘Sam, I have some interesting physics to tell you about!’ When they had told each other, the meeting was cut short and the noon-time seminar was announced.
W and Z Boson Discovered (1983)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
Rubbia1 was born in Gorizia (also Görz or Gurize), a town in the north-east of Italy, which for centuries had been influenced by Austrians, Italians, and Slovenians and, in 1945, became part of Yugoslavia. Rubbia’s family – his father was an electrical engineer, his mother a school teacher – fled to Venice and then to Udine. He studied at the prestigious Scuola Normale Superiore in Pisa, Fermi’s alma mater, and obtained his doctorate under Conversi2. In 1958 Rubbia went to Columbia University.
Bose–Einstein Condensation of Atoms (1995)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
Einstein used double quotes on two words, because in the concept of an ideal gas there is no interaction between its constituents, whereas condensation and saturation are properties of a real gas of interacting atoms or molecules. The ‘interaction’ bringing about Bose–Einstein condensation is the symmetry requirement for multi-particle wave functions of bosons, sometimes called exchange force (see page 176). For this to become effective, the wave functions of individual bosons have to overlap, i.e., the average (or thermal ) de Broglie wavelength of the bosons has to be on the order of or larger than the average distance between them. In other words, a Bose–Einstein condensate is expected to form if the ratio of wavelength and distance exceeds a certain value. (The third power of this ratio is called phase-space density, see margin.) At very low temperature the average distance can be quite large; interactions between bosons become unimportant and the situation of an ideal gas is well approximated. We saw in Episode 97 how such temperatures for samples of neutral atoms were reached. These methods, greatly simplified and extended, were the basis for the achievement of Bose–Einstein condensates by the groups ofWieman and Cornell [2] and of Ketterle [3] in 1995, seventy years after Einstein’s prediction.
Cooling and Trapping Neutral Atoms (1985)
Authors: Brandt Siegmund 
Published: November 2023

Abstract
Atomic beams, pioneered by Stern (Episodes 30 and 52), opened the way to study non-interacting atoms which, essentially, have only one component in velocity, namely, that in beam direction. Ions could even be confined in a trap(Episode 80) with small values of all three velocity components. We shall see now how that was achieved also for neutral atoms. A measure of quality for a gas of trapped atoms is its temperature, i.e., the average kinetic energy of the atoms expressed in Kelvin. By carefully exploiting the inner structure of atoms it became possible, with the help of laser light and magnetic fields, to cool and trap small samples of highly dilute atomic gases, reaching temperatures as low as 180 nK (180 × 10‒9 K).
Quarks and leptons and their interactions
Authors: Perkins D H 
Published: November 2023

Abstract
High-energy particle physics is concerned with the study of the fundamental constituents of matter and the interactions between them. Experiments in this field have been carried out with giant accelerators and their associated detection equipment, which have probed the structure of matter down to very small scales, of order 10 m, that is, about one hundredth of the radius of a proton. In contrast, astrophysics is concerned with the structure and evolution of the universe in the large, including the study of the behaviour of matter and radiation on enormous scales, up to around 10 m. The experimental observations have been made with telescopes on the Earth or on satellites, covering the visible, infrared, and ultraviolet regions of the spectrum, as well as with detectors of radio waves, X-rays, γ-rays, and neutrinos. These have revealed an astonishing range of extra-terrestrial phenomena from the most distant regions of the cosmos. In describing this scientific adventure into what is, even today, still very largely unknown territory, the object of this text has been to show how studies of particles on a laboratory scale have helped in our understanding of the development of the universe, and conversely how celestial observations have, in turn, shed light on our understanding of particle interactions. Although in this chapter we discuss the constitution of matter as determined by accelerator experiments on Earth, it is becoming clear that on cosmological scales, other quite different forms of matter and energy may be important or even dominant, as will be discussed in the later chapters. Nevertheless, it is clear that a thorough understanding of the properties and interactions of elementary particles in laboratory experiments is essential in the discussion of astrophysical phenomena on the grandest scales.
Equal Pay And Discrimination
Authors: Palca Julia , Taylor Catherine 
Published: November 2023

Abstract
Employers who adopt discriminatory practices do so at their peril. The Equal Pay Act 1970 (EqPA 1970), the Sex Discrimination Act 1975 (SDA 1975), the Race Relations Act 1976 (RRA 1976), the Disability Discrimination Act 1995 (DDA 1995), the Employment Equality (Religion or Belief ) Regulations 2003, SI 2003/1660 (RBR 2003), the Employment Equality (Sexual Orientation) Regulations 2003, SI 2003/1661 (SOR 2003), and the Employment Equality (Age) Regulations 2006, SI 2006/1031 (EEAR 2006) between them provide that employers cannot discriminate between people of different sexes and races, against those who intend to undergo, are undergoing or who have undergone gender reassignment, against those who suffer from a disability, against employees because of their religion or belief or sexual orientation or age in their selection procedures, contractual terms, and treatment of employees. In addition, Article 141 (formerly Article 119) of the EC Treaty, and the Equal Treatment Directive (76/207/EEC [1976] OJ L39/40, as amended by Directive 2002/73/EC [2002] OJ L269/15) give additional protection to employees who are discriminated against on grounds of sex. There is also protection from discrimination of those who are or are not trade union members (see para 6.23), take up other offices as part of their employment or who are whistle-blowers (see para 7.94), those who work part-time (see paras 4.61–4.68), and those who work under fixed-term contracts (see paras 1.92 above and 7.114 below).
Rights On Maternity And Adoption
Authors: Palca Julia , Taylor Catherine 
Published: November 2023

Abstract
On 6 April 2003, as part of the UK Government’s ‘family-friendly’ initiative, simplified and enhanced rights relating to maternity came into force. At the same time, a completely new set of rights, relating to adoption, were introduced. The scheme of the new rights relating to adoption follows the existing maternity scheme closely. These rights were improved in 2006 in relation to employees whose expected week of childbirth begins on or after 1 April 2007. So employees on both childbirth and adoption are entitled to receive a minimum period of 52 weeks’ leave. Over and above those basic rights, the employee will have other rights subject to the employee having sufficient length of employment. These rights include the right to receive maternity or adoption pay for up to 39 weeks and to return to work (although the specific terms of that right will still depend on the length of the leave taken). This chapter will cover all of these rights as well as the connected rights relating to antenatal care and the suspension from work for maternity-related reasons.