How Carbon-14 Sparked a Scientific Revolution & ‘Left an Imprint’
By BETH HARPAZ
You’ve probably heard the term “carbon dating.” It’s a technique used to determine the age of ancient objects and the remains of living organisms. Carbon dating proved that the Shroud of Turin — originally revered as Jesus’ burial shroud — dates only to the Middle Ages, not Biblical times. Carbon dating also revealed that Otzi the Iceman, whose mummified body was found in the Alps in 1991, was a prehistoric man who lived 5,000 years ago.
But how does carbon dating work? And what else can we learn, asks Professor John Marra (Brooklyn College, The Graduate Center), by using carbon-14 as “the tag, the message, for what organic molecules are, their history, and how they act”? Marra explores the topic in his book, Hot Carbon: Carbon-14 and a Revolution in Science, which was nominated for the 2020 PEN/E.O. Wilson Science Writing Award.
Carbon-14 is a naturally occurring radioactive form of carbon created in the upper atmosphere through interactions with cosmic rays. It reacts with oxygen to create carbon dioxide, which mixes into the Earth’s waterways and is absorbed by plants during photosynthesis. Every living thing eventually comes to contain trace amounts of carbon-14.
Because carbon-14 decays at a constant rate, with a half-life of 5,730 years, it leaves a time stamp. It “can be measured everywhere life occurs, or has left an imprint,” Marra writes, providing insight into “all life’s metabolism, down to the position of each carbon atom in a biomolecule.” That discovery, and its application, revolutionized anthropology, archaeology, oceanography, and climate science, and has led to advances in medicine, nutrition, and nuclear science.
Marra’s engaging narrative also includes the human drama behind the science. Among the most colorful stories is that of Martin Kamen, who discovered carbon-14 in a lab in Berkeley, California, in 1940. In a bedraggled state after a few sleepless nights at the lab, the poor man was briefly held by cops because he resembled a murder suspect. A few years later, he was investigated on trumped up charges of being a Soviet spy. Kamen never got full credit for his work, initially losing out to a collaborator, Sam Ruben, who was more adept at university politics. Kamen then lived long enough to see the Nobel Prize for carbon dating awarded to another man, Willard Libby.