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The cosmic microwave background is the oldest light we can see. It was released about 380,000 years after the Big Bang, when the universe had cooled enough for atoms to form, and it still fills the whole sky as a faint glow of microwaves.

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The story behind the card

Before that moment the universe was a hot fog of charged particles that scattered light in every direction, like the inside of a cloud. Once it cooled to about 2,700 °C, electrons and atomic nuclei joined into atoms and light could travel freely. The expansion of space has since stretched that light into microwaves, and its temperature is now only 2.725 degrees above absolute zero, about −270 °C. Arno Penzias and Robert Wilson found it by accident in 1964 at Bell Labs in New Jersey, while trying to trace a stubborn hiss in a large horn-shaped antenna; along the way they even cleared out pigeons nesting in it. They shared the 1978 Nobel Prize in Physics. Later satellites, COBE, WMAP and Planck, mapped tiny temperature differences in this light, the seeds of the first galaxies.

Türkçe oku
Kozmik mikrodalga arka plan ışıması, görebildiğimiz en eski ışıktır. Büyük Patlama'dan yaklaşık 380.000 yıl sonra, evren atomların oluşabileceği kadar soğuyunca serbest kaldı; bugün hâlâ gökyüzünün her yanını sönük bir mikrodalga ışıltısıyla doldurur.

O zamana kadar evren, yüklü parçacıklardan oluşan sıcak bir sisle doluydu; ışık bu siste, bir bulutun içindeymiş gibi her yöne saçılıyordu. Sıcaklık yaklaşık 2.700 °C'ye düşünce elektronlar ve atom çekirdekleri birleşip atomları oluşturdu ve ışık serbestçe yol almaya başladı. Uzayın genişlemesi o zamandan beri bu ışığın dalga boyunu uzatarak onu mikrodalgaya çevirdi; bugün sıcaklığı mutlak sıfırın yalnızca 2,725 derece üstünde, yani yaklaşık −270 °C'dir. Arno Penzias ve Robert Wilson bu ışımayı 1964'te New Jersey'deki Bell Laboratuvarları'nda rastlantıyla buldu. Huni biçimli büyük bir antenin yakaladığı inatçı bir cızırtının kaynağını arıyorlardı; bu arada antene yuva yapmış güvercinleri bile çıkarmışlardı. İkili 1978 Nobel Fizik Ödülü'nü paylaştı. Daha sonra COBE, WMAP ve Planck uyduları bu ışımadaki küçük sıcaklık farklarının haritasını çıkardı; bu farklar ilk galaksilerin tohumlarıydı.

Sources and further reading

Background reading: Cosmic microwave background
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The Industrial Revolution put the clock in charge of the working day. Before factories, most people worked by daylight, the seasons and the task in hand; from the 1770s, mills such as Richard Arkwright's at Cromford in Derbyshire ran day and night in twelve-hour shifts.

The historian E. P. Thompson traced this change in a famous essay of 1967, “Time, Work-Discipline, and Industrial Capitalism”. Farm and craft work, he argued, had been measured by tasks: milking, harvesting, finishing a piece. Factory work was measured in hours. Cromford Mill, opened in 1771, was the world's first water-powered cotton-spinning mill. It started with about 200 workers, most of them women and children, the youngest only seven. Bells rang at 5 in the morning and 5 in the evening, the gates were shut at exactly 6, and anyone late lost that day's pay and was fined another. In industrial towns, where alarm clocks were not yet cheap or reliable, “knocker-ups” were paid a few pence a week to tap on upstairs windows with long poles.

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Less than 66 years, well within a single lifetime, separate the first powered aeroplane flight from the first Moon landing. Orville Wright flew for 12 seconds and 37 metres on 17 December 1903; Apollo 11 landed on the Moon on 20 July 1969.

The Wright brothers, bicycle makers from Dayton, Ohio, flew near Kitty Hawk, North Carolina, and that first hop was shorter than the wingspan of a Boeing 747. What followed came fast. In 1919 John Alcock and Arthur Brown flew non-stop across the Atlantic; in 1927 Charles Lindbergh did it alone, from New York to Paris; and in 1947 Chuck Yeager flew faster than sound. Orville Wright died in 1948, nine years before the Soviet satellite Sputnik opened the space age. Yuri Gagarin orbited the Earth in 1961, and in July 1969 Neil Armstrong took a scrap of the 1903 Flyer's wood and fabric with him to the Moon.

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The Cold War between the United States and the Soviet Union (1947–1991) was fought mostly without direct battles between the two. They competed instead through weapons, science, sport, films, propaganda and the race into space.

George Orwell used the phrase “cold war” in 1945, and the American journalist Walter Lippmann made it popular in 1947. Because nuclear weapons made open war between the superpowers too dangerous, the rivalry spread into other arenas. After the Soviet Union launched the Sputnik satellite in 1957, the United States passed the National Defense Education Act of 1958 to fund science, maths and language teaching. In 1959, at an American exhibition in Moscow, Vice-President Richard Nixon and the Soviet leader Nikita Khrushchev argued about capitalism and communism in a model kitchen, an exchange remembered as the Kitchen Debate. In 1972 in Reykjavík, the American Bobby Fischer beat the Soviet champion Boris Spassky for the world chess title. The Olympics were boycotted in turn: the United States and many allies stayed away from Moscow in 1980, and most of the Soviet bloc from Los Angeles in 1984.

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The computer was designed at the MIT Instrumentation Laboratory from 1962 and built by Raytheon, and one flew in every Apollo command module and lunar module. The chip was still a new invention: Jack Kilby and Robert Noyce had made the first ones in 1958 and 1959. MIT used almost a single type throughout, a simple logic circuit designed by Fairchild Semiconductor, repeated thousands of times. According to the Computer History Museum, Apollo bought some 200,000 of them at 20 to 30 dollars each, and by 1965 the Minuteman missile programme had become the bigger buyer. Orders like these kept the young industry going until prices fell: the average chip cost 50 dollars in 1962 and 2.33 dollars in 1968. The Space Race is often credited with GPS too, but GPS was a separate US Department of Defense project, begun in 1973.

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On 12 April 1961 the Soviet cosmonaut Yuri Gagarin, aged 27, became the first human in space. His Vostok 1 spacecraft circled the Earth once, and the flight lasted 108 minutes from launch to landing.

Gagarin, who had trained as a foundry worker before becoming an air force pilot, was launched from Baikonur, in today's Kazakhstan. As the rocket lifted off he called out “Poyekhali!” (“Let's go!”). His orbit took him as high as 327 kilometres. On the way back he ejected from the capsule about 7 kilometres above the ground and came down by his own parachute near Engels, in the Saratov region, where a farm worker and her granddaughter were the first to meet him. Because the record rules of the day required pilots to land inside their craft, the Soviet Union claimed he had, and admitted the truth only in 1971. Gagarin became famous around the world. He died in a training-jet crash in 1968, aged 34. Since 2011 the United Nations has marked 12 April as the International Day of Human Space Flight.

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Next card in the archiveApart from hydrogen, which dates from the Big Bang, almost every element in your body was made by stars. Earlier generations of stars forged carbon, oxygen, iron and much more, then scattered them into space before the Sun and Earth formed.Read next →