諾貝爾化學獎得主威拉德·利比意識到，一種名為碳-14的放射性同位素可以像時鐘一樣，用於解開考古謎團。
1949年，他開發了放射性碳定年法，也稱為碳-14定年法。這種方法利用放射性衰變來確定有機物的年齡，幫助專家重寫歷史，揭示了「史前荒野」的真相，並更準確地確定了歷史謎團的核心年代。例如，它確定了在阿爾卑斯山發現的冰人奧茨的遺骸被冰封了5300年，並且北美末次冰期結束於大約1萬年前，而不是地質學家之前認為的2.5萬年前。
碳-14在大氣中受到宇宙輻射的作用而形成，然後衰變。生物體會吸收碳-14。當生物體死亡，大氣中的碳供應停止時，碳-14的含量會以固定的速率經由放射性衰變而下降。專家可以透過計算有機物中殘留的碳-14原子，精確測定其年齡，最高可達6萬年。
利比最初用龐貝古城出土的燒焦麵包和古埃及一塊古代箱子的碎片來測試他的年代測定方法。但他發現碳原子可以作為死亡時間的標記，這項發現不僅徹底改變了考古學領域，也幫助科學家了解地球的地質和氣候變化，並揭示了我們身體的運作機制。
在提名利比角逐諾貝爾獎（他於1960年獲獎）時，一位科學家說：“很少有化學領域的單一發現能對如此眾多人類活動的領域產生如此深遠的影響。也很少有單一發現能引起如此廣泛的公眾關注。”
了解更多關於他的生活：https://www.nobelprize.org/....../1960/libby/biographical
Chemistry laureate Willard Libby realised that a radioactive isotope called carbon-14 can act like a clock and be put to use to solve archaeological mysteries.
In 1949, he developed radiocarbon dating or carbon-14 dating, a method that harnesses radioactive decay to determine the age of organic materials that has helped experts re-write history books by shedding light on “the wilderness of prehistory” and more accurately dating at the centre of historical mysteries. For example, it determined that Ötzi the Iceman, whose remarkable remains were found in the Alps, was frozen for 5,300 years and that the last North American ice age ended about 10,000 years ago, not 25,000 years ago as previously believed by geologists.
Carbon-14 forms in the atmosphere when acted upon by cosmic radiation and then deteriorates. Living organisms absorb carbon-14. When an organism dies and the supply of carbon from the atmosphere ceases, the content of carbon-14 declines through radioactive decay at a fixed rate. Experts can accurately determine the age of organic materials up to 60,000 years old by counting carbon-14 atoms left in the materials.
Libby initially tested his dating method on charred bread from Pompeii and a fragment of an ancient chest from Ancient Egypt, but his discovery that carbon atoms act as a marker of time of death has not only revolutionised the field of archaeology but has also helped scientists understand Earth’s geology and changing climate, as well as revealing how our bodies work.
In nominating Libby for the Nobel Prize (which he was awarded in 1960), one scientist said: “Seldom has a single discovery in chemistry had such an impact on the thinking in so many fields of human endeavour. Seldom has a single discovery generated such wide public interest.”
Learn more about his life: https://www.nobelprize.org/....../1960/libby/biographical
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