History of science / 1850 CE — 1944 CE
Modern Science
From elements to spacetime
Research on evolution, atoms, microbes and computation changes the scales at which people understand the world.
Selected stories
On the Origin of Species argues for natural selection
Darwin assembled a sustained case for natural selection. Wallace had independently developed a similar mechanism; their writings were jointly presented in 1858.
The periodic table becomes a tool for prediction
Mendeleev arranged elements by atomic weight and chemical properties, leaving gaps for missing elements. Meyer and other chemists also contributed to the periodic system.
Koch reports the bacterium behind tuberculosis
Koch combined staining, culture and animal experiments to connect the tubercle bacillus with tuberculosis, advancing experimental investigation of infectious disease.
Radioactivity leads the Curies to new elements
Marie and Pierre Curie used radioactivity measurements to investigate unknown components of ores. Their radium report also included collaborator Gustave Bémont.
Special relativity rethinks space and time
Einstein used the relativity principle and the constant speed of light in vacuum to reconsider how inertial observers compare time, length and motion.
Scattering experiments reveal a concentrated atomic center
Rutherford interpreted Geiger and Marsden’s scattering results with a model placing positive charge and most atomic mass in a very small central region.
Quantum mechanics develops through several formulations
Heisenberg, Born, Jordan, Schrödinger, Dirac and others developed matrix, wave and probabilistic approaches, transforming descriptions of microscopic matter.
Penicillin begins with an observation, not a ready-made drug
Fleming observed bacteria failing to grow near a mold colony. Turning penicillin into a usable, widely produced medicine required later collaborative breakthroughs.
Raman and Krishnan identify shifted scattered light
Working in Calcutta, Raman and Krishnan observed frequency changes in a small portion of scattered light, opening a new route to identifying molecular properties.
Turing models the limits of computation
Turing used an abstract symbol-reading machine to investigate computation and describe a universal machine. This was a mathematical model, not a completed electronic computer.