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The Manhattan Project, a secret American programme run with Britain and Canada during the Second World War, built the first atomic bombs. The first was tested in New Mexico on 16 July 1945, and in August two were dropped on Hiroshima and Nagasaki.

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In 1939 Albert Einstein signed a letter, drafted by the physicist Leo Szilard, warning President Franklin D. Roosevelt that Germany might build a bomb from uranium. The project took shape in 1942 under General Leslie Groves, with J. Robert Oppenheimer directing the Los Alamos laboratory in New Mexico, where the bombs were designed. At its peak it employed nearly 130,000 people, and it cost nearly 2 billion US dollars. The bombings of 6 and 9 August 1945 killed between 150,000 and 246,000 people, most of them civilians. The Soviet Union declared war on Japan on 8 August, and Japan announced its surrender on 15 August; historians still debate how much each event weighed in that decision. In August 1949 the Soviet Union tested its own bomb, and the nuclear arms race began.

Türkçe oku
Manhattan Projesi, ABD'nin İkinci Dünya Savaşı sırasında Birleşik Krallık ve Kanada ile gizlice yürüttüğü programdı; ilk atom bombaları bu projede yapıldı. İlk bomba 16 Temmuz 1945'te New Mexico'da denendi, ağustosta da iki bomba Hiroşima ve Nagazaki'ye atıldı.

1939'da Albert Einstein, fizikçi Leo Szilard'ın kaleme aldığı bir mektubu imzalayarak ABD Başkanı Franklin D. Roosevelt'i, Almanya'nın uranyumdan bomba yapabileceği konusunda uyardı. Proje 1942'de General Leslie Groves'un yönetiminde hayata geçti; bombaların tasarlandığı New Mexico'daki Los Alamos laboratuvarını J. Robert Oppenheimer yönetti. En yoğun döneminde projede 130.000'e yakın kişi çalıştı, maliyeti de 2 milyar dolara yaklaştı. Hiroşima ve Nagazaki'ye 6 ve 9 Ağustos 1945'te atılan bombalar, çoğu sivil 150.000 ile 246.000 arasında insanın ölümüne yol açtı. Sovyetler Birliği 8 Ağustos'ta Japonya'ya savaş ilan etti, Japonya da 15 Ağustos'ta teslim olacağını duyurdu. Tarihçiler bu olayların teslim kararındaki payını hâlâ tartışıyor. Sovyetler Birliği Ağustos 1949'da kendi bombasını denedi ve nükleer silahlanma yarışı başladı.

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Background reading: Manhattan Project
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When Neil Armstrong radioed “Houston, Tranquility Base here. The Eagle has landed” on 20 July 1969, his words reached Earth about 1.3 seconds later. Radio waves travel at the speed of light, and the Moon is about 384,000 km (239,000 miles) away.

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The Apollo Guidance Computer that steered astronauts to the Moon had about 4 kilobytes of rewritable memory and 72 kilobytes of permanent memory. Its programs were woven by hand into “rope memory”: a wire threaded through a tiny magnetic ring stored a 1, and a wire passing it by stored a 0.

Designed at the MIT Instrumentation Laboratory and built by Raytheon, the computer was one of the first to use silicon chips (integrated circuits) and fitted into about 28 litres. Its memory was counted in “words” of 16 bits, or binary digits: 2,048 rewritable and 36,864 permanent. During Apollo 11's descent on 20 July 1969 it flashed 1202 and 1201 alarms: a radar left on in case the landing had to be abandoned was stealing processing time and overloading it. Its operating system, designed by J. Halcombe Laning, dropped less urgent jobs and restarted in a moment while the landing programs kept running, so Mission Control told the crew to carry on. The flight software was written by a team led by Margaret Hamilton, who received the Presidential Medal of Freedom in 2016. Its power was similar to that of the first home computers of the late 1970s.

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The Antikythera mechanism, an ancient Greek geared device probably made in the 2nd century BC, had a spiral dial covering 223 lunar months for predicting eclipses. Symbols on the dial marked the months when an eclipse of the Sun or Moon was expected, and inscriptions gave details such as the hour.

Sponge divers found the mechanism in 1901, a corroded lump among treasures from a Roman-era ship that sank off the Greek island of Antikythera around 70 to 60 BC. Its hand-turned bronze gears modelled the movements of the Sun and Moon, and it is called the oldest known analogue computer, a machine that calculates with moving parts rather than digits. The eclipse dial follows the Saros cycle: after 223 lunar months (new moon to new moon), about 18 years and 11 days, the Sun, Earth and Moon return to almost the same positions, so eclipses repeat in a similar pattern. Symbols in 51 of the dial's cells mark 38 lunar and 27 solar eclipses. Much of this was read only in the 2000s, when researchers including Mike Edmunds and Tony Freeth used X-ray scans to see inside the fragments. The front, which probably showed the planets, is largely lost.

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Paper money was first used in China. In the early 11th century, merchants in Sichuan began issuing paper notes called jiaozi in place of heavy iron coins, and in 1023 the Song government took over issuing them. Europe's first banknotes appeared in Sweden in 1661.

The idea had roots in the Tang dynasty (618–907): by 804, merchants were using “flying cash”, paper certificates that let them move money across China without carrying coins. In Sichuan, where iron coins were too heavy for large payments, private firms in the regional capital, Chengdu, began issuing jiaozi notes. When some issuers went bankrupt, the state set up its own office in 1023 and printed the first government notes the following year. Paper money rested on trust: a note was worth only what its issuer promised. That trust could be abused, and when the Song printed far more notes than they could back with coins, prices soared. Europeans learnt of paper money from travellers such as Marco Polo, who described the Mongol emperor Kublai Khan's notes in the 13th century. Europe's first banknotes came from Stockholms Banco in 1661; the bank failed six years later.

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The magnetic compass began in China as a tool for fortune-telling and geomancy, the art of siting houses and tombs in harmony with the land. The first records of Chinese sailors steering by a magnetised needle date from the early 12th century.

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