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Albert Einstein's equation E=mc², published in 1905, says that mass and energy are equivalent: E is energy, m is mass and c is the speed of light. Because c² is so huge, one gram of mass corresponds to about 90 trillion joules, the energy of some 21,000 tonnes of TNT.

Annalen der Physik, 1905

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The story behind the card

Einstein was 26 and working at the patent office in Bern when the idea appeared, in a short paper of November 1905 titled “Does the Inertia of a Body Depend Upon Its Energy Content?”. It was one of four papers from what is called his miracle year. The equation does not mean matter is easily turned into energy. In a nuclear power station, splitting uranium atoms converts only about 0.1% of their mass; chemical reactions change mass too, but by amounts far too small to weigh. The Sun, fusing hydrogen into helium, turns about four million tonnes of mass into light and heat every second. After the atomic bombs of 1945, E=mc² became linked in the public mind with nuclear weapons and turned into the most famous equation in the world.

Türkçe oku
Albert Einstein'ın 1905'te yayımladığı E=mc² denklemi, kütle ile enerjinin eşdeğer olduğunu söyler: E enerjiyi, m kütleyi, c ise ışık hızını gösterir. c² çok büyük bir sayı olduğundan tek bir gram kütle yaklaşık 90 trilyon joule enerjiye karşılık gelir; bu, 21.000 ton kadar TNT'nin patlama enerjisidir.
Annalen der Physik, 1905

Einstein bu fikri ortaya attığında 26 yaşındaydı ve Bern'deki patent ofisinde çalışıyordu. Denklem, Kasım 1905'te yayımlanan “Bir Cismin Eylemsizliği Enerji İçeriğine Bağlı mıdır?” başlıklı kısa bir makalede yer aldı. Bu makale, Einstein'ın “mucize yılı” denen 1905'te yayımladığı dört makaleden biriydi. Denklem, maddenin kolayca enerjiye dönüştürülebileceği anlamına gelmez. Nükleer santrallerde uranyum atomları bölündüğünde kütlelerinin yalnızca binde biri kadarı enerjiye dönüşür. Kimyasal tepkimeler de kütleyi değiştirir, ama tartılamayacak kadar az. Güneş ise hidrojeni helyuma dönüştürürken her saniye yaklaşık 4 milyon ton kütleyi ışık ve ısıya çevirir. 1945'teki atom bombalarından sonra E=mc² kamuoyunun gözünde nükleer silahlarla özdeşleşti ve dünyanın en ünlü denklemi oldu.

Sources and further reading

Background reading: Mass–energy equivalence
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