Science Milestones

Today in Science History

Milestones in science, mathematics, and technology for today, October 25th

(Hybrid AI composite image by Author)

“Everything is theoretically impossible until it is done. One could write a history of science in reverse by assembling the solemn pronouncements of highest authority about what could not be done and could never happen.”
— Robert A. Heinlein (1907–1988)

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Welcome to “Science Milestones.” Here, we highlight some of the extraordinary people and transformative accomplishments in science, mathematics, and technology over the centuries.

What Happened This Day in History: October 25th

• 1671: Italian-French astronomer Giovanni Domenico Cassini discovers Iapetus, the second known moon of Saturn. Using a new refracting telescope at the Paris Observatory, he noticed that the moon was visible only when it was on the western side of the planet. His conclusion was that Iapetus always keeps the same face toward Saturn and that one of its hemispheres is darker than the other. Three centuries later, spacecraft confirmed his conclusion. In his honor, the moon’s dark region is now named Cassini Regio. Cassini went on to discover three more Saturnian moons as well as the gap in Saturn’s rings known as the Cassini Division. The NASA–ESA Cassini–Huygens mission bears his name.

Iapetus as seen by the Cassini spacecraft. (Source)

• 1811: French mathematician Évariste Galois is born. While still a teenager, Galois answered a question that had puzzled mathematicians since the Renaissance: which polynomial equations can be solved by a formula like the quadratic formula? To do this, he studied the symmetries of an equation’s roots. In the process, he laid the foundations of group theory and what is now called Galois theory. On the night before a fatal duel, he wrote out a summary of his ideas in a letter to his friend Auguste Chevalier. He died in 1832 at the age of twenty. In 1846, Joseph Liouville published Galois’s papers, and they went on to reshape modern algebra.

A portrait of Évariste Galois at about age 15. (Source)

• 1877: American astronomer Henry Norris Russell is born. Working independently of the Danish astronomer Ejnar Hertzsprung, Russell plotted the brightness of stars against their spectral type. The result is now known as the Hertzsprung–Russell diagram, one of the most important tools in astrophysics and the basic framework for understanding how stars are structured and how they evolve. With Frederick Saunders, Russell also worked out Russell–Saunders coupling, a cornerstone of atomic spectroscopy. In 1929, his own analysis confirmed that the Sun is made mostly of hydrogen, confirming a conclusion Cecilia Payne had reached four years earlier. Russell directed the Princeton University Observatory from 1912 to 1947 and was widely regarded as the dean of American astronomers.
• 1888: American naval officer, aviator, and polar explorer Richard Evelyn Byrd is born. On May 9, 1926, Byrd and pilot Floyd Bennett claimed the first flight over the North Pole. Historians have disputed that claim ever since. Uncontroversial was when, on November 28–29, 1929, Byrd and a crew of three made the first flight over the South Pole. Over the following decades, he led five Antarctic expeditions, which mapped large parts of the continent from the air and helped establish the long-term U.S. scientific presence there. In 1934, he spent five winter months alone at a weather station on the ice and nearly died of carbon monoxide poisoning. He recounted the ordeal in his 1938 book Alone.
• 1906: American inventor Lee de Forest files a patent application for a “Device for Amplifying Feeble Electrical Currents.” The application described the “Audion,” the first three-electrode vacuum tube that later became known as the “triode.” The patent was issued on January 15, 1907. De Forest himself did not fully understand how the device worked, and he initially used it mainly to detect radio signals. Once engineers learned to use it as an amplifier, the triode became the foundation of radio broadcasting, long-distance telephony, sound film, and the first electronic computers. That legacy earned de Forest the title “Father of Radio.”

The audion, invented in 1906 by Lee De Forest, was the first tube consisting of three electrodes: a filament, grid, and plate. (Source)

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