2 Islamic contributions to physics

When the power of Greek civilization was eclipsed by the Roman Empire, many Greek doctors began to practice medicine for the Roman elite, but sadly the physical sciences were not so well supported. Following the collapse of the Roman Empire, Europe entered the so-called Dark Ages, and almost all scientific research ground to a halt. The rise of Christianity saw the suppression and destruction of most classical Greek philosophy (along with Greek and Roman art, literature and religious iconography) as heretical and pagan. In the Middle East, however, many Greek natural philosophers were able to find support in the newly created Arab Caliphate (Empire), and the Islamic scholars built upon previous work in astronomy and mathematics while developing such new fields as alchemy (chemistry). For example, the scholar Muhammad ibn Musa al-Khwarizmi gave his name to what we now call an algorithm, and the word algebra is derived from al-jabr, the beginning of the name of one of his publications in which he developed a system of solving quadratic equations, thus beginning Al-gebra, without which modern physics could hardly exist.

3 Indian contributions to physics

Modern physics can hardly be imagined without a system of arithmetic in which simple calculation is easy enough to make large calulations even possible. The positional number system and the concept of zero were first developed in India and were adopted by the Islamic empire.

4 The Middle Ages

The monk Roger Bacon conducted experiments into optics, although much of it was similar to what had been done and was being done at the time by Arab scholars. He did make a major contribution to the development of science in medieval Europe by writing to the Pope to encourage the study of natural science in university courses and compiling several volumes recording the state of scientific knowledge in many fields at the time. He described the possible construction of a telescope, but there is no strong evidence of his having made one. He recorded the manner in which he conducted his experiments in precise detail so that others could reproduce and independently test his results - a cornerstone of the scientific method, and a continuation of the work of researchers like Al-Batani.

The annexation of the last Muslim states on the Iberian Peninsula (1492) by the recently formed Hispanic monarchy, and the fall of Constantinople in hands of the Turks (1453) coincided with the dawn of the Renaissance. This "rebirth" of European culture was in part brought about by the re-discovery of those elements of ancient Greek, Indian, Chinese and Islamic culture preserved and further developed by Islam from the 8th to the 15th centuries, and translated by Christian Monks into Latin, such as the Almagest.

1 The scientific revolution

The scientific revolution can be viewed as a flowering of the Renaissance and the portal to modern civilization. It started with only a few researchers, evolving into an enterprise which continues to the present day. Starting with astronomy, the principles of natural philosophy crystallized into fundamental laws of physics which were enunciated and improved in the succeeding centuries. By the 19th century, the sciences had segmented into multiple fields with specialized researchers and the field of physics, although logically pre-eminent, no longer could claim sole ownership of the entire field of scientific research.

1.1 16th century

In the 16th century Nicholas Copernicus revived the heliocentric model of the solar system devised by Aristarchus (which survives primarily in a passing mention in the Sand Reckoner of Archimedes). When this model was published at the end of his life, it was with a preface by Osiander that piously represented it as only a mathematical convenience for calculating the positions of planets, and not an account of the true nature of the planetary orbits.

In England William Gilbert (1544-1603) studied magnetism and published a seminal work, De Magnete (1600), in which he thoroughly presented his numerous experimental results.

1.2 17th century

In the early 17th century Kepler formulated a model of the solar system based upon the five Platonic solids, in an attempt to explain why the orbits of the planets had the relative sizes they did. His access to extremely accurate astronomical observations by Tycho Brahe enabled him to determine that his model was inconsistent with the observed orbits. After a heroic seven-year effort to more accurately model the motion of the planet Mars (during which he laid the foundations of modern integral calculus) he concluded that the planets follow not circular orbits, but elliptical orbits with the Sun at one focus of the ellipse. This breakthrough overturned a millennium of dogma based on Ptolemy's idea of "perfect" circular orbits for the "perfect" heavenly bodies. Kepler then went on to formulate his three laws of planetary motion. He also proposed the first known model of planetary motion in which a force emanating from the Sun deflects the planets from their "natural" motion, causing them to follow curved orbits.

During the early 17th century, Galileo pioneered the use of experiment to validate physical theories, which is the key idea in the scientific method. Galileo's use of experiment, and the insistence of Galileo and Kepler that observational results must always take precedence over theoretical results (in which they followed the precepts of Aristotle if not his practice), brushed away the acceptance of dogma, and gave birth to an era where scientific ideas were openly discussed and rigorously tested. Galileo formulated and successfully tested several results in dynamics, including the correct law of accelerated motion, the parabolic trajectory, the relativity of unaccelerated motion, and an early form of the Law of Inertia.

In 1687, Isaac Newton published the Principia Mathematica, detailing two comprehensive and successful physical theories: Newton's laws of motion, from which arise classical mechanics; and Newton's Law of Gravitation, which describes the fundamental force of gravity. Both theories agreed well with experiment. Classical mechanics would be exhaustively extended by Lagrange, Hamilton, and others, who produced new formulations, principles, and results. The Law of Gravitation initiated the field of astrophysics, which describes astronomical phenomena using physical theories.

We should include something here about Huygens' observations of Saturn's rings, and his debates with Newton about whether light was a wave or a particle.

1.3 18th century

From the 18th century onwards, thermodynamic concepts were developed by Boyle, Young, and many others, concurrently with the development of the steam engine, onward into the next century. In 1733, Daniel Bernoulli used statistical arguments with classical mechanics to derive thermodynamic results, initiating the field of statistical mechanics. Benjamin Franklin conducted his researches into the nature of electricity in 1752. In 1798, Thompson demonstrated the conversion of unlimited mechanical work into heat; it would take the work of Joule to demonstrate the conservation of energy in the next century.

1.4 19th century

In a letter to the Royal Society in 1800, Alessandro Volta described his invention of the electric battery, thus providing for the first time the means to generate a constant electric current, and opening up a new field of physics for investigation.

In 1847 Joule stated the law of conservation of energy, in the form of heat as well as mechanical energy. However, the principle of conservation of energy had been suggested or enunciated in various forms by perhaps a dozen German, French, British and other scientists during the first half of the 19th Century.

The behavior of electricity and magnetism was studied by Faraday, Ohm, and others. Faraday, who began his career in chemistry working under Humphrey Davy at the Royal Institution, demonstrated that electrostatic phenomena, the action of the newly discovered electric pile or battery, electrochemical phenomena, and lightning were all different manifestations of electrical phenomena. Faraday further discovered in 1821 that electricity can cause rotational mechanical motion, and in 1831 discovered the principle of electromagnetic induction, by which means mechanical motion is converted into electricity. Thus it was Faraday who laid the foundations for both the electric motor and the electric generator.

In 1855, Maxwell unified the two phenomena into a single theory of electromagnetism, described by Maxwell's equations. A prediction of this theory was that light is an electromagnetic wave. A more subtle part of Maxwell's deduction was that the observed speed of light does not depend on the speed of the observer, a premonition of the development of special relativity by Einstein.

In 1887 the Michelson-Morley experiment is conducted and it is interpertated as counter to the general held theory of the day, that the Earth was moving through a " luminiferous aether". The development of what later became Einstein's Special Theory of Relativity provided a complete explanation which did not require an aether, and was consistent with the results of the experiment. Michelson and Morely are not convinced of the non-existence of the aether. Morely goes on to conduct experiments with Miller.

In 1887, Tesla investigates X-rays using his own devices as well as Crookes tubes. In 1895, Röntgen observes and analysies X-rays, which turned out to be high-frequency electromagnetic radiation. Radioactivity was discovered in 1896 by Henri Becquerel, and further studied by the Pierre Curie and Marie Curie and others. This initiated the field of nuclear physics.

In 1897, Thomson studies the electron, the elementary particle which carries electrical current in circuits. He deduces that cathode rays existed and were negatively charged "particles", which he called "corpuscles".

1.5 20th century

The beginning of the 20th century brought the start of a revolution in physics. The long-held theories of Newton were shown not to be correct in all circumstances. Not only did quantum mechanics show that the laws of motion didn't hold on small scales, but even more disturbingly, general relativity showed that the fixed background of spacetime, on which both Newtonian mechanics and special relativity depended, could not exist.

In 1904, Thomson proposed the first model of the atom, known as the plum pudding model. (The existence of the atom had been proposed in 1808 by Dalton.)

In 1905, Einstein formulated the theory of special relativity, unifying space and time into a single entity, spacetime. Relativity prescribes a different transformation between reference frames than classical mechanics, necessitating the development of relativistic mechanics as a replacement for classical mechanics. In the regime of low (relative) velocities, the two theories agree. In 1915, Einstein extended special relativity to explain gravity with the general theory of relativity, which replaces Newton's law of gravitation. In the regime of low masses and energies, the two theories agree. One principal result of General Relativity is gravitational collapse into black holes, which was anticipated two centuries earlier, but elucidated by Robert Oppenheimer. Oppenheimer would later direct the Manhattan project in Los Alamos. Important exact soultion of Einstein's field equation were found by Karl Schwarzschild in 1915 and Roy Kerr only in 1963.

In 1911, Rutherford deduced from scattering experiments the existence of a compact atomic nucleus, with positively charged constituents dubbed protons. Neutrons, the neutral nuclear constituents, were discovered in 1932 by Chadwick.

Beginning in 1900, Planck, Einstein, Bohr, and others developed quantum theories to explain various anomalous experimental results by introducing discrete energy levels. In 1925, Heisenberg and Schrödinger formulated quantum mechanics, which explained the preceding quantum theories. In quantum mechanics, the outcomes of physical measurements are inherently probabilistic. The theory describes the calculation of these probabilities. It successfully describes the behavior of matter at small distance scales.

Quantum mechanics also provided the theoretical tools for condensed matter physics, which studies the physical behavior of solids and liquids, including phenomena such as crystal structures, semiconductivity, and superconductivity. The pioneers of condensed matter physics include Bloch, who created a quantum mechanical description of the behavior of electrons in crystal structures in 1928.

In 1929, Edwin Hubble published his discovery that the speed at which galaxies recede positively correlates with their distance. This is the basis for understanding that the universe is expanding. Thus, the universe must have been smaller and therefore hotter in the past. By the 1940s, researchers like George Gamow proposed the Big Bang theory, evidence for which was discovered in 1964; Enrico Fermi and Fred Hoyle were among the doubters, in the the 1940s and 1950s. Hoyle had dubbed Gamow's theory the Big Bang in order to debunk it. Today, it is one of the principal results of cosmology, with a well-accepted age of the universe.

During World War II, research was conducted by each side into nuclear physics, for the purpose of creating a nuclear bomb. The German effort, led by Heisenberg, did not succeed, but the Allied Manhattan Project reached its goal. In America, a team led by Fermi achieved the first man-made nuclear chain reaction in 1942, and in 1945 the world's first nuclear explosive was detonated at Trinity Site, north of Alamogordo, New Mexico.

Quantum field theory was formulated in order to extend quantum mechanics to be consistent with special relativity. It achieved its modern form in the late 1940s with work by Feynman, Schwinger, Tomonaga, and Dyson. They formulated the theory of quantum electrodynamics, which describes the electromagnetic interaction.

Quantum field theory provided the framework for modern particle physics, which studies fundamental forces and elementary particles. In 1954, Yang and Mills developed a class of gauge theories, which provided the framework for the Standard Model. The Standard Model, which was completed in the 1970s, successfully describes almost all elementary particles observed to date.

At the same time, Stephen Hawking had discovered the spectrum of radiation emanating during the collapse of matter into black holes; by 2004, even Hawking would admit that some Hawking radiation could escape a black hole.

1.6 Developments since 1990

Attempts to unify quantum mechanics and general relativity made signficant progress during the 1990s. At the close of the century, a Theory of everything was still not in hand, but some of its characteristics were taking shape. Loop quantum gravity, string theory, and black hole thermodynamics all predicted quantized spacetime on the Planck scale.

1.7 Developments since 2000

A new experiment demonstrated that gravity propagates at approximately the speed of light, confirming one prediction of both general relativity and loop quantum gravity.

-- add stuff on convergence of superstring stuff to M-theory

See also: History of science and technology

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