1Egyptian alchemy [3,000 BCE – 400 BCE], formulate early "element" theories such as the Ogdoad.
2Greek alchemy [332 BCE – 642 CE], the Macedonian king Alexander the Great conquers Egypt and founds Alexandria, having the world's largest library, where scholars and wise men gather to study.
3Islamic alchemy [642 CE – 1200], the Muslim conquest of Egypt; development of alchemy by Jābir ibn Hayyān, al-Razi and others; Jābir modifies Aristotle's theories; advances in processes and apparatus.
4European alchemy [1300 – present], Pseudo-Geber builds on Arabic chemistry.[citation needed] From the 12th century, major advances in the chemical arts shifted from Arab lands to western Europe.
5.Chemistry [1661], Boyle writes his classic chemistry text The Sceptical Chymist.
6.Chemistry [1787], Lavoisier writes his classic Elements of Chemistry.
7.Chemistry [1803], Dalton publishes his Atomic Theory.
8.Chemistry [1869], Dmitri Mendeleev presented his Periodic table being the framework of the modern chemistry
Monday, September 12, 2011
Newton's law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. (Separately it was shown that large spherically symmetrical masses attract and are attracted as if all their mass were concentrated at their centers.) This is a general physical law derived from empirical observations by what Newton called induction.[2] It is a part of classical mechanics and was formulated in Newton's work Philosophiae Naturalis Principia Mathematica ("the Principia"), first published on 5 July 1687. (When Newton's book was presented in 1686 to the Royal Society, Robert Hooke made a claim that Newton had obtained the inverse square law from him – see History section below.) In modern language, the law states the following:Every point mass attracts every single other point mass by a force pointing along the line intersecting both points. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between them:
Assuming SI units, F is measured in newtons (N), m1 and m2 in kilograms (kg), r in meters (m), and the constant G is approximately equal to 6.674×10−11 N m2 kg−2.[4] The value of the constant G was first accurately determined from the results of the Cavendish experiment conducted by the British scientist Henry Cavendish in 1798, although Cavendish did not himself calculate a numerical value for G.[5] This experiment was also the first test of Newton's theory of gravitation between masses in the laboratory. It took place 111 years after the publication of Newton's Principia and 71 years after Newton's death, so none of Newton's calculations could use the value of G; instead he could only calculate a force relative to another force.
Newton's law of gravitation resembles Coulomb's law of electrical forces, which is used to calculate the magnitude of electrical force between two charged bodies. Both are inverse-square laws, in which force is inversely proportional to the square of the distance between the bodies. Coulomb's Law has the product of two charges in place of the product of the masses, and the electrostatic constant in place of the gravitational constant.
Newton's law has since been superseded by Einstein's theory of general relativity, but it continues to be used as an excellent approximation of the effects of gravity. Relativity is required only when there is a need for extreme precision, or when dealing with gravitation for extremely massive and dense objects.
Saturday, September 3, 2011
Albert Einstein
The Annus Mirabilis papers (from Latin annus mīrābilis, "extraordinary year") are the papers of Albert Einstein published in the Annalen der Physik scientific journal in 1905. These four articles contributed substantially to the foundation of modern physics and changed views on space, time, and matter. The Annus Mirabilis is often called the "Miracle Year" in English or Wunderjahr in German.
Background
At the time the papers were written, Einstein did not have easy access to a complete set of scientific reference materials, although he did regularly read and contribute reviews to Annalen der Physik. Additionally, scientific colleagues available to discuss his theories were few. He worked as an examiner at the Patent Office in Bern, Switzerland, and he later said of a co-worker there, Michele Besso, that he "could not have found a better sounding board for his ideas in all of Europe". In addition to co-workers and the other members of the self-styled "Olympian Academy" (Solovine and Habicht), his wife, Mileva Marić, may have had some influence on Einstein's work but how much is unclear. Through these papers, Einstein tackles some of the era's most important physics questions and problems. In 1900, a lecture titled "Nineteenth-Century Clouds over the Dynamical Theory of Heat and Light", by Lord Kelvin, suggested that physics had no satisfactory explanations for the results of the Michelson-Morley experiment and for black body radiation. As introduced, special relativity provided an account for the results of the Michelson-Morley experiments. Einstein's theories for the photoelectric effect extended the quantum theory which Max Planck had developed in his successful explanation of black body radiation.
Despite the greater fame achieved by his other works, such as that on special relativity, it was his work on the photoelectric effect which won him his Nobel Prize in 1921: "For services to theoretical physics and especially for the discovery of the law of the photoelectric effect." The Nobel committee had waited patiently for experimental confirmation of special relativity; however none was forthcoming until the time dilation experiments of Ives and Stilwell (1938),(1941)and Rossi and Hall (1941)
1.Photoelectric effect
2.Brownian motion
3.Special relativity
4.Matter and energy equivalence
http://en.wikipedia.org/wiki/Annus_Mirabilis_papers
Background
At the time the papers were written, Einstein did not have easy access to a complete set of scientific reference materials, although he did regularly read and contribute reviews to Annalen der Physik. Additionally, scientific colleagues available to discuss his theories were few. He worked as an examiner at the Patent Office in Bern, Switzerland, and he later said of a co-worker there, Michele Besso, that he "could not have found a better sounding board for his ideas in all of Europe". In addition to co-workers and the other members of the self-styled "Olympian Academy" (Solovine and Habicht), his wife, Mileva Marić, may have had some influence on Einstein's work but how much is unclear. Through these papers, Einstein tackles some of the era's most important physics questions and problems. In 1900, a lecture titled "Nineteenth-Century Clouds over the Dynamical Theory of Heat and Light", by Lord Kelvin, suggested that physics had no satisfactory explanations for the results of the Michelson-Morley experiment and for black body radiation. As introduced, special relativity provided an account for the results of the Michelson-Morley experiments. Einstein's theories for the photoelectric effect extended the quantum theory which Max Planck had developed in his successful explanation of black body radiation.
Despite the greater fame achieved by his other works, such as that on special relativity, it was his work on the photoelectric effect which won him his Nobel Prize in 1921: "For services to theoretical physics and especially for the discovery of the law of the photoelectric effect." The Nobel committee had waited patiently for experimental confirmation of special relativity; however none was forthcoming until the time dilation experiments of Ives and Stilwell (1938),(1941)and Rossi and Hall (1941)
1.Photoelectric effect
2.Brownian motion
3.Special relativity
4.Matter and energy equivalence
http://en.wikipedia.org/wiki/Annus_Mirabilis_papers
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