The line of GMT at the Greenwich Royal Observatory © Oli Scarff/Getty Images
1880 - Greenwich Mean Time adopted by Parliament
The Definition of Time Act receives the Royal Assent, finally providing Britain with a unified standard time. The development of a national rail network and the electrical telegraph system that needed to be set to precise times encouraged this Parliamentary Act.
1932 - Positron discovered
American physicist Carl D. Anderson discovers the positron, the antiparticle to the electron. In 1928, Paul Dirac used Einstein’s Theory of Relativity to theorise that every particle corresponded to an antiparticle with the same mass but the opposite charge. Anderson’s discovery provided the first experimental evidence of this.
The breakthrough came when Anderson detected a particle that moved in the wrong direction in a magnetic field to be a negatively-charged electron, but was much too light to be the heavy, positively-charged proton.
1939 - Einstein and Szilárd write to Roosevelt, prompting Manhattan project
Hungarian physicist Leó Szilárd convinces Albert Einstein to sign a letter to President Franklin D. Roosevelt, encouraging him to consider action concerning the possibility of Germany developing nuclear weapons.
The discovery of nuclear fission earlier that year by German chemists Otto Hahn and Fritz Strassmann and the potential for Germany to access uranium through Belgium’s mines in the Congo was of great concern to Szilárd. At their recommendation, Roosevelt initiated the Manhattan project, leading to the use of atomic bombs in 1945.
1989 - Three of Neptune’s moons discovered
NASA confirms that the Voyager 2 space probe has discovered three more moons in orbit around Neptune, later named as Galatea, Despina and Larissa.
Discover more history of science