Enrico Fermi was an Italian and naturalized-American physicist and the creator of the world's first nuclear reactor, the Chicago Pile-1. He has been called the "architect of the nuclear age" and the "architect of the atomic bomb", he was one of few physicists to excel in both theoretical physics and experimental physics. Fermi held several patents related to the use of nuclear power, was awarded the 1938 Nobel Prize in Physics for his work on induced radioactivity by neutron bombardment and for the discovery of transuranium elements, he made significant contributions to the development of statistical mechanics, quantum theory, nuclear and particle physics. Fermi's first major contribution involved the field of statistical mechanics. After Wolfgang Pauli formulated his exclusion principle in 1925, Fermi followed with a paper in which he applied the principle to an ideal gas, employing a statistical formulation now known as Fermi–Dirac statistics. Today, particles that obey the exclusion principle are called "fermions".
Pauli postulated the existence of an uncharged invisible particle emitted along with an electron during beta decay, to satisfy the law of conservation of energy. Fermi took up this idea, developing a model that incorporated the postulated particle, which he named the "neutrino", his theory referred to as Fermi's interaction and now called weak interaction, described one of the four fundamental interactions in nature. Through experiments inducing radioactivity with the discovered neutron, Fermi discovered that slow neutrons were more captured by atomic nuclei than fast ones, he developed the Fermi age equation to describe this. After bombarding thorium and uranium with slow neutrons, he concluded that he had created new elements. Although he was awarded the Nobel Prize for this discovery, the new elements were revealed to be nuclear fission products. Fermi left Italy in 1938 to escape new Italian racial laws that affected his Jewish wife, Laura Capon, he emigrated to the United States, where he worked on the Manhattan Project during World War II.
Fermi led the team that designed and built Chicago Pile-1, which went critical on 2 December 1942, demonstrating the first human-created, self-sustaining nuclear chain reaction. He was on hand when the X-10 Graphite Reactor at Oak Ridge, went critical in 1943, when the B Reactor at the Hanford Site did so the next year. At Los Alamos, he headed F Division, part of which worked on Edward Teller's thermonuclear "Super" bomb, he was present at the Trinity test on 16 July 1945, where he used his Fermi method to estimate the bomb's yield. After the war, Fermi served under J. Robert Oppenheimer on the General Advisory Committee, which advised the Atomic Energy Commission on nuclear matters. After the detonation of the first Soviet fission bomb in August 1949, he opposed the development of a hydrogen bomb on both moral and technical grounds, he was among the scientists who testified on Oppenheimer's behalf at the 1954 hearing that resulted in the denial of Oppenheimer's security clearance. Fermi did important work in particle physics related to pions and muons, he speculated that cosmic rays arose when material was accelerated by magnetic fields in interstellar space.
Many awards and institutions are named after Fermi, including the Enrico Fermi Award, the Enrico Fermi Institute, the Fermi National Accelerator Laboratory, the Fermi Gamma-ray Space Telescope, the Enrico Fermi Nuclear Generating Station, the synthetic element fermium, making him one of 16 scientists who have elements named after them. Enrico Fermi was born in Rome, Italy, on 29 September 1901, he was the third child of Alberto Fermi, a division head in the Ministry of Railways, Ida de Gattis, an elementary school teacher. His sister, was two years older than he, his brother Giulio a year older. After the two boys were sent to a rural community to be wet nursed, Enrico rejoined his family in Rome when he was two and a half. Although he was baptised a Roman Catholic in accordance with his grandparents' wishes, his family was not religious; as a young boy he shared the same interests as his brother Giulio, building electric motors and playing with electrical and mechanical toys. Giulio died during an operation on a throat abscess in 1915 and Maria died in an airplane crash near Milan in 1959.
At a local market Fermi found a physics book, the 900-page Elementorum physicae mathematicae. Written in Latin by Jesuit Father Andrea Caraffa, a professor at the Collegio Romano, it presented mathematics, classical mechanics, astronomy and acoustics as they were understood at the time of its 1840 publication. With scientifically inclined friend, Enrico Persico, Fermi pursued projects such as building gyroscopes and measuring the acceleration of Earth's gravity. A colleague of Fermi's father gave him books on physics and mathematics which he assimilated quickly. Fermi graduated from high school in July 1918, at Amidei's urging applied to the Scuola Normale Superiore in Pisa. Having lost one son, his parents only reluctantly allowed him to live in the school's lodgings for four years. Fermi took first place in the difficult entrance exam, which included an essay on the theme of "Specific characteristics of Sounds". At the Scuola Normale Superiore Fermi played pranks with fellow student Franco Rasetti.
Fermi was advised by Luigi Puccianti, director of the physics laborat
Weyl fermions are massless chiral fermions that play an important role in quantum field theory and the standard model. They are considered a building block for fermions in quantum field theory, were predicted from a solution to the Dirac equation derived by Hermann Weyl called the Weyl equation. For example, one-half of a charged Dirac fermion of a definite chirality is a Weyl fermion, they have not been observed as a fundamental particle in nature. Weyl fermions may be realized as emergent quasiparticles in a low-energy condensed matter system; this prediction was first proposed by Conyers Herring in the context of electronic band structures of solid state systems such as electronic crystals. The first liquid state, suggested has emergent but neutral excitation and theoretically interpreted superfluid's chiral anomaly as observation of Fermi points is in Helium-3 A liquids. Crystalline tantalum arsenide is the first discovered topological Weyl fermion semimetal exhibiting topological surface Fermi arcs where Weyl fermion is electrically charged along the line of original suggestion by Herring.
An electronic Weyl fermion is not only charged but stable at room temperature where there is no such superfluid or liquid state known. A Weyl semimetal is a solid state crystal whose low energy excitations are Weyl fermions that carry electrical charge at room temperatures. A Weyl semimetal enables realization of Weyl fermions in electronic systems, it is a topologically nontrivial phase of matter, together with Helium-3 A superfluid phase, that broadens the topological classification beyond topological insulators. The Weyl fermions at zero energy correspond to points of bulk band degeneracy, the Weyl nodes, that are separated in momentum space. Weyl fermions have distinct chiralities, either left handed or right handed. In a Weyl semimetal crystal, the chiralities associated with the Weyl nodes can be understood as topological charges, leading to monopoles and anti-monopoles of Berry curvature in momentum space, which serve as the topological invariant of this phase. Comparable to the Dirac fermions in graphene or on the surface of topological insulators, Weyl fermions in a Weyl semimetal are the most robust electrons and do not depend on symmetries except the translation symmetry of the crystal lattice.
Hence the Weyl fermion quasiparticles in a Weyl semimetal possess a high degree of mobility. Due to the nontrivial topology, a Weyl semimetal is expected to demonstrate Fermi arc electron states on its surface; these arcs are discontinuous or disjoint segments of a two dimensional Fermi contour, which are terminated onto the projections of the Weyl fermion nodes on the surface. A 2012 theoretical investigation of superfluid Helium-3 suggested Fermi arcs in neutral superfluids. On 16 July 2015 the first experimental observations of Weyl fermion semimetal and topological Fermi arcs in an inversion symmetry-breaking single crystal material tantalum arsenide were made. Both Weyl fermions and Fermi arc surface states were observed using direct electronic imaging using ARPES spectroscopy, which established its topological character for the first time; this discovery was built upon previous theoretical predictions proposed in November 2014 by a team led by Bangladeshi scientist M Zahid Hasan. Weyl points were observed in non-electronic systems such as photonic crystals and Helium-3 superfluid quasiparticle spectrum.
This article is about Weyl semimetals. TaAs is the first discovered Weyl semimetal. Large-size, high-quality TaAs single crystals can be obtained by chemical vapor transport method using iodine as the transport agent. TaAs crystallizes in a body-centered tetragonal unit cell with lattice constants a = 3.44 Å and c = 11.64 Å and space group I41md. Ta and As atoms are six coordinated to each other, it should be noted that this structure lacks a horizontal mirror plane and thus inversion symmetry, essential to realize Weyl semimetal. TaAs single crystals have shiny facets, which can be divided into three groups: the two truncated surfaces are, the trapezoid or isosceles triangular surfaces are, the rectangular ones. TaAs belongs to point group 4mm, the equivalent and planes should form a ditetragonal appearance; the observed morphology can be vary of degenerated cases of the ideal form. The Weyl fermions in the bulk and the Fermi arcs on the surfaces of Weyl semimetals are of interest in physics and materials technology.
The high mobility of charged Weyl fermions may find use in computing. In 2017, a research team from Vienna University of Technology carrying out experimental work to develop new materials, a team at Rice University carrying out theoretical work, have produced material which they term Weyl-Kondo semimetals. A group of international researchers led by a team from Boston College discovered in 2019 that the Weyl semimetal Tantalum Arsenide delivers the largest intrinsic conversion of light to electricity of any material, more than ten times larger than achieved. Johnston, Hamish. "Weyl fermions are spotted at long last". Physics World. Retrieved 22 November 2018. Ciudad, David. "Massless yet real". Nature Materials. 14: 863–863. Doi:10.1038/nmat4411. ISSN 1476-1122. Vishwanath, Ashvin. "Where the Weyl Things Are". APS Physics. Retrieved 22 November 2018
Superconductivity is a phenomenon of zero electrical resistance and expulsion of magnetic flux fields occurring in certain materials, called superconductors, when cooled below a characteristic critical temperature. It was discovered by Dutch physicist Heike Kamerlingh Onnes on April 1911, in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum mechanical phenomenon, it is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor during its transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood as the idealization of perfect conductivity in classical physics; the electrical resistance of a metallic conductor decreases as temperature is lowered. In ordinary conductors, such as copper or silver, this decrease is limited by impurities and other defects. Near absolute zero, a real sample of a normal conductor shows some resistance.
In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature. An electric current through a loop of superconducting wire can persist indefinitely with no power source. In 1986, it was discovered that some cuprate-perovskite ceramic materials have a critical temperature above 90 K; such a high transition temperature is theoretically impossible for a conventional superconductor, leading the materials to be termed high-temperature superconductors. The cheaply-available coolant liquid nitrogen boils at 77 K, thus superconduction at higher temperatures than this facilitates many experiments and applications that are less practical at lower temperatures. There are many criteria; the most common are: A superconductor can be Type I, meaning it has a single critical field, above which all superconductivity is lost and below which the magnetic field is expelled from the superconductor. These points are called vortices. Furthermore, in multicomponent superconductors it is possible to have combination of the two behaviours.
In that case the superconductor is of Type-1.5. It is conventional if it can be explained by the BCS theory or its derivatives, or unconventional, otherwise. A superconductor is considered high-temperature if it reaches a superconducting state when cooled using liquid nitrogen – that is, at only Tc > 77 K) – or low-temperature if more aggressive cooling techniques are required to reach its critical temperature. Superconductor material classes include chemical elements, ceramics, superconducting pnictides or organic superconductors. Most of the physical properties of superconductors vary from material to material, such as the heat capacity and the critical temperature, critical field, critical current density at which superconductivity is destroyed. On the other hand, there is a class of properties. For instance, all superconductors have zero resistivity to low applied currents when there is no magnetic field present or if the applied field does not exceed a critical value; the existence of these "universal" properties implies that superconductivity is a thermodynamic phase, thus possesses certain distinguishing properties which are independent of microscopic details.
The simplest method to measure the electrical resistance of a sample of some material is to place it in an electrical circuit in series with a current source I and measure the resulting voltage V across the sample. The resistance of the sample is given by Ohm's law as R = V / I. If the voltage is zero, this means. Superconductors are able to maintain a current with no applied voltage whatsoever, a property exploited in superconducting electromagnets such as those found in MRI machines. Experiments have demonstrated that currents in superconducting coils can persist for years without any measurable degradation. Experimental evidence points to a current lifetime of at least 100,000 years. Theoretical estimates for the lifetime of a persistent current can exceed the estimated lifetime of the universe, depending on the wire geometry and the temperature. In practice, currents injected in superconducting coils have persisted for more than 23 years in superconducting gravimeters. In such instruments, the measurement principle is based on the monitoring of the levitation of a superconducting niobium sphere with a mass of 4 grams.
In a normal conductor, an electric current may be visualized as a fluid of electrons moving across a heavy ionic lattice. The electrons are colliding with the ions in the lattice, during each collision some of the energy carried by the current is absorbed by the lattice and converted into heat, the vibrational kinetic energy of the lattice ions; as a result, the energy carried by the current is being dissipated. This is the phenomenon of electrical Joule heating; the situation is different in a superconductor. In a conventional superconductor, the electronic fluid cannot be resolved into individual electrons. Instead, it consists of bound pairs of electrons known as Cooper pairs; this pairing is caused by an attractive force between electrons from the exchange of phonons. Due to quantum mechanics, the energy spectr
A Majorana fermion referred to as a Majorana particle, is a fermion, its own antiparticle. They were hypothesized by Ettore Majorana in 1937; the term is sometimes used in opposition to a Dirac fermion, which describes fermions that are not their own antiparticles. With the exception of the neutrino, all of the Standard Model fermions are known to behave as Dirac fermions at low energy, none are Majorana fermions; the nature of the neutrinos is not settled – they may be either Dirac or Majorana fermions. In condensed matter physics, bound Majorana fermions can appear as quasiparticle excitations – the collective movement of several individual particles, not a single one, they are governed by non-abelian statistics; the concept goes back to Majorana's suggestion in 1937 that neutral spin-1⁄2 particles can be described by a real wave equation, would therefore be identical to their antiparticle. The difference between Majorana fermions and Dirac fermions can be expressed mathematically in terms of the creation and annihilation operators of second quantization: The creation operator γ j † creates a fermion in quantum state j, whereas the annihilation operator γ j annihilates it.
For a Dirac fermion the operators γ j † and γ j are distinct, whereas for a Majorana fermion they are identical. The ordinary fermionic annihilation and creation operators f and f † can be written in terms of two Majorana operators γ 1 and γ 2 by f = / 2, f † = / 2. In supersymmetry models, neutralinos — superpartners of gauge bosons and Higgs bosons — are Majorana. Another common convention for the normalization of the Majorana fermion operator is f = / 2 f † = / 2 This convention has the advantage that the Majorana operator squares to the identity. Using this convention, a collection of Majorana fermions γ i obey the following commutation identities = 2 δ i j ∑ i j k l = ∑ i j 4 γ i i j γ j where A and B are antisymmetric matrices; because particles and antiparticles have opposite conserved charges, Majorana fermions have zero charge. All of the elementary fermions of the Standard Model have gauge charges, so they cannot have fundamental Majorana masses. However, the right-handed sterile neutrinos introduced to explain neutrino oscillation could have Majorana masses.
If they do at low energy, by the seesaw mechanism, the neutrino fields would behave as six Majorana fields, with three of them expected to have high masses and the other three expected to have low masses. If right-handed neutrinos exist but do not have a Majorana mass, the neutrinos would instead behave as three Dirac fermions and their antiparticles with masses coming directly from the Higgs interaction, like the other Standard Model fermions; the seesaw mechanism is appealing because it would explain why the observed neutrino masses are so small. However, if the neutrinos are Majorana they violate the conservation of lepton number and of B − L. Neutrinoless double beta decay, which has not been observed, it can be viewed as two ordinary beta decay events whose resultant antineutrinos annihilate with each other, is only possible if neutrinos are their own antiparticles. The high-energy analog of the neutrinoles
A proton is a subatomic particle, symbol p or p+, with a positive electric charge of +1e elementary charge and a mass less than that of a neutron. Protons and neutrons, each with masses of one atomic mass unit, are collectively referred to as "nucleons". One or more protons are present in the nucleus of every atom; the number of protons in the nucleus is the defining property of an element, is referred to as the atomic number. Since each element has a unique number of protons, each element has its own unique atomic number; the word proton is Greek for "first", this name was given to the hydrogen nucleus by Ernest Rutherford in 1920. In previous years, Rutherford had discovered that the hydrogen nucleus could be extracted from the nuclei of nitrogen by atomic collisions. Protons were therefore a candidate to be a fundamental particle, hence a building block of nitrogen and all other heavier atomic nuclei. In the modern Standard Model of particle physics, protons are hadrons, like neutrons, the other nucleon, are composed of three quarks.
Although protons were considered fundamental or elementary particles, they are now known to be composed of three valence quarks: two up quarks of charge +2/3e and one down quark of charge –1/3e. The rest masses of quarks contribute only about 1% of a proton's mass, however; the remainder of a proton's mass is due to quantum chromodynamics binding energy, which includes the kinetic energy of the quarks and the energy of the gluon fields that bind the quarks together. Because protons are not fundamental particles, they possess a physical size, though not a definite one. At sufficiently low temperatures, free protons will bind to electrons. However, the character of such bound protons does not change, they remain protons. A fast proton moving through matter will slow by interactions with electrons and nuclei, until it is captured by the electron cloud of an atom; the result is a protonated atom, a chemical compound of hydrogen. In vacuum, when free electrons are present, a sufficiently slow proton may pick up a single free electron, becoming a neutral hydrogen atom, chemically a free radical.
Such "free hydrogen atoms" tend to react chemically with many other types of atoms at sufficiently low energies. When free hydrogen atoms react with each other, they form neutral hydrogen molecules, which are the most common molecular component of molecular clouds in interstellar space. Protons are composed of three valence quarks, making them baryons; the two up quarks and one down quark of a proton are held together by the strong force, mediated by gluons. A modern perspective has a proton composed of the valence quarks, the gluons, transitory pairs of sea quarks. Protons have a positive charge distribution which decays exponentially, with a mean square radius of about 0.8 fm. Protons and neutrons are both nucleons, which may be bound together by the nuclear force to form atomic nuclei; the nucleus of the most common isotope of the hydrogen atom is a lone proton. The nuclei of the heavy hydrogen isotopes deuterium and tritium contain one proton bound to one and two neutrons, respectively. All other types of atomic nuclei are composed of two or more protons and various numbers of neutrons.
The concept of a hydrogen-like particle as a constituent of other atoms was developed over a long period. As early as 1815, William Prout proposed that all atoms are composed of hydrogen atoms, based on a simplistic interpretation of early values of atomic weights, disproved when more accurate values were measured. In 1886, Eugen Goldstein discovered canal rays and showed that they were positively charged particles produced from gases. However, since particles from different gases had different values of charge-to-mass ratio, they could not be identified with a single particle, unlike the negative electrons discovered by J. J. Thomson. Wilhelm Wien in 1898 identified the hydrogen ion as particle with highest charge-to-mass ratio in ionized gases. Following the discovery of the atomic nucleus by Ernest Rutherford in 1911, Antonius van den Broek proposed that the place of each element in the periodic table is equal to its nuclear charge; this was confirmed experimentally by Henry Moseley in 1913 using X-ray spectra.
In 1917, Rutherford proved that the hydrogen nucleus is present in other nuclei, a result described as the discovery of protons. Rutherford had earlier learned to produce hydrogen nuclei as a type of radiation produced as a product of the impact of alpha particles on nitrogen gas, recognize them by their unique penetration signature in air and their appearance in scintillation detectors; these experiments were begun when Rutherford had noticed that, when alpha particles were shot into air, his scintillation detectors showed the signatures of typical hydrogen nuclei as a product. After experimentation Rutherford traced the reaction to the nitrogen in air, found that when alphas were produced into pure nitrogen gas, the effect was larger. Rutherford determined that this hydrogen could have come only from the nitrogen, therefore nitrogen must contain hydrogen nuclei. One hydrogen nucleus was being knocked off by the impact of the alpha particle, producing oxygen-17 in the process; this was 14N + α → 17O + p.
(This reaction wo
In quantum physics, quantum state refers to the state of an isolated quantum system. A quantum state provides a probability distribution for the value of each observable, i.e. for the outcome of each possible measurement on the system. Knowledge of the quantum state together with the rules for the system's evolution in time exhausts all that can be predicted about the system's behavior. A mixture of quantum states is again a quantum state. Quantum states that cannot be written as a mixture of other states are called pure quantum states, all other states are called mixed quantum states. Mathematically, a pure quantum state can be represented by a ray in a Hilbert space over the complex numbers; the ray is a set of nonzero vectors differing by just a complex scalar factor. A unit vector is picked, but its phase factor can be chosen anyway; such factors are important when state vectors are added together to form a superposition. Hilbert space is a generalization of the ordinary Euclidean space and it contains all possible pure quantum states of the given system.
If this Hilbert space, by choice of representation, is exhibited as a function space the representatives are called wave functions. For example, when dealing with the energy spectrum of the electron in a hydrogen atom, the relevant state vectors are identified by the principal quantum number n, the angular momentum quantum number l, the magnetic quantum number m, the spin z-component sz. A more complicated case is given by the spin part of a state vector. | ψ ⟩ = 1 2, which involves superposition of joint spin states for two particles with spin 1⁄2. A mixed quantum state corresponds to a probabilistic mixture of pure states. Mixed states are described by so-called density matrices. A pure state can be recast as a density matrix. For example, if the spin of an electron is measured in any direction, e.g. with a Stern–Gerlach experiment, there are two possible results: up or down. The Hilbert space for the electron's spin is therefore two-dimensional. A pure state here is represented with a length of one.
A mixed state, in this case, has the structure of a 2 × 2 matrix, Hermitian, positive-definite, has trace 1. Before a particular measurement is performed on a quantum system, the theory gives only a probability distribution for the outcome, the form that this distribution takes is determined by the quantum state and the observable describing the measurement; these probability distributions arise for both mixed states and pure states: it is impossible in quantum mechanics to prepare a state in which all properties of the system are fixed and certain. This is exemplified by the uncertainty principle, reflects a core difference between classical and quantum physics. In quantum theory, for every observable there are some states that have an exact and determined value for that observable. In the mathematical formulation of quantum mechanics, pure quantum states correspond to vectors in a Hilbert space, while each observable quantity is associated with a mathematical operator; the operator serves as a linear function.
The eigenvalues of the operator correspond to the possible values of the observable, i.e. it is possible to observe a particle with a momentum of 1 kg⋅m/s if and only if one of the eigenvalues of the momentum operator is 1 kg⋅m/s. The corresponding eigenvector with eigenvalue 1 kg⋅m/s would be a quantum state with a definite, well-defined value of momentum of 1 kg⋅m/s, with no quantum uncertainty. If its momentum were measured, the result is guaranteed to be 1 kg⋅m/s. On the other hand, a system in a linear combination of multiple different eigenstates does in general have quantum uncertainty for the given observable. We can represent this linear combination of eigenstates as: | Ψ ⟩ = ∑ n C n | Φ n ⟩; the coefficient which corresponds to a particular state in the linear combination is a complex number, thus allowing interference effects between states. The coefficients are time dependent. How a quantum system chang
The electron is a subatomic particle, symbol e− or β−, whose electric charge is negative one elementary charge. Electrons belong to the first generation of the lepton particle family, are thought to be elementary particles because they have no known components or substructure; the electron has a mass, 1/1836 that of the proton. Quantum mechanical properties of the electron include an intrinsic angular momentum of a half-integer value, expressed in units of the reduced Planck constant, ħ; as it is a fermion, no two electrons can occupy the same quantum state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of both particles and waves: they can collide with other particles and can be diffracted like light; the wave properties of electrons are easier to observe with experiments than those of other particles like neutrons and protons because electrons have a lower mass and hence a longer de Broglie wavelength for a given energy. Electrons play an essential role in numerous physical phenomena, such as electricity, magnetism and thermal conductivity, they participate in gravitational and weak interactions.
Since an electron has charge, it has a surrounding electric field, if that electron is moving relative to an observer, it will generate a magnetic field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law. Electrons absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields. Special telescopes can detect electron plasma in outer space. Electrons are involved in many applications such as electronics, cathode ray tubes, electron microscopes, radiation therapy, gaseous ionization detectors and particle accelerators. Interactions involving electrons with other subatomic particles are of interest in fields such as chemistry and nuclear physics; the Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms.
Ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the main cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of an indivisible quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge'electron' in 1891, J. J. Thomson and his team of British physicists identified it as a particle in 1897. Electrons can participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of radioactive isotopes and in high-energy collisions, for instance when cosmic rays enter the atmosphere; the antiparticle of the electron is called the positron. When an electron collides with a positron, both particles can be annihilated, producing gamma ray photons.
The ancient Greeks noticed. Along with lightning, this phenomenon is one of humanity's earliest recorded experiences with electricity. In his 1600 treatise De Magnete, the English scientist William Gilbert coined the New Latin term electrica, to refer to those substances with property similar to that of amber which attract small objects after being rubbed. Both electric and electricity are derived from the Latin ēlectrum, which came from the Greek word for amber, ἤλεκτρον. In the early 1700s, Francis Hauksbee and French chemist Charles François du Fay independently discovered what they believed were two kinds of frictional electricity—one generated from rubbing glass, the other from rubbing resin. From this, du Fay theorized that electricity consists of two electrical fluids and resinous, that are separated by friction, that neutralize each other when combined. American scientist Ebenezer Kinnersley also independently reached the same conclusion. A decade Benjamin Franklin proposed that electricity was not from different types of electrical fluid, but a single electrical fluid showing an excess or deficit.
He gave them the modern charge nomenclature of negative respectively. Franklin thought of the charge carrier as being positive, but he did not identify which situation was a surplus of the charge carrier, which situation was a deficit. Between 1838 and 1851, British natural philosopher Richard Laming developed the idea that an atom is composed of a core of matter surrounded by subatomic particles that had unit electric charges. Beginning in 1846, German physicist William Weber theorized that electricity was composed of positively and negatively charged fluids, their interaction was governed by the inverse square law. After studying the phenomenon of electrolysis in 1874, Irish physicist George Johnstone Stoney suggested that there existed a "single definite quantity of electricity", the charge of a monovalent ion, he was able to estimate the value of this elementary charge e by means of Faraday's laws of electrolysis. However, Stoney could not be removed. In 1881, German physicist Hermann von Helmholtz argued that both positive and negative charges were divided into elementary parts, each of which "behaves like atoms of electricity".
Stoney coined the term