The history of virology – the scientific study of viruses and the infections they cause – began in the closing years of the 19th century. Although Edward Jenner and Louis Pasteur developed the first vaccines to protect against viral infections, they did not know that viruses existed. The first evidence of the existence of viruses came from experiments with filters that had pores small enough to retain bacteria. In 1892, Dmitri Ivanovsky used one of these filters to show that sap from a diseased tobacco plant remained infectious to healthy tobacco plants despite having been filtered. Martinus Beijerinck called the filtered, infectious substance "contagium vivum fluidum." Although the particles could not be seen yet, his discovery is considered to be the beginning of virology.

The subsequent discovery and partial characterization of bacteriophages by Frederick Twort and Félix d'Herelle further catalyzed the field, and by the early 20th century many viruses had been discovered. In 1926, Thomas Milton Rivers defined viruses as obligate parasites. Viruses were demonstrated to be particles, rather than a fluid, by Wendell Meredith Stanley, and the invention of the electron microscope in 1931 allowed their complex structures to be visualised. (Full article...)

In this detail from an early 14th century copy of Euclid's Elements, a woman is shown teaching geometry. It is a detail of a scene in the bowl of the letter 'P'; the woman, with a set-square and dividers, uses a compass to measure distances on a diagram. In her left hand she holds a square, an implement for testing or drawing right angles. She is watched by a group of students. In images from the Middle Ages, it is unusual to see women represented as teachers, in particular when the students appear to be monks. She may be the personification of Geometry.

...that the travel narrative The Malay Archipelago, by biologist Alfred Russel Wallace, was used by the novelist Joseph Conrad as a source for his novel Lord Jim?

...that the seventeenth century philosophers René Descartes, Baruch Spinoza, and Gottfried Leibniz, along with their Empiricist contemporary Thomas Hobbes all formulated definitions of conatus, an innate inclination of a thing to continue to exist and enhance itself?

...that according to the controversial Hockney-Falco thesis, the rise of realism in Renaissance art, such as Jan Van Eyck's Arnolfini Portrait (pictured), was largely due to the use of curved mirrors and other optical aids?

Portrait by Joseph Duplessis, 1785

Benjamin Franklin (January 17, 1706 [O.S. January 6, 1705] – April 17, 1790) was an American polymath: a writer, scientist, inventor, statesman, diplomat, printer, publisher and political philosopher. Among the most influential intellectuals of his time, Franklin was one of the Founding Fathers of the United States; a drafter and signer of the Declaration of Independence; and the first postmaster general.

Born in the Province of Massachusetts Bay, Franklin became a successful newspaper editor and printer in Philadelphia, the leading city in the colonies, publishing The Pennsylvania Gazette at age 23. He became wealthy publishing this and Poor Richard's Almanack, which he wrote under the pseudonym "Richard Saunders". After 1767, he was associated with the Pennsylvania Chronicle, a newspaper known for its revolutionary sentiments and criticisms of the policies of the British Parliament and the Crown. He pioneered and was the first president of the Academy and College of Philadelphia, which opened in 1751 and later became the University of Pennsylvania. He organized and was the first secretary of the American Philosophical Society and was elected its president in 1769. He was appointed deputy postmaster-general for the British colonies in 1753, which enabled him to set up the first national communications network. (Full article...)

May 17

• 1749 - Birth of Edward Jenner, English physician and developer of the smallpox vaccine (d. 1823)
• 1758 - Birth of John St Aubyn, British fossil collector (d. 1839)
• 1765 - Death of Alexis Claude Clairault, French mathematician (b. 1713)
• 1897 - Birth of Odd Hassel, Norwegian chemist and Nobel Prize laureate (d. 1981)
• 1902 - Archaeologist Valerios Stais finds the Antikythera mechanism.
• 1916 - Death of Boris Borisovich Galitzine, Russian physicist (b. 1862)
• 1943 - The United States Army contracts with the University of Pennsylvania's Moore School to develop the ENIAC.
• 1969 - The Soviet spaceprobe Venera 6 begins its descent into the atmosphere of Venus, sending back atmospheric data before being crushed by pressure.
• 2004 - The Stockholm Convention, an international treaty limiting the use of DDT and other persistent organic pollutants, goes into effect.