Fruit flies and biplanes. Pap smears and CAT scans. Radar and lasers. Insulin, penicillin, LSD and ESP. Artificial hearts. Artificial intelligence. A few of the advances that powered this extraordinary century
--By Andrea Dorfman and Mary Hart
1900
1900 Sigmund Freud publishes The Interpretation of Dreams
1900 Max Planck presents his quantum theory at a meeting of the German Physical Society in Berlin
1901 Austrian physician Karl Landsteiner shows that there are at least three types of human blood, which he labels A, B and O. These distinctions make blood transfusions possible. Landsteiner will also discover the Rh factor
1902 Scottish cardiologist James Mackenzie invents the polygraph machine, better known as the lie detector
1903 Marie Curie shares the Nobel Prize for Physics with Henri Becquerel and her husband Pierre for their discovery of radioactivity; she will win a second Nobel, for Chemistry, in 1911, for isolating the radioactive element radium
1903 The Flyer, a plane built by American inventors Wilbur and Orville Wright, makes the first powered flight
1905 French psychologist Alfred Binet devises the first intelligence tests
1905 German chemist Walther Nernst explains why absolute zero (about -273[degrees]C) can never be reached; this becomes the third law of thermodynamics
1906 British biochemist Frederick Hopkins postulates that "accessory food factors" are required for human health; these are now known as vitamins
1906 German neurologist Alois Alzheimer identifies a disorder that causes the progressive loss of intellectual functioning
1907 Italian educator Maria Montessori establishes her first preschool, in Rome
1907 Belgian-American chemist Leo Baekeland patents Bakelite, the world's first true plastic
1908 Hans Geiger invents a machine that translates invisible nuclear radiation into audible clicks
1910
1910 German bacteriologist Paul Ehrlich uses a form of arsenic to combat syphilis; his work forms the basis of modern chemotherapy
1910 Working with fruit flies, U.S. biologist Thomas Hunt Morgan discovers that some genetic traits are sex-linked and that the genes governing these traits are located on chromosomes
1910 Publication of Volume I of Principia Mathematica, a three-volume work by Bertrand Russell and Alfred North Whitehead that attempts to link mathematics and logic
1911 Ernest Rutherford, Hans Geiger and Ernest Marsden discover the structure of the atom
1911 Austrian-American physicist Victor Hess detects radiation coming from outer space; it is later dubbed cosmic rays
1911 Hiram Bingham finds Machu Picchu, a 15th century Inca settlement high in the Peruvian Andes
1912 German meteorologist Alfred Wegener proposes the theory of continental drift
1912 Charles Dawson announces that he has found the fossilized remains of a human-like creature on Piltdown Common in Sussex, England. Christened Eoanthropus dawsoni, "Piltdown Man" will be exposed as a fraud in 1953
1913 Dr. Albert Schweitzer, a missionary, opens a hospital in Lambarene, French Equatorial Africa (now Gabon), for the treatment of leprosy and sleeping sickness