THE PIONEERS OF PHYSICS

FROM ARCHIMEDES TO CARLO RUBBIA

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Webmaster & Author: Antonino Cucinotta
Graduate in Physics
Copyright 2002 - All rights reserved


ARCHIMEDES

GALILEO GALILEI

ISAAC NEWTON

ALESSANDRO VOLTA

MICHAEL FARADAY

ANDRE'-MARIE AMPERE

GEORG SIMON OHM

GUSTAV ROBERT KIRCHHOFF

JAMES CLERK MAXWELL

WILLIAM THOMSON (LORD KELVIN)

HEINRICH RUDOLPH HERTZ

WIHLELM CONRAD ROENTGEN

ANTOINE HENRI BECQUEREL

PIERRE CURIE

MARIE SKLODOWSKA CURIE

MAX PLANCK

ALBERT EINSTEIN

LORD ERNEST RUTHERFORD

NIELS BOHR

LOUIS-VICTOR PIERRE RAYMOND DE BROGLIE

WERNER HEISENBERG

ERWIN SCHROEDINGER

PAUL ANDRIEN MAURICE DIRAC

ENRICO FERMI

WOLFGANG PAULI

EUGENE PAUL WIGNER

SIN-ITIRO TOMONAGA

JULIEN SCHWINGER

RICHARD FEYNMAN

MURRAY GELL-MANN

SHELDON LEE GLASHOW

ALVIN WEINBERG

ABDUS SALAM

CARLO RUBBIA

SIMON VAN DER MEER

LORD ERNEST RUTHERFORD

English physicist ( 1871-1937 ).

Are fundamental his researches on the radioactive phenomena, effected from 1897 to 1907 together with J.J. Thomson and F.Soddy, to determine the laws of a and b decay of the radioelements of the three natural families (the ones of uranium-radium, of thorium and of   actinium).
In each series the founder, that is the element with the most long mean life ( some billions of years ), decaying is transforming into the following radioelement, and so away across all the consecutive unstable elements, until is produced a stable element (an isotope of  lead ).
His principal discovery concerns the atomic nucleus.
In 1911 Rutherford, after two years of researches together with Geiger and Marsden, bombarding some thin gold layers with a particles and studying the angular distribution of the a particles that were scattered in all the directions, realized the impossibility to accept the atomic model proposed in 1902 by J.J. Thomson, who supposed the electrons are dispersed in a sphere with a positive electric charge uniformly distributed and equal to the negative one of electrons, in such a mode that were kept electric neutrality.
The experimental data were instead compatible with the existence of a nucleous with a positive electric charge and containing nearly whole the mass of an atom, since the events relating to the scattering of  particles at great angles or, although with a small frequency, backwards, were only compatible with a massive nucleus having a positive electric charge .
Rutherford enunciated therefore the discovery of the atomic nucleus, giving a decisive impulse to the development of atomic physics.
It is owing besides to Rutherford to have produced the first artificial nuclear reaction.
In fact, in 1919, bombarding with a particle  a target containing nitrogen, he got as reaction products an isotope of the oxygen and hydrogen nuclei (protons), of which he could measure kinetic energy. In 1908 he was conferred the Nobel prize for the chemistry.

NIELS BOHR

Danish physicist ( 1885-1951 ).

He was a pupil of J.J. Thomson and Rutherford.
In 1913 he elaborated the first theory of the atomic structure, founding on Rutherford's atomic model and applying to the most simple atom, the one of hydrogen, the laws of classical mechanics and some postulations that held account of the quantization of energy and angular momentum of the only electron orbiting about the nucleus (a proton), positively charged.
The atomic model that was builded up, which is known as Bohr-Rutherford's model, allowed to develope an elementary atomic theory, that represented the first important step toward the construction of atomic physics.
He founded the Copenaghen physics school, in which are formed in  '20 years the most illustrious exponents of the European atomic physics.
In nuclear physics he introduced the drop model of the atomic nucleus, which had a fundamental importance for studying the fission of  uranium and the one of plutonium by slow neutrons.
He was given the Nobel prize in 1922.

LOUIS-RAYMOND PIERRE VICTOR DE BROGLIE

French physicist (1892- 1987).

His hypothesis ( 1924 ) of the wave-like behaviour of elementary particles, that gave impulse to the creation of Schroedinger's quantum mechanics (that is even known as wave mechanics), was suggested by analogy with Einstein's wave-particle-like dualism (the theory of photons, 1905 ),introduced to explain the photoelectric effect.
De Broglie thought that, by analogy with electromagnetic radiation, that in the interaction with the bodies of microcosm ( atoms and particles), shows particle-like properties, because photons ( packets of electromagnetic energy) are involved as if they were really material particles, so even for bodies of microcosm it was possible to evidence
wave-like properties, and that therefore to any particle having a linear momentum MV, had to be associated a probability wave with the length l = h/( MV ), where h is universal Planck's constant that characterizes the physical phenomena of microcosm.
De Broglie's hypothesis was verified experimentally (1927 ) by Davisson and Thomson, that showed by means of diffraction experiments the wave-like properties  of electrons, getting some photos of diffraction rings much similar to the ones produced by Laue and Bragg, in the first tens years of XX century,by X-rays, that  are electromagnetic waves.
He was conferred the Nobel prize in 1929.

WERNER HEISENBERG

German physicist ( 1901-1976 ).

After the degree was a Bohr's student at the Copenhagen school.
In 1925, independently from Schroedinger, created quantum mechanics, introducing the matrix formalism.
It is famous his uncertainty principle, enunciated in 1927 as a fundamental postulate for studying the physical phenomena of  microcosm.
He was one of the founders of quantum electrodynamics.
Are fundamental his researches in the quantum field theory and in the physics of elementary particles.
He was conferred the Nobel prize in 1932.

ERWIN SCHROEDINGER

Austrian physicist ( 1887-1961 ).

In 1925, independently from Heisenberg, he created quantum mechanics, introducing as a fundamental equation his wave equation, whose solution is the wave function.
Schroedinger's equation,that is even said the probability wave equation, describing an atom as a probability cloud, allows to calculate the probability to find electron in a point of assigned coordinates referred to nucleus.
In 1933 he was conferred the Nobel prize together with P.A.M. Dirac.

PAUL ANDRIEN MAURICES DIRAC

English physicist ( 1902-1984 ).

After the publication of Heisenberg and Schroedinger's works, he furnished in 1928 a relativistic version of the wave equation, that produced several fundamental results in the physics of elementary particles with spin 1/2 ( electron, muon, neutrino, proton ), since it implicates the existence of antiparticles ( positron, antimuon, antineutrino, antiproton ).
Positron was discovered in 1932 by Anderson in the particle showers of cosmic radiation.
The relativistic wave equation is fundamental for the development of quantum electrodynamics, of which Dirac is considered one of the founders.
He was conferred the Nobel prize in 1933 together with Schroedinger.

ENRICO FERMI

Italian physicist ( 1901-1954 ).

He is an extraordinary example of both theoretical and experimental physicist .
He effected researches of fundamental importance in all the sectors of physics, bringing contributions whose ingeniousness is recognized by  the whole international science community.
After having worked with some of the most illustrious physicists of the XX century, at Gottinga and Leyden, and having been appointed  academician of Italy when he was only 27 years old, from 1923 to 1938, the year when he emigrated in the U.S.A., he brought fundamental contributions to the quantum statistics of elementary particles with a half-odd spin, denominated fermions in honor of him,to the theory of weak forces (1934 ), known even as Fermi's forces, that determine the b decay, and to production of many artificial radioactive isotopes by bombardment of atomic nuclei by slow neutrons.
His researches about neutrons, effected at the Rome university
(1934-1938 ), were the starting point for the discovery of nuclear fission of uranium by Hahn and Strassman ( 1939 ).
In U.S.A. he realized and tested ( 1942 ), within the Manhattan project, the first nuclear reactor (the so-called atomic pile), on which was based the realization of the first nuclear bomb.
In the post-war period, passed initially at the university of Chicago, he devoted himself primarily to some researches in high energy physics, studying cosmic radiation and using the first particle accelerators,derived  from the Lawrence cyclotron, for the study of collisions of pions against nucleons, with the aid of the first electronic computers.
In 1938 he was conferred the Nobel prize for his researches on  neutrons.

WOLFGANG PAULI

Austrian physicist( 1900-1958 ).

His most important discovery is the exclusion principle (1925).
In 1925, following the creation of quantum mechanics by Heisenberg and Schroedinger, he studied atomic structure as it was described by the new mechanics, realizing that, to be able to represent the energetic levels of atoms coherently with the experimental data furnished by  optical and X-ray atomic spectra , it was needful to admit that two atomic electrons cannot be in the same quantum state, individuated by four quantum numbers: one connected with energy, two with orbital angular momentum and the remainder with the intrinsic angular momentum (spin).
As a particular case, if two electrons have three quantum numbers equals each other, their spins must be oriented in opposite directions.
His principle, that is a law of nature which must be applied to all the elementary particles with an half-odd spin, is fundamental to explain not only the atomic structure of chemical elements, but even the behaviour of any quantum system, whose particles (fermions) obey to the Fermi-Dirac's statistics.
It is needful in fact to explain the electric conductibility of metals.
His ingeniousness as a theoretical physicist, permitted him to foresee in 1931 the existence of neutrino,a particle with no mass neither electric charge, and to explain the apparent violation of the energy conservation principle,that was  evidenced measuring the strange energetic distribution of electrons in b decay phenomena.
Starting from his hypothesis of existence of neutrino, Enrico Fermi built his theory of weak forces ( 1934 ).
Neutrinos, difficult to be detected because of  their zero charge and their zero mass,that currently, according to the most recent researches, it is thought to be very small, are able to cross the whole Earth without interact, and have a fundamental role in the controlling the speed of  reactions of thermonuclear fusion that happen in the Sun and in all the other stars.
Neutrino has been observed for the first time by Cowan and Reines, in  1956, studying the weak interactions induced  by neutrinos produced in nuclear reactors as a consequence of the radioactive decay of fission fragments.
Pauli, which is considered one of the founders of the quantum electrodynamics, was given the Nobel prize in 1945.

EUGENE PAUL WIGNER

Native Hungarian U.S.A. physicist ( 1902-1995 )

He is considered, after Enrico Fermi, one of the most illustrious nuclear physicists.
Toward the end of the '30 years he studied the application of  quantum mechanics to the atomic nucleus, discovering fundamental theorems concerning any space-time symmetries of nuclear forces, that can be applied even to other sectors of physics, as the physics of elementary particles.
The theorem of the temporal invariance establishes that physical phenomena of   microcosm are evolving in the same way when time is reversed.
That is the temporal reversibility at a microscopic level, that is applicable to only three of four universal interactions.
In the particular case of electromagnetic interactions, the validity of  Wigner's theorem has been verified experimentally ( 1964 ) by the physicist Antonino Zichichi.
The contributions of Wigner to study of nuclear structure have a fundamental importance.
He worked actively with Enrico Fermi within the Manhattan project for the construction of the first nuclear bomb.
In 1963 he was conferred the Nobel prize together with Maria Goeppert-Mayer and Hans J D. Jensen.

SIN ITIRO TOMONAGA

( Japanese physicist, 1906-1979 )

JULIEN SCHWINGER

( U.S.A. physicist, 1918-1994 )

RICHARD FEYNMAN

( U.S.A. physicist, 1918-1988)

Their researches concerned the improvement of quantum electrodynamics, introduced in the last twenties by Dirac, Heisenberg and Pauli, that applied the principles of quantum mechanics to the interactions between charged elementary particles and the electromagnetic field.
The original theory introduced several drawbacks deriving from not having considered the interactions of charged particles (electrons, positrons, muons, protons, etc...) with all the virtual particle-antiparticle pairs that characterize the vacuum state of   quantum fields (the so-called polarization of vacuum).
Because of such a motive the calculations gave infinite contributions, that weren't   acceptable physically.
Tomonaga, Schwinger and Feynman elaborated, independently each from the others, some particular methods of renormalization, so that quantum electrodynamics became one of the most accurate theories that never have been developed.
The results of his theory were brightly confirmed by experimental data (the discovery in 1947 of Lamb's shift for the spectral line of the hydrogen atom), connected with virtual physics, that describes the fluctuations of the vacuum state of quantum fields.
The calculation methods used to improve Q.E.D. (Quantum-Electro-Dynamics ) have been subsequently used in the standard model, in the electro-weak theory (the unified theory of   electromagnetic and weak forces ), and in the quantum chromodynamics ( Q.C.D.- Quantum-Chromo- Dynamics ), that studies the strong interactions among quarks, inside hadrons.
They were conferred the Nobel prize in 1965.

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