The Origins of Quantum Physics

The so called classical physics in which the main Isaac Newton  (1642-1727)´s ideas are in the center of  an organized set of analytical tools used to explains matter and energy at the macroscopic level, including the behavior of astronomical bodies. It remains the key to measurement for much of modern science and technology; but at the end of the 19th Century observers discovered phenomena in both the large (macro) and the small (micro) worlds that classical physics could not explain Coming to terms with these limitations led to the development of quantum mechanics, a major revolution in physics. Some aspects of quantum mechanics can seem counter-intuitive, because they describe behavior quite different than that seen at larger length scales, where classical physics is an excellent approximation. New concepts are arise so dare in propositions such as the concept of a “ pack unit of light” named “ photon” that  behave in some respects like particles and in other respects like waves. Quantum mechanics predicts the energies, the colours, and the spectral intensities of all forms of electromagnetic radiation and that explains the behavior of matter and its interactions with energy on the scale of atoms and atomic particles as well.
Quantum mechanics ordains that the more closely one pins down one measure (such as the position of a particle), the less precise another measurement pertaining to the same particle (such as its momentum) must become. Put another way, measuring position first and then measuring momentum does not have the same outcome as measuring momentum first and then measuring position; the act of measuring the first property necessarily introduces additional energy into the micro-system being studied, thereby perturbing that system. Even more disconcerting, pairs of particles can be created as "entangled twins." As is described in more detail in the article on Quantum entanglement, entangled particles seem to exhibit what Einstein called "spooky action at a distance," matches between states that classical physics would insist must be random even when distance and the speed of light ensure that no physical causation could account for these correlations.
Quantum physics in a general sense became the branch of science that deals with the evolution of discrete, indivisible units of energy called quanta as described by the Quantum Theory in which five main ideas are in the basis of its methodology:

1. Energy is not continuous, but comes in small but discrete units.
2. The elementary particles behave both like particles and like waves.
3. The movement of these particles is inherently random.
4. It is physically impossible to know both the position and the momentum of a particle at the same time. The more precisely one is known, the less precise the measurement of the other is.
5. The atomic world is nothing like the world we live in.  

Particle/Wave Duality
Particle/wave duality is perhaps the easiest way to get aquatinted with quantum theory because it shows, in a few simple experiments, how different the atomic world is from our world.

The behavior of light in its interaction with matter was indeed a key problem of 19^th century physics. Max Planck (1848 – 1047) was interested in the two theories that overlapped in this domain. The first was the electrodynamics, the theory of electricity, magnetism, and light waves, brought to final form by James Clerk Maxwell (1831 – 1879) in the 1870s.

The second, dating from roughly the same period, was thermodynamics and statistical mechanics, governing transformations of energy and its behavior in time. A pressing question was whether these two grand theories could be fused into one, since they started from different fundamental notions.

Beginning in the mid-1890s, Planck took up a seemingly narrow problem, the interaction of an oscillating charge with its electromagnetic field. These studies, however, brought him into contact with a long tradition of work on the emission of light. As a practical result of the related developments, Planck made a very remarkable discovery: the law of radiation of bodies as a function of temperature could not be derived solely from the Laws of Maxwellian electrodynamics. To arrive at results consistent with the relevant experiments, radiation of a given frequency f had to be treated as though it consisted of energy atoms (photons) of the individual energy hf, where h is Planck's universal constant. This concept turned to be the beginning of a quantum revolution that continues to unfurl its veil today.

REFERENCES:

1.      Wikipedia (2012) ; Introduction to quantum mechanics ; http://en.wikipedia.org/wiki/Introduction_to_quantum_mechanics

2.      Think Quest (2012) ; http://library.thinkquest.org/3487/qp.html

3.      Carson, Cathyrin (2000) ; The origins of quantum theory ; http://www.slac.stanford.edu/pubs/beamline/30/2/30-2-carson.pdf

4.      The Quantum Theory of Albert Einstein (2012) ; http://www.spaceandmotion.com/quantum-theory-albert-einstein-quotes.htm

5.       The Solvay Congress of 1927´s photo source : American Institute of Physics  http://www.aip.org/history/einstein/quantum1.htm