Portal:Physics/2010 Selected articles
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In physics and chemistry, plasma is a gas, in which a certain proportion of its particles are ionized. The presence of a non-negligible number of charge carriers makes the plasma electrically conductive so that it responds strongly to electromagnetic fields. Plasma therefore has properties quite unlike those of solids, liquids, or gases and is considered to be a distinct state of matter. Plasma typically takes the form of neutral gas-like clouds, as seen, for example, in the case of stars. Like gas, plasma does not have a definite shape or a definite volume unless enclosed in a container; unlike gas, in the influence of a magnetic field, it may form structures such as filaments, beams and double layers (see section 3, below).
Plasma was first identified in Crookes tube, and so described by Sir William Crookes in 1879 (he called it "radiant matter"). The nature of the Crookes tube "cathode ray" matter was subsequently identified by British physicist Sir J.J. Thomson in 1897, and dubbed "plasma" by Irving Langmuir in 1928, perhaps because it reminded him of a blood plasma. Langmuir wrote, "Except near the electrodes, where there are sheaths containing very few electrons, the ionized gas contains ions and electrons in about equal numbers so that the resultant space charge is very small. We shall use the name plasma to describe this region containing balanced charges of ions and electrons.
In optics, chromatic aberration (also called achromatism or chromatic distortion) is the failure of a lens to focus all colors to the same point. It occurs because lenses have a different refractive index for different wavelengths of light (the dispersion of the lens). The refractive index decreases with increasing wavelength.
Chromatic aberration manifests itself as "fringes" of color along boundaries that separate dark and bright parts of the image, because each color in the optical spectrum cannot be focused at a single common point on the optical axis.
Since the focal length f of a lens is dependent on the refractive index n, different wavelengths of light will be focused on different positions. Chromatic aberration can be both longitudinal, in that different wavelengths are focused at a different distance from the lens; and transverse or lateral, in that different wavelengths are focused at different positions in the focal plane (because the magnification of the lens also varies with wavelength).
A Light cone is the path that a flash of light, emanating from a single event E (localized to a single point in space and a single moment in time) and traveling in all directions, would take through spacetime. Imagine the light confined to a two-dimensional plane, the light from the flash spreads out in a circle after the event E occurs—and when graphed the growing circle with the vertical axis of the graph representing time, the result is a cone, known as the future light cone (some animated diagrams depicting this concept can be seen here). The past light cone behaves like the future light cone in reverse, a circle that contracts in radius at the speed of light until it converges to a point at the exact position and time of the event E. In reality, there are three space dimensions, so the light would actually form an expanding or contracting sphere in 3D space rather than a circle in 2D, and the light cone would actually be a four-dimensional shape. However, the concept is easier to visualize with the number of spatial dimensions reduced from three to two.
Because signals and other causal influences cannot travel faster than light in relativity, the light cone plays an essential role in defining the concept of causality. For a given event E, the set of events that lie on or inside the past light cone of E would also be the set of all events that could send a signal that would have time to reach E and influence it in some way. For example, at a time ten years before E, if we consider the set of all events in the past light cone of E that occur at that time, the result is a sphere with a radius of ten light-years centered on the future position E will occur. So, any point on or inside the sphere could send a signal moving at the speed of light or slower that would have time to influence the event E, while points outside the sphere at that moment would not be able to have any causal influence on E. Likewise, the set of events that lie on or inside the future light cone of E would also be the set of events that could receive a signal sent out from the position and time of E. Events that lie neither in the past or future light cone of E cannot influence or be influenced by E in relativity.
Introduction to Quantum mechanics is an introductory version of Quantum mechanics. It describes Quantum mechanics as the set of scientific principles describing the behavior of energy and matter on the atomic and subatomatic scale. Much like the universe on the large and very vast scale (i.e., general relativity), so the universe on the small scale (i.e., quantum mechanics) does not neatly conform to the rules of classical physics. As such, it presents a set of rules that is counterintuitive and difficult to understand for the human mind, as humans are accustomed to the world on a scale dominated by classical physics. In other words, as stated by Richard Feynman: quantum mechanics deals with "Nature as She is—absurd." (see biography below) 
Many elementary parts of the universe, such as photons (discrete units of light) have some behaviours which resemble a particle but other behaviours that resemble a wave. Radiators of photons such as neon lights have spectra, but the spectra are chopped up instead of being continuous. The energies carried by photons form a discontinuous and colour coded series. The energies, the colours, and the spectral intensities of electromagnetic radiation produced are all interconnected by laws. But the same laws ordain that the more closely one pins down one measure (such as the position of a particle) the more wildly another measure relating to the same thing (such as momentum) must fluctuate. Put another way, measuring position first and then measuring momentum is not the same as measuring momentum first and then measuring position. Even more disconcerting, particles can be created as twins and therefore as entangled entities -- which means that doing something that pins down one characteristic of one particle will determine something about its entangled twin even if it is millions and millions of miles away.
Around the turn of the twentieth century, it became clear that classical physics was unable to explain several phenomena. As Thomas Kuhn explains in his analysis of the philosophy of science, The Structure of Scientific Revolutions, understanding these limitations of classical physics led to a revolution in physics and resulted in a shift of the original scientific paradigm: the development of quantum mechanics in the early decades of the last century.
Introduction to Quantum mechanics is a simpified version of Quantum mechanics. It describes Quantum mechanics as the set of scientific principles describing the behavior of energy and matter on the atomic and subatomatic scale. Much like the universe on the large and very vast scale (i.e., general relativity), so the universe on the small scale (i.e., quantum mechanics) does not neatly conform to the rules of classical physics. As such, it presents a set of rules that is counterintuitive and difficult to understand for the human mind, as humans are accustomed to the world on a scale dominated by classical physics. In other words, quantum mechanics deals with "Nature as She is—absurd."
Many elementary parts of the universe, such as photons (discrete units of light) have some behaviours which resemble a particle but other behaviours that resemble a wave. The energies carried by photons form a discontinuous and colour coded series. The energies, the colours, and the spectral intensities of electromagnetic radiation produced are all interconnected by laws. But the same laws ordain that the more closely one pins down one measure (such as the position of a particle) the more wildly another measure relating to the same thing (such as momentum) must fluctuate.
Around the turn of the twentieth century, it became clear that classical physics was unable to explain several phenomena. Understanding these limitations of classical physics led to a revolution in physics: the development of quantum mechanics in the early decades of the last century.
- For the rest of the article see: Introduction to Quantum mechanics
Physicist Biography: Richard Feynman
Richard Phillips Feynman (// FYEN-mən; May 11, 1918 – February 15, 1988) was an American physicist known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics (he proposed the parton model). For his contributions to the development of quantum electrodynamics, Feynman, jointly with Julian Schwinger and Sin-Itiro Tomonaga, received the Nobel Prize in Physics in 1965. He developed a widely used pictorial representation scheme for the mathematical expressions governing the behavior of subatomic particles, which later became known as Feynman diagrams. During his lifetime, Feynman became one of the best-known scientists in the world.
He assisted in the development of the atomic bomb and was a member of the panel that investigated the Space Shuttle Challenger disaster. In addition to his work in theoretical physics, Feynman has been credited with pioneering the field of quantum computing, and introducing the concept of nanotechnology. He held the Richard Chace Tolman professorship in theoretical physics at the California Institute of Technology.
Feynman was a keen popularizer of physics through both books and lectures, notably a 1959 talk on top-down nanotechnology called There's Plenty of Room at the Bottom and The Feynman Lectures on Physics. Feynman also became known through his semi-autobiographical books (Surely You're Joking, Mr. Feynman! and What Do You Care What Other People Think?) and books written about him, such as Tuva or Bust!
Feynman also had a deep interest in biology, and was a friend of the geneticist and microbiologist Esther Lederberg, who developed replica plating and discovered bacteriophage lambda. They had several mutual physicist friends who, after beginning their careers in nuclear research, moved for moral reasons into genetics, among them Leó Szilárd, Guido Pontecorvo, and Aaron Novick.
- The subject of the month is Radio
Below are several introductions to Wikipedia articles related to radio: History of radio, Invention of radio, an article entitled Radio and the radio "Antenna". Also below, is a biography of an individual who contributed to this technology.
- History of radio - is the history of technology that produced radio instruments that use radio waves. Within the timeline of radio, many people contributed theory and inventions in what became radio. Radio development began as "wireless telegraphy". Later radio history increasingly involves matters of programming and content. During its early development and long after wide use of the technology, disputes persisted as to who could claim sole credit for this obvious boon to mankind. Closely related, radio was developed along with two other key inventions, the telegraph and the telephone.
- Invention of radio - Within the history of radio, several people were involved in the invention of radio and there were many key inventions in what became the modern systems of wireless. Radio development began as "wireless telegraphy". Closely related, radio was developed along with two other key inventions, the telegraph and the telephone. During the early development of wireless technology and long after its wide use, disputes persisted as to who could claim credit for the invention of radio. The matter was important for economic, political and nationalistic reasons.
- Radio - is the transmission of signals by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. Information is carried by systematically changing (modulating) some property of the radiated waves, such as amplitude, frequency, phase, or pulse width. When radio waves pass an electrical conductor, the oscillating fields induce an alternating current in the conductor. This can be detected and transformed into sound or other signals that carry information.
- Antenna (radio) - An antenna (or aerial) is a transducer that transmits or receives electromagnetic waves. In other words, antennas convert electromagnetic radiation into electrical current, or vice versa. Antennas generally deal in the transmission and reception of radio waves, and are a necessary part of all radio equipment. Antennas are used in systems such as radio and television broadcasting, point-to-point radio communication, wireless LAN, cell phones, radar, and spacecraft communication.
Selected biography: Jagadish Chandra Bose
Sir Jagadish Chandra Bose CSI CIE FRS (Bengali: জগদীশ চন্দ্র বসু Jôgodish Chôndro Boshu) (November 30, 1858 – November 23, 1937) born in a Bengali Hindu Kayasth family was a polymath: a physicist, biologist, botanist, archaeologist, and writer of science fiction. He pioneered the investigation of radio and microwave optics, made very significant contributions to plant science, and laid the foundations of experimental science in the Indian subcontinent. He is considered one of the fathers of radio science, and is also considered the father of Bengali science fiction. He was the first person from the Indian subcontinent to get a US patent, in 1904.
- The theme of the month is "Light". The following articles discuss different aspects of light that have been researched and discovered over time.
- Light can have two general meanings. Light is what occurs as we experience the visible spectrum of electromagnetic radiation, and in physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not.
- Speed of light is a quantity that does not vary, and expresses how fast light travels in a vacuum. Moreover, according to the theory of relativity, this value appears in the famous equation of E = mc2. This invariance of the speed of light was postulated by Albert Einstein in 1905, motivated by Maxwell's theory of electromagnetism and the lack of evidence for the luminiferous ether. Study of this phenomenon explores consequences such as moving objects will shorten, and time dilation (moving clocks run slower).
- Photon has several interrelated descriptions. One of these is that the photon is the basic unit of light, and all electromagnetic radiation. It is also a carrier of the "force" that causes the interaction between electrically charged particles in electromagnetism and electrodynamics. It also has a dual nature. This means it can travel and transfer energy from one point to another; propagating (traveling) through space and time as a wave. Or it can be viewed as a fundamental particle that is not known to be made up of smaller particles. Hence, it is considered to be one of the basic building blocks of the universe.
- Optics is the branch of physics which studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties. In addition, the sub-fields of optics are briefly discussed and linked to their respective main articles.
Sir Arthur Schuster (FRS) (12 September 1851 – 17 October 1934) was a versatile German-born British physicist known for his work in spectroscopy, electrochemistry, optics, X-radiography and the application of harmonic analysis to physics. He contributed enormously to making the University of Manchester a centre for the study of physics. (Click on the name to read the entire article)
John Strutt, 3rd Baron Rayleigh (OM) (12 November 1842 – 30 June 1919) was an English physicist who, with William Ramsay, discovered the element argon, an achievement for which he earned the Nobel Prize for Physics in 1904. He also discovered the phenomenon now called Rayleigh scattering, explaining why the sky is blue, and predicted the existence of the surface waves now known as Rayleigh waves. In 1910 Lord Rayleigh discovered that an electrical discharge in nitrogen gas produced "active nitrogen", an allotrope considered to be monatomic. The "whirling cloud of brilliant yellow light" produced by his apparatus reacted with quicksilver to produce explosive mercury nitride. (Click on the name to read the entire article)
Time is the theme for this month. A description of time, crafted by a Wikipedia editor, which is derived from reliable sources, is as follows:
- Time is a one-dimensional quantity used to sequence events, to quantify the durations of events and the intervals between them, and (used together with space) to quantify and measure the motions of objects. Time is quantified in comparative terms (such as longer, shorter, faster, quicker, slower) or in numerical terms using units (such as seconds, minutes, hours, days). Time has been a major subject of religion, philosophy, and science, but defining it in a non-controversial manner applicable to all fields of study has consistently eluded the greatest scholars.
2007 description of time
Previously, in January of 2007, the opening lead for the article entitled Time read as follows:
There are two distinct views on the meaning of time. One view is that time is part of the fundamental structure of the universe, a dimension in which events occur in sequence. This is the realist view, to which Sir Isaac Newton  subscribed, in which time itself is something that can be measured.
A contrasting view is that time is part of the fundamental intellectual structure (together with space and number) within which we sequence events, quantify the duration of events and the intervals between them, and compare the motions of objects. In this view, time does not refer to any kind of entity that "flows", that objects "move through", or that is a "container" for events. This view is in the tradition of Gottfried Leibniz and Immanuel Kant, in which time, rather than being an objective thing to be measured, is part of the mental measuring system. The question, perhaps overly simplified and allowing for no middle ground, is thus: is time a "real thing" that is "all around us", or is it nothing more than a way of speaking about and measuring events?
Many fields avoid the problem of defining time itself by using operational definitions that specify the units of measurement that quantify time. Regularly recurring events and objects with apparent periodic motion have long served as standards for units of time. Examples are the apparent motion of the sun across the sky, the phases of the moon, and the swing of a pendulum.
Time has long been a major subject of science, philosophy and art. The measurement of time has also occupied scientists and technologists, and was a prime motivation in astronomy. Time is also a matter of significant social importance, having economic value ("time is money") as well as personal value, due to an awareness of the limited time in each day and in human lifespans. This article looks at some of the main philosophical and scientific issues relating to time.
- For further reading see the main article: Time. Below are other articles related to time:
Time in physics is largely defined by its measurement: time is what a clock reads. One can measure time and treat it as a geometrical dimension, such as length, and perform mathematical operations on it. It is a scalar quantity and, like length, mass, and charge, is usually listed in most physics books as a fundamental quantity. Time can be combined mathematically with other fundamental quantities to derive other concepts such as motion, energy and fields. Timekeeping is a complex of technological and scientific issues, and part of the foundation of recordkeeping.
Time occurs in orders of magnitude from less than one billionth of a second (nanosecond), to billions of years (age of the universe) and beyond.
According to certain Euclidean space perceptions, the universe has three dimensions of space and one dimension of time. By combining space and time into a single manifold, physicists have significantly simplified a large number of physical theories, as well as described in a more uniform way the workings of the universe at both the supergalactic and subatomic levels.
In physical cosmology, the Planck epoch (or Planck era), named after Max Planck, is the earliest period of time in the history of the universe. At this point approximately, 13.7 billion years ago one could also say that it is the earliest moment in time, as the Planck time is perhaps the shortest possible interval of time, and the Planck epoch lasted only this brief instant.
In computer science and computer programming, system time represents a computer system's notion of the passing of time. In this sense, time also includes the passing of days on the calendar. System time is measured by a system clock, which is typically implemented as a simple count of the number of ticks that have transpired since some arbitrary starting date, called the epoch. For example, Unix and POSIX-compliant systems encode system time as the number of seconds elapsed since the start of the epoch at 1 January 1970 00:00:00 UT. Windows NT counts the number of 100-nanosecond ticks since 1 January 1601 00:00:00 UT as reckoned in the proleptic Gregorian calendar, but returns the current time to the nearest millisecond.
Atomic clocks are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, to control the frequency of television broadcasts, and in global navigation satellite systems such as GPS. The clocks maintain a continuous and stable time scale, International Atomic Time (TAI). For civil time, another time scale is disseminated, Coordinated Universal Time (UTC). UTC is derived from TAI, but synchronized, by using leap seconds, to UT1, which is based on actual rotations of the earth with respect to the solar time.
- Template: Time measurement and standards
Wikipedia has a number of articles related to "Time". See our template entitled Time measurement and standards , and click on the link entitled "show".
- The theme for this month is unsolved problems in physics. Some of these problems are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result. Other unsolved problems are the result of an inability to in create an experiment to test a proposed theory, or investigate a phenomenon in greater detail.
- Hence, theoretical problems are part of quantum gravity, cosmology, general relativity, high energy physics (particle physics), nuclear physics, and others. Empirical phenomena lacking clear scientific explanation are part of cosmology and astronomy, high energy physics(particle physics), astronomy, astrophysics, condensed matter physics, and biological problems approached with physics. Click on the following link to read about this subject, which is supplied with references, and other types of information for further reading.
Elements of what became physics were drawn primarily from the fields of astronomy, optics, and mechanics, which were methodologically united through the study of geometry. These mathematical disciplines began in Antiquity with the Babylonians and with Hellenistic writers such as Archimedes and Ptolemy. Meanwhile, philosophy, including what was called “physics”, focused on explanatory (rather than descriptive) schemes, largely developed around the Aristotelian idea of the four types of “causes”. Descartes, like Galileo, was convinced of the importance of mathematical explanation, and he and his followers were key figures in the development of mathematics and geometry in the 17th century
The history of science and technology in China is both long and rich with many contributions to science and technology. In antiquity, independently of Greek philosophers and other civilizations, ancient Chinese philosophers made significant advances in science, technology, mathematics, and astronomy. The first recorded observations of comets, solar eclipses, and supernovae were made in China. Traditional Chinese medicine, acupuncture and herbal medicine were also practiced. Among the earliest inventions were the abacus, the "shadow clock," and the first flying machines such as kites and Kongming lanterns. The four Great Inventions of ancient China: the compass, gunpowder, papermaking, and printing, were among the most important technological advances, only known in Europe by the end of the Middle Ages. The Tang Dynasty (AD 618 - 906) in particular, was a time of great innovation. A good deal of exchange occurred between Western and Chinese discoveries up to the Qing Dynasty.
The Jesuit China missions of the 16th and 17th centuries introduced Western science and astronomy, then undergoing its own revolution, to China, and knowledge of Chinese technology was brought to Europe. Much of the early Western work in the history of science in China was done by Joseph Needham.
The history of science and technology in India begins with prehistoric human activity at Mehrgarh, in present-day Pakistan, and continues through the Indus Valley Civilization to early states and empires. The British colonial rule introduced western education in India. The British system of education, in its efforts to give rise to a native class of civil servants, exposed a number of Indians to foreign institutes of higher learning. Following independence science and technology in the Republic of India has included automobile engineering, information technology, communications as well as space, polar, and nuclear sciences.
The theme for this month is the recipients of the Nobel Prize in Physics in the new millennium, between 2010 and the year 2001.
The Nobel Prize in Physics (Swedish: Nobelpriset i fysik) is awarded once a year by the Royal Swedish Academy of Sciences. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901. The first Nobel Prize in Physics was awarded to Wilhelm Conrad Röntgen "in recognition of the extraordinary services he has rendered by the discovery of the remarkable rays (or x-rays)." This award is administered by the Nobel Foundation. A maximum of three Nobel laureates and two different works may be selected for the Nobel Prize in Physics. The nomination and selection process for the prize in Physics is long and rigorous. This is a key reason it has grown in importance over the years to become the most important prize in Physics.
- 2010 awarded jointly to Andre Geim and Konstantin Novoselov "for groundbreaking experiments regarding the two-dimensional material graphene"
- 2009 divided, one half awarded to Charles Kuen Kao ' for groundbreaking achievements concerning the transmission of light in fibers for optical communication ',the other half jointly to Willard S. Boyle and George E. Smith "for the invention of an imaging semiconductor circuit – the CCD sensor ".
- 2008 divided, one half awarded to Yoichiro Nambu "for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics ",the other half jointly to Makoto Kobayashi and Toshihide Maskawa "for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature".
- 2007 awarded jointly to Albert Fert and Peter Grünberg "for the discovery of Giant Magnetoresistance ."
- 2006 awarded jointly to John C. Mather and George F. Smoot "for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation."
- 2005 divided, one half awarded to Roy J. Glauber "for his contribution to the quantum theory[disambiguation needed] of optical coherence", and the other half jointly to John L. Hall and Theodor W. Hänsch "for their contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique".
- 2004 awarded jointly to David J. Gross, H. David Politzer and Frank Wilczek " for the discovery of asymptotic freedom in the theory of the strong interaction".
- 2003 awarded jointly to Alexei A. Abrikosov, Vitaly L. Ginzburg and Anthony J. Leggett" for pioneering contributions to the theory of superconductors and superfluids ".
- 2002 divided, one half jointly to Raymond Davis Jr. and Masatoshi Koshiba " for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos " and the other half to Riccardo Giacconi " for pioneering contributions to astrophysics, which have led to the discovery of cosmic X-ray sources".
- 2001 awarded jointly to Eric A. Cornell, Wolfgang Ketterle and Carl E. Wieman " for the achievement of Bose-Einstein condensation in dilute gases of alkali atoms, and for early fundamental studies of the properties of the condensates ".
- See also: List of Nobel laureates in Physics
Albert Einstein (1879–1955) was a renowned theoretical physicist of the 20th century who is best known for his theories of special relativity and general relativity. He also made important contributions to statistical mechanics, especially his treatment of Brownian motion, his resolution of the paradox of specific heats, and his connection of fluctuations and dissipation. Despite his reservations about its interpretation, Einstein also made seminal contributions to quantum mechanics and, indirectly, quantum field theory, primarily through his theoretical studies of the photon.
- In 1905, Einstein developed the theory of special relativity, which reconciled the relativity of motion with the observed constancy of the speed of light (a paradox of 19th-century physics).
- Likewise in 1905, Einstein developed a theory of Brownian motion in terms of fluctuations in the number of molecular collisions with an object, providing further evidence that matter was composed of atoms.
- Also in 1905, Einstein proposed the existence of the photon, an elementary particle associated with electromagnetic radiation (light), which was the foundation of quantum theory.
- In 1907 and again in 1911, Einstein developed the first quantum theory of specific heats by generalizing Planck's law.
- Between 1907 and 1915, Einstein developed the theory of general relativity, a classical field theory of gravitation that provides the cornerstone for modern astrophysics and cosmology
- In 1917, Einstein published the idea for the Einstein-Brillouin-Keller method for finding the quantum mechanical version of a classical system.
- In 1918, Einstein developed a general theory of the process by which atoms emit and absorb electromagnetic radiation (his A and B coefficients), which is the basis of lasers (stimulated emission) and shaped the development of modern quantum electrodynamics, the best-validated physical theory at present.
- In 1924, together with Satyendra Nath Bose, Einstein developed the theory of Bose-Einstein statistics and Bose-Einstein condensates, which form the basis for superfluidity, superconductivity, and other phenomena.
- In 1935, together with Boris Podolsky and Nathan Rosen, Einstein put forward what is now known as the EPR paradox, and argued that the quantum-mechanical wave function must be an incomplete description of the physical world.
- Crookes presented a lecture to the British Association for the Advancement of Science, in Sheffield, on Friday, 22 August 1879  
- Announced in his evening lecture to the Royal Institution on Friday, 30th April 1897, and published in Philosophical Magazine. 44: 293. 1897 http://web.lemoyne.edu/~GIUNTA/thomson1897.html. Missing or empty
- I. Langmuir (1928). "Oscillations in ionized gases". Proc. Nat. Acad. Sci. U.S. 14: 628. doi:10.1073/pnas.14.8.627.
- Richard P. Feynman, QED, p. 10
- Kuhn, Thomas S. The Structure of Scientific Revolutions. Fourth ed. Chicago ;London: The University of Chicago Press, 2012. Print.
- Richard P. Feynman, QED, p. 10
- West, Jacob (July 2003). "The Quantum Computer" (PDF). Xootic. Retrieved 2009-09-20.
- Edwards 2006, pp. 15–17.
- "Esther M. Zimmer Lederberg Memorial Web Site".
- The Invention of Radio inventors.about.com/od/rstartinventions/a/radio.htm
- Dictionary of Electronics By Rudolf F. Graf (1974). Page 467.
- Newton's Views on Space, Time, and Motion - Stanford University http://plato.stanford.edu/entries/newton-stm/
- Leibniz on Space, Time, and Indiscernibles - Against the Absolute Theory -- Internet Encyclopedia of Philosophy http://www.iep.utm.edu/l/leib-met.htm#H7
- Critique of Pure Reason - Lecture notes of G. J. Mattey, UC Davis http://www-philosophy.ucdavis.edu/mattey/kant/TIMELEC.HTM
- Kant's Transcendental Idealism - Internet Encyclopedia of Philosophy http://www.iep.utm.edu/k/kantmeta.htm#H4
- Considine, Douglas M.; Considine, Glenn D. (1985). Process instruments and controls handbook (3 ed.). McGraw-Hill. p. 18-61. ISBN 0-070-12436-1.
- Ancient Chinese Astronomy
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- Agustín Udías, p.53
- Pais, pp. 93–100.