study of matter and its motion through space and time, along with related concepts such as
energy and force. More broadly, and conflating with science as a whole, it is the general
analysis of nature, conducted in order to understand how the universe behaves.
Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of
astronomy. Over the last two millennia, physics was a part of natural philosophy along with
chemistry, certain branches of mathematics, and biology, but during the scientific revolution
in the 17th century, the natural sciences emerged as unique research programs in their own
right. Physics intersects with many interdisciplinary areas of research, such as biophysics and
quantum chemistry, and the boundaries of physics are not rigidly defined. New ideas in
physics often explain the fundamental mechanisms of other sciences while opening new
avenues of research in areas such as mathematics and philosophy.
Physics also makes significant contributions through advances in new technologies that arise
from theoretical breakthroughs. For example, advances in the understanding of
electromagnetism or nuclear physics led directly to the development of new products that
have dramatically transformed modern-day society, such as television, computers, domestic
appliances, and nuclear weapons; advances in thermodynamics led to the development of
industrialization, and advances in mechanics inspired the development of calculus.
History
Ancient astronomy
Ancient Egyptian astronomy is evident in monuments like the ceiling of Senemut's tomb from
the Eighteenth Dynasty of Egypt.
Astronomy is the oldest of the natural sciences. The earliest civilizations dating back to
beyond 3000 BCE, such as the Sumerians, ancient Egyptians, and the Indus Valley
Civilization, all had a predictive knowledge and a basic understanding of the motions of the
Sun, Moon, and stars. The stars and planets were often a target of worship, believed to
represent their gods. While the explanations for these phenomena were often unscientific and
lacking in evidence, these early observations laid the foundation for later astronomy.According to Asger Aaboe, the origins of Western astronomy can be found in Mesopotamia,
and all Western efforts in the exact sciences are descended from late Babylonian astronomy.
Egyptian astronomers left monuments showing knowledge of the constellations and the
motions of the celestial bodies, while Greek poet Homer wrote of various celestial objects in
his Iliad and Odyssey; later Greek astronomers provided names, which are still used today, for
most constellations visible from the northern hemisphere.
Classical physics
Sir Isaac Newton (1643–1727), whose laws of motion and universal gravitation were major
milestones in classical physics
Physics became a separate science when early modern Europeans used experimental and
quantitative methods to discover what are now considered to be the laws of physics.
Major developments in this period include the replacement of the geocentric model of the
solar system with the helio-centric Copernican model, the laws governing the motion of
planetary bodies determined by Johannes Kepler between 1609 and 1619, pioneering work on
telescopes and observational astronomy by Galileo Galilei in the 16th and 17th Centuries, and
Isaac Newton's discovery and unification of the laws of motion and universal gravitation that
would come to bear his name. Newton also developed calculus, the mathematical study of
change, which provided new mathematical methods for solving physical problems.
The discovery of new laws in thermodynamics, chemistry, and electromagnetics resulted from
greater research efforts during the Industrial Revolution as energy needs increased. The laws
comprising classical physics remain very widely used for objects on everyday scales
travelling at non-relativistic speeds, since they provide a very close approximation in such
situations, and theories such as quantum mechanics and the theory of relativity simplify to
their classical equivalents at such scales. However, inaccuracies in classical mechanics for
very small objects and very high velocities led to the development of modern physics in the
20th century.
Modern physics
Albert Einstein (1879–1955), whose work on the photoelectric effect and the theory of
relativity led to a revolution in 20th century physics
Max Planck (1858–1947), the originator of the theory of quantum mechanics
Modern physics began in the early 20th century with the work of Max Planck in quantum
theory and Albert Einstein's theory of relativity. Both of these theories came about due to
inaccuracies in classical mechanics in certain situations. Classical mechanics predicted a
varying speed of light, which could not be resolved with the constant speed predicted by
Maxwell's equations of electromagnetism; this discrepancy was corrected by Einstein's theory
of special relativity, which replaced classical mechanics for fast-moving bodies and allowed
for a constant speed of light. Black body radiation provided another problem for classical
physics, which was corrected when Planck proposed that light comes in individual packets
known as photons; this, along with the photoelectric effect and a complete theory predicting
discrete energy levels of electron orbitals, led to the theory of quantum mechanics taking over
from classical physics at very small scales.
Quantum mechanics would come to be pioneered by Werner Heisenberg, Erwin Schrödinger
and Paul Dirac. From this early work, and work in related fields, the Standard Model of
particle physics was derived. Following the discovery of a particle with properties consistent
with the Higgs boson at CERN in 2012, all fundamental particles predicted by the standard
model, and no others, appear to exist; however, physics beyond the Standard Model, with
theories such as supersymmetry, is an active area of research.
Application and influencerelativity led to a revolution in 20th century physics
Max Planck (1858–1947), the originator of the theory of quantum mechanics
Modern physics began in the early 20th century with the work of Max Planck in quantum
theory and Albert Einstein's theory of relativity. Both of these theories came about due to
inaccuracies in classical mechanics in certain situations. Classical mechanics predicted a
varying speed of light, which could not be resolved with the constant speed predicted by
Maxwell's equations of electromagnetism; this discrepancy was corrected by Einstein's theory
of special relativity, which replaced classical mechanics for fast-moving bodies and allowed
for a constant speed of light. Black body radiation provided another problem for classical
physics, which was corrected when Planck proposed that light comes in individual packets
known as photons; this, along with the photoelectric effect and a complete theory predicting
discrete energy levels of electron orbitals, led to the theory of quantum mechanics taking over
from classical physics at very small scales.
Quantum mechanics would come to be pioneered by Werner Heisenberg, Erwin Schrödinger
and Paul Dirac. From this early work, and work in related fields, the Standard Model of
particle physics was derived. Following the discovery of a particle with properties consistent
with the Higgs boson at CERN in 2012, all fundamental particles predicted by the standard
model, and no others, appear to exist; however, physics beyond the Standard Model, with
theories such as supersymmetry, is an active area of research.
Applied physics
Archimedes' screw, a simple machine for lifting
The application of physical laws in lifting liquids
Applied physics is a general term for physics research which is intended for a particular use.An applied physics curriculum usually contains a few classes in an applied discipline, like
geology or electrical engineering. It usually differs from engineering in that an applied
physicist may not be designing something in particular, but rather is using physics or
conducting physics research with the aim of developing new technologies or solving a
problem.
The approach is similar to that of applied mathematics. Applied physicists can also beinterested in the use of physics for scientific research. For instance, people working on
accelerator physics might seek to build better particle detectors for research in theoretical
physics.
Physics is used heavily in engineering. For example, statics, a subfield of mechanics, is used
in the building of bridges and other static structures. The understanding and use of acoustics
results in sound control and better concert halls; similarly, the use of optics creates better
optical devices. An understanding of physics makes for more realistic flight simulators, video
games, and movies, and is often critical in forensic investigations.
With the standard consensus that the laws of physics are universal and do not change with
time, physics can be used to study things that would ordinarily be mired in uncertainty. For
example, in the study of the origin of the earth, one can reasonably model earth's mass,
temperature, and rate of rotation, as a function of time allowing one to extrapolate forward
and backward in time and so predict prior and future conditions. It also allows for simulations
in engineering which drastically speed up the development of a new technology.
But there is also considerable interdisciplinarity in the physicist's methods, so many other
important fields are influenced by physics (e.g., the fields of econophysics and sociophysics).
Research
Scientific method
Physicists use the scientific method to test the validity of a physical theory, using a
methodical approach to compare the implications of the theory in question with the associated
conclusions drawn from experiments and observations conducted to test it. Experiments and
observations are collected and compared with the predictions and hypotheses made by a
theory, thus aiding in the determination or the validity/invalidity of the theory.
A scientific law is a concise verbal or mathematical statement of a relation which expresses a
fundamental principle of some theory, such as Newton's law of universal gravitation.
Theoretical physics and Experimental physics
The astronaut and Earth are both in free-fall
Lightning is an electric current
Theorists seek to develop mathematical models that both agree with existing experiments and
successfully predict future experimental 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, which
inspire new experiments.
Research fields
Contemporary research in physics can be broadly divided into condensed matter physics;
atomic, molecular, and optical physics; particle physics; astrophysics; geophysics and
biophysics. Some physics departments also support physics education research and physics
outreach.
Since the 20th 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.
atomic, molecular, and optical physics; particle physics; astrophysics; geophysics and
biophysics. Some physics departments also support physics education research and physics
outreach.
Since the 20th 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.
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