Portal:History of science

Tests of general relativity serve to establish observational evidence for the theory of general relativity. The first three tests, proposed by Albert Einstein in 1915, concerned the "anomalous" precession of the perihelion of Mercury, the bending of light in gravitational fields, and the gravitational redshift. The precession of Mercury was already known; experiments showing light bending in accordance with the predictions of general relativity were performed in 1919, with increasingly precise measurements made in subsequent tests; and scientists claimed to have measured the gravitational redshift in 1925, although measurements sensitive enough to actually confirm the theory were not made until 1954. A more accurate program starting in 1959 tested general relativity in the weak gravitational field limit, severely limiting possible deviations from the theory.

In the 1970s, scientists began to make additional tests, starting with Irwin Shapiro's measurement of the relativistic time delay in radar signal travel time near the Sun. Beginning in 1974, Hulse, Taylor and others studied the behaviour of binary pulsars experiencing much stronger gravitational fields than those found in the Solar System. Both in the weak field limit (as in the Solar System) and with the stronger fields present in systems of binary pulsars the predictions of general relativity have been extremely well tested. (Full article...)

...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?

Segrè in 1959

Emilio Gino Segrè (Italian: [seˈgrɛ]; 1 February 1905 – 22 April 1989) was an Italian and naturalized-American physicist and Nobel laureate, who discovered the elements technetium and astatine, and the antiproton, a subatomic antiparticle, for which he was awarded the Nobel Prize in Physics in 1959 along with Owen Chamberlain.

Born in Tivoli, near Rome, Segrè studied engineering at the University of Rome La Sapienza before taking up physics in 1927. Segrè was appointed assistant professor of physics at the University of Rome in 1932 and worked there until 1936, becoming one of the Via Panisperna boys. From 1936 to 1938 he was director of the Physics Laboratory at the University of Palermo. After a visit to Ernest O. Lawrence's Berkeley Radiation Laboratory, he was sent a molybdenum strip from the laboratory's cyclotron accelerator in 1937, which was emitting anomalous forms of radioactivity. Using careful chemical and theoretical analysis, Segrè was able to prove that some of the radiation was being produced by a previously unknown element, named technetium, the first artificially synthesized chemical element that does not occur in nature. (Full article...)

• 1583 - Birth of Jean-Baptiste Morin, French scientist (d. 1656)

• 1603 - Death of Andrea Cesalpino, Italian philosopher, physician, and botanist (b. 1519)

• 1855 - Death of Carl Friedrich Gauss, German mathematician, astronomer, and physicist (b. 1777)

• 1922 - Death of Albert Victor Bäcklund, Swedish physicist (b. 1845)

• 1941 - Plutonium was first produced and isolated by Dr. Glenn T. Seaborg

• 1987 - Supernova 1987a: A supernova is seen in the Large Magellanic Cloud