Ikigai Daily
Menu
WonderHistory fact

The Eiffel Tower was built for the 1889 World's Fair in Paris with a permit to stand for only 20 years. It survived beyond 1909 largely because it had become a valuable radio mast.

History

HistoryTechnology

The story behind the card

Gustave Eiffel's contract let him run the tower for 20 years after the 1889 fair. In 1909 it was due to pass to the City of Paris, which could then have taken it down. Its height gave it a new purpose. Wireless experiments began there in 1898, and from 1903 the army engineer Gustave Ferrié set up a military radio transmitter on it, whose range grew from about 400 km to 6,000 km by 1908. In 1909 a permanent underground radio station was built near the south pillar, and it still exists. The tower was allowed to stay, and from 1910 it sent daily time signals that ships at sea used to set their clocks.

Türkçe oku
Eyfel Kulesi, 1889 Paris Dünya Fuarı için yalnızca 20 yıl ayakta kalmak üzere yapıldı. 1909'dan sonra yıkılmamasının başlıca nedeni, o zamana kadar değerli bir radyo direğine dönüşmüş olmasıydı.

Gustave Eiffel'in sözleşmesi, kuleyi 1889 fuarından sonra 20 yıl işletme hakkı veriyordu. 1909'da kule Paris Belediyesi'ne geçecekti ve belediye onu yıktırabilirdi. Kuleyi kurtaran, yüksekliği oldu. Orada 1898'de telsiz deneyleri başladı. 1903'ten itibaren asker mühendis Gustave Ferrié kuleye askerî bir radyo vericisi kurdu; bu vericinin menzili 1908'e kadar yaklaşık 400 kilometreden 6.000 kilometreye çıktı. 1909'da güney ayağının yakınına kalıcı bir yeraltı radyo istasyonu yapıldı; istasyon bugün de duruyor. Kulenin yerinde kalmasına izin verildi ve 1910'dan itibaren buradan her gün yayımlanan saat sinyalleri, denizdeki gemilerin saatlerini ayarlamasına yaradı.

Sources and further reading

Background reading: Eiffel Tower
Get the mobile appAbout our cards

Related cards

These cards share a subject or reading mode with the card above.

WonderHistory

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.

Eagle was the lunar module that carried Armstrong and Buzz Aldrin down to the surface. Light, and so radio, travels at almost 300,000 km per second. At the Moon's average distance of about 384,400 km, a signal takes roughly 1.28 seconds each way, so every exchange with Mission Control in Houston had a built-in pause of about 2.6 seconds before an answer could arrive. Large dish antennas at Goldstone in California and at Honeysuckle Creek and Parkes in Australia picked up the signals; the clearest pictures of the first steps came through Australia and were watched live by an estimated 600 million people. Before leaving, the crew set up a panel of reflectors on the surface. Scientists still fire lasers at it and time the light's return, which is how we know the Moon is drifting away from Earth by about 3.8 cm a year.

Ikigai DailyRead card
WonderTechnology

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.

Ikigai DailyRead card
WonderTechnology

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.

Antikythera Mechanism Research Project / NatureRead card
WonderTechnology

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.

Ikigai DailyRead card
WonderTechnology

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.

The first Chinese direction-finders were probably “south-pointing spoons” made of lodestone, a naturally magnetic iron ore. Placed on a smooth bronze board marked with directions, the spoon turned until its handle pointed south. Texts from the Han dynasty (206 BC to AD 220) appear to describe such devices, although archaeologists have not yet found one. The big step came under the Song dynasty. In 1088 the scholar Shen Kuo described needles magnetised by rubbing them on lodestone, and noticed that they do not point exactly north-south, the effect now called magnetic declination. A few decades later the writer Zhu Yu recorded that sailors steered by the stars at night and the sun by day, and turned to the south-pointing needle when the sky was overcast. In Europe, the first written mention of a compass dates from about 1190.

Ikigai DailyRead card
Next card in the archiveIn experiments, bees can learn to recognise individual human faces by treating them as patterns of features.Read next →