Halley's Comet © Harvard College Observatory/Science Photo Library/Getty Images
240 BC – First recorded sighting of Halley’s Comet
The first certain perihelion passage of Halley’s Comet is recorded in China.
The sighting fits Edmond Halley’s computed orbit, who realised that comets seen in 1531, 1607 and 1682 were the same one. Halley’s Comet comes close to Earth about every 75 years, with the next sighting due in 2061.
1842 – Idea of Doppler Effect proposed
The idea of the Doppler Effect is presented to the Royal Bohemian Society, Prague by Austrian physicist Christian Doppler.
The Doppler Effect occurs when an emitted wave (sound, light or other) changes in frequency when the source or observer moves in relation to one another. The frequency increases as they move towards one another, and decreases as they move further apart. This has been used to explain the change in pitch of a passing siren and redshift in astronomy.
1940 – Penicillin first tested on mice
Four mice recover from lethal bacterial infection after being injected with penicillin.
Penicillin was tested by Howard Florey and Ernst Chain, who inoculated eight mice a lethal dose of the Streptococcus bacteria. Four of the mice were then injected with penicillin who all survived, while the others died. Penicillin was the first antibiotic used to successfully treat infectious diseases, and now comprises a whole group of antibiotics.
1961 – JFK announces plan to put a man on the Moon
President John F. Kennedy addresses Congress and proclaims that the USA should land a man on the Moon by the end of the decade.
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