1570day.year
Cartographer Abraham Ortelius issues Theatrum Orbis Terrarum, the first modern atlas.
Abraham Ortelius publishes the Theatrum Orbis Terrarum in 1570, the first modern atlas that standardized map-making.
On May 20, 1570, Flemish cartographer Abraham Ortelius released Theatrum Orbis Terrarum ('Theatre of the World') in Antwerp.
This groundbreaking work compiled 53 copper-engraved maps, unifying style and geographic information in a single volume.
Ortelius drew on the latest explorations and collaborated with leading mapmakers to ensure accuracy and detail.
The publication introduced the term 'atlas' for a cohesive collection of maps and established a new standard in cartography.
Its influence spurred further global voyages and advanced the scientific study of geography.
The Theatrum Orbis Terrarum remains a landmark achievement in the history of map-making and exploration.
1570
Cartographer
Abraham Ortelius
Theatrum Orbis Terrarum
atlas
1873day.year
Levi Strauss and Jacob Davis receive a U.S. patent for blue jeans with copper rivets.
Levi Strauss and Jacob Davis receive a U.S. patent for riveted blue jeans, transforming durable workwear.
On May 20, 1873, Bavarian-born merchant Levi Strauss and tailor Jacob Davis received U.S. Patent No. 139,121 for using copper rivets to reinforce denim work pants. This innovation greatly improved the durability of workwear worn by laborers during the American West gold rushes. The patented design marked the birth of blue jeans as a practical garment. Within years, the new trousers gained popularity among miners, cowboys, and factory workers. This milestone laid the foundation for one of the world’s most iconic articles of clothing.
1873
Levi Strauss
Jacob Davis
patent
jeans
copper
1875day.year
Signing of the Metre Convention by 17 nations leading to the establishment of the International System of Units.
Seventeen nations sign the Metre Convention, establishing the framework for the International System of Units.
On May 20, 1875, seventeen nations convened in Paris and signed the Metre Convention, establishing an international framework for uniform measurement. The treaty created the International Bureau of Weights and Measures to oversee standardized units and scientific cooperation. It laid the groundwork for the metric system’s global adoption, promoting accuracy in commerce, industry, and research. Member countries agreed to base their measurements on physical prototypes and shared reference standards. The Metre Convention remains a cornerstone of international collaboration in science and engineering.
1875
Metre Convention
International System of Units
1891day.year
History of cinema: The first public display of Thomas Edison's prototype kinetoscope.
Thomas Edison publicly unveils his kinetoscope prototype, offering audiences their first glimpse of moving pictures.
On May 20, 1891, Thomas Edison publicly demonstrated his prototype kinetoscope in a New York lab, offering viewers a peek at short moving images through a peep-hole viewer. The display marked a crucial step in motion picture history, combining Edison’s innovations in photography and electricity. Though only one person could watch at a time, the kinetoscope captivated audiences with its lifelike motion. Edison’s invention paved the way for future projection systems and the birth of the film industry. This milestone foreshadowed the global cultural phenomenon of cinema that would emerge in the 20th century.
1891
History of cinema
Thomas Edison
kinetoscope
1927day.year
Charles Lindbergh takes off for Paris from Roosevelt Field in Long Island, N.Y., aboard the Spirit of St. Louis on the first nonstop solo flight across the Atlantic Ocean, landing 33+1⁄2 hours later.
On May 20, 1927, Charles Lindbergh launched the Spirit of St. Louis from Long Island, completing the first solo nonstop transatlantic flight when he landed in Paris 33½ hours later.
Lindbergh's daring flight represented a major leap forward in aviation engineering and human endurance. Flying alone without a radio or parachute, he navigated through fog, storms, and darkness. His custom-built Ryan NYP monoplane, the Spirit of St. Louis, carried extra fuel tanks, making the journey possible. Upon landing at Le Bourget Field, he was greeted as an international hero and earned the Orteig Prize. The feat spurred public interest in commercial aviation and inspired technological advancements in aircraft design and navigation.
1927
Charles Lindbergh
Spirit of St. Louis
1932day.year
Amelia Earhart takes off from Newfoundland to begin the world's first solo nonstop flight across the Atlantic Ocean by a female pilot, landing in Ireland the next day.
On May 20, 1932, Amelia Earhart departed Newfoundland to make history as the first woman to solo nonstop across the Atlantic, landing in Ireland the following day.
Amelia Earhart's flight challenged gender norms and showcased advances in aviation technology. Piloting a Lockheed Vega 5B, she navigated over 2,000 miles of open ocean using celestial navigation. Enduring fatigue and stormy weather, she landed near Londonderry, Northern Ireland, on May 21. Her achievement earned her the United States Distinguished Flying Cross, making her the first woman recipient. Earhart's flight inspired a generation of female aviators and contributed to growing support for women's rights and equality in the 20th century.
1932
Amelia Earhart
Newfoundland
1943day.year
The Luttra Woman, a bog body from the Early Neolithic period (radiocarbon-dated c. 3928–3651 BC), was discovered near Luttra, Sweden.
On May 20, 1943, peat cutters in Sweden uncovered the remarkably preserved bog body known as the Luttra Woman, offering a window into Early Neolithic life.
The Luttra Woman was discovered in a shallow peat bog near the village of Luttra and later radiocarbon-dated to around 3928–3651 BC. Preservation of her skin, hair, and clothing provided archaeologists with unique insights into Neolithic diets, textiles, and burial rituals. Analysis of stomach contents revealed details about her last meals, while botanical fragments suggested seasonal context. Exhibited in museums, her remains continue to shed light on prehistoric human societies in northern Europe. The discovery underscored the scientific value of bog bodies for understanding ancient daily life and environmental conditions.
1943
Luttra Woman
bog body
Neolithic
radiocarbon-dated
Luttra
1949day.year
In the United States, the Armed Forces Security Agency, the predecessor to the National Security Agency, is established.
On May 20, 1949, the U.S. established the Armed Forces Security Agency, consolidating military cryptologic functions and laying the groundwork for the NSA.
Post-World War II, the United States sought to centralize its signals intelligence capabilities, leading to the creation of the Armed Forces Security Agency (AFSA). AFSA absorbed disparate Army, Navy, and Air Force cryptologic units but faced coordination challenges. Its formation set a precedent for unified intelligence efforts during the early Cold War. In 1952, AFSA was reorganized and renamed the National Security Agency (NSA), reflecting an expanded mandate. The NSA would go on to become the world's largest collector of electronic communications, profoundly shaping global intelligence operations.
1949
National Security Agency
1956day.year
In Operation Redwing, the first United States airborne hydrogen bomb is dropped over Bikini Atoll in the Pacific Ocean.
On May 20, 1956, as part of Operation Redwing, the United States conducted its first airborne hydrogen bomb test over Bikini Atoll in the Pacific Ocean.
Operation Redwing was a series of nuclear tests designed to evaluate the performance of thermonuclear weapons in various delivery modes. The bomb dropped by a B-52 bomber exploded at altitude, demonstrating advances in yield-to-weight ratios. The test's fallout raised concerns about radioactive contamination of marine ecosystems and islanders. It underscored the escalating arms race of the Cold War and influenced future nuclear test ban discussions. Findings from Redwing informed U.S. defense strategies and contributed to technical improvements in warhead design.
1956
Operation Redwing
hydrogen bomb
Bikini Atoll
1964day.year
Discovery of the cosmic microwave background radiation by Robert Woodrow Wilson and Arno Penzias.
Wilson and Penzias detect the cosmic microwave background radiation, providing crucial evidence for the Big Bang theory.
On May 20, 1964, radio astronomers Robert W. Wilson and Arno Penzias announced the detection of the cosmic microwave background radiation at Bell Labs in Holmdel, New Jersey. They discovered a persistent, uniform noise in their radio antenna, which they eventually identified as relic radiation from the early universe. This observation provided strong empirical support for the Big Bang model of cosmology. Their groundbreaking work earned them the Nobel Prize in Physics in 1978. The discovery revolutionized our understanding of the universe's origins.
1964
Discovery
cosmic microwave background radiation
Robert Woodrow Wilson
Arno Penzias
1983day.year
First publications of the discovery of the HIV virus that causes AIDS in the journal Science by a team of French scientists including Françoise Barré-Sinoussi, Jean-Claude Chermann, and Luc Montagnier.
French researchers publish the discovery of the HIV virus in Science, a landmark in understanding AIDS.
On May 20, 1983, a team of French scientists led by Françoise Barré-Sinoussi, Jean-Claude Chermann, and Luc Montagnier published their groundbreaking findings in the journal Science, identifying the human immunodeficiency virus (HIV) as the causative agent of AIDS. Using advanced virology techniques, they isolated the virus from patient samples and demonstrated its role in destroying immune cells. This discovery paved the way for diagnostic tests, antiretroviral therapies, and global health initiatives. In 2008, the key researchers received the Nobel Prize in Physiology or Medicine for their work. Their findings transformed the fight against HIV/AIDS worldwide.
1983
HIV
virus
AIDS
Science
Françoise Barré-Sinoussi
Jean-Claude Chermann
Luc Montagnier
2019day.year
The International System of Units (SI): The base units are redefined, making the international prototype of the kilogram obsolete.
On May 20, 2019, the SI base units were redefined in terms of fundamental constants, rendering the kilogram prototype obsolete.
On May 20, 2019, representatives from 60 countries adopted a historic resolution at the 26th General Conference on Weights and Measures.
They redefined the kilogram, ampere, kelvin, and mole in terms of fundamental physical constants.
The international prototype of the kilogram—a metal cylinder kept in France—was rendered obsolete.
By fixing the values of the Planck constant, elementary charge, Boltzmann constant, and Avogadro constant, unit definitions became more stable.
This overhaul enhances measurement precision for science, industry, and commerce worldwide.
The new SI system took effect on World Metrology Day, cementing a legacy of innovation in metrology.
2019
International System of Units
international prototype of the kilogram