1897day.year
J. J. Thomson of the Cavendish Laboratory announces his discovery of the electron as a subatomic particle, over 1,800 times smaller than a proton (in the atomic nucleus), at a lecture at the Royal Institution in London.
In 1897, J. J. Thomson announced the discovery of the electron at a lecture at the Royal Institution in London, revolutionizing the understanding of atomic structure.
Working at the Cavendish Laboratory, J. J. Thomson conducted experiments with cathode rays to explore the nature of electrical conduction. On April 30, 1897, he presented evidence that these rays consisted of particles much smaller than atoms, which he called electrons. By measuring the charge-to-mass ratio, Thomson demonstrated that electrons were fundamental components of all atoms. This discovery upended the traditional view of atoms as indivisible units and laid the groundwork for modern atomic physics. Thomson's work earned him the Nobel Prize in Physics in 1906. His findings opened the door to quantum theory and nuclear science, profoundly shaping the course of 20th-century physics.
1897
J. J. Thomson
Cavendish Laboratory
electron
subatomic particle
proton
Royal Institution
1905day.year
Albert Einstein completes his doctoral thesis at the University of Zurich.
In 1905, Albert Einstein completed his groundbreaking doctoral thesis at the University of Zurich.
At the University of Zurich, Einstein worked under the guidance of Professor Alfred Kleiner and focused on the molecular dimensions of dilute solutions. His 1905 doctoral thesis, entitled A New Determination of Molecular Dimensions, analyzed the viscosity of solutions to derive Avogadro's number. This research provided strong evidence for the atomic theory of matter and helped explain Brownian motion. The thesis was one of several groundbreaking papers Einstein published during his annus mirabilis. His findings solidified his reputation in the scientific community and paved the way for future contributions to theoretical physics. Einstein's doctoral work remains a landmark in the history of modern science.
1905
Albert Einstein
University of Zurich
1939day.year
NBC inaugurates its regularly scheduled television service in New York City, broadcasting President Franklin D. Roosevelt's N.Y. World's Fair opening day ceremonial address.
NBC launches the first regularly scheduled television service by broadcasting FDR's World's Fair address.
On April 30, 1939, NBC began its first regularly scheduled television broadcasts in New York City, featuring President Franklin D. Roosevelt's opening address for the New York World's Fair.
This inaugural transmission marked a pivotal moment in mass media, bringing live political events into American living rooms.
At a time when only a few hundred television sets existed, NBC's pioneering service showcased the medium's potential.
Engineers used early iconoscope cameras and a makeshift transmitter to beam the President's image across the city.
The broadcast foreshadowed television's post-war expansion as a primary source of news and entertainment.
Audiences who witnessed the event gained a glimpse of the future of real-time communication.
NBC
television
Franklin D. Roosevelt
N.Y. World's Fair
1961day.year
K-19, the first Soviet nuclear submarine equipped with nuclear missiles, is commissioned.
The world's first Soviet nuclear submarine armed with ballistic missiles is commissioned into service.
On April 30, 1961, K-19 became the Soviet Navy's first nuclear-powered submarine equipped to launch nuclear ballistic missiles. Designed to counter U.S. Polaris submarines, K-19 represented a leap in Cold War naval technology. Commissioned into active duty, she showcased the USSR's growing undersea strategic capabilities. Her introduction heightened tensions as both superpowers raced to establish nuclear deterrent forces. The vessel's pioneering reactor and missile systems set a precedent for future Soviet submarine classes. Despite early technical challenges, K-19 marked a significant milestone in military maritime history.
1961
K-19
Soviet
nuclear submarine
nuclear missiles
commissioned
1993day.year
CERN announces World Wide Web protocols will be free.
CERN declares that the World Wide Web's underlying protocols will be released free of charge, fueling its global expansion.
On April 30, 1993, the European Organization for Nuclear Research (CERN) announced that the World Wide Web's protocols and code would be made available at no cost. Developed by Tim Berners-Lee, the Web quickly gained traction as an open information-sharing platform. CERN's decision to forgo royalties removed barriers to adoption and sparked an internet revolution. Academic institutions, businesses, and individuals worldwide began building on the Web's foundation. Within a few years, the Web had transformed communication, commerce, and culture on a global scale. This historic announcement laid the groundwork for the digital age and reshaped how people access knowledge and connect online.
1993
CERN
World Wide Web
2008day.year
Two skeletal remains found near Yekaterinburg are confirmed by Russian scientists to be the remains of Alexei and Anastasia, two of the children of the last Tsar of Russia, whose entire family was executed at Yekaterinburg by the Bolsheviks.
On April 30, 2008, Russian scientists announced that skeletal fragments found near Yekaterinburg belonged to Tsar Nicholas II's children Alexei and Anastasia.
Fragments of two skeletons discovered in 1991 near the site where the Romanov family was killed were subjected to extensive DNA analysis. Scientists compared mitochondrial and Y-chromosome markers with living relatives of the Romanovs to confirm identities. On April 30, 2008, officials announced a positive match to Tsarevich Alexei and Grand Duchess Anastasia. This finding completed the identification of all members of Russia's last imperial family, executed by Bolshevik forces in 1918. The confirmation provided closure to decades of historical debate and mystery. It paved the way for a formal reburial ceremony in St. Petersburg's Peter and Paul Cathedral to honor the Romanov legacy.
2008
Yekaterinburg
Alexei
Anastasia