YEAR  DISCOVERY  WHO OR WHERE/WHAT IT IS 
50,000 B.C.E.  Counting  Counting was probably one of the earliest forms of speech, and in many tribes it still presents a relieving simplicity. Perhaps it began during the Upper Paleolithic period. 
35,000  Tally stick/ Lunar calendar  Scholars believe the Lebombo bone found in Swaziland to be a tally stick; it has 29 separate intentionally cut notches in a baboon’s fibula. Presentday Namibian Bushmen use similar calendar sticks. 
10^{th} millennium  Trephining
 Eurasia; trephining of the skull was practiced by primitive medicinemen from the ancient Peruvian Indians to the modern Melanesians; the latter averaged nine successes out of every ten operations, while in 1786 the same operation was invariably fatal at the HôtelDieu in Paris. 
4223  Beginnings of the modern calendar  The Egyptians establish the “modern” calendar on a day that Sirius heliacally rose. 
4000  Opium  Near East 
3500  Astronomic periods
 The Mesopotamians determine the solar year, the lunar month, and the sevenday week. The division of our month into four weeks, of our clock into twelve hours (instead of twentyfour), of our hour into sixty minutes, and of our minute into sixty seconds, are unsuspected Mesopotamian vestiges in our contemporary world. 
3000  Ayurveda
Miasma theory of disease  This “the science of longevity” is the oldest system of Hindu medicine. In it illness is attributed to a disorder in one of the four humors (air, water, phlegm, and blood), and treatment is recommended with herbs and charms. The RigVeda names over a thousand such herbs and advocates water as the best cure for most diseases. Even in Vedic times physicians and surgeons were being differentiated from magic doctors, and were living in houses surrounded by gardens in which they cultivated medicinal plants. It may have influenced later physicians such as Hippocrates and Galen.
At first people around the globe think that disease is a punishment from the gods, but it is probably the Hindus who first consider it as something brought on by foul vapors/air i.e. miasma. 
2700  Acupuncture  The ancient Chinese use this method of controlling the body’s flow of energy to heal. By the 17^{th} century, it reaches the West. 
2000  Planetary movement
Sex in plants  Mesopotamian observations reveal that there are “stars” that move in the sky and follow patterns, demonstrating that the Earth is part of a solar system of planets separate from the fixed stars.
Mesopotamia 
1900  Law of “Pythagoras” a^{2} + b^{2} = c^{2}  Thirteen hundred years before Pythagoras’ birth, the Mesopotamians understood this quite well.

1800  Geometry problems
Quadratic equation  Egyptian Moscow mathematical papyrus
In Berlin Papyrus 6619, Egyptian mathematicians deal with a quadratic equation and provide its solution. 
17^{th} century  Venus tablet
 Mesopotamian astronomers of Ammisaduqa’s time make the first known observations on Venus. 
1650  Fractions, first degree algebraic equations  In the Rhind mathematical papyrus the Egyptians displayed their knowledge of fractions, but always with the numerator 1; to express ¾ they wrote ½ + ¼. The Arabs of the Islamic Golden Age added a horizontal bar between numerator and denominator to give us our modern form of the fraction. The Rhind illustrates by examples the computation of the capacity of a barn or the area of a field, and passes to algebraic equations of the first degree. 
1600  Basic empirical methodology in medicine  The Edwin Smith papyrus, an Egyptian medical textbook, employs the procedure of examination, diagnosis, treatment, and prognosis, to the curing of disease—precisely the procedure we use today. 
1500  Cosmological theory  “The Hindu Rigveda of ancient India,” writes Luke Mastin “describes the origin of the universe in which a ‘cosmic egg’ or Brahmanda, containing the Sun, Moon, planets and the whole universe, expands out of a single concentrated point before subsequently collapsing again, reminiscent of the much later Big Bang and oscillating universe theories.” 
15001200  Infinity  The Hindu Yajurveda makes the earliest extant reference to it 
1150  Navigation using the pole star  Phoenicians 
1000  Magnetism  The ancient Greeks learn about the magnetic properties of the lodestone and its ability to attract iron. 
9^{th} century  Heliocentric theory
 Yajnavalkya, a Hindu philosopher, speculates that the Sun lay at “the center of the spheres” of the universe. Contemporaneously, his fellow countryman Mahidasa Aitareya also proclaims this doctrine in his Brahmana. As late as the 3^{rd} century B.C.E., Aristarchus of Samos also proposes a Suncentered universe. 
800600  Geometry, quadratic equations, the square root of two, the Pythagorean theorem and Pythagorean triplets  The Hindu Shulba Sutra 
7^{th} century  Magic square  Mathematical table discovered in China and brought west in the 14^{th} century via Islam. 
6^{th} century  Communicable diseases
Geometric theorems
Electricity, static
Row cultivation of crops/ Intensive hoeing  The Old Testament, like most ancient peoples, recognized that some diseases were communicable and isolated individuals thought to carry “infections.” This included the shunning of lepers, which occurs even today.
Thales of Miletus, born of Phoenician parents, pursued the fascinatingly logical study of geometry as a deductive science, and demonstrated several of the theorems later collected by Euclid.
Thales of Miletus
China

5^{th} century  Geobotanical prospecting  China 
495  Formal geometry  Death of Pythagoras in whose academy geometry now definitely received the form of axiom, theorem, and demonstration. 
460  Atomic theory  Leucippus and his student Democritus conceive the theory that everything is composed of tiny indivisible atoms; in 1808, John Dalton proposes that a different atom with a different weight comprises each element. 
4^{th} century  Precursor of Newton’s first law of motion
Recognition of sunspots as solar phenomenon  China; this is found in the Mo jing, a Mohist philosophical compilation of Mozi’s thought. Alhazen also independently formulated this concept in the 11^{th} century.
The Chinese first make this discovery which then comes to European notice in the 15^{th} century via Islam. 
360  Planetary models  Eudoxus of Cnidus 
355  Advances in geometry  Death of Eudoxus of Cnidus whose contributions to geometry were fundamental. He invented the theory of proportion, and most of the propositions, transmitted to us in the fifth book of Euclid; and he devised the method of exhaustion, which made it possible to calculate the area of the circle and the volume of the sphere, the pyramid, and the cone; without this preliminary work, Archimedes would have been impossible. 
350  Earth’s rotation
The ideal of science and formalized logic  Heraclides of Pontus
Aristotle’s Posterior Analytics defends the process of science as one that moves from unquestioned axioms to demonstrable proof. He also sets down the rules for correct reasoning in his Organon. 
343  Disease prevention  Aristotle teaches Alexander the Great to boil drinking water and bury feces to prevent disease. 
3^{rd} century  Ephedrine
Euclidean geometry
Conics
Method of finding prime numbers
Archimedes’ early form of integration  China
Euclid of Alexandria
Apollonius of Perga, after years of study in Euclid’s school, took Euclid’s Conics as the starting point of his own Conics, and explored in eight “books” and 387 propositions the properties of the curves generated by the intersection of a cone by a plane. To three of these curves (the fourth being the circle) he gave their lasting names—parabola, ellipse, and hyperbola. His discoveries made possible the theory of projectiles, and substantially advanced mechanics, navigation, and astronomy.
Eratosthenes of Cyrene
We must rank Archimedes of Syracuse (287212 B.C.E.) with Isaac Newton, and credit him with “a sum of mathematical achievement unsurpassed by any one man in the world’s history” according to Sir Thomas Heath. 
270  Force of compressed air  Ctesibius of Alexandria 
250  Archimedes’ principle
Size of the Earth
Heart valves  Archimedes of Syracuse
Eratosthenes of Alexandria calculates the size of the earth and its distance from the sun and the moon.
Erasistratus of Ceos 
2^{nd} century  Science of endocrinology  China 
150  Lunar causation of tides
Founding of trigonometry  Seleucus of Seleucia
His mathematical studies of astronomic relations led Hipparchus of Nicaea to formulate a table of sines, and thereby to create the science of trigonometry. 
85 C.E.  Scientific method  Chinese thinker Wang Chong publishes his Lunheng (“Disquisitions”) in which he as a rationalist “insisted upon the necessity of supporting any theory with concrete evidence and experimental proof,” so says the Encylopedia Britannica. 
2^{nd} century  Negative numbers
“Gaussian” elimination
“Horner’s” method
Decimal fractions  China
China
First discovered in China, this appears in Nine Chapters on the Mathematical Art, a Chinese textbook, which receives its final form at about this time. In the Nine Chapters, positive quantities are shown as red rods and negative ones as black rods. Additionally, “Gaussian” elimination also finds its first expression in this text.
China 
150  Geocentric cosmology  Ptolemy of Alexandria did not claim to do more than systematize the work and observation of previous astronomers Hipparchus above all. Ptolemy pictured the universe as spherical and as daily revolving around a spherical, motionless earth. He suggested further a theory of eccentrics to explain the orbits of the planets, and discovered the evection, or orbital aberration, of the moon. 
3^{rd} century  Biological pest control
Algebra treatise
Mensuration, arithmetic, fractions, simple, cubic, and quartic equations, permutations and combinations, geometry, and number theory  China
Diophantus of Alexandria composes Arithmetica, his chief surviving work, which is a treatise on algebra. It solves determinate equations of the first degree, determinate quadratic equations, and indeterminate equations up to the sixth degree. For the unknown quantity which we denote by x, and which he called arithmos (the number)—he used a Greek sigma; and for the other powers he used the letters of the Greek alphabet. Algebra owes its name to the Arabs, who extensively developed this detective science. The great figure here was alKhwarizmi for the word algebra (aljabr—“restitution,” or “completion”) entered the West from the title of one of his books; another of his books introduced a great deal of Muslim trigonometry.
From the Sthananga Sutra, a Jain text from India 
Late 4^{th} century  Mathematical commentaries
 The most interesting figure in the science of this age is that of the pagan mathematician and philosopher Hypatia. Her father Theon is the last man whose name is recorded as a professor at the Alexandrian Museum; he wrote a commentary on Ptolemy’s Syntaxis, and acknowledged the share of his daughter in its composition. Hypatia, says Suidas, wrote commentaries on Diophantus, on the Astronomical Canon of Ptolemy, and on the Conics of Apollonius of Perga. None of these works survives. 
499  Mathematics textbook  The greatest of Hindu astronomers and mathematicians, Aryabhata, discussed in verse such poetic subjects as quadratic equations, sines, and the value of π. He explained eclipses, solstices and equinoxes, announced the sphericity of the earth and its diurnal revolution on its axis, and wrote, in daring anticipation of Renaissance science: “The sphere of the stars is stationary, and the earth, by its revolution, produces the daily rising and setting of planets and stars.” 
6^{th} century  Discovery of the solar wind  China 
550  Inoculation  Unknown to Europe before the eighteenth century, it is known in India by this date if we may judge from a text attributed to Dhanwantari, one of the earliest Hindu physicians. “Take the fluid of the pock on the udder of the cow . . . upon the point of a lancet, and lance with it the arms between the shoulders and elbows until the blood appears; then, mixing the fluid with the blood, the fever of the smallpox will be produced.” To prevent smallpox the Chinese, probably in imitation of India, begin to practice inoculation around the 10^{th} century; they use weakened virus from a smallpoxinfected human being. This practice spreads westwards. Lady Mary Wortley Montagu had found inoculation customary in Constantinople in 1717; on her return to England in 1724, she recommended the procedure. It was tried upon criminals, then upon orphans, with considerable success. 
575  Astronomy treatise  Varahamihira authors the Panchasiddhantika (“Five Treatises”), a compendium of Egyptian, Greek, Roman, and Indian astronomy that frankly acknowledged his dependence upon the Greeks. In it, he notes the shifting of the equinox as 50.32 seconds. 
7^{th} century  The use of chopped thyroid gland for the treatment of goiter  China 
628  Gravity as a force of attraction  Brahmagupta states, “[b]odies fall towards the earth as it is in the nature of the earth to attract bodies, just as it is in the nature of water to flow.” 
9^{th} century  Magnetic declination
Alchemy becomes chemistry
Refutation of the transmutation of the elements
Heavenly bodies subject to earthly physical law
Earth measurements
Refutation of the Aristotelian classical elements and Galenic humors  China
“Distillation, the means of separating liquids through differences in their boiling points,” writes Paul Vallely “was discovered in prehistoric times but perfected around the year 800 by Islam’s foremost scientist, Jabir ibn Hayyan, who transformed alchemy into chemistry, inventing many of the basic processes and apparatus still in use today—liquefaction, crystallization, distillation, purification, oxidization, evaporation and filtration. As well as discovering sulphuric and nitric acid, he invented the alembic still, giving the world . . . perfumes and alcoholic spirits (although drinking them is haram, or forbidden, in Islam). Ibn Hayyan emphasized systematic experimentation and was the founder of modern chemistry.”
AlKindi also develops frequency analysis, which initiates the study of cryptology.
Jafar Muhammad ibn Musa (one of the Banu Musa brothers) posits the existence of gravitation between heavenly bodies; this is a precursor to what became Newton’s law of Universal Gravitation.
The Caliph alMa’mun engaged a staff of astronomers to make observations and records. Taking for granted the sphericity of the earth, they measured a terrestrial degree by simultaneously taking the position of the sun from both Palmyra and the plain of Sinjar; their measurement gave 91.2 kilometers—0.8 kilometers more than our present calculation; and from their results they estimated the earth’s circumference to be a little over 32,000 kilometers.
Rhazes also differentiates measles from smallpox, and distills kerosene from petroleum.

10^{th} century  Modern surgical instruments
Advancement of algebra  “Many modern surgical instruments,” writes Paul Vallely “are of exactly the same design as those devised in the 10^{th} century by a Muslim surgeon called alZahrawi [Abulcasis]. His scalpels, bone saws, forceps, fine scissors for eye surgery, and many of the 200 instruments he devised are recognizable to a modern surgeon. He discovered that catgut used for internal stitches dissolves away naturally (a discovery he made when his monkey ate his lute strings) and that it can be used to make medicine capsules. . . .” Muslim doctors also invented anesthesia by inhalation, which they practiced in some surgical operations; in others, hashish and other drugs were used to induce deep sleep.
Abu Kamil Shuja ibn Aslam

929  Advancement of trigonometry  Death of Abu Abdallah alBattani, a Sabaean of Raqqa known to Europe as Albategnus, who advanced trigonometry far beyond its beginnings in Hipparchus and Ptolemy by substituting triangular for Ptolemy’s quadrilateral solutions, and the sine for Hipparchus’ chord; he formulated the trigonometrical ratios essentially as we use them today. 
964  Andromeda Galaxy  AbdelRahman alSufi 
984  “Snell’s” law  Ibn Sahl discovers the law of refraction later incorrectly termed Snell’s law. 
11^{th} century  Binary system
Astronomy/ physics advances  “The Chinese book I Ching . . .” writes Roger Bridgman “showed how to make predictions from binary patterns. The 11^{th} century Chinese philosopher Shao Yung was influenced by the book, and it is possible that German mathematician Gottfried Leibniz was made aware of the binary system through his writings.”
Abu Rayhan Muhammad alBiruni notes “the attraction of all things towards the center of the earth,” and proves that gravitation also works on heavenly bodies/celestial spheres. He also disparages Aristotle’s opinion that circular motion is their inherent property. 
101121  Use of mathematics to explain the principles of light  Besides discovering a precursor to Newton’s first law of motion, we know alHaitham (Alhazen) chiefly by his Kitab alManazir, or Book of Optics; of all medieval productions, this is probably the most thoroughly scientific in its method and thought. AIHaitham studied the refraction of light through transparent mediums like air and water, and came so close to discovering the magnifying lens that Roger Bacon, Witelo, and other Europeans three centuries later based upon his work their own advances toward the microscope and the telescope. He rejected the theory of Euclid and Ptolemy that vision results from a ray leaving the eye and reaching the object; rather “the form of the perceived object passes into the eye, and is transmitted there by the transparent body”—the lens. He remarked on the effect of the atmosphere in increasing the apparent size of sun or moon when near the horizon; showed that through atmospheric refraction the light of the sun reaches us even when the sun is as much as nineteen degrees below the horizon; and on this basis he calculated the height of the atmosphere at about forty kilometers. He analyzed the correlation between the weight and the density of the atmosphere, and the effect of atmospheric density upon the weight of objects. He studied with complex mathematical formulas the action of light on spherical or parabolic mirrors, and through the burning glass. He observed the halfmoon shape of the sun’s image, during eclipses, on the wall opposite a small hole made in the window shutters; this is the first known mention of the camera obscura (from the Arabic word qamara or dark chamber), on which all photography depends. We could hardly exaggerate the influence of alHaitham on European science. Without him, we might never have heard of Roger Bacon; Bacon quotes him or refers to him at almost every step in that part of the Opus maius that deals with optics; and Part VI rests almost entirely on the findings of the Cairene physicist. As late as Kepler and Leonardo European studies of light were based upon alHaitham’s work. Continued research by Sir Isaac Newton (1704), Thomas Young (early nineteenth century), and Albert Einstein (1905) leads to a more specific knowledge of light’s nature, behavior, and mode of transmission. 
1020  Experimental medicine  Avicenna discovers the contagious character of infectious diseases including pulmonary tuberculosis, the sexually transmitted diseases amongst others, and that water and soil frequently transmit them. He likewise discovers the difference between mediastinitis and pleurisy, and writes a medical text that includes mention of various parasitic worms. 
12^{th} century  Threefield system
Precursor of Newton’s second law of motion
Precursor of Newton’s third law of motion  Europe
Abu’lBarakat alBaghdadi
Ibn Bajjah (Avempace) 
1121  Gravitation/ Air density  AlKhazini makes breakthroughs in gravitation, discovers that its potential energy varies with the distance from the center of the Earth, and that air density decreases with increasing elevation. 
1185  Differential calculus  Death of Bhaskara II who crudely anticipated this branch of calculus 
1260  Pulmonary circulation of the blood  A physician of Damascus, Ala’aldin ibnalNafis, expounded the pulmonary circulation of the blood 270 years (1260?) before Servetus. Almost three hundred years later William Harvey experimentally proved how the heart circulates blood around the body. 
1269  Magnetic poles  Petrus Peregrinus de Maricourt 
14^{th} century  Multivariate polynomials/Solutions to simultaneous polynomial equations
Ockham’s “Razor”  Chinese mathematicians discover this but it is not till the 17^{th} century that it reaches the West.
William of Ockham determines that the theory with the fewest assumptions provides the simplest explanation and is the one closest to the truth. 
1543  Human anatomy textbook
Heliocentric theory, Revived  Andreas Vesalius dissects human corpses, uncovers exhaustive data regarding human anatomy, and amends Galen’s views. Vesalius thinks that the comprehension of anatomy is vital to successfully carrying out surgery and therefore dissects human corpses himself (a rarity for that time). He publishes De Humani Corporis Fabrica and revolutionizes anatomy.
Nicolaus Copernicus places the sun, not the Earth, at the center of the solar system. 
1545  Complex numbers  Gerolamo Cardano creates “complex numbers” which are numbers such as 3 + 9i, or a real number plus an imaginary number. 
1546  Theory of contagion  Girolamo Fracastoro develops the concept that minute bodies (“germs”) capable of selfreplication, transmitted from infector to infected, cause infectious disease. He is said to have named syphilis. 
1570  Detailed planetary observations  Tycho Brahe compiles the data, which leads Kepler to formulate his famous laws. 
1572  Supernova  Tycho Brahe 
1582  Calendar, Gregorian  Aloysius Lilius and Christopher Clavius 
1600  Earth’s magnetic field/study of electricity  William Gilbert 
1603  “Valves” in veins  Girolamo Fabrizio 
1604  Law of falling bodies  Galileo Galilei upends the Aristotelian conviction that heavy things fall faster than light things by demonstrating that all bodies fall with the same acceleration. 
1605–09  Planetary orbits are elliptical  Johannes Kepler 
1614  Logarithms  John Napier 
1633  Slide rule  William Oughtred 
1637  XY coordinate graph  René Descartes 
1661  Blood capillaries  Marcello Malpighi 
1662  Boyle’s law  Robert Boyle discovers the this the first in a series leading to the Ideal Gas Law. 
1663  Electrostatic investigations  Otto von Guericke 
1665  Number theory, analytic geometry, and calculus  Death of Pierre de Fermat who worked on all these areas 
166566  Fundamental Theorem of Calculus  The power to find a function once we know the derivative allows us to calculate quantities that change over time. Sir Isaac Newton discovered this mathematical method for determining the total pull applied by the Earth on the moon; however, he was reluctant to publish. The investigation of motion in space also inspired German philosopher Gottfried W. Leibniz to work out his calculus, and he published it between 1684 and 1686. Leibniz also popularized the symbols currently in use. 
1666  Laws of Motion  Sir Isaac Newton discovers three laws of motion that change our understanding of the universe. The second law leads him to develop a mathematical formula for gravitation.^{*} 
1674  Microorganisms  Anton van Leeuwenhoek, a microscope lens maker, inadvertently discovers microorganisms in a drop of water. With his own microscopes, he views sperm, bacteria, and blood cells. His examinations lay the groundwork for the science of microbiology. 
1676  Measurement of the speed of light  Olaus Roemer 
1690  Wave theory of light  Christiaan Huygens 
1727  Euler’s Number e ≈ 2.71828. . . .  The irrational number e serves as the base of natural logarithms. It appears quite frequently in calculus wherever one is working with either logarithmic or exponential functions, because the natural logarithm function is the inverse of the exponential function. It occurs in some mathematical problems: those concerning nonlinear growth or decay (e.g. compound interest), the statistical “bell curve,” certain areas of probability, various counting problems, in Stirling’s Formula which approximates factorials (!), and even in the analysis of the distribution of prime numbers. Additionally there is a link between e and complex numbers via Euler’s Equation. Mathematicians calculate it by adding: 1/0! + 1/1! + 1/2! + 1/3! + 1/4! . . . ≈ 2.71828. . . . 
1735  Classification of species  Carl Linnaeus, the “father of taxonomy,” advances a method for the nomenclature and classification of every form of life. It is still in use (though modified). 
1738  Bernoulli’s principle  Daniel Bernoulli 
1752  Nature of electricity  Benjamin Franklin 
1766  Hydrogen  Henry Cavendish 
1774  Oxygen  Both Carl Scheele and Joseph Priestley discover oxygen. Antoine Lavoisier names the new element oxygen and correctly explains its role in combustion. 
1785  The Milky Way is a gigantic disk of stars  Astronomer William Herschel, aided by his sister Carolyn, maps the whole sky and demonstrates that the Milky Way is an enormous disk of stars that protrudes at its center and that our solar system exists within it. 
1792  Metric system  In 1791 the French Revolutionary government appointed a commission, headed by JosephLouis Lagrange, to devise, for a newly unified France, a new system of weights and measures; the resultant metric system was officially adopted in 1792, and was made law in 1799; it had to fight its way through the provinces, and its victory was not complete till 1840. Now the world uses it. 
1796  Vaccination  In England in 1760, Drs. Robert and Daniel Sutton reported that in thirty thousand cases of smallpox inoculation they had had twelve hundred fatalities. Could there be found a surer method of preventing smallpox? Edward Jenner was led to a better way by noting that many milkmaids in his native Gloucestershire contract cowpox from the infected nipples of cows, and that these women are thereafter immune to smallpox. It occurs to him that a like immunity might be established by inoculating with a vaccine (vacca is Latin for cow) made from the virus of a poxinfected cow. 
1799  Stratigraphy  William Smith 
1801  Ultraviolet light  Johann Ritter 
1806  Morphine  F. W. A. Sertürner 
1811  Atoms combine to form molecules  Amedeo Avogadro discovers that the atoms of elements combine to produce molecules. Additionally, he states that equal volumes of gases under equal conditions of temperature and pressure hold an equal number of molecules (6.02214 x 10^{23}) now known as Avogadro’s number. 
1813  Math analysis, number theory, algebra, and differential calculus  Death of JosephLouis Lagrange who worked in numerous areas of mathematics. 
181730  NonEuclidean geometry  C. F. Gauss or János Bolyai or Nikolay Lobachevsky 
1820  Electromagnetism
Quinine, purified  Hans Christian Oersted discovers that a pivoted magnetic needle turns at right angles to an object carrying an electric current during one of his classroom lectures; the word oersted enters into all European and American languages to indicate a unit of strength of a magnetic field. As a result, French mathematician and physicist André Marie Ampère creates mathematical principles relating the actions of electric currents and magnets.
South American Indians for centuries knew of the curative properties of cinchona bark to treat fevers particularly those caused by malaria. However, Pierre Pelletier and Joseph Caventou isolate and purify the active ingredient. 
1822  Fourier analysis  Joseph Fourier 
1827  Ohm’s law  Georg Ohm 
1828  Synthesis of urea  Friedrich Wöhler 
1831  Cell nucleus  Robert Brown 
1834  Precursor of the germ theory of disease  Agostino Bassi is the first to show that a microorganism could cause disease; in the case of a fungal disease of silkworms, he demonstrates that it was contagious, could be transmitted naturally by direct contact, in infected food, or experimentally by means of a pin previously sterilized in a flame. In 1840, Friedrich G. J. Henle too proposes that microorganisms might directly cause disease. One of his student was Robert Koch. 
1839  Cell theory of life  Theodor Schwann and Matthias Jakob Schleiden 
1842  Doppler effect  Christian Doppler 
1843  Nosocomial infections  Oliver Wendell Holmes Sr. notes that it was safer to give birth at home than in hospital, and postulated something present in a hospital is causing disease. 
1845  Fungal blight  M.J. Berkeley shows that a fungus causes the Irish potato blight. 
1848  Puerperal disease reduction  Ignaz Semmelweis, in charge of a lyingin hospital in Vienna, proves that puerperal fever can be reduced if physicians use calcium hypochlorite Ca(ClO)_{2} to wash their hands before treating patients. Chloride of lime washing reduced puerperal fever death rates. 
1849  Electrical nature of nerve impulses  Emil Du BoisReymond 
1850  Bacillus anthracis  Casimir Davaine observes little threadlike bodies in the blood of anthraxkilled animals. 
1853  Hypodermic syringe  An Egyptian surgeon, as early as the 9^{th} century, used a syringe device with a glass suction tube to remove cataracts from a patient, but Charles Gabriel Pravaz and Alexander Wood separately develop one with needles fine enough to pierce skin. 
1854  Cholera epidemic etiology
Boolean algebra  John Snow deduces that the contaminated Broad Street Pump caused the cholera epidemic in London.
George Boole 
1856  Aniline dye  William Perkin 
1859  Theory of evolution via natural selection  Charles Darwin publishes On the Origin of Species by Means of Natural Selection. In it, he challenges current dogmas about the creation of life on Earth. Darwin had worked as an unpaid naturalist aboard the HMS Beagle and the information he amassed on the voyage, particularly samples from the Galapagos Islands, was the stimulus for his theory of evolution by the means of natural selection. Contemporaneously, Alfred R. Wallace also conceives of natural selection as the driving force behind evolution. 
185990  Germ theory  French chemist Louis Pasteur refutes the doctrine of spontaneous generation and discovers that specific microbes are disease causing. He believes that the causes of contagious diseases are similar to the causes of fermentation. He receives the title “father of bacteriology” for his efforts, which bring about a novel field of scientific inquiry. Robert Koch becomes the first scientist to develop a sequence of proofs utilized to confirm the germ theory of disease. Koch’s Postulates are published in 1890, and result from his work in which he proves that the bacterium Bacillus anthracis produces anthrax.^{*} 
1861  Speech center of the brain  Paul Broca 
1864  Pasteurization  Louis Pasteur 
1865  Chemical structure  August Kekule von Stradonitz deciphers the structure of the chemical benzene, and emphasizes the study of molecular structure in chemistry. 
1866  Heredity, rules of
Math analysis, number theory, differential geometry, nonEuclidean geometry, and the “Riemann Hypothesis.”  Gregor Mendel, Austrian monk and botanist, determines how genetic information passes down the generations. In experiments on pea plants, he observes that a plant’s traits transmit to its offspring in a recessive or dominant manner.
Bernhard Riemann dies this year but leaves a lasting legacy in many fields of mathematics. 
1867  Phenol as an antiseptic  Joseph Lister introduces the use of phenol as an antiseptic: whether in surgical dressings, sprayed into the air, or applied directly it reduces wound infections dramatically. 
1869  Periodic table of the elements  Dmitry Mendeleev and Lothar Meyer independently recognize that if one organizes each of the 63 identified elements by their atomic weight, their chemical characteristics recur in regular periodic groups. They independently devise the periodic table of the elements and Mendeleev predicts that other elements yet undiscovered must exist. Three of them are during his lifetime: gallium, scandium, and germanium. 
1880  Vaccines, attenuated  Louis Pasteur and Charles Chamberland culture chicken cholera repeatedly, and find that it loses its virulence but can still confer immunity when injected. 
1883  “Edison effect”  Thomas Edison uncovers a phenomenon that he calls “Etheric Force.” He discovers that a separate wire, grid, or plate put between the ends of the filament of an incandescent lamp works as a “damper” or valve to manipulate the flow of current. This discovery—together with his “carbon button” invention—contain the groundwork principles upon which the diode was subsequently invented, and upon which radio, television, and computer transistors are based! 
188688  Radio waves  Heinrich Hertz 
1887  Fractals  Giuseppe Peano 
1892  Viruses  Dmitry Ivanovsky or Martinus Beijerinck 
1894  Topology  Jules Henri Poincaré 
1895  Xray imaging  Wilhelm C. Röentgen 
1896  Radioactivity  After Henri Becquerel finds radioactivity in uranium, Marie and Pierre Curie chemically separate it from its ore, and Marie observes that the remaining material is more “active” than the uranium itself. She surmises that the original ore contained new elements that are likewise radioactive. 
1897  Aspirin
Electron  Felix Hoffmann (Bayer)
J.J. Thomson determines that the negatively charged particles discharged by cathode ray tubes are tiny and form a part of every atom. He names these particles, currently identified as electrons, “corpuscles.” 
1898  Vitamins  Sir Frederick Hopkins et al. ascertain that deficiencies of particular nutrients cause certain diseases. Via feeding experiments on laboratory animals, Hopkins infers that these “accessory food factors” are vital to health. “In 1912,” writes Roger Bridgman “Polish biochemist Casimir Funk identified one of these in rice. Finding that it was . . . an amine, he proposed the name ‘vitamine.’” 
1900–30  Quantum theory  “In 1900 physicists had some problems,” writes Roger Bridgman. “One was that the light from redhot objects was not of the expected color. German physicist Max Planck found that he could predict the color correctly by assuming the energy was radiated only in multiples of a fixed amount, or quantum. This also explained why the energy of electrons ejected from metals by light depended on the color, not the brightness of the light.” Max Planck, Albert Einstein, Werner Heisenberg, Niels Bohr, and Erwin Schrödinger et al. create a counterintuitive set of physical laws that explain the behavior of particles that form the structure of matter and transmit energy. 
1901  Blood groups  Karl Landsteiner 
1902  The hormone secretin is purified  Sir William Bayliss and Ernest Starling 
1905  Function of chromosomes  Nettie Stevens or Edmund Wilson 
190516  Relativity, special and general
 Albert Einstein explains how clocks tick slower and objects appear to contract as they approach the speed of light, which overturns fundamental suppositions about time and space. His renowned formula E=mc² demonstrates that mass and energy are different expressions of the same thing (which is conserved), and that a tiny quantity of mass can be changed into an enormous amount of energy. One repercussion of his theory is that nothing with mass can ever exceed the speed of light. In 1916, he publishes the theory of General Relativity in which he posits that mass warps spacetime and spacetime directs the motion of matterenergy; consequently, large masses can bend the path of a beam of light. In 2016, gravitational waves, a prediction of the theory, were confirmed to exist. 
1909  Nitrogen synthesis
Antisyphilitic drug  Fritz Haber
Paul Ehrlich searches for a “magic bullet” that would poison pathogens but not patients. He develops Salvarsan, an arsenic compound against syphilis. 
1910  Genes lie next to each other on chromosomes
 Beginning this year, Thomas Hunt Morgan determines that genes reside on chromosomes. Performing his work on fruit flies, he infers that particular traits are linked to gender and that they are undoubtedly transmitted on one of the sex chromosomes (X or Y). He conjectures that additional genes are also transmitted on specific chromosomes. Utilizing the technique of chromosome recombination, he and his students map the positions of genes. Morgan and his students compose the formative book The Mechanism of Mendelian Heredity. 
1911  Superconductors  Heike Kamerlingh Onnes discovers that certain materials offer no resistance to a current of electricity. 
1912  Continental drift/plate tectonics
 Alfred Wegener suggests that the continents of the world previously formed a solitary, huge landmass that ultimately fragmented in what has come to be termed “continental drift.” In 1962, Harry Hess proposes that continental drift is a consequence of seafloor spreading. By the 1960s, the research of numerous scientists reveals that the Earth’s surface is fragmented into many interlocking plates of rock. The grinding at plate boundaries creates mountains, volcanoes, and earthquakes. 
1913  Electrons form chemical bonds  Niels Bohr publishes his theory of atomic configuration; electrons move in certain “quantized” orbits about the nucleus, and the quantity of electrons in an atom’s external shell mainly governs the chemical traits of that element. 
1916  Black hole  Using the newly published theory of general relativity, Karl Schwarzschild theorizes that not even light can escape the clutches of a supermassive object that has collapsed to a point. 
1917  Hybrid corn  Donald F. Jones 
1920  Number theory  Death of Srinivasa Ramanujan who worked in this area 
1921  Insulin, extraction and preparation of  Sir Frederick Grant Banting and Charles H. Best 
1927  The universe is expanding
Big Bang theory
Uncertainty principle  Edwin Hubble ascertains the distance to numerous nearby galaxies and determines that the remoter the galaxy, the quicker they are racing away from us. His calculations show that the universe is expanding. Taking his cue from Hubble, Georges Lemaître reasons that at some point in the remote past the universe must have occupied the size of a “primeval atom.”
Werner Heisenberg 
1928  DNA is the genetic material  Oswald Avery demonstrates that DNA transmits genetic information. 
1928–45  Penicillin  Alexander Fleming notes the inhibition of staphylococcus growth on plates contaminated with Penicillium notatum and dubs the compound produced by the fungus “penicillin”; Howard Florey and Boris Chain isolate and concentrate it, creating (not quite) the first antibiotic. Florey and Chain subsequently discover that it cures mice with bacterial infections, and Dorothy Hodgkin determines its chemical structure. 
1929  Particle accelerator
Hubble’s constant (67.80 ± 0.77 (km/s)/Mpc)  Sir John D. Cockcroft and Ernest T. S. Walton
Edwin Hubble 
1930  Genes control biochemical events  George Beadle and Edward Tatum conduct experiments on neurospora, a bread mold, and find that genes cause the production of enzymes. 
1932  Neutron
Sulfa drugs  James Chadwick
Gerhard Domagk finds that Prontosil, an orangered dye, cures infections produced by the common bacteria streptococci. 
1937  The Krebs cycle  Hans Krebs details the numerous steps a cell takes to transform sugars, fats, and proteins into energy. 
1938  Nuclear fission  Otto Hahn and Fritz Strassmann 
1940  Blood bank
Jumping genes  Charles Richard Drew
Barbara McClintock finds transposons—genes that can jump on a chromosome—while pursuing an explanation for color differences in corn. These may trigger mutations and increase (or decrease) the quantity of DNA in the genome. 
1941  Periodic ice ages  Serbian geophysicist Miultin Milankovitch advances a theory connecting the Earth’s motion to longterm environmental changes leading to ice ages. His theory postulates that cyclical deviations in the EarthSun geometry, for example orbit shape and axis angle, cause differing levels of solar energy to reach Earth. 
1943  Axiomatic theory, invariant theory, algebraic number theory, class field theory, and functional analysis  Death of David Hilbert who contributed to each of these areas 
1946  Carbon14 dating  Willard F. Libby

195160  Contraceptives, oral  Carl Djerassi, Gregory Pincus, John Rock, and Min Chueh Chang 
1953  DNA is a double helix  By 1944, Linus Pauling had determined that numerous proteins take the form of a spiral, like a coil spring, and hypothesized that so did DNA. In 1950, biochemist Erwin Chargaff discovered the ratio of certain nitrogen bases in DNA is always 1to1 when forming base pairs, and in 1952 Rosalind Franklin produced Xray diffraction imagery implying that DNA was a helix. James Watson and Francis Crick propose that DNA is built from two chains of helically intertwined nucleotides. Crick suggests that matching base pairs bond together at the middle of the double helix to maintain a steady gap between the chains. They demonstrate that each of the strands serves as a template for the other, and that DNA can replicate itself without altering its structure, aside from sporadic errors or mutations. 
195569  Insulin, structure of  Fred Sanger or Dorothy Hodgkin 
1957  Nuclear forces
Pure and applied mathematics  ChenNing Yang and TsungDao Lee theorize, and ChienShiung Wu verifies, that the weak interaction “maximally violates parity.” Further discoveries of the basic forces at work on the subatomic level lead to the realization that every interaction in the universe results from one of four fundamental forces in nature—the strong force, the electromagnetic force, weak nuclear force, and gravitation.
Death of John von Neumann who advanced knowledge in these areas 
1958  Van Allen radiation belt  James Van Allen 
1960  Quasars  Allan Sandage 
196166  Cracking the genetic code  Marshall Nirenberg heads one team, and Har Gobind Khorana heads another, that determines the genetic code, and demonstrates that a sequence of three nucleotide bases codes for each of the twenty amino acids. 
1962  Quarks  Murray GellMann 
1964  Structure of tRNA
Cosmic microwave background radiation  Robert William Holley Arno Penzias and Robert Wilson detect the cosmic microwave background radiation, which they suspect is the afterglow of the big bang. 
1966  Pulsars  Jocelyn Bell 
1970  Restriction enzymes
Cloning, animal  Daniel Nathans, Werner Arber, and Hamilton O. Smith discover restriction enzymes—biological scissors that recognize and cut specific DNA sequences. John B. Gurdon 
1973  Genetic engineering  Herbert W. Boyer and Stanley N. Cohen 
1974  Australopithecus Afarensis  Donald Johanson unearths an incomplete skeleton of a 3.2 millionyearold female hominid in Ethiopia. 
1976  RNA splicing  Phillip Allen Sharp and Richard J. Roberts et al. realize that for cells to make protein, DNA is initially transcribed into premessenger RNA. For unknown reasons, premessenger RNA molecules are subsequently spliced to make the final messenger RNA. In numerous genetic diseases, gene mutations produce mistakes in this RNA splicing procedure. 
1977  Gene exons and introns  Phillip Sharp or Richard Roberts 
1978  In vitro fertilization (IVF), human
Laetoli footprints  Patrick Steptoe and Robert Edwards
A group led by Mary Leaky uncovers fossilized Australopithecus footprints at Laetoli, Tanzania. These footprints, acknowledged to be 3.5 million years old, were formed when two individuals walked over wet volcanic ash that later solidified into a kind of cement. These individuals moved with perfect twofooted strides proving that the hominids walked erect. 
1980  KT asteroid theory of dinosaur extinction
Protein targeting
G proteins  Walter Alvarez hypothesizes that elevated levels of iridium unearthed in rock core samples around the world provides evidence that an asteroid collision triggered the extinction of dinosaurs.
Günter Blobel
Martin Rodbell and Alfred Gilman 
1981  Synthetic skin  Ioannis V. Yannas and John F. Burke 
1983  HIV virus  Competing scientists Luc Montagnier (1983) and Robert Gallo (1984) separately discover a new retrovirus later dubbed HIV (human immunodeficiency virus), and determine that it is the causative agent of AIDS. 
1984  DNA fingerprinting
Polymerase chain reaction  Alec Jeffreys determines that certain DNA sequences are exclusive to every individual, leading to the beginnings of DNA forensics.
Kary Mullis 
1986  Hightemperature superconductors  Georg Bednorz and Alex Müller 
1987  Vision correction, laser  Stephen Trokel 
1988  Planets orbit other stars  Canadian astronomers Bruce Campbell, G. A. H. Walker, and S. Yang produce the first published finding that is later corroborated. Astronomers will later discover a multitude of extra solar planets due to better telescope technology although none yet looks like Earth. 
1995  Proof of Fermat’s last theorem  Andrew Wiles 
1998  RNA interference
Universal expansion is accelerating  Andrew Fire and Craig Mello detect RNA interference (RNAi), in which the existence of little pieces of doublestranded RNA (dsRNA) whose sequence complements a given gene inhibits the expression of that gene. Scientists think that dsRNAs that trigger RNAi may function as drugs in the future.
Adam Riess, Saul Perlmutter et al. are astonished that instead of decreasing due to the pull of gravity, the expansion of the universe at great distances is increasing. 
2003  Humans have approximately 24,000 genes  Upon sequencing the human genome, it’s determined that humans have about 24,000 genes, far less than the majority of scientists had forecast. Scientists expect that understanding the genome will advance the disciplines of medicine and biotechnology, ultimately providing cures for diseases. 
2012  Higgs boson  Peter Higgs and François Englert 
* Koch was the first to demonstrate that a bacillary agent was a pathogen, and used criteria suggested to him by his teacher Henle that are now called Koch’s postulates. They are standards by which a bacterium may be said to cause a disease. 1. Microscopic examination must find the bacillus in the blood of all animals with anthrax. 2. A culture of a single colonyisolated bacillus must be made on solid media. (The idea for isolating pure cultures came from his observation of a spoiling cut potato. Also required, as developed in his lab by his assistant Friedrich Loeffler, were a nutrient broth and stains. Walther Hesse’s wife, Angelina Fannie, suggested using agar to solidify this medium on which to grow bacteria. Julius Petri developed shallow dishes for this culture.) 3. Inject the pure culture into healthy animals, and see if they get anthrax. 4. Isolate the same organism from animals experimentally given anthrax.