Timelines for medicine and technology are listed separately.

Physics.United States.
==Apr.22 > The future nuclear physicist J. Robert Oppenheimer is born in New York City to a successful Jewish businessman

Physics.Britain.
==1904 > Physicist J. J. Thomson theorizes that electrons are imbedded in atoms like raisins in a cake - the first electronic theory of valency

Physics.Japan.
==1904 > Hantaro Nagaoka postulates the Saturnian model of the atom, with the positive nucleus surrounded by a ring of thousands of electrons (or 1903)

Physics.France.
==1904 > After four years of work, the Curies have managed to isolate a single gram of radium from eight tons of uranium residue

Physics.United States.
==1904 > Working with radium, Bertram Borden Boltwood and others discover that one element can decay into another

Astronomy.Germany.
==1904 > Johannes Franz Hartmann discovers interstellar matter

Astronomy.United States.
==1904 > Mount Wilson Observatory is established in California

Chemistry.Germany.
==1904 > Richard Abegg speculates that chemical reactions are caused by transfers of electrons between atoms

Chemistry.Britain.
==1904 > Frederick Stanley Kipping discovers silicones

Earth Science.Japan.
==1904 > The word tsunami is used to describe ‘tidal waves’

Meteorology.United States.
==1904 > Bjerknes publishes Weather Forecasting as a Problem in Mechanics and Physics, one of the first attempts at a scientific approach to meteorology

Biology.Spain.
==1904 > Santiago Ramón y Cajal demonstrates that the nervous system is composed essentially of neurons

Archaeology.India.
==1904 > The British establish an Archaeological Department in India

Archaeology.Egypt.
==1904-1927 > George Reisner’s American expedition makes a meticulous excavation of the ancient cemetery near the pyramids of Giza

Archaeology.Mexico.
==1904 > The American archaeologist E. H. Thompson begins excavating the sacred well at Chichén Itzá in the Yucatan

Archaeology.Scandinavia.
==1904 > A Viking burial ship is unearthed at Oseberg in Norway

Physics.Germany/Switzerland.
EINSTEIN’S GREAT YEAR:
==Mar.17 > While he is still working as a patent clerk in Switzerland, Albert Einstein’s first great paper is published in Germany - he postulates the light-quantum in explaining photo-electric effect
==Apr-May > In a paper on Brownian Motion, Einstein proves that atoms actually exist and ends debate on the fundamental nature of the chemical elements
==Jun.30 > The submission to the Annalen der Physik of EINSTEIN’S FIRST PAPER ON THE SPECIAL THEORY OF RELATIVITY, WHICH DESCRIBES TIME AS RELATIVE
==Sep.27 > EINSTEIN’S SECOND PAPER ON THE SPECIAL THEORY OF RELATIVITY, WHICH STATES E=mc2
==1905 > Einstein earns his doctorate from the University of Zurich

Physics.France.
==Jun.--- > Pierre and Marie Curie accept their Nobel Prize for Physics (awarded in 1903): Pierre predicts that “In the hands of evil men radium can become very dangerous...a terrible means of destruction in the hands of war-makers...”

Astronomy.United States.
==1905 > Thomas Chrowder Chamberlin and Forest Ray Moulton theorize that the solar system was formed by the accretion of smaller particles (‘plantesimals’)
==1905 > Percival Lowell predicts the existence of a ninth planet far beyond Neptune, and begins a search for Pluto

Astronomy.Scandinavia.
==1905-1907 > Danish astronomer Ejnar Hertzsprung describes both giant and dwarf stars, though his work is not well known

Biochemistry.Britain.
==1905 > Arthur Harden describes ‘catalysts’ (enzymes)

Biology.Germany.
==1905 > Richard Willstätter discovers the structure of chlorophyll

Biology.International.
==1905 > Publication of the International rules of zoological nomenclature, the first attempt to impose global guidelines for zoological classifications

Genetics.Britain.
==1905 > William Bateson and Reginald Crundall Punnett describe linkage and gene interaction

Genetics.United States.
==1905 > Clarence McClung and Nettie Stevens identify the X and Y chromosomes and their role in determining sex

Genetics.Scandinavia.
==1905 > Danish biologist Wilhelm Johanssen publishes Elements of Genetics

Archaeology.South-central Africa.
==1905 > David Randall-McIver establishes that the ruins of Great Zimbabwe were built by native Africans, not by Phoenicians or Arabs as earlier believed

Sociology.United States.
==1905 > The Charities Publication Committee is established to undertake serious social surveys in America

Geopolitics.Scandinavia.
==1905 > Conservative Swedish political scientist Rudolf Kjellen publishes Stormakterna - ~the origins of the ‘science’ of geopolitics

Physics.France.
==Apr.19 > Pierre Curie dies after being struck by a horse cart
==Nov.06 > Taking over her late husband’s course, Marie Curie teaches her inaugural class as the first female instructor at the Sorbonne

Sociology.United States.
==Dec.27 > The first annual meeting of the American Sociological Society

Rocketry.Russia.
==Dec.30 > The birth of Sergei Korolev, the central figure in the Soviet missile and space programs

Physics.Germany.
==1906 > Walther Hermann Nernst formulates the third law of thermodynamics, stating that all bodies at absolute zero would have the same entropy

Physics.Britain.
==1906 > J. J. Thomson wins the Nobel Prize in Physics for his discovery of electrons - also in 1906, Thomson shows that the hydrogen atom has only one electron

Physics.International.
==1906 > Radium has become the world’s most valuable substance, worth $10 million (1990’s) per gram

Chemistry.Russia.
==1906 > Botanist M. S. Tsvett develops paper chromatography

Earth Science.Britain.
==1906 > R. D. Oldham shows that the earth has a core

Genetics.Britain.
==1906 > William Bateson coins the word ‘genetics’ (or 1905)

Archaeology.Anatolia.
==1906 > Hugo Winckler’s German-Ottoman team begins the excavation of Hattusas (Boghazköy), the capital of the Hittites - they discover a tablet archive that shows the extent of the Hittite Empire

Archaeology.Sinkiang.
==1906-1907 > British explorer/archaeologist Aurel Stein’s second expedition to Chinese central Asia - in 1907, he discovers an ancient Chinese library hidden in the ‘Caves of the Thousand Buddhas’ near Tunhwang, close to the Kansu-Sinkiang frontier, including the world’s oldest preserved printed text from 868 AD

Eugenics.Germany.
==1906 > Zoologist Haeckel establishes the Monist League to promote eugenics

Chemistry.Russia.
==Feb.02 > The great chemist D. I. Mendeleev dies at age 73, while listening to a reading of Jules Verne's Journey to the North Pole

Chemistry.Switzerland.
==Nov.--- > Alfred Werner proves his co-ordination theory - the scientific understanding of inorganic chemistry is seemingly complete

Physics.Britain.
==Dec.17 > The death of physicist William Thomson, Lord Kelvin

Physics.Germany.
==1907 > Einstein’s principle of equivalence equates gravitational and mechanical acceleration, and deduces that energy and time are affected by gravity
==1907 > Einstein begins work on General Relativity

Physics.Earth Science.United States.
==1907 > Boltwood conceives of radioactive dating

Physics.Britain.
==1907-1919 > Ernest Rutherford holds the chair in physics at the University of Manchester

Physics.Austria-Hungary.
==1907 > Austria-Hungary halts the export of uranium ore and builds a radium factory in Joachimsthal

Biochemistry.Germany.
==1907 > Emil Fischer artificially synthesizes a polypeptide from amino acids

Paleoanthropology.Germany.
==1907 > German quarry workers at Mauer discover a hominid mandible, which is later shown to be from Heidelberg Man, a form of Homo erectus

Sociology.United States.
==1907 > William Graham Sumner publishes Folkways, which analyzes the effect of social custom and introduces the concept of ethnocentrism

Physics.Austria-Hungary.United States.
==Jan.15 > Phycisist Edward Teller is born in Budapest

Chemistry.Low Countries.
==Jul.10 > Dutch physicist Heike Kamerlingh-Onnes liquefies helium

Astronomy.Russia.
==Jun.30 > A colossal explosion occurs near the Tunguska River in remote central Siberia, probably caused by a meteor - the site is not visited till 1927

Paleoanthropology.France.
==Aug.05 > A nearly complete Neanderthal skeleton (le Viellard) is found at La Chapelle-aux-Saints - the body was evidently deliberately buried

Mathematics.Germany.
==1908 > Ernst Zermelo axiomatizes set theory, establishing the basis of modern mathematics

Physics.Britain.
==1908 > Ernest Rutherford wins the Nobel Prize in Chemistry for his work on radioactivity
==1908 > Working in Rutherford’s lab, the German physicist Johannes Geiger invents the Geiger counter

Physics.Germany.
==1908 > Expanding on the theory of relativity, Hermann Minkowski postulates that time is the fourth dimension

Physics.France.
==1908 > Jean-Baptiste Perrin calculates the approximate size of an atom

Physics.International.
==1908 > An international conference adopts the ampere as the basic unit of electric current

Astronomy.United States.
==1908 > A sixty-inch reflector telescope is erected at Mount Wilson Observatory in California

Genetics.Britain.Germany.
==1908 > British mathematician G. H. Hardy and German physician Wilhelm Weinberg independently formulate the mathematical basis for population genetics.

Genetics.United States.
==1908 > Thomas Hunt Morgan begins working with the genetics of Drosophila (fruit flies) at Columbia University

Genetics.Britain.
==1908 > Archibald Garrod recognizes that gene products are proteins, and publishes Inborn Errors of Metabolism, the earliest discussion of biochemical genetics

Sociology.Britain.
==1908-1909 > Trotter’s essays on The Herd Instinct in Sociological Review opines that humans are motivated mostly by irrational impulses, and that it is likely that “...man will prove but one more of nature’s failures.”

Archaeology.Ottoman.
==1908-1910 > George Reisner’s American team carefully excavates the ancient city of Samaria in Palestine

Archaeology.North Africa.
==1908-1913 > French expeditions salvage a Roman-era shipwreck found off Mahdia in Tunisia

Archaeology.United States.
==1908 > The first Folsom points (ancient arrowheads) are found in New Mexico
==1908 > The School of American Archaeology is established in Santa Fe

Miscellaneous.Scandinavia.
==1908 > The noted Swedish chemist Svante Arrhenius suggests that life might have originated from spores that drifted though outer space - he predicts the greenhouse effect from the use of coal and oil

Cultural Anthropology.Germany.
==Aug-Apr 1910 > The German Südsee Expedition studies cultures in the Caroline and the Marshall Islands in the Central Pacific

Physics.Germany.
==1909 > Einstein is recognized throughout German-speaking Europe as one of the leading scientists of the age

Physics.United States.
==1909 > Robert Andrews Millikan measures the charge on the electron

Physics.Britain.
==1909 > Hans Geiger and Ernest Marsden detect alpha-ray scattering in passage through foil, suggesting that atoms have a small, dense, positively charged nucleus

Rocketry.United States.
==1909 > ~New England physics professor Robert Hutchings Goddard begins experimenting with rockets - ~the origins of modern rocketry

Chemistry.Scandinavia.
==1909 > Danish biochemist Soren Peter Lauritz Sørensen introduces pH as a method of measuring acidity or alkalinity

Chemistry.Austria-Hungary.
==1909 > Fritz Pregl devises the earliest methods for analyzing minute amounts of organic chemicals

Biochemistry.United States.
==1909 > Russian-American chemist Levene discovers RNA

Earth Science.Croatia.
==1909 > Geologist Andrija Mohorovcic discovers the Moho twenty miles beneath the earth’s surface, the interface between the Earth’s crust and its mantle

Oceanography.International.
==1909 > Underway since 1898, the German Valdividia oceanographic expedition to the Atlantic and Indian Oceans is completed

Genetics.Scandinavia.
==1909 > Danish botanist Wilhelm Johanssen (or Johannsen) coins the words ‘genotype’, ‘phenotype’, and  ‘gene’

Genetics.United States.
==1909 > Morgan observes sex-linked inheritance in Drosophila

Sociology.United States.
==1909-1914 > The ambitious six volume Pittsburgh Survey exhaustively studies all aspects of life in an industrial city

Science.Germany.
==1909 > Biologist Jacob von Uexküll believes that ‘scientific truth’ is only the embodiment of the misconceptions of a particular age

Astronomy.International.
==May.10 > Halley's Comet closest 1910 approach to the Earth
==May.19 > The Earth passes through the tail of Halley’s Comet, provoking widespread panic throughout the world (or May 18)

Cultural Anthropology.Pacific.
==Jun.02 > Pygmies are discovered in Dutch New Guinea

Archaeology.Palestine.
==Jul.09 > A tablet describing the fall of Jerusalem is unearthed by archaeologists

Science.Germany.
==Oct.11 > The Kaiser Wilhelm Institute for the Promotion of the Sciences is established

Physics.Russia.
==Dec.--- > Geologist Vladimir I. Vernadsky lectures the Russian Academy that atomic energy will be an immense new source of power and urges that exploration for radioactive minerals be undertaken to strengthen Russia - ~expeditions to Central Asia

Mathematics.Britain.
==1910-1913 > Bertrand Russell and Alfred North Whitehead publish Principia Mathematica, unsuccessfully attempting to derive all of mathematics from pure logic

Physics.Britain.
==1910 > Working with neon, J. J. Thomson confirms the existence of isotopes

Physics.Germany.
==1910 > Einstein postulates why the sky is blue

Astronomy.United States.
==1910 > The Mount Wilson Observatory’s hundred-inch telescope is completed

Archaeology.Scandinavia.
==1910 > Swedish archaeologist Gustav Oscar Montelius establishes the first absolute dates for the European Bronze and Iron Ages

Archaeology.Palestine.
==1910 > Captain Parker’s profit-driven archaeological digs near Jerusalem provoke strong Moslem protest

Archaeology.Syria.
==Mar.13-Jun.1914 > Woolley’s British expedition - including T. E. Lawrence - begins the excavation of Hittite ruins at Carchemish in northern Syria

Physics.Britain.
==May.07 > Ernest Rutherford introduces the nuclear model of atomic structure, describing it as a miniature solar system

Astronomy.Egypt.
==Jun.28 > A dog is killed by an eighteen-pound meteorite in Nakhla, Egypt; the only recorded case of a mammal being killed by space debris

Archaeology.Peru.
==Jul.24 > American archaeologist Hiram Bingham finds the Incan fortress of Machu Picchu

Physics.International.
==Oct.30-Nov.03 > The First Solvay Congress of physicists in Brussels on radioactivity and quantum theory, with Einstein, Planck, Lorenz, Poincare, Marie Curie, Langevin, and Rutherford attending - modern physics is emerging

Physics.France.
==Dec.--- > Marie Curie is awarded her second Nobel Prize, this time in Chemistry

Physics.Low Countries.
==1911 > Dutch physicist Heike Kamerlingh-Onnes discovers superconductivity

Physics.Germany.
==1911 > Einstein calculates the deflection of light caused by sun’s gravity

Astronomy.Russia.
==1911 > Konstantin E. Tsiolkovsky’s Investigation of Universal Space by Means of Reactive Devices, elaborating on a 1903 article, accurately formulates the principles of space flight

Astronomy.Austria-Hungary.
==1911-1913 > In a series of balloon ascents, Victor Franz Hess verifies the existence of cosmic rays, for which he will receive the 1936 Nobel Prize

Astronomy.Scandinavia.
==1911-1913 > Astronomer Ejnar Hertzsprung establishes the stellar luminosity scale, describing the evolution of stars

Chemistry.Germany.
==1911 > Fritz Haber, who will later invent poison gas, is appointed director of the Kaiser Wilhelm Institute for Physical Chemistry in Berlin

Meteorology.Arctic.
==1911 > Norway establishes meteorological stations in Spitsbergen

Paleoanthropology.France.
==1911-1913 > Pierre Boule publishes his inaccurate reconstruction of Neanderthal man - his stooped, brutish version becomes the popular archetype of the ‘cave-man’

Paleontology.East Africa.
==1911 > German entomologist Kattwinkil literally stumbles into Olduvai gorge, and first notices the abundant fossils

Genetics.United States.
==1911 > Thomas Hunt Morgan proposes that inheritance factors are arranged in a line on chromosomes and begins mapping genes on fruit fly chromosomes with Alfred Henry Sturtevant - Morgan publishes Evolution and Adaption

Archaeology.Mexico.
==1911 > Manuel Gamio begins working out the sequence of ancient cultures in the Valley of Mexico

Cultural Anthropology.United States.
==1911 > Anthropologist Franz Boas publishes the influential, anti-racist The Mind of Primitive Man

Eugenics.International.
==1911 > Eugenicists hold the First International Monists’ Congress in Hamburg

Earth Sciences.Germany.
==Jan.--- > Alfred Lothar Wegener first presents his early theory of continental drift - the theory is ridiculed until long after his death

Paleoanthropology.Britain.
The beginning of the Piltdown Hoax:
==Feb.--- > Hominid bones are reported to have been found at Piltdown in southern England - the Piltdown hoax to 1953
==Dec.18 > The formal public presentation of the Piltdown Man finds - the discovery is at first greeted with widespread skepticism

Astronomy.Germany.
==Mar.23 > Werner von Braun is born in Wirsitz to a prominent Prussian baron

Eugenics.International.
==Jul.24-30 > The First International Eugenics Congress is held at the University of London

Physics.Britain.
==1912 > Rutherford identifies the hydrogen nucleus as the unit of positive charge, which he will later call the proton
==1912 > J. J. Thomson develops mass spectrometry and separates isotopes

Physics.Britain.Scandinavia.
==1912-1916 > Young Danish physicist Niels Bohr works under Rutherford at the University of Manchester

Physics.Germany.
==1912 > Einstein explains the curvature of space-time and proposes the theories behind the laser

Physics.Germany.Britain.
==1912 > Physicists Max von Laue in Germany and the Braggs in Britain develop x-ray crystallography

Astronomy.United States.
==1912 > Harvard astronomer Henrietta Leavitt’s work on Cepheids' periods enables astronomers to measure distances to very far stars

Chemistry.Low Countries.
==1912 > Dutch chemist Debye describes polar molecules, or dipoles

Chemistry.United States.
==1912 > At UC Berkeley, G. N. Lewis begins forming what will be the leading American chemistry research school through World War II

Oceanography.Britain.
==1912 > John Murray and Johan Hjort publish The Depths of the Oceans

Archaeology.Egypt.
==1912 > German archaeologist Borchardt discovers the famous Egyptian bust of Queen Nefertiti at Tell al-Amarna

Archaeology.Mesopotamia.
==1912 > German archaeologists begin excavations at Uruk

Eugenics.United States.
==1912 > Psychologist Henry H. Goddard publishes The Kallikak Family, to warn against breeding with ‘inferiors’

Mathematics.India.
==Jan.16 > The self-educated Indian genius Srinivasa Ramanujan sends a long list of brilliant theorems to British mathematician G. H. Hardy, and begins to come to the attention of academia

Physics.Britain.Scandinavia.
==Mar.06 > Working with Rutherford, Niels Bohr proposes the modern model of the atom after applying quantum theory to atomic structure - he will receive the 1922 Nobel Prize for this achievement

Biology.Britain.
==Nov.07 > Naturalist Alfred Russel Wallace dies at the age of 91

Physics.Britain.
==Nov.--- > The gifted young physicist Henry Moseley discovers the correspondence of nuclear charge and atomic number

Physics.Britain.
==1913 > Chemist Frederick Soddy coins the term ‘isotope’

Physics.United States.
==1913 > America enters the international uranium market; within a few years it has a virtual monopoly

Biochemistry.Germany.
==1913 > Chemists Leonor Michaelis and Maud Menten formulate the Michaelis-Menten equation to describe enzyme reaction rates

Meteorology.France.
==1913 > Physicist Charles Fabry confirms the existence of the ozone layer

Earth Sciences.United States.
==1913 > Albert Michelson measures tides in the solid body of the Earth

Paleontology.East Africa.
==1913 > Hans Reck discovers rich deposits of early mammalian fossils at Olduvai Gorge in German East Africa

Genetics.United States.
==1913 > Sturtevant produces the first genetic map

Archaeology.Palestine.
==1913 > Weill excavates the City of David in Jerusalem - the first Jewish archaeological dig of a Jewish site

Archaeology.Sinkiang.
==1913-1916 > Third expedition of explorer/archaeologist Aurel Stein, to Sinkiang

Archaeology.Italy.
==1913 > A major excavation of the Etruscan city of Veii begins

Archaeology.Egypt.
==1913 > American archaeologist George Reisner makes a careful excavation of Kerma in Nubia

Meteorology.United States.
==Jan.01 > The United States Weather Bureau begins publishing a daily Northern Hemisphere weather map to aid aviators

Archaeology.Egypt.
==Jan-Mar > A British ‘archaeological’ party (including T. E. Lawrence) surveys the eastern Sinai-Aqaba area under secret orders from Kitchener

Rocketry.United States.
==Jul.07 > Robert Goddard receives the first of over 200 first rocket-related patents

Physics.Britain.
==1914 > Rutherford coins the word ‘proton’

Physics.Germany.
==1914 > James Franck and Gustav Hertz observe atomic excitation and confirm Bohr’s model of atomic structure
==1914 > Einstein is appointed to a highly prestigious professorship at the Kaiser-Wilhelm Gesellschaft in Berlin; he never again teaches classes

Chemistry.Germany.
==1914 > German medical chemist Leonor Michaelis popularizes the pH scale among chemists

Biochemistry.Britain.
==1914 > Henry Hallet Dale suggests that acetylcholine is a neurotransmitter

Earth Sciences.Germany.
==1914 > German geologist Beno Gutenberg discovers the discontinuity between Earth's mantle and core

Genetics.United States.
==1914 > Thomas Hunt Morgan and his associates publish the epochal The Mechanism of Mendelian Heredity

Archaeology.Crete.
==1914 > British archaeologist Arthur Evans largely wraps up his excavation at Knossus in Crete, underway since 1900, which has revealed the existence of Minoan civilization

Archaeology.Mesopotamia.
==1914 > German archaeologist Walter Andrae ends his careful excavation of ancient Ashur, ongoing since 1902

Science.China.
==1914 > Chinese students at Cornell establish the Science Society of China