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Quantum Physics

Mystery of the atomic structure

 Automatic translation  Automatic translation Updated June 01, 2013

In the fourth century BC, the Greek philosophers Leucippus and Democritus hypothesized that all matter consists of tiny particles in constant motion, very strong and eternal, called 'atomos' (indivisible).
In 1811, Amedeo Avogadro estimated the size of atoms, to 10-10 m.
In 1911, Ernest Rutherford specifies the structure of the atom and gives the atomic nucleus size of about 10-14 meters.
In classical physics the atoms consist of a number of negatively charged electrons spot and a point-like nucleus, positively charged, but it raises a paradox. In classical physics, the field should disappear, because annihilate an electron that radiates around a nucleus loses energy (Maxwell's theory) and therefore should fall on the core.
This means that the stability of an atom is incomprehensible in the context of the classical theory. By cons, quantum physics explains the mystery of the atom and the stability of matter. Quantum physics has appeared between 1925 and 1927, derived from quantum mechanics initiated by Max Planck in 1900, then developed by Albert Einstein, Niels Bohr, Arnold Sommerfeld, Hendrik Anthony Kramers, Werner Heisenberg, Wolfgang Pauli and Louis de Broglie between 1905 and 1924. This conceptual revolution in science and explains the existence of matter, is the basis of our physical understanding of the world.


Quantum theory is a theory by definition non-deterministic, meaning that even if we know all the parameters at the start, there are phenomena that we can not predict.
This uncertainty and indeterminacy that are intrinsic to the theory. In addition to the uncertainty in the locality, quantum mechanics tolerate the existence of entangled states, i.e. at the quantum level more spatially separated objects can form a single quantum object, which react globally. In summary, in the quantum world objects can be both here and there, in a state or more.
Now that we have direct access to the world of atoms, it is possible to verify these paradoxical properties of the quantum world.
We can determine the state of a quantum system in observing, which has the effect of destroying the state in question.
Quantum mechanics explains the existence of matter, is for scientists, the greatest intellectual adventure of the 20th century.

NB: Maxwell's theory says that any accelerated charge radiates energy in the form of electromagnetic wave. The accelerated electrons on their orbits within the atom, should lose energy and fall onto the core characteristic of a period of about 10 ns.


Image: 10-14 meter or 10 fermi, is the distance at which you can see the nucleus of an atom. In the late nineteenth century, it was discovered that the atom is not an element of matter indivisible. The proton is a nucleon, as the neutron, which enters the composition of matter which we have made a representation.

Light and photon


For French René Descartes (1596-1650), was composed of light particles.
The light wave was introduced in 1690 by the Dutch Christian Huygens (1629-1695), who had the intuition that the light was spreading like waves in a medium he called the ether.
English Isaac Newton (1643-1727) believed that light was composed of particles and the early 19th century, French Augustin Fresnel (1788-1827), the origin of modern optics, offers an explanation for all optical phenomena in the context of the wave theory of light.
During the 19th century we accept that light is a wave phenomenon as a result of successful experiences.
At the end of the 19th, the Scot James Clerk Maxwell (1831-1879) in a single set of equations, Maxwell's equations, unifies the phenomena of light, electricity, magnetism and induction.
It was during the more unified model of electromagnetism.
Maxwell's equations describe the light wave fully, but they always propagate in a medium called ether.


Max Planck explains that light and matter exchange energy in the form of discrete quanta of energy (E = hv).
At the end of the 19th century, two physicists, Albert Abraham Michelson (1852-1931) and Edward Williams Morley (1838-1923) sought to determine the flow of the ether by measuring the speed of light between two directions perpendicular to two distinct periods of the year.
They expected to measure variations in the speed but the result was surprising, all rays of light had the same speed. In 1905, Albert Einstein found that there is an inconsistency between Maxwell's equations and assumptions Planck. We had small grains (particles) of light to the assumptions of Planck are correct. The concept of photon grains was hardly accepted by all physicists until the American Robert Andrews Millikan (1868-1953) provides compelling experimental evidence in 1915, in perfect agreement with the description of particle proposed by Einstein.
These wave-like corpuscles, will find an explanation in quantum physics to come.

 annular eclipse or ring of fire

Image: The grains of light from our sun. These grains are called photons. The light has a wave-particle duality, Louis de Broglie proposed to generalize this duality to all known particles.

The wave nature of the electron


In 1925, the French mathematician and physicist Louis de Broglie (1892-1987), wonders if we can not from a particle to obtain a wave phenomenon. He was awarded the Nobel Prize in Physics 1929 "for his theory on the wave nature of electrons".
This theoretical thesis was later confirmed in 1927 by two American experimenters Clinton Davisson and Lester Germer.
In 1925 it was all wave and particle at a time and that troubled the physicists who two years later explain these phenomena through quantum physics. The photon has no mass is a quantum object, like all massive particles that constitute matter.


Image: Illustration of the electron.
The electron does not have a precise location. It appears and disappears continuously in a vacuum, in a vague sort of timeless, both a little here and a little there.

 electron wave or particle

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