Mechanics Quantum

Quantum
The following are categorized as being part of quantum mechanics:
Schrödinger wave mechanics, used to describe the movements of the wavefunction of a

single particle.
Matrix mechanics is an alternative formulation that allows considering systems with
a finite-dimensional state space.
Quantum statistical mechanics generalizes ordinary quantum mechanics to consider
systems in an unknown state; often used to derive thermodynamic properties.
Particle physics, the motion, structure, and reactions of particles
Nuclear physics, the motion, structure, and reactions of nuclei
Condensed matter physics, quantum gases, solids, liquids, etc.
Historically, classical mechanics had been around for nearly a quarter millennium
before quantum mechanics developed. Classical mechanics originated with Isaac
Newton's laws of motion in Philosophiæ Naturalis Principia Mathematica, developed
over the seventeenth century. Quantum mechanics developed later, over the
nineteenth century, precipitated by Planck's postulate and Albert Einstein's
explanation of the photoelectric effect. Both fields are commonly held to
constitute the most certain knowledge that exists about physical nature.
Classical mechanics has especially often been viewed as a model for other so-called
exact sciences. Essential in this respect is the extensive use of mathematics in
theories, as well as the decisive role played by experiment in generating and
testing them.
Quantum mechanics is of a bigger scope, as it encompasses classical mechanics as a

sub-discipline which applies under certain restricted circumstances. According to
the correspondence principle, there is no contradiction or conflict between the two
subjects, each simply pertains to specific situations. The correspondence principle
states that the behavior of systems described by quantum theories reproduces
classical physics in the limit of large quantum numbers, i.e. if quantum mechanics
is applied to large systems (for e.g. a baseball), the result would almost be the
same if classical mechanics had been applied. Quantum mechanics has superseded
classical mechanics at the foundation level and is indispensable for the
explanation and prediction of processes at the molecular, atomic, and sub-atomic
level. However, for macroscopic processes classical mechanics is able to solve
problems which are unmanageably difficult (mainly due to computational limits) in
quantum mechanics and hence remains useful and well used. Modern descriptions of
such behavior begin with a careful definition of such quantities as displacement
(distance moved), time, velocity, acceleration, mass, and force. Until about 400
years ago, however, motion was explained from a very different point of view. For
example, following the ideas of Greek philosopher and scientist Aristotle,
scientists reasoned that a cannonball falls down because its natural position is in
the Earth; the sun, the moon, and the stars travel in circles around the earth
because it is the nature of heavenly objects to travel in perfect circles.
Often cited as father to modern science, Galileo brought together the ideas of
other great thinkers of his time and began to calculate motion in terms of distance
travelled from some starting position and the time that it took. He showed that the
speed of falling objects increases steadily during the time of their fall. This
acceleration is the same for heavy objects as for light ones, provided air friction
(air resistance) is discounted. The English mathematician and physicist Isaac
Newton improved this analysis by defining force and mass and relating these to
acceleration. For objects traveling at speeds close to the speed of light, Newton's
laws were superseded by Albert Einstein's theory of relativity. [A sentence
illustrating the computational complication of Einstein's theory of relativity.]
For atomic and subatomic particles, Newton's laws were superseded by quantum
theory. For everyday phenomena, however, Newton's three laws of motion remain the
cornerstone of dynamics, which is the study of what causes motion.

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Quantum

The following are categorized as being part of quantum mechanics:

Schrödinger wave mechanics, used to describe the movements of the wavefunction of a

Quantum mechanics is of a bigger scope, as it encompasses classical mechanics as a

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