# Physics: Wikis

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Physics
$E = m c^2\,$
Mass–energy equivalence
History of physics

Physics (Greek: physis – φύσις meaning "nature") is a natural science that involves the study of matter[1] and its motion through spacetime, as well as all applicable concepts, such as energy and force.[2] More broadly, it is the general analysis of nature, conducted in order to understand how the world and universe behave.[3][4][5]

Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of astronomy.[6] Over the last two millennia, physics had been considered synonymous with philosophy, chemistry, and certain branches of mathematics and biology, but during the Scientific Revolution in the 16th century, it emerged to become a unique modern science in its own right.[7] However, in some subject areas such as in mathematical physics and quantum chemistry, the boundaries of physics remain difficult to distinguish.

Physics is both significant and influential, in part because advances in its understanding have often translated into new technologies, but also because new ideas in physics often resonate with the other sciences, mathematics and philosophy. For example, advances in the understanding of electromagnetism or nuclear physics led directly to the development of new products which have dramatically transformed modern-day society (e.g., television, computers, domestic appliances, and nuclear weapons); advances in thermodynamics led to the development of motorized transport; and advances in mechanics inspired the development of calculus.

## Scope and aims

This parabola-shaped lava flow illustrates Galileo's law of falling bodies as well as blackbody radiation – the temperature is discernible from the color of the blackbody.

Physics covers a wide range of phenomena, from the smallest sub-atomic particles (such as quarks, neutrinos and electrons), to the largest galaxies. Included in these phenomena are the most basic objects from which all other things are composed, and therefore physics is sometimes called the "fundamental science".[8]

Physics aims to describe the various phenomena that occur in nature in terms of simpler phenomena. Thus, physics aims to both connect the things we see around us to root causes, and then to try to connect these causes together in the hope of finding an ultimate reason for why nature is as it is. For example, the ancient Chinese observed that certain rocks (lodestone) were attracted to one another by some invisible force. This effect was later called magnetism, and was first rigorously studied in the 17th century.

A little earlier than the Chinese, the ancient Greeks knew of other objects such as amber, that when rubbed with fur would cause a similar invisible attraction between the two. This was also first studied rigorously in the 17th century, and came to be called electricity. Thus, physics had come to understand two observations of nature in terms of some root cause (electricity and magnetism). However, further work in the 19th century revealed that these two forces were just two different aspects of one force – electromagnetism. This process of "unifying" forces continues today (see section Current research for more information).

## The scientific method

Physics uses 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 to be collected and matched with the predictions and hypotheses made by a theory, thus aiding in the determination or the validity/invalidity of the theory.

Theories which are very well supported by data and have never failed any competent empirical test are often called scientific laws, or natural laws. Of course, all theories, including those called scientific laws, can always be replaced by more accurate, generalized statements if a disagreement of theory with observed data is ever found.[9]

## Theory and experiment

The astronaut and Earth are both in free-fall

The culture of physics has a higher degree of separation between theory and experiment than many other sciences. Since the twentieth century, most individual physicists have specialized in either theoretical physics or experimental physics. 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, which inspire new experiments.

It is also worth noting there are some physicists who work at the interplay of theory and experiment who are called phenomenologists. Phenomenologists look at the complex phenomena observed in experiment and work to relate them to fundamental theory.

Theoretical physics has historically taken inspiration from philosophy and metaphysics; electromagnetism was unified this way.[10] Beyond the known universe, the field of theoretical physics also deals with hypothetical issues,[11] such as parallel universes, a multiverse, and higher dimensions. Theorists invoke these ideas in hopes of solving particular problems with existing theories. They then explore the consequences of these ideas and work toward making testable predictions.

Experimental physics informs, and is informed by, 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. Feynman has noted that experimentalists may seek areas which are not well explored by theorists.[citation needed]

### Relation to mathematics and the other sciences

In the Assayer (1622), Galileo noted that mathematics is the language in which Nature expresses its laws.[12] Most experimental results in physics are numerical measurements, and theories in physics use mathematics to give numerical results to match these measurements.

Physics relies upon mathematics to provide the logical framework in which physical laws may be precisely formulated and predictions quantified. Whenever analytic solutions of equations are not feasible, numerical analysis and simulations may be utilized. Thus, scientific computation is an integral part of physics, and the field of computational physics is an active area of research.

A key difference between physics and mathematics is that since physics is ultimately concerned with descriptions of the material world, it tests its theories by comparing the predictions of its theories with data procured from observations and experimentation, whereas mathematics is concerned with abstract patterns, not limited by those observed in the real world. The distinction, however, is not always clear-cut. There is a large area of research intermediate between physics and mathematics, known as mathematical physics.

Physics is also intimately related to many other sciences, as well as applied fields like engineering and medicine. The principles of physics find applications throughout the other natural sciences as some phenomena studied in physics, such as the conservation of energy, are common to all material systems. Other phenomena, such as superconductivity, stem from these laws, but are not laws themselves because they only appear in some systems.

Physics is often said to be the "fundamental science" (chemistry is sometimes included), because each of the other disciplines (biology, chemistry, geology, material science, engineering, medicine etc.) deals with particular types of material systems that obey the laws of physics.[8] For example, chemistry is the science of collections of matter (such as gases and liquids formed of atoms and molecules) and the processes known as chemical reactions that result in the change of chemical substances.

The structure, reactivity, and properties of a chemical compound are determined by the properties of the underlying molecules, which may be well-described by areas of physics such as quantum mechanics, or quantum chemistry, thermodynamics, and electromagnetism.

## Philosophical implications

Physics in many ways stems from ancient Greek philosophy. From Thales' first attempt to characterize matter, to Democritus' deduction that matter ought to reduce to an invariant state, the Ptolemaic astronomy of a crystalline firmament, and Aristotle's book Physics, different Greek philosophers advanced their own theories of nature. Well into the 18th century, physics was known as "Natural philosophy".

By the 19th century physics was realized as a positive science and a distinct discipline separate from philosophy and the other sciences. Physics, as with the rest of science, relies on philosophy of science to give an adequate description of the scientific method.[13] The scientific method employs a priori reasoning as well as a posteriori reasoning and the use of Bayesian inference to measure the validity of a given theory.[14]

 “ Truth is ever to be found in the simplicity, and not in the multiplicity and confusion of things. ” —Isaac Newton

The development of physics has answered many questions of early philosophers, but has also raised new questions. Study of the philosophical issues surrounding physics, the philosophy of physics, involves issues such as the nature of space and time, determinism, and metaphysical outlooks such as empiricism, naturalism and realism.[15]

Many physicists have written about the philosophical implications of their work, for instance Laplace, who championed causal determinism,[16] and Erwin Schrödinger, who wrote on Quantum Mechanics.[17] The mathematical physicist Roger Penrose has been called a Platonist by Stephen Hawking,[18] a view Penrose discusses in his book, The Road to Reality.[19] Hawking refers to himself as an "unashamed reductionist" and takes issue with Penrose's views.[20]

## History

The Greek mathematician Archimedes (c. 287 BC – c. 212 BC) laid the foundations of statics, hydrostatics, and gave an explanation for the principle of the lever.

Since antiquity, people have tried to understand the behavior of the natural world. One great mystery was the predictable behavior of celestial objects such as the Sun and the Moon. Several theories were proposed, the majority of which were disproved.

The Greek philosophers Thales (ca. 624 BC–ca. 546 BC), and Leucippus (first half of 5th century BC) refused to accept various supernatural, religious or mythological explanations for natural phenomena, proclaiming that every event had a natural cause. Early physical theories were largely couched in philosophical terms, and never verified by systematic experimental testing as is popular today. Many of the commonly accepted works of Ptolemy and Aristotle are not always found to match everyday observations.

Even so, many ancient philosophers and astronomers gave many correct descriptions in atomism and astronomy, and the Greek thinker Archimedes derived many correct quantitative descriptions of mechanics and hydrostatics. A more experimental physics began taking shape among medieval Muslim physicists, while modern physics largely took shape among early modern European physicists.

## Core theories of physics

While physics deals with a wide variety of systems, there are certain theories that are used by all physicists. Each of these theories were experimentally tested numerous times and found correct as an approximation of Nature (within a certain domain of validity). For instance, the theory of classical mechanics accurately describes the motion of objects, provided they are much larger than atoms and moving at much less than the speed of light. These theories continue to be areas of active research, and a remarkable aspect of classical mechanics known as chaos was discovered in the 20th century, three centuries after the original formulation of classical mechanics by Isaac Newton (1642–1727).

These central theories are important tools for research into more specialized topics, and any physicist, regardless of his or her specialization, is expected to be literate in them. These include classical mechanics, quantum mechanics, thermodynamics and statistical mechanics, electromagnetism, and special relativity.

## 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 research in Physics education.

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.[21]

#### Condensed matter

Velocity-distribution data of a gas of rubidium atoms, confirming the discovery of a new phase of matter, the Bose–Einstein condensate

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 temperature, 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. 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.[22] Condensed matter physics has a large overlap with chemistry, materials science, nanotechnology and engineering.

#### 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; they can treat their subject from a microscopic view (in contrast to a macroscopic view).

Atomic physics studies the electron shells of atoms. 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. Atomic physics is influenced by the nucleus (see, e.g., hyperfine splitting), but intra-nuclear phenomenon such as fission and fusion are considered part of high energy physics.

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/particle physics

A simulated event in the CMS detector of the Large Hadron Collider, featuring a possible appearance of the Higgs boson.

Particle physics is the study of the elementary constituents of matter and energy, and the interactions between them. It may also be called "high energy physics", because many elementary particles do not occur naturally, but are created only during high energy collisions of other particles, as can be detected in particle accelerators.

Currently, the interactions of elementary particles are described by the Standard Model. The model accounts for the 12 known particles of matter that interact via the strong, weak, and electromagnetic fundamental forces. Dynamics are described in terms of matter particles exchanging messenger particles that carry the forces. These messenger particles are known as gluons; W and W+ and Z bosons; and the photons, respectively. The Standard Model also predicts a particle known as the Higgs boson, the existence of which has not yet been verified.

#### Astrophysics

The deepest visible-light image of the universe, the Hubble Ultra Deep Field

Astrophysics and astronomy are 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 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 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.

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 includes cosmic inflation, dark energy and dark matter.

## Fundamental physics

The basic domains of physics

While physics aims to discover universal laws, its theories lie in explicit domains of applicability. Loosely speaking, the laws of classical physics accurately describe systems whose important length scales are greater than the atomic scale and whose motions are much slower than the speed of light. Outside of this domain, observations do not match their predictions. Albert Einstein contributed the framework of special relativity, which replaced notions of absolute time and space with spacetime and allowed an accurate description of systems whose components have speeds approaching the speed of light. Max Planck, Erwin Schrödinger, and others introduced quantum mechanics, a probabilistic notion of particles and interactions that allowed an accurate description of atomic and subatomic scales. Later, quantum field theory unified quantum mechanics and special relativity. General relativity allowed for a dynamical, curved spacetime, with which highly massive systems and the large-scale structure of the universe can be well described. General relativity has not yet been unified with the other fundamental descriptions.

## Application and influence

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 be interested 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 structures. The understanding and use of acoustics results in 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, over time. 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, and so many other important fields are influenced by physics: e.g. presently the fields of econophysics plays an important role, as well as sociophysics.

## Current research

A typical event studied and described by the science of physics: a magnet levitating above a superconductor demonstrates the Meissner effect.

Research in physics is continually progressing on a large number of fronts.

In condensed matter physics, an important unsolved theoretical problem is that of high-temperature superconductivity. Many condensed matter experiments are aiming to fabricate workable spintronics and quantum computers.

In particle physics, the first pieces of experimental evidence for physics beyond the Standard Model have begun to appear. Foremost among these are indications that neutrinos have non-zero mass. These experimental results appear to have solved the long-standing solar neutrino problem, and the physics of massive neutrinos remains an area of active theoretical and experimental research. In the next several years, particle accelerators will begin probing energy scales in the TeV range, in which experimentalists are hoping to find evidence[23] for the Higgs boson and supersymmetric particles.

Theoretical attempts to unify quantum mechanics and general relativity into a single theory of quantum gravity, a program ongoing for over half a century, have not yet been decisively resolved. The current leading candidates are M-theory, superstring theory and loop quantum gravity.

Many astronomical and cosmological phenomena have yet to be satisfactorily explained, including the existence of ultra-high energy cosmic rays, the baryon asymmetry, the acceleration of the universe and the anomalous rotation rates of galaxies.

Although much progress has been made in high-energy, quantum, and astronomical physics, many everyday phenomena involving complexity, chaos, or turbulence are still poorly understood. Complex problems that seem like they could be solved by a clever application of dynamics and mechanics remain unsolved; examples include the formation of sandpiles, nodes in trickling water, the shape of water droplets, mechanisms of surface tension catastrophes, and self-sorting in shaken heterogeneous collections.

These complex phenomena have received growing attention since the 1970s for several reasons, including the availability of modern mathematical methods and computers, which enabled complex systems to be modeled in new ways. Complex physics has become part of increasingly interdisciplinary research, as exemplified by the study of turbulence in aerodynamics and the observation of pattern formation in biological systems. In 1932, Horace Lamb said:

 “ I am an old man now, and when I die and go to heaven there are two matters on which I hope for enlightenment. One is quantum electrodynamics, and the other is the turbulent motion of fluids. And about the former I am rather optimistic. ” —Horace Lamb[24]

General
Related fields
Interdisciplinary fields incorporating physics

## References

1. ^ Richard Feynman begins with the atomic hypothesis, as his most compact statement of all scientific knowledge: "If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generations ..., what statement would contain the most information in the fewest words? I believe it is ... that all things are made up of atoms – little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. ..." R.P. Feynman, R.B. Leighton, M. Sands (1963). The Feynman Lectures on Physics. 1. p. I-2. ISBN 0-201-02116-1.
2. ^ J.C. Maxwell (1878). Matter and Motion. D. Van Nostrand. p. 9. "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular succession of events."
3. ^ H.D. Young, R.A. Freedman (2004). University Physics with Modern Physics (11th ed.). Addison Wesley. p. 2. "Physics is an experimental science. Physicists observe the phenomena of nature and try to find patterns and principles that relate these phenomena. These patterns are called physical theories or, when they are very well established and of broad use, physical laws or principles."
4. ^ S. Holzner (2006). Physics for Dummies. Wiley. p. 7. "Physics is the study of your world and the world and universe around you."
5. ^ Note: The term 'universe' is defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them. However, the term 'universe' may also be used in slightly different contextual senses, denoting concepts such as the cosmos or the philosophical world.
6. ^ Evidence exists that 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 very basic understanding of the motions of the Sun, Moon, and stars.
7. ^ Francis Bacon's 1620 Novum Organum was critical in the development of scientific method.
8. ^ a b The Feynman Lectures on Physics Volume I. Feynman, Leighton and Sands. ISBN 0-201-02115-3 See Chapter 3 : "The Relation of Physics to Other Sciences" for a general discussion. For the philosophical issue of whether other sciences can be "reduced" to physics, see reductionism and special sciences).
9. ^ Some principles, such as Newton's laws of motion, are still generally called "laws" even though they are now known to be limiting cases of newer theories. Thus, for example, in Thomas Brody (1993, Luis de la Peña and Peter Hodgson, eds.) The Philosophy Behind Physics ISBN 0-387-55914-0, pp 18–24 (Chapter 2), explains the 'epistemic cycle' in which a student of physics discovers that physics is not a finished product but is instead the process of creating [that product].
10. ^ See, for example, the influence of Kant and Ritter on Oersted.
11. ^ Concepts which are denoted hypothetical can change with time. For example, the atom of nineteenth century physics was denigrated by some, including Ernst Mach's critique of Ludwig Boltzmann's formulation of statistical mechanics. By the end of World War II, the atom was no longer deemed hypothetical.
12. ^ "Philosophy is written in that great book which ever lies before our eyes. I mean the universe, but we cannot understand it if we do not first learn the language and grasp the symbols in which it is written. This book is written in the mathematical language, and the symbols are triangles, circles and other geometrical figures, without whose help it is humanly impossible to comprehend a single word of it, and without which one wanders in vain through a dark labyrinth." – Galileo (1623), The Assayer, as quoted by G. Toraldo Di Francia (1976), The Investigation of the Physical World ISBN 0-521-29925-X p.10
13. ^ Rosenberg, Alex (2006). Philosophy of Science. Routledge. ISBN 0-415-34317-8.  See Chapter 1 for a discussion on the necessity of philosophy of science.
14. ^ Peter Godfrey-Smith (2003), Chapter 14 "Bayesianism and Modern Theories of Evidence" Theory and Reality: an introduction to the philosophy of science ISBN 0-226-30063-3
15. ^ Peter Godfrey-Smith (2003), Chapter 15 "Empiricism, Naturalism, and Scientific Realism?" Theory and Reality: an introduction to the philosophy of science ISBN 0-226-30063-3
16. ^ See Laplace, Pierre Simon, A Philosophical Essay on Probabilities, translated from the 6th French edition by Frederick Wilson Truscott and Frederick Lincoln Emory, Dover Publications (New York, 1951)
17. ^ See "The Interpretation of Quantum Mechanics" Ox Bow Press (1995) ISBN 1-881987-09-4. and "My View of the World" Ox Bow Press (1983) ISBN 0-918024-30-7.
18. ^ Stephen Hawking and Roger Penrose (1996), The Nature of Space and Time ISBN 0-691-05084-8 p.4 "I think that Roger is a Platonist at heart but he must answer for himself."
19. ^ Roger Penrose, The Road to Reality ISBN 0-679-45443-8
20. ^ Penrose, Roger; Abner Shimony, Nancy Cartwright, Stephen Hawking (1997). The Large, the Small and the Human Mind. Cambridge University Press. ISBN 0-521-78572-3.
21. ^ Yet, universalism is encouraged in the culture of physics. For example, the World Wide Web, which was innovated at CERN by Tim Berners-Lee, was created in service to the computer infrastructure of CERN, and was/is intended for use by physicists worldwide. The same might be said for arXiv.org
22. ^
23. ^ 584 co-authors "Direct observation of the strange 'b' baryon $\Xi_{b}^{-}$" Fermilab-Pub-07/196-E, June 12, 2007 http://arxiv.org/abs/0706.1690v2 finds a mass of 5.774 GeV for the $\Xi_{b}^{-}$
24. ^ Goldstein, Sydney (1969). "Fluid Mechanics in the First Half of this Century". Annual Reviews in Fluid Mechanics 1: 1–28. doi:10.1146/annurev.fl.01.010169.000245.

General textbooks
• Crowell, Benjamin (2001). Simple Nature.
• Feynman, Richard; Leighton, Robert; Sands, Matthew (1989). Feynman Lectures on Physics. Addison-Wesley. ISBN 0-201-51003-0.
• Feynman, Richard. Exercises for Feynman Lectures Volumes 1-3. Caltech. ISBN 2-35648-789-1.
• Knight, Randall (2004). Physics for Scientists and Engineers: A Strategic Approach. Benjamin Cummings. ISBN 0-8053-8685-8.
• Halliday, David; Resnick, Robert; Walker, Jearl. Fundamentals of Physics 8th ed. ISBN 978-0-471-75801-3.
• Hewitt, Paul (2001). Conceptual Physics with Practicing Physics Workbook (9th ed.). Addison Wesley. ISBN 0-321-05202-1.
• Giancoli, Douglas (2005). Physics: Principles with Applications (6th ed.). Prentice Hall. ISBN 0-13-060620-0.
• Schiller, Christoph (2007). Motion Mountain: The Free Physics Textbook.
• Serway, Raymond A.; Jewett, John W. (2004). Physics for Scientists and Engineers (6th ed.). Brooks/Cole. ISBN 0-534-40842-7.
• Tipler, Paul (2004). Physics for Scientists and Engineers: Mechanics, Oscillations and Waves, Thermodynamics (5th ed.). W. H. Freeman. ISBN 0-7167-0809-4.
• Tipler, Paul (2004). Physics for Scientists and Engineers: Electricity, Magnetism, Light, and Elementary Modern Physics (5th ed.). W. H. Freeman. ISBN 0-7167-0810-8.
• Wilson, Jerry; Buffa, Anthony (2002). College Physics (5th ed.). Prentice Hall. ISBN 0-13-067644-6.
• Verma, H. C. (2005). Concepts of Physics. Bharti Bhavan. ISBN 81-7709-187-5.

General
Organizations

# Quotes

Up to date as of January 14, 2010

### From Wikiquote

Physics is the science of the natural world, which deals with the fundamental particles the universe is made of, the interactions between them, and the interactions of objects composed of them (nuclei, atoms, molecules, etc).

## Sourced

• Physicists use the wave theory on Mondays, Wednesdays and Fridays and the particle theory on Tuesdays, Thursdays and Saturdays
• William Henry Bragg; quoted in Dictionary of Scientific Quotations by Alan L. Mackay, Institute of Physics Publishing, Bristol, 1994, p. 37 [1]
• Variant: On Mondays, Wednesdays and Fridays we teach the wave theory and on Tuesday, Thursdays and Saturdays the corpuscular theory.
• Quoted in Physically Speaking: A Dictionary of Quotations on Physics and Astronomy by C.C. Gaither, 1997, ISBN 0750304707. [2]
• unsourced variant: God runs electromagnetics by wave theory on Monday, Wednesday, and Friday, and the Devil runs them by quantum theory on Tuesday, Thursday, and Saturday. [3]
• Physics and philosophy are at most a few thousand years old, but probably have lives of thousands of millions of years stretching away in front of them. They are only just beginning to get under way.
• Physics and Philosophy (1942), p.217.

## Unsourced

• All science is either physics or stamp collecting.
• Sir Ernest Rutherford
• Variant: In science there is only physics; all the rest is stamp collecting.
• Even if there is only one possible unified theory, it is just a set of rules and equations. What is it that breathes fire into the equations and makes a universe for them to describe?
• Guests at a cocktail party in the Southern Hemisphere tend to circulate in an anticlockwise direction.
• Corollary to Parkinson's 2nd Law
• I think I can safely say that nobody understands quantum mechanics.
• If [quantum theory] is correct, it signifies the end of physics as a science.
• My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all.
• Nothing is more interesting to the true theorist than a fact which directly contradicts a theory generally accepted up to that time, for this is his particular work.
• Physics is like sex. Sure, it may give some practical results, but that's not why we do it.
• The theory of quanta can be likened to medicine that cures the disease but kills the patient.
• Hendrick Kramers
• Toast always lands buttered-side down, and a cat always lands feet first. I propose we strap buttered toast to the back of a cat; the two will hover, spinning inches from the ground. With a giant buttered-toast/cat array, a hovering monorail could easily link New York with Chicago.

Look up physics in Wiktionary, the free dictionary

# Study guide

Up to date as of January 14, 2010
(Redirected to School:Physics and Astronomy article)

### From Wikiversity

Welcome to the School of Physics and Astronomy!
FACULTY OF SCIENCES
Biology · Chemistry · Electronics · Geology · Mathematics · Physics and Astronomy
Other Major Wikiversity Schools

A school is a large organizational structure which can contain various departments and divisions. The departments and divisions should be listed in the departments and divisions section. The school should not contain any learning resources. The school can contain projects for developing learning resources.

## Improvement drive

These pages are in need of expansion and improvement:

## Courses

The following courses are incorporated within several of the departments below as core curriculum and are common to all types of physics degrees. Additional courses, relevant to particular degree types, are specified in individual departments named below. For more information please review the Bachelor of Science in Physics requirements.

Courses are grouped by level of difficulty, and each one roughly corresponds to an academic year at degree level. Normally you should not study a subject at a higher level until you have completed, or are at least familiar, with the previous level.

### Courses in Other Schools

#### School of Computer Science

(work in progress)

#### School of Engineering

• GRE Physics Subject Test

## Departments

Three-dimensional visualization of space-time distortion. The presence of matter changes the geometry of spacetime, this (curved) geometry being interpreted as gravity.

## Learning resources

A Superconductor demonstrating the Meissner Effect.

As with all Wikiversity disciplines the courses here are supported by the texts at Wikibooks specifically of interest are the books on the Physics bookshelf . The books below are representative of what is available.

## People

• Roadrunner - I am currently trying to create a degree plan Wikiversity:Bachelor of Science in Physics that will be an open architecture degree which replicates the Course 8 experience at the Massachusetts Institute of Technology
• Alisone
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• Aquistive bud - Anyone interested in discussing any topic related to physics is warmly invited at my talk page.
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• David - interested in Quantum Gravity. I have postgraduate degrees in physics, mathematics and astrophysics.
• User:fibonacci101 - I have a great interest in physics and astronomy.

# Source material

Up to date as of January 22, 2010
(Redirected to Physics (Aristotle) article)

### From Wikisource

 Physics by Aristotle, translated by Wikisource
 Physics (or "Physica", or "Physicae Auscultationes" meaning "lessons") is a key text in the philosophy of Aristotle. The ancient Greek title of these treatises—τὰ φυσικά—meant "the [writings] on nature" or "natural philosophy".— Excerpted from Physics (Aristotle) on Wikipedia, the free encyclopedia.

## Content

 This work is in the public domain worldwide because it has been so released by the copyright holder.

# Wikibooks

Up to date as of January 23, 2010
(Redirected to Physics Course article)

## Introduction

This book covers everything from Ancient Physics to Modern Physics Concepts , Theorems, Laws

## Authors

• Quach Trung Thanh . B.Sc.E.E. University Manitoba . 1984 - 1988

# Simple English

Physics is the science of matter and how matter interacts.

## = What is physics?

=

Physics is the study of matter and energy in space and time and how they are related to each other. Physicists assume (take as given) the existence of mass, length, time and electric charge and then define (give the meaning of) all other physical quantities in terms of these basic units. Mass, length, time, and electric charge are never defined but the standard units used to measure them are always defined. In the International System of Units (abbreviated SI from the French Système International), the meter is the basic unit of length, the kilogram is the basic unit of mass, the second is the basic unit of time, the ampere is the basic unit of electric current.

Physics studies how things move, and the forces that make them move. For example, velocity and acceleration are used by physics to show how things move. Also, physicists study the forces of gravity, electricity, magnetism and the forces that hold stuff together.

Physics studies very large things, and very small things. For example, physics studies stars, planets and galaxies and other big pieces of matter. Physics also studies small pieces of matter, such as atoms and electrons.

Physics also studies sound, light and other waves. Physics studies energy, heat and radioactivity, and even space and time. Physics not only helps people understand how objects move, but how they change form, how they make noise, how hot or cold they will be, and what they are made of at the smallest level.

### Physics uses numbers

Physics is a quantitative science because it is based on measuring with numbers. Math is used in physics to make models that try to guess what will happen in nature. The guesses are compared to the way the real world works. Physicists are always working to make their models of the world better.

## Less simple

#### General description

Physics is the science of matter and how matter interacts. Matter is any physical material in the universe. Everything is made of matter. Physics is used to describe the physical universe around us, and to predict how it will behave. Physics is the science concerned with the discovery and characterization of the universal laws which govern matter, movement and forces, and space and time, and other features of the natural world.

#### Breadth and goals of physics

The sweep of physics is broad, from the smallest components of matter and the forces that hold it together, to galaxies and even larger things. There are only four forces that appear to operate over this whole range. However, even these four forces (gravity, electromagnetism, the weak force associated with radioactivity, and the strong force which holds atoms together) are believed to be different parts of a single force.

Physics is mainly focused on the goal of making ever simpler, more general, and more accurate rules that define the character and behavior of matter and space itself. One of the major goals of physics is making theories that apply to everything in the universe. In other words, physics can be viewed as the study of those universal laws which define, at the most basic level possible, the behavior of the physical universe.

#### Physics uses the scientific method

Physics uses the scientific method. That is, data from experiments and observations are collected. Theories which attempt to explain these data are produced. Physics uses these theories to not only describe physical phenomena, but to model physical systems and predict how these physical systems will behave. Physicists then compare these predictions to observations or experimental evidence to show whether the theory is right or wrong.

The theories that are well supported by data and are especially simple and general are sometimes called scientific laws. Of course, all theories, including those known as laws, can be replaced by more accurate and more general laws, when a disagreement with data is found.[1]

#### Physics is Quantitative

Physics is more quantitative than most other sciences. That is, many of the observations in physics may be represented in the form of numerical measurements. Most of the theories in physics use mathematics to express their principles. Most of the predictions from these theories are numerical. This is because of the areas which physics has addressed are more amenable to quantitative approaches than other areas. Sciences also tend to become more quantitative with time as they become more highly developed, and physics is one of the oldest sciences.

#### Fields of physics

Classical physics normally includes the fields of mechanics, optics, electricity, magnetism, acoustics and thermodynamics. Modern physics is a term normally used to cover fields which rely on quantum theory, including quantum mechanics, atomic physics, nuclear physics, particle physics and condensed matter physics, as well as the more modern fields of general and special relativity. Although this distinction can be found in older writings, it is of little recent interest as quantum effects are now understood to be of importance even in fields previously considered classical.[2]

#### Approaches in physics

There are many approaches to studying physics, and many different kinds of actitivies in physics. There are two main types of activities in physics; the collection of data and the development of theories.

The data in some subfields of physics is amenable to experiment. For example, condensed matter physics and nuclear physics benefit from the ability to perform experiments. Experimental physics focuses mainly on an empirical approach. Sometimes experiments are done to explore nature, and in other cases experiments are performed to produce data to compare with the predictions of theories.

Some other fields in physics like astrophysics and geophysics are primarily observational sciences because most their data has to be collected passively instead of through experimentation. Nevertheless, observational programs in these fields uses many of the same tools and technology that are used in the experimental subfields of physics.

Theoretical physics often uses quantitative approaches to develop the theories that attempt to explain the data. In this way, theoretical physics often relies heavily on tools from mathematics. Theoretical physics often can involve creating quantitative predictions of physical theories, and comparing these predictions quantitatively with data. Theoretical physics sometimes creates models of physical systems before data is available to test and validate these models.

These two main activities in physics, data collection and theory production and testing, draw on many different skills. This has led to a lot of specialization in physics, and the introduction, development and use of tools from other fields. For example, theoretical physicists apply mathematics and numerical analysis and statistics and probability and computers and computer software in their work. Experimental physicists develop instruments and techniques for collecting data, drawing on engineering and computer technology and many other fields of technology. Often the tools from these other areas are not quite appropriate for the needs of physics, and need to be adapted or more advanced versions have to be produced.

## Physicists

There are many famous physicists. Isaac Newton studied gravity. Galileo Galilei studied light and how planets move. Albert Einstein made a theory for how light can make electrons move, and studied how gravity affects light and space. James Clerk Maxwell proved that light is a type of electromagnetic wave.

Ernest Rutherford said that "Physics is the only real science. The rest are just stamp collecting."

## References

1. Some principles, such as Newton's laws of motion, are still generally called "laws" even though they are now known not to be of such universal applicability as was once thought.
2. Different people, however, have different definitions of what they regard physics to be, and another common definition is that, "physics is the science of nature" [1,2,3,4,5,6].