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Gravitational waves are ripples in space and time, set off by huge masses in violent motion, such as two black holes colliding. Einstein predicted them in 1916, and on 14 September 2015 the two LIGO detectors in the United States caught one for the first time.

Physical Review Letters, 2016

Science

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Einstein's general theory of relativity describes gravity as a curving of space and time. When heavy objects accelerate, for example by circling each other, that curve ripples outwards at the speed of light, very slightly stretching and squeezing everything in its path. LIGO looks for these ripples with laser beams sent along two 4-kilometre arms set at right angles, at observatories in Hanford, Washington, and Livingston, Louisiana. The 2015 signal came from two black holes, about 36 and 29 times the mass of the Sun, merging more than a billion light-years away. By the time it reached Earth, it changed the length of each arm by about a thousandth of the width of a proton. The discovery was announced in February 2016, and Rainer Weiss, Barry Barish and Kip Thorne shared the 2017 Nobel Prize in Physics for it.

Türkçe oku
Kütleçekim dalgaları, uzay-zamanda yayılan dalgalanmalardır. İki kara deliğin çarpışması gibi, çok büyük kütlelerin şiddetle hareket ettiği olaylarda doğarlar. Einstein bu dalgaları 1916'da öngörmüştü; ilkini 14 Eylül 2015'te ABD'deki iki LIGO dedektörü yakaladı.
Physical Review Letters, 2016

Einstein'ın genel görelilik kuramına göre kütleçekimi, uzay ile zamanın bükülmesinden doğar. Ağır cisimler hızlandığında, örneğin birbirlerinin çevresinde döndüklerinde, bu bükülme ışık hızıyla dalga dalga yayılır ve geçtiği yerdeki her şeyi çok az uzatıp kısaltır. LIGO bu dalgaları ABD'deki iki gözlemevinde arar: Biri Washington eyaletindeki Hanford'da, öteki Louisiana eyaletindeki Livingston'dadır. Her gözlemevinde birbirine dik iki kol uzanır; 4'er kilometrelik bu kollarda lazer ışınları gidip gelir. 2015'teki sinyal, bir milyar ışık yılından daha uzakta birleşen iki kara delikten geliyordu; kütleleri Güneş'in yaklaşık 36 ve 29 katıydı. Dalga Dünya'ya ulaştığında her kolun boyunu bir proton çapının yaklaşık binde biri kadar değiştirdi. Sonuç Şubat 2016'da duyuruldu; Rainer Weiss, Barry Barish ve Kip Thorne bu keşfe katkılarıyla 2017 Nobel Fizik Ödülü'nü paylaştı.

Sources and further reading

Background reading: Gravitational wave
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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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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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