:''This is a discussion of a present category of science. For the work by
Aristotle, see “
Physics (Aristotle)â€.''
'Physics' (
Greek: '' (''phúsis''), "
nature" and '' (''phusiké''), "knowledge of nature") is the branch of
science concerned with discovering and characterizing universal laws that govern
matter,
energy,
space, and
time. Discoveries in physics resonate throughout the
natural sciences, and physics has been described as the "fundamental science" because other fields such as
chemistry and
biology investigate systems whose properties depend on the laws of physics.
[1]
The development of physics as a
science distinct from
natural philosophy began with the
scientific revolution of the 16th and 17th centuries, and continued through the dawn of
modern physics in the early 20th century. The field has continued to expand, with a growing body of
research leading to discoveries such as the
Standard Model of fundamental particles and a detailed
history of the universe, along with revolutionary new technologies like
nuclear energy and
semiconductors. Research today progresses on a vast array of topics, including high-temperature
superconductivity,
quantum computing, the search for the
Higgs boson, and the
attempt to develop a theory of
quantum gravity. Grounded in observations and
experiments and supported by deep, far-reaching
theories, physics has made a multitude of contributions to
science,
technology, and
philosophy.
Core theories
Although physics encompasses a wide variety of phenomena, all physicists are expected to be familiar with the basic theories of
classical mechanics,
electromagnetism,
thermodynamics,
quantum mechanics, and
relativity. Each of these theories has been tested in numerous experiments and proven to be an accurate model of nature within its domain of validity. For example,
classical mechanics correctly describes the motion of objects in everyday experience, but it breaks down at the atomic scale, where it is superseded by
quantum mechanics, and at speeds approaching the
speed of light, where
relativistic effects become important. While these theories have long been well-understood, they continue to be areas of active research—for example, a remarkable aspect of classical mechanics known as
chaos theory was developed in the 20th century, three centuries after the original formulation of mechanics by Isaac Newton (1642–1727). The basic theories form a foundation for the study and research of more specialized topics. A table of these theories, along with many of the concepts they employ, can be found
here.
Classical mechanics
Main articles: Classical mechanics
Classical mechanics is a model of the physics of
forces acting upon bodies. It is often referred to as "Newtonian mechanics" after Newton and his
laws of motion. Mechanics is subdivided into
statics, which models objects at rest,
kinematics, which models objects in motion, and
dynamics, which models objects subjected to forces. The classical mechanics of continuous and deformable objects is
continuum mechanics, which can itself be broken down into
solid mechanics and
fluid mechanics according to the state of matter being studied. The latter, the mechanics of
liquids and
gases, includes
hydrostatics,
hydrodynamics,
pneumatics,
aerodynamics, and other fields.
Classical mechanics produces very accurate results within the domain of everyday experience. It is superseded by
relativistic mechanics for systems moving at large velocities near the
speed of light,
quantum mechanics for systems at small distance scales, and
relativistic quantum field theory for systems with both properties. Nevertheless, classical mechanics is still very useful, because it is much simpler and easier to apply than these other theories, and it has a very large range of approximate validity. Classical mechanics can be used to describe the motion of human-sized objects (such as tops and baseballs), many astronomical objects (such as planets and galaxies), and certain microscopic objects (such as organic molecules.)
An important concept of mechanics is the identification of conserved
energy and
momentum, which lead to the
Lagrangian and
Hamiltonian reformulations of Newton's laws. Theories such as
fluid mechanics and the
kinetic theory of gases result from applying classical mechanics to macroscopic systems. A relatively recent result of considerations concerning the dynamics of nonlinear systems is
chaos theory, the study of systems in which small changes in a variable may have large effects.
Newton's law of universal gravitation, formulated within classical mechanics, explained
Kepler's laws of planetary motion and helped make classical mechanics an important element of the
Scientific Revolution.
Electromagnetism
Main articles: Electromagnetism
Magnetic lines of force of a bar magnet shown by iron filings on paper
describes the interaction of charged particles with electric and magnetic fields. It can be divided into
electrostatics, the study of interactions between electric
charges at rest, and
electrodynamics, the study of interactions between moving charges and
radiation. The classical theory of electromagnetism is based on the
Lorentz force law and
Maxwell's equations.
Electrostatics is the study of phenomena associated with charged bodies at rest. Such bodies exert forces on each other, as described by
Coulomb’s law, and their behavior can be analyzed in terms of the concept of an
electric field surrounding any charged body such that another charged body located at any point in the field is subject to a
force proportional to the magnitude of its charge and its attraction or repulsion, depending on the
polarity of the charge. Electrostatics has many applications, ranging from the analysis of phenomena such as thunderstorms to the study of the behavior of electron tubes.
Electrodynamics is the study of phenomena associated with
charged bodies in motion and varying
electric and
magnetic fields. Since a moving charge produces a magnetic field, electrodynamics is concerned with effects such as magnetism, electromagnetic
radiation, and
electromagnetic induction, including such practical applications as the
electric generator and the
electric motor. This area of electrodynamics, known as classical electrodynamics, was first systematically explained by
James Clerk Maxwell, and Maxwell’s equations describe the phenomena of this area with great generality. A more recent development is
quantum electrodynamics, which incorporates the laws of
quantum theory in order to explain the interaction of electromagnetic radiation with matter.
Dirac,
Heisenberg, and
Pauli were pioneers in the formulation of quantum electrodynamics. Relativistic electrodynamics accounts for
relativistic corrections to the motions of charged particles when their speeds approach the speed of light. It applies to phenomena involved with
particle accelerators and electron tubes carrying high
voltages and
currents.
Electromagnetism encompasses various real-world electromagnetic
phenomena. For example,
light is an oscillating
electromagnetic field that is radiated from accelerating charged particles. Aside from
gravity, most of the forces in everyday experience are ultimately a result of electromagnetism.
The principles of electromagnetism find applications in various allied disciplines such as
microwaves,
antennas, electric machines,
satellite communications, bioelectromagnetics,
plasmas,
nuclear research,
fiber optics, electromagnetic interference and compatibility, electromechanical energy conversion,
radar meteorology, and
remote sensing. Electromagnetic devices include
transformers, electric
relays,
radio/
TV,
telephones,
electric motors,
transmission lines,
waveguides,
optical fibers, and
lasers.
Thermodynamics and statistical mechanics
Main articles: Thermodynamics
Thermodynamics studies the effects of changes in
temperature,
pressure, and
volume on
physical systems at the
macroscopic scale, and the transfer of energy as
heat.
[ A to Z of Thermodynamics, Perrot, Pierre, , , Oxford University Press, 1998, ISBN 0-19-856552-6 ][2] Historically, thermodynamics developed out of need to increase the
efficiency of early
steam engines.
[3]
The starting point for most thermodynamic considerations are the
laws of thermodynamics, which postulate that
energy can be exchanged between physical systems as heat or
work.
[4] They also postulate the existence of a quantity named
entropy, which can be defined for any system.
[5] In thermodynamics, interactions between large ensembles of objects are studied and categorized. Central to this are the concepts of
system and
surroundings. A system is composed of particles, whose average motions define its properties, which in turn are related to one another through
equations of state. Properties can be combined to express
internal energy and
thermodynamic potentials, which are useful for determining conditions for
equilibrium and
spontaneous processes.
Statistical mechanics analyzes
macroscopic systems by applying
statistical principles to their microscopic constituents. It provides a framework for relating the microscopic properties of individual atoms and molecules to the macroscopic or bulk properties of materials that can be observed in everyday life, therefore explaining
thermodynamics as a natural result of statistics and mechanics (classical and quantum) at the microscopic level. In particular, it can be used to calculate the thermodynamic properties of bulk materials from the spectroscopic data of individual molecules.
Relativity
Main articles: Special relativity,
General relativity
High-precision test of general relativity by the
Cassini space probe (artist's impression):
radio signals sent between the Earth and the probe (green wave) are
delayed by the warpage of
space and time (blue lines).
is a generalization of classical mechanics that describes fast-moving or very massive systems. It includes
special and
general relativity.
The theory of
special relativity was proposed in
1905 by
Albert Einstein in his article "
On the Electrodynamics of Moving Bodies". It is based on
two postulates:
#The mathematical forms of the
laws of physics are invariant in all
inertial systems.
#The
speed of light in a
vacuum is constant and independent of the source or observer.
Reconciling the two postulates requires a unification of
space and
time into the frame-dependent concept of
spacetime.
Special relativity has a variety of surprising consequences that seem to violate common sense, but all have been experimentally verified. It overthrows
Newtonian notions of absolute space and time by stating that distance and
time depend on the observer, and that time and space are perceived differently, depending on the observer. The theory leads to the assertion of change in
mass,
dimension, and
time with increased
velocity. It also yields the equivalence of
matter and
energy, as expressed in the
mass-energy equivalence formula ''E'' = ''mc''², where ''c'' is the speed of light in a vacuum. Special relativity and the
Galilean relativity of Newtonian mechanics agree when velocities are small compared to the speed of light. Special relativity does not describe gravitation; however, it can handle accelerated motion in the absence of gravitation.
[6]
General relativity is the
geometrical theory of
gravitation published by
Albert Einstein in 1915/16.
[ Die Feldgleichungun der Gravitation, , Albert, Einstein, Sitzungsberichte der Preussischen Akademie der Wissenschaften zu Berlin, ][ The Foundation of the General Theory of Relativity, , Albert, Einstein, Annalen der Physik, ] It unifies
special relativity,
Newton's law of universal gravitation, and the insight that gravitation can be described by the
curvature of
space and
time. In general relativity, the curvature of
space-time is produced by the
energy of matter and radiation. General relativity is distinguished from other
metric by its use of the
Einstein field equations to relate space-time content and space-time curvature. Local
Lorentz Invariance requires that the manifolds described in GR be 4-dimensional and Lorentzian instead of
Riemannian. In addition, the principle of
general covariance forces that mathematics be expressed using
tensor calculus.
The first success of general relativity was in explaining the anomalous
perihelion precession of
Mercury. Then in 1919,
Sir Arthur Eddington announced that observations of
stars near the
eclipsed
Sun confirmed general relativity's prediction that massive objects bend
light. Since then, many other
observations and experiments have confirmed many of the
predictions of general relativity, including
gravitational time dilation, the
gravitational redshift of light,
signal delay, and
gravitational radiation. In addition, numerous observations are interpreted as confirming one of general relativity's most mysterious and exotic predictions, the existence of
black holes.
Quantum mechanics
Main articles: Quantum mechanics
Quantum mechanics is the branch of physics treating
atomic and
subatomic systems and their interaction with
radiation in terms of
observable quantities. It is based on the observation that all forms of energy are released in discrete units or bundles called "
quanta". Remarkably, quantum theory typically permits only
probable or
statistical calculation of the observed features of subatomic particles, understood in terms of
wavefunctions. The
Schrödinger equation plays the role in quantum mechanics that
Newton's laws and
conservation of energy serve in classical mechanics -- i.e., it predicts the future behavior of a
dynamic system -- and is a
wave equation in terms of the wavefunction which predicts analytically and precisely the probability of events or outcomes.
According to the older theories of
classical physics, energy is treated solely as a continuous phenomenon, while matter is assumed to occupy a very specific region of space and to move in a continuous manner. According to the quantum theory, energy is held to be emitted and absorbed in tiny, discrete amounts. An individual bundle or packet of energy, called a quantum (pl. quanta), thus behaves in some situations much like particles of matter; particles are found to exhibit certain
wavelike properties when in motion and are no longer viewed as localized in a given region but rather as spread out to some degree. For example, the light or other radiation given off or absorbed by an atom has only certain
frequencies (or
wavelengths), as can be seen from the
line spectrum associated with the chemical element represented by that atom. The quantum theory shows that those frequencies correspond to definite energies of the light quanta, or
photons, and result from the fact that the
electrons of the atom can have only certain allowed energy values, or levels; when an electron changes from one allowed level to another, a quantum of energy is emitted or absorbed whose frequency is directly proportional to the energy difference between the two levels.
The restriction of the energy levels of the electrons is explained in terms of the wavelike properties of their motions: electrons occupy only those orbits for which their associated wave is a
standing wave (i.e., the circumference of the orbit is exactly equal to a whole number of wavelengths) and thus can have only those energies that correspond to such orbits. Moreover, the electrons are no longer thought of as being at a particular point in the orbit but rather as being spread out over the entire orbit. Just as the results of relativity approximate those of Newtonian physics when ordinary speeds are involved, the results of the quantum theory agree with those of classical physics when very large “
quantum numbers†are involved, i.e., on the ordinary large scale of events; this agreement in the classical limit is required by the
correspondence principle of
Niels Bohr. The quantum theory thus proposes a dual nature for both waves and particles (or a "
wave-particle duality"), one aspect predominating in some situations, the other predominating in other situations.
The quantum theory was developed principally over a period of thirty years through the efforts of many scientists. The first contribution was the explanation of
black body radiation in 1900 by
Max Planck, who proposed that the energies of any
harmonic oscillator, such as the atoms of a black body radiator, are restricted to certain values, each of which is an integral (whole number) multiple of a basic, minimum value. The energy E of this basic quantum is directly proportional to the frequency
of the oscillator, or E=h
, where h is a constant, now called
Planck’s constant, having the value 6.625x10
-34 joule-second. In 1905,
Albert Einstein proposed that the radiation itself is also quantized according to this same formula, and he used the new theory to explain the
photoelectric effect. Following the discovery of the nuclear atom by
Rutherford (1911), Bohr used the quantum theory in 1913 to explain both atomic structure and atomic spectra, showing the connection between the electrons’ energy levels and the frequencies of light emitted and absorbed.
Quantum mechanics, the final mathematical formulation of the quantum theory, was developed during the 1920s. In 1924,
Louis de Broglie proposed that not only do light waves sometimes exhibit particle-like properties, as in the photoelectric effect and atomic spectra, but particles may also exhibit wavelike properties. Two different formulations of quantum mechanics were presented following de Broglie’s suggestion. The
wave mechanics of
Erwin Schrödinger (1926) involves the use of a mathematical entity, the wave function, which is related to the probability of finding a particle at a given point in space. The
matrix mechanics of
Werner Heisenberg (1925) makes no mention of wave functions or similar concepts but was shown to be mathematically equivalent to Schrödinger’s theory. A particularly important discovery of the quantum theory is the
uncertainty principle, enunciated by Heisenberg in 1927, which places an absolute theoretical limit on the accuracy of certain measurements; as a result, the assumption by earlier scientists that the physical state of a system could be measured exactly and used to predict future states had to be abandoned. Quantum mechanics was combined with the theory of relativity in the formulation of
P. A. M. Dirac (1928), which, in addition, predicted the existence of
antiparticles. Other developments of the theory include
quantum statistics, presented in one form by Einstein and
S. N. Bose (the
Bose-Einstein statistics) and in another by Dirac and
Enrico Fermi (the
Fermi-Dirac statistics);
quantum electrodynamics, concerned with interactions between charged particles and electromagnetic fields; its generalization,
quantum field theory; and
quantum electronics. The discovery of quantum mechanics in the early 20th century revolutionized physics, and quantum mechanics is fundamental to most areas of current research.
Research
Contemporary research in physics can be broadly divided into
condensed matter physics;
atomic, molecular, and optical physics;
particle physics; and
astrophysics. Since the
twentieth century, the individual fields of physics have become increasingly
specialized, and today most physicists work in a single field for their entire careers. "Universalists" such as
Albert Einstein (
1879–
1955) and
Lev Landau (
1908–
1968), who worked in multiple fields of physics, are now very rare. A table of the major fields of physics, along with their subfields and the theories they employ can be found
here.
Theory and experiment
The culture of physics research differs from most sciences in the separation of
theory and
experiment. Since the
twentieth century, most individual physicists have specialized in either
theoretical physics or
experimental physics. The great
Italian physicist
Enrico Fermi (
1901–
1954), who made fundamental contributions to both theory and experimentation in
nuclear physics, was a notable exception. In contrast, almost all the successful theorists in
biology and
chemistry (e.g. American
quantum chemist and
biochemist Linus Pauling) have also been experimentalists, although this is changing as of late.
Theorists seek to develop
mathematical models that both agree with existing experiments and successfully predict future results, while experimentalists devise and perform experiments to test theoretical predictions and explore new phenomena. Although theory and experiment are developed separately, they are strongly dependent upon each other. Progress in physics frequently comes about when experimentalists make a discovery that existing theories cannot explain, or when new theories generate experimentally testable predictions. Theorists working closely with experimentalists frequently employ
phenomenology.
Theoretical physics is closely related to
mathematics, which provides the language of physical theories, and large areas of mathematics, such as
calculus, have been invented specifically to solve problems in physics.
Theorists may also rely on
numerical analysis and
computer simulations, which play an ever richer role in the formulation of physical models. The fields of
mathematical and
computational physics are active areas of research. Theoretical physics sometimes relates to
philosophy and
metaphysics when it deals with speculative ideas like multidimensional spaces and
parallel universes.
Experimental physics is closely related to
engineering and
technology. Experimental physicists involved in
basic research design and perform experiments with equipment such as
particle accelerators and
lasers, whereas those involved in
applied research often work in industry, developing technologies such as
magnetic resonance imaging (MRI) and
transistors.
Fields
Condensed matter
Main articles: Condensed matter physics
Condensed matter physics is the field of physics that deals with the macroscopic physical properties of
matter. In particular, it is concerned with the "condensed"
phases that appear whenever the number of constituents in a system is extremely large and the interactions between the constituents are strong. The most familiar examples of condensed phases are
solids and
liquids, which arise from the bonding and
electromagnetic force between
atoms. More exotic condensed phases include the
superfluid and the
Bose-Einstein condensate found in certain atomic systems at very low
temperatures, the
superconducting phase exhibited by
conduction electrons in certain materials, and the
ferromagnetic and
antiferromagnetic phases of
spins on
atomic lattices.
Condensed matter physics is by far the largest field of contemporary physics. Much progress has also been made in theoretical condensed matter physics. By one estimate, one third of all American
physicists identify themselves as condensed matter physicists. Historically, condensed matter physics grew out of
solid-state physics, which is now considered one of its main subfields. The term "condensed matter physics" was apparently coined by
Philip Anderson when he renamed his research group - previously "solid-state theory" - in
1967. In
1978, the Division of Solid State Physics at the
American Physical Society was renamed as the Division of Condensed Matter Physics.
[ Division of Condensed Matter Physics Governance History ] Condensed matter physics has a large overlap with
chemistry,
materials science,
nanotechnology and
engineering.
Atomic, molecular, and optical
Main articles: Atomic, molecular, and optical physics
Atomic,
molecular, and
optical physics (AMO) is the study of
matter-matter and
light-matter interactions on the scale of single
atoms or structures containing a few atoms. The three areas are grouped together because of their interrelationships, the similarity of methods used, and the commonality of the
energy scales that are relevant. All three areas include both
classical and
quantum treatments.
Atomic physics studies the
electron hull of
atoms. This branch of physics is distinct from
nuclear physics, despite their association in the public consciousness. Atomic physics is not concerned with the intra-nuclear processes studied in nuclear physics, although properties of the nucleus can be important in atomic physics (e.g.,
hyperfine structure). Current research focuses on activities in quantum control, cooling and trapping of atoms and ions, low-temperature collision dynamics, the collective behavior of atoms in weakly interacting gases (Bose-Einstein Condensates and dilute Fermi degenerate systems), precision measurements of fundamental constants, and the effects of electron correlation on structure and dynamics.
Molecular physics focuses on multi-atomic structures and their internal and external interactions with matter and light.
Optical physics is distinct from
optics in that it tends to focus not on the control of classical light fields by macroscopic objects, but on the fundamental properties of
optical fields and their interactions with matter in the microscopic realm.
High energy
Main articles: Particle physics
Particle physics is the study of
elementary constituents of
matter and
radiation, and the interactions between them. It is also called "high energy physics", because many elementary particles do not occur under normal circumstances in nature, but can be created and detected during energetic
collisions of other particles, as is done in
particle accelerators.
The current state of the classification of elementary particles is the Standard Model. It describes the
strong,
weak, and
electromagnetic fundamental forces, using mediating
gauge bosons. The species of gauge bosons are the
gluons,
W- and W+ and
Z bosons, and the
photon, respectively. The model also contains 24
fundamental particles (12 particle/anti-particle pairs), which are the constituents of
matter. Finally, it predicts the existence of a type of
boson known as the
Higgs boson, which has yet to be discovered.
Astrophysics
Main articles: Astrophysics,
Physical cosmology
Astrophysics is the application of the theories and methods of physics to the study of
stellar structure,
stellar evolution, the origin of the
solar system, and related problems of
cosmology. Because astrophysics is a very broad subject, astrophysicists typically apply many disciplines of physics, including mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum mechanics, relativity, nuclear and particle physics, and atomic and molecular physics. The distinction between astrophysics and modern
astronomy is disappearing in scientific usage.
Astronomy is one of the oldest sciences. Astronomers of early civilizations performed methodical observations of the night sky, and astronomical artifacts have been found from much earlier periods.
Thales, an
Ionian philosopher of the 6th cent. B.C., is credited with introducing geometrical ideas into astronomy. About a hundred years later
Pythagorus imagined the universe as a series of concentric spheres and
Eudoxus introduced the idea of rotating spheres to account for the observed complexities of the planets' motions.
Hipparchus developed
trigonometry and applied it to astronomy and later
Ptolemy created a scheme of epicycles and a
parallax technique. European astronomy lay dormant for fourteen centuries until
Nicolaus Copernicus retained the uniform circular motion of the
Ptolemaic system in
his system, but by placing the sun at the center, he was able to reduce the number of epicycles. The observations of
Tycho Brahe led
Johannes Kepler to the three laws of planetary motion that bear his name (see
Kepler's laws of planetary motion). The invention of the
telescope, which was first applied to astronomy by
Galileo, helped the discipline develop into a modern science, which is today often referred to as astrophysics. Isaac Newton succeeded in uniting the sciences of astronomy and physics. His laws of motion and theory of universal gravitation provided a physical, dynamic basis for the merely descriptive laws of Kepler.
Celestial mechanics, the application of Newtonian gravity and Newton's laws to explain Kepler's laws of planetary motion, was the first unification of astronomy and physics. By the early 19th cent., the science of celestial mechanics had reached a highly developed state at the hands of
Leonhard Euler,
J. L. Lagrange,
P. S. Laplace, and others. Powerful new mathematical techniques allowed solution of most of the remaining problems in classical gravitational theory as applied to the solar system.
At the end of the
19th century, it was discovered that, when decomposing the light from the Sun, a multitude of
spectral lines were observed (regions where there was less or no light), which would go on to revolutionize astronomy. Experiments with hot gases showed that the same lines could be observed in the spectra of gases, specific lines corresponding to unique
chemical elements. In this way it was proved that the chemical elements found in the Sun (chiefly
hydrogen) were also found on Earth. Indeed, the element
helium was first discovered in the spectrum of the Sun and only later on Earth,
hence its name. During the
20th century,
spectroscopy (the study of these spectral lines) advanced, particularly as a result of the advent of
quantum physics that was necessary to understand the astronomical and experimental observations.
[7] Interest shifted from determining the positions and distances of stars to studying their physical composition (see
stellar structure and
stellar evolution).
Physical cosmology is the study of the formation and evolution of the universe on its largest scales. Albert Einstein’s theory of relativity plays a central role in all modern cosmological theories. In the early
20th century,
Hubble's discovery that the universe was expanding, as shown by the
Hubble diagram, prompted rival explanations known as the
steady state universe and the
Big Bang. The Big Bang was confirmed by the success of
Big Bang nucleosynthesis and the discovery of the
cosmic microwave background in 1964. The Big Bang model rests on two theoretical pillars: Albert Einstein's general relativity and the
cosmological principle. Cosmologists have recently established a
precise model of the evolution of the universe, which include
cosmic inflation,
dark energy and
dark matter.
The discovery by
Karl Jansky in 1931 that radio signals were emitted by celestial bodies initiated the science of
radio astronomy. Most recently, the frontiers of astronomy have been expanded by space exploration. Perturbations and interference from the earth’s atmosphere make space-based observations necessary for
infrared,
ultraviolet,
gamma-ray, and
X-ray astronomy. The
Hubble Space Telescope, launched in 1990, has made possible visual observations of a quality far exceeding those of earthbound instruments.
Applied physics
Main articles: Applied physics
Applied physics is physics that is intended for a particular technological or practical use, as for example in
engineering, as opposed to
basic research. Applied physics is rooted in the fundamental truths and basic concepts of the physical sciences, but is concerned with the use of scientific principles in practical devices and systems, and in the application of physics in other areas of science. The approach is similar to that of
applied mathematics. "Applied" is distinguished from "pure" by a subtle combination of factors such as the motivation and attitude of researchers and the nature of the relationship to the technology or science that may be affected by the work.
History
Main articles: History of physics
Notes
1. ''The Feynman Lectures on Physics'' Volume I, Chapter III. Feynman, Leighton and Sands. ISBN 0-201-02115-3 For the philosophical issues of whether other sciences can be "reduced" to physics, see reductionism and special sciences.
2. The Essential Dictionary of Science, Clark, John, O.E., , , Barnes & Noble Books, 2004, ISBN 0-7607-4616-8
3. On the Motive Power of Heat, and on the Laws which can be deduced from it for the Theory of Heat, , Ruldolf, Clausius, Poggendorff's ''Annalen der Physick'', LXXIX (Dover Reprint), 1850, ISBN 0-486-59065-8
4. Understanding Thermodynamics, Van Ness, H.C., , , Dover Publications, Inc., 1969, ISBN 0-486-63277-6
5. Entropy and its Physical Meaning, Dugdale, J.S., , , Taylor and Francis, 1998, ISBN 0-7484-0569-0
6.
See, for example, ''The Relativistic Rocket'', Problem #58, page 141, and its worked answer.
7. Frontiers of Astrophysics: Workshop Summary, H. Falcke, P. L. Biermann
Further reading
★ A large number of textbooks, popular books, and webpages about physics are available for
further reading.
★
Important publications in physics
Organizations
★
AIP.org is the website of the
American Institute of Physics
★
IOP.org is the website of the
Institute of Physics
★
APS.org is the website of the
American Physical Society
★
SPS National is the website of the American
Society of Physics Students
★
CAP.ca is the website of the
Canadian Association of Physicists
★
EPS.org is the website of the
European Physical Society
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