वैज्ञानिक अभिकलन का कालक्रम

यहाँ वैज्ञानिक परिकलन की कालरेखा दी गयी है। आधुनिक कम्प्यूतरों के पूर्व १८वीं शताब्दी 1733 - फ्रान्सीसी प्रकृतिविज्ञानी कॉम्त दी बफों (Comte de Buffon) ने अपनी सुई समस्या (Buffon's needle) प्रस्तुत की।Buffon, G. Editor's note concerning a lecture given 1733 by Mr. Le Clerc de Buffon to the Royal Academy of Sciences in Paris. Histoire de l'Acad. Roy. des Sci., pp. 43-45, 1733; according to Weisstein, Eric W. "Buffon's Needle Problem." https://web.archive.org/web/20110524030519/http://mathworld.wolfram.com/BuffonsNeedleProblem.html 24 मई 2011 From MathWorld--A Wolfram Web Resource. 20 Dec 2012 20 Dec 2012.Buffon, G. "Essai d'arithmétique morale." Histoire naturelle, générale er particulière, Supplément 4, 46-123, 1777; according to Weisstein, Eric W. "Buffon's Needle Problem." https://web.archive.org/web/20110524030519/http://mathworld.wolfram.com/BuffonsNeedleProblem.html 24 मई 2011 From MathWorld--A Wolfram Web Resource. 20 Dec 2012 आइलर ने आइलर समाकलन (Euler integration) प्रस्तुत किया जो समाकलन की एक सरल संख्यात्मक विधि था। Euler, L. Institutionum calculi integralis. Impensis Academiae Imperialis Scientiarum, 1768.Butcher, John C. (2003), Numerical Methods for Ordinary Differential Equations, New York: John Wiley & Sons, 978-0-471-96758-3.Hairer, Ernst; Nørsett, Syvert Paul; Wanner, Gerhard (1993), Solving ordinary differential equations I: Nonstiff problems, Berlin, New York: Springer-Verlag, 978-3-540-56670-0. १९वीं शताब्दी First formulation of Gram-Schmidt orthogonalisation by Laplace,Laplace, PS. (1816). Théorie Analytique des Probabilités :First Supplement, p. 497ff. to be further improved decades later. Gram J. P. 1883 Ueber die Entwickelung reeler Funtionen in Reihen mittelst der Methode der kleinsten Quadrate, Jrnl. für die reine und angewandte Math. 94 71–73 Schmidt E. Zur Theorie der linearen und nichtlinearen Integralgleichungen. I. Teil: Entwicklung willkürlicher Funktionen nach Systemen vorgeschriebener, Math. Ann. 63 1907 Earliest Known Uses of Some of the Words of Mathematics (G). https://web.archive.org/web/20180726222410/http://jeff560.tripod.com/g.html#GRAM-SCHMIDT%20ORTHOGONALIZATION 26 जुलाई 2018 As of Aug 2017.Farebrother RW Linear Least Squares Computations 1988 CRC Press 9780824776619 https://books.google.com/books?id=aCS0zw7SztEC 19 August 2017 Babbage in 1822, began work on a machine made to compute/calculate values of polynomial functions automatically by using the method of finite differences. This was eventually called the Difference engine. Lovelace's note G on the Analytical Engine (1842) describes an algorithm for generating Bernoulli numbers. It is considered the first algorithm ever specifically tailored for implementation on a computer, and thus the first-ever computer programme.Simonite Tom https://www.newscientist.com/blogs/shortsharpscience/2009/03/ada-lovelace-day.html Short Sharp Science: Celebrating Ada Lovelace: the 'world's first programmer' New Scientist 24 March 2009 14 April 2012 https://web.archive.org/web/20090327073325/https://www.newscientist.com/blogs/shortsharpscience/2009/03/ada-lovelace-day.html 27 मार्च 2009 liveTom Stoppard’s “Arcadia,” at Twenty. https://web.archive.org/web/20140219030235/http://www.newyorker.com/online/blogs/books/2013/08/tom-stoppards-arcadia-at-twenty.html 19 फ़रवरी 2014 By Brad Leithauser. The New Yorker, August 8, 2013. The engine was never completed, however, so her code was never tested.Ada and the first computer https://archive.org/details/sim_scientific-american_1999-05_280_5/page/70 Kim Eugene Eric Toole Betty Alexandra Scientific American May 1999 280 5 70–71 10.1038/scientificamerican0599-76 In applied mathematics, Jacobi develops technique for solving numerical equations.Jacobi’s Ideas on Eigenvalue Computation in a modern context https://web.archive.org/web/20061210163746/http://canum2006.univ-rennes1.fr/exposes_et_posters/vandervorst.pdf 10 दिसंबर 2006 , Henk van der Vorst.Jacobi method, https://web.archive.org/web/20141110104707/http://www.encyclopediaofmath.org/index.php/Jacobi_method 10 नवंबर 2014 Encyclopedia of Mathematics.The Early History of Matrix Iterations: With a Focus on the Italian Contribution https://web.archive.org/web/20140707153213/https://www.siam.org/meetings/la09/talks/benzi.pdf 7 जुलाई 2014 , Michele Benzi, 26 October 2009. SIAM Conference on Applied Linear Algebra, Monterey Bay – Seaside, California. १९०० का दशक 1900 - कार्ल रुंगे (Carl Runge) और मार्टिन कुटा (Martin Kutta) ने रुंगा-कुटा विधि का विकास किया जो अवकल समीकरणों के समाकलन की एक विधि थी।MW Kutta. "Beiträge zur näherungsweisen Integration totaler Differentialgleichungen" [Contributions to the approximate integration of total differential equations] (in German). Thesis, University of Munich. 1901 - Reprinted Z. Math. Phys. 46 1901 435–453 and in B.G Teubner, 1901.Runge, C., "Über die numerische Auflösung von Differentialgleichungen" [About the numerical solution of differential equations](in German), Math. Ann. 46 (1895) 167-178. १९१० का दशक 1910 - A-M Cholesky creates a matrix decomposition scheme.Commandant Benoit Note sur une méthode de résolution des équations normales provenant de l'application de la méthode des moindres carrés à un système d'équations linéaires en nombre inférieur à celui des inconnues (Procédé du Commandant Cholesky) Bulletin Géodésique 2 1924 67–77Cholesky André-Louis Cholesky Sur la résolution numérique des systèmes d'équations linéaires 1910 (manuscript) १९२० का दशक 1922 - Lewis Fry Richardson introduces numerical weather forecasting by manual calculation, using methods originally developed by Vilhelm Bjerknes as early as 1895.L F Richardson, Weather Prediction by Numerical Process. कैम्ब्रिज यूनिवर्सिटी प्रेस (1922).Lynch Peter The origins of computer weather prediction and climate modeling Journal of Computational Physics March 2008 227 7 3431–44 10.1016/j.jcp.2007.02.034 2008JCoPh.227.3431L University of Miami http://www.rsmas.miami.edu/personal/miskandarani/Courses/MPO662/Lynch,Peter/OriginsCompWF.JCP227.pdf 2010-12-23 dead https://web.archive.org/web/20100708191309/http://www.rsmas.miami.edu/personal/miskandarani/Courses/MPO662/Lynch,Peter/OriginsCompWF.JCP227.pdf 2010-07-08 1926 - Grete Hermann publishes foundational paper for computer algebra, which established the existence of algorithms (including complexity bounds) for many of the basic problems of abstract algebra, such as ideal membership for polynomial rings.Grete Hermann Die Frage der endlich vielen Schritte in der Theorie der Polynomideale Mathematische Annalen 1926 95 736–788 http://gdz.sub.uni-goettingen.de/index.php?id=11&PPN=PPN235181684_0095&DMDID=DMDLOG_0044&L=1 10.1007/bf01206635 21 जुलाई 2018 https://web.archive.org/web/20161009190144/http://gdz.sub.uni-goettingen.de/index.php?id=11&PPN=PPN235181684_0095&DMDID=DMDLOG_0044&L=1 9 अक्तूबर 2016 dead 1927 - Douglas Hartree creates what is later known as the Hartree–Fock method, the first ab initio quantum chemistry methods. However, manual solutions of the Hartree–Fock equations for a medium-sized atom were laborious and small molecules required computational resources far beyond what was available before 1950. १९३० का दशक This decade marks the first major strides to a modern computer, and hence the start of the modern era. Fermi's Rome physics research group (informal name I ragazzi di Via Panisperna) develop statistical algorithms based on Comte de Buffon's work, that would later become the foundation of the Monte Carlo method. See also FERMIAC. John Vincent Atanasoff and Clifford Berry create the first electronic non-programmable, digital computing device, the Atanasoff–Berry Computer, from 1937-42. Complex number calculator created by Stibitz. १९४० का दशक 1947 - Monte Carlo simulation (voted one of the top 10 algorithms of the 20th century) invented at Los Alamos by von Neumann, Ulam and Metropolis.Metropolis N. The Beginning of the Monte Carlo method Los Alamos Science 1987 No. 15, Page 125 http://library.lanl.gov/cgi-bin/getfile?15-12.pdf 21 जुलाई 2018 https://web.archive.org/web/20111017191400/http://library.lanl.gov/cgi-bin/getfile?15-12.pdf 17 अक्तूबर 2011 dead. Accessed 5 may 2012.S. Ulam, R. D. Richtmyer, and J. von Neumann(1947). Statistical methods in neutron diffusionदिसंबर 2024 InternetArchiveBot . Los Alamos Scientific Laboratory report LAMS–551. Metropolis N. Ulam S. 1949 The Monte Carlo method https://archive.org/details/sim_journal-of-the-american-statistical-association_1949-06_44_246/page/n182 Journal of the American Statistical Association 44 335–341 10.1080/01621459.1949.10483310 George Dantzig introduces the simplex method (voted one of the top 10 algorithms of the 20th century) in 1947.SIAM News, November 1994. http://www.stanford.edu/group/SOL/dantzig.html 6 June 2012 https://web.archive.org/web/20090416184457/http://www.stanford.edu/group/SOL/dantzig.html 16 अप्रैल 2009 live Systems Optimization Laboratory, Stanford University Huang Engineering Center (site host/mirror). Ulam and von Neumann introduce the notion of cellular automata.Von Neumann, J., Theory of Self-Reproduiing Automata, Univ. of Illinois Press, Urbana, 1966. Turing formulated the LU decomposition method.A. M. Turing, Rounding-off errors in matrix processes. Quart. J Mech. Appl. Math. 1 (1948), 287–308 (according to Poole, David (2006), Linear Algebra: A Modern Introduction (2nd ed.), Canada: Thomson Brooks/Cole, 0-534-99845-3.) . Philips creates (invents?) the MONIAC hydraulic computer at LSE, better known as "Philip's Economic Computer".The computer model that once explained the British economy. https://web.archive.org/web/20180818043008/https://www.theguardian.com/business/2008/may/08/bankofenglandgovernor.economics 18 अगस्त 2018 Larry Elliott, The Guardian, Thursday 8 May 2008.Phillip's Economic Computer, 1949. https://web.archive.org/web/20141003075541/http://www.sciencemuseum.org.uk/objects/computing_and_data_processing/1995-210.aspx 3 अक्तूबर 2014 Exhibit at London Science Museum. First hydro simulations occurred at Los Alamos.Richtmyer, R. D. (1948). Proposed Numerical Method for Calculation of Shocks. Los Alamos, NM: Los Alamos Scientific Laboratory LA-671. Von Neumann J. Richtmyer R. D. 1950 A Method for the Numerical Calculation of Hydrodynamic Shocks https://archive.org/details/sim_journal-of-applied-physics_1950-03_21_3/page/232 Journal of Applied Physics 21 232–237 10.1063/1.1699639 1950JAP....21..232V १९५० का दशक First successful weather predictions on a computer occurred. Charney J. Fjørtoft R. von Neumann J. 1950 Numerical Integration of the Barotropic Vorticity Equation 10.1111/j.2153-3490.1950.tb00336.x Tellus 2 4 237–254See the review article:- Smagorinsky J The Beginnings of Numerical Weather Prediction and General Circulation Modelling: Early Recollections Advances in Geophysics 1983 25 http://docs.lib.noaa.gov/rescue/JNWP/50th_Symp_2004_CD.PDF/JNWPU_2004_All/1010.pdf 6 June 2012 https://web.archive.org/web/20140822055804/http://docs.lib.noaa.gov/rescue/JNWP/50th_Symp_2004_CD.PDF/JNWPU_2004_All/1010.pdf 22 अगस्त 2014 live Hestenes, Stiefel, and Lanczos, all from the Institute for Numerical Analysis at the National Bureau of Standards, initiate the development of Krylov subspace iteration methods.Magnus R. Hestenes and Eduard Stiefel, Methods of Conjugate Gradients for Solving Linear Systems, J. Res. Natl. Bur. Stand. 49, 409-436 (1952).Eduard Stiefel,U¨ ber einige Methoden der Relaxationsrechnung (in German), Z. Angew. Math. Phys. 3, 1-33 (1952).Cornelius Lanczos, Solution of Systems of Linear Equations by Minimized Iterations, J. Res. Natl. Bur. Stand. 49, 33-53 (1952).Cornelius Lanczos, An Iteration Method for the Solution of the Eigenvalue Problem of Linear Differential and Integral Operators, J. Res. Natl. Bur. Stand. 45, 255-282 (1950). Voted one of the top 10 algorithms of the 20th century. Equations of State Calculations by Fast Computing Machines introduces the Metropolis–Hastings algorithm. Metropolis N. Rosenbluth A.W. Rosenbluth M.N. Teller A.H. Teller E. 1953 Equations of State Calculations by Fast Computing Machines http://www.aliquote.org/pub/metropolis-et-al-1953.pdf PDF Journal of Chemical Physics 21 6 1087–1092 10.1063/1.1699114 1953JChPh..21.1087M 21 जुलाई 2018 https://web.archive.org/web/20160305195820/http://www.aliquote.org/pub/metropolis-et-al-1953.pdf 5 मार्च 2016 dead Molecular dynamics invented by Bernie Alder and Wainwright Alder B. J. Wainwright T. E. 1957 Phase Transition for a Hard Sphere System https://archive.org/details/sim_journal-of-chemical-physics_1957-11_27_5/page/1208 J. Chem. Phys. 27 5 1208 10.1063/1.1743957 Alder B. J. Wainwright T. E. 1962 Phase Transition in Elastic Disks https://archive.org/details/sim_physical-review_1962-07-15_127_2/page/n28 Phys. Rev. 127 2 359–361 10.1103/PhysRev.127.359 Householder invents his eponymous matrices and transformation method (voted one of the top 10 algorithms of the 20th century).A. S. Householder Unitary Triangularization of a Nonsymmetric Matrix https://archive.org/details/sim_association-for-computing-machinery-journal_1958-10_5_4/page/339 Journal of the ACM 5 4 1958 339–342 10.1145/320941.320947 0111128 1940 - Enrico Fermi, John Pasta, Stanislaw Ulam, and Mary Tsingou discover the Fermi–Pasta–Ulam–Tsingou problem through computer simulations of a vibrating string.Fermi, E. (posthumously); Pasta, J.; Ulam, S. (1955) : Studies of Nonlinear Problems (accessed 25 Sep 2012) https://web.archive.org/web/20170618200534/https://www.osti.gov/accomplishments/documents/fullText/ACC0041.pdf 18 जून 2017 . Los Alamos Laboratory Document LA-1940. Also appeared https://web.archive.org/web/20140821071336/http://www.cs.princeton.edu/courses/archive/fall09/cos323/papers/fpu55.pdf 21 अगस्त 2014 in 'Collected Works of Enrico Fermi', E. Segre ed. , University of Chicago Press, Vol.II,978–988,1965. Recovered 21 Dec 2012 A team led by Backus develops the FORTRAN compiler and programming language at IBM's research centre in San Jose, California. This sped the adoption of scientific programming,W.W. McDowell Award citation: W. Wallace McDowell Award http://www.computer.org/portal/site/ieeecs/menuitem.c5efb9b8ade9096b8a9ca0108bcd45f3/index.jsp?&pName=ieeecs_level1&path=ieeecs/about/awards&file=WallaceMcD_recipients.xml&xsl=generic.xsl& April 15, 2008 https://web.archive.org/web/20070929133553/http://www.computer.org/portal/site/ieeecs/menuitem.c5efb9b8ade9096b8a9ca0108bcd45f3/index.jsp?&pName=ieeecs_level1&path=ieeecs%2Fabout%2Fawards&file=WallaceMcD_recipients.xml&xsl=generic.xsl& 29 सितंबर 2007 deadNational Medal of Science citation: The President's National Medal of Science: John Backus National Science Foundation https://www.nsf.gov/od/nms/recip_details.cfm?recip_id=25 March 21, 2007 https://web.archive.org/web/20070929111636/http://www.nsf.gov/od/nms/recip_details.cfm?recip_id=25 29 सितंबर 2007 live ACM Turing Award Citation: John Backus Association for Computing Machinery http://www.acm.org/awards/turing_citations/backus.html March 22, 2007 https://web.archive.org/web/20070204114319/http://www.acm.org/awards/turing_citations/backus.html February 4, 2007 dead and is one of the oldest extant programming languages, as well as one of the most popular in science and engineering. १९६० का दशक 1960 - First recorded use of the term "finite element method" by Ray Clough to describe the earlier methods of Richard Courant, Alexander Hrennikoff and Olgierd Zienkiewicz in structural analysis.RW Clough, "The Finite Element Method in Plane Stress Analysis," Proceedings of 2nd ASCE Conference on Electronic Computation, Pittsburgh, PA, Sept. 8, 9, 1960. 1961 - John G.F. Francis Francis J.G.F. 1961 The QR Transformation, I The Computer Journal 4 3 265–271 10.1093/comjnl/4.3.265 Francis J.G.F. 1962 The QR Transformation, II The Computer Journal 4 4 332–345 10.1093/comjnl/4.4.332 and Vera Kublanovskaya Kublanovskaya Vera N. 1961 On some algorithms for the solution of the complete eigenvalue problem USSR Computational Mathematics and Mathematical Physics 1 3 637–657 10.1016/0041-5553(63)90168-X Also published in: Zhurnal Vychislitel'noi Matematiki i Matematicheskoi Fiziki [Journal of Computational Mathematics and Mathematical Physics], 1(4), pages 555–570 (1961). invent QR factorization (voted one of the top 10 algorithms of the 20th century). 1963 - Edward Lorenz discovers the butterfly effect on a computer, attracting interest in chaos theory.Lorenz Edward N. Deterministic Nonperiodic Flow Journal of the Atmospheric Sciences 20 2 130–141 1963 http://www.nd.edu/~powers/ame.60611/lorenz.article.pdf 10.1175/1520-0469(1963)020<0130:dnf>2.0.co;2 21 जुलाई 2018 https://web.archive.org/web/20140821153438/http://www3.nd.edu/~powers/ame.60611/lorenz.article.pdf 21 अगस्त 2014 live 1961 - Using computational investigations of the 3-body problem, Michael Minovitch formulates the gravity assist method.Minovitch, Michael: "A method for determining interplanetary free-fall reconnaissance trajectories," Jet Propulsion Laboratory Technical Memo TM-312-130, pages 38-44 (23 August 1961).Christopher Riley and Dallas Campbell, Oct 22, 2012. "The maths that made Voyager possible" https://web.archive.org/web/20170220175602/http://acn.com.ve/ 20 फ़रवरी 2017 . BBC News Science and Environment. Recovered 16 Jun 2013. 1964 - Molecular dynamics invented independently by Aneesur Rahman.Rahman A Correlations in the Motion of Atoms in Liquid Argon Phys Rev 1964 136 2A A405–A41 10.1103/PhysRev.136.A405 1964PhRv..136..405R 1965 - Fast Fourier Transform developed by James W. Cooley and John W. Tukey. Cooley James W. Tukey John W. 1965 An algorithm for the machine calculation of complex Fourier series http://attach3.bdwm.net/attach/0Announce/groups/GROUP_3/MathTools/D6714701A/D69595345/M.1089260001.A/CooleyJ_AlgMCC.pdf Math. Comput. 19 297–301 10.1090/s0025-5718-1965-0178586-1 नवंबर 2022 InternetArchiveBot 1964 - Walter Kohn, with Lu Jeu Sham and Pierre Hohenberg, instigates the development of density functional theory, Kohn Walter Hohenberg Pierre 1964 Inhomogeneous Electron Gas Physical Review 136 B864-B871 3B 10.1103/PhysRev.136.B864 1964PhRv..136..864H Kohn Walter Sham Lu Jeu 1965 Self-Consistent Equations Including Exchange and Correlation Effects Physical Review 140 A1133–A1138 4A 10.1103/PhysRev.136.B864 1965PhRv..140.1133K for which he shares the 1998 Nobel Chemistry Prize with John Pople. The Nobel Prize in Chemistry 1998 Nobelprize.org http://nobelprize.org/nobel_prizes/chemistry/laureates/1998/index.html 2008-10-06 https://www.webcitation.org/6HYiCE9Jr?url=http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1998/index.html 22 जून 2013 live This contribution is arguably the first Nobel given for a computer program or computational technique. १९७० का दशक 1975 - Benoit Mandelbrot coins the term "fractal" to describe the self-similarity found in the Fatou, Julia and Mandelbrot sets. Fractals become the first mathematical visualization tool extensively explored with computing.B. Mandelbrot; Les objets fractals, forme, hasard et dimension (in French). Publisher: Flammarion (1975), 9782082106474 ; English translation Fractals: Form, Chance and Dimension. Publisher: Freeman, W. H & Company. (1977). 9780716704737. 1977 - Kenneth Appel and Wolfgang Haken prove the four colour theorem, the first theorem to be proved by computer. Appel Kenneth Haken Wolfgang 1977 Every planar map is four colorable, Part I: Discharging https://archive.org/details/sim_illinois-journal-of-mathematics_1977-09_21_3/page/429 Illinois Journal of Mathematics 21 429–490 Appel K. Haken W. 1977 Every Planar Map is Four-Colorable, II: Reducibility https://archive.org/details/sim_illinois-journal-of-mathematics_1977-09_21_3/page/491 Illinois J. Math. 21 491–567 Appel K. Haken W. 1977 The Solution of the Four-Color Map Problem https://archive.org/details/sim_scientific-american_1977-10_237_4/page/108 Sci. Am. 237 108–121 10.1038/scientificamerican1077-108 १९८० का दशक Fast multipole method (voted one of the top 10 algorithms of the 20th century) invented by Vladimir Rokhlin and Leslie Greengard.L. Greengard, The Rapid Evaluation of Potential Fields in Particle Systems, MIT, Cambridge, (1987).Rokhlin, Vladimir (1985). "Rapid Solution of Integral Equations of Classic Potential Theory." J. Computational Physics Vol. 60, pp. 187-207. Greengard L. Rokhlin V. 1987 A fast algorithm for particle simulations https://archive.org/details/journal-of-computational-physics_1987-12_73_2/page/325 J. Comput. Phys. 73 2 325–348 10.1016/0021-9991(87)90140-9 १९९० का दशक 1990 - In computational genomics and sequence analysis, the Human Genome Project, an endeavour to sequence the entire human genome, begins. 1998 - Kepler conjecture is almost all but certainly proved algorithmically by Thomas Hales. The appearance of the first research grids using volunteer computing - GIMPS (1996), distributed.net (1997) and Seti@Home (1999). २००० का दशक 2000 - The Human Genome Project completes a rough draft of human genome. 2003 - The Human Genome Project completed. 2002 - The BOINC architecture is launched in 2002. २०१० का दशक फोल्डित खिलाडियों ने विषाणु की संरचना का हल निकाला। यह खेल द्वारा वैज्ञानिक प्रशन हल करने के प्रथम कुछ मामलों में से एक है। इन्हें भी देखें वैज्ञानिक अभिकलन अभिकलन का इतिहास गणित का इतिहास गणित की कालरेखा कलनविधियों की कालरेखा अभिकलन हार्डवेयर का इतिहास सन्दर्भ 30em बाहरी कड़ियाँ SIAM (Society for Industrial and Applied Mathematics) News. Top 10 Algorithms of the 20th Century. The History of Numerical Analysis and Scientific Computing @ SIAM (Society for Industrial and Applied Mathematics) Ruttimann Jacqueline 2006 2020 computing: Milestones in scientific computing http://www.nature.com/nature/journal/v440/n7083/full/440399a.html Nature 440 399–405 10.1038/440399a 16554772 21 जुलाई 2018 https://web.archive.org/web/20170503040713/http://www.nature.com/nature/journal/v440/n7083/full/440399a.html 3 मई 2017 live Anderson H. L. 1986 Scientific Uses of the MANIAC https://archive.org/details/journal-of-statistical-physics_1986-06_43_5-6/page/731 Journal of Statistical Physics 43 5–6 731–748 10.1007/BF02628301 1986JSP....43..731A श्रेणी:अभिकलन विज्ञान श्रेणी:विज्ञान कालरेखा