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Jun 6, 2018 · by Colm Gorey. Though one of the most essential tools for determining an ancient object’s age, carbon dating might not be as accurate as we once thought. When news is announced on the discovery ...
- Overview
- Counting carbon
- Challenges of the method
For nearly 70 years, archaeologists have been measuring carbon-14 levels to date sites and artifacts.
Nothing good can last—and in the case of carbon-14, a radioactive isotope found in Earth’s atmosphere, that’s great news for archaeologists.
While plants are alive, they take in carbon through photosynthesis. Humans and other animals ingest the carbon through plant-based foods or by eating other animals that eat plants. Carbon is made up of three isotopes. The most abundant, carbon-12, remains stable in the atmosphere. On the other hand, carbon-14 is radioactive and decays into nitrogen-14 over time. Every 5,730 years, the radioactivity of carbon-14 decays by half.
That half-life is critical to radiocarbon dating. Since carbon-12 doesn’t decay, it’s a good benchmark against which to measure carbon-14’s inevitable demise. The less radioactivity a carbon-14 isotope emits, the older it is. And since animals and plants stop absorbing carbon-14 when they begin to decay, the radioactivity of the carbon-14 that’s left behind reveals their age.
There’s a catch: Atmospheric carbon fluctuates over time. But the amount of carbon-14 in tree rings with known ages can help scientists correct for those fluctuations. To date an object, researchers use mass spectrometers or other instruments to determine the ratio of carbon-14 and carbon-12. The result is then calibrated and presented along with a margin of error. (Discover other archaeological methods used to date sites.)
Chemist Willard Libby first realized that carbon-14 could act like a clock in the 1940s. He won the 1960 Nobel Prize in Chemistry for coming up with the method. Since Libby’s discovery, radiocarbon dating has become an invaluable tool for archaeologists, paleontologists, and others looking for reliable dates for organic matter.
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How carbon-14 can help stop elephant poachers
The method has limitations: Samples can be contaminated by other carbon-containing materials, like the soil that surrounds some bones or labels that contain animal-based glue. Inorganic materials can’t be dated using radiocarbon analysis, and the method can be prohibitively expensive. Age is also a problem: Samples that are older than about 40,000 years are extremely difficult to date due to tiny levels of carbon-14. Over 60,000 years old, and they can’t be dated at all.
Calibration presents another challenge. With the dawn of the Industrial Age, humans began emitting much more carbon dioxide, diluting the amount of radiocarbon in the atmosphere. Nuclear testing affects radiocarbon levels, too, and dramatically increased carbon-14 levels starting in the 1950s. Modern statistical methods and updated databases allow scientists to take humans’ effects on Earth’s atmosphere into account. (See how radiocarbon dating helped researchers determine when this ship sank.)
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Sep 8, 2022 · September 8, 2022. Radiocarbon dating only works half the time. We may have found the solution. by Eran Elhaik, The Conversation. Credit: AI-generated image (disclaimer) Dating is everything in ...
Jul 27, 2015 · Researchers have pinned the age the Earth to around 4.54 billion years old. The earliest evidence of the genus Homo dates back to 2.8 million years ago and the oldest artwork was created about ...
Oct 5, 2021 · Here’s how. Radiometric dating puts pieces of the past in context. Here’s how. The famous skeleton Lucy is too old for radiocarbon dating. But using argon-argon dating on tiny crystals in ...
Sep 11, 2024 · However, several fields of the Earth sciences also need high-precision dating when dealing with rare but dramatic events, such as earthquakes and tsunamis 25, extreme weather events such as ...
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Aug 12, 2020 · With the new IntCal20 curve, our best estimate for the creation of the oldest radiocarbon-dated painting in the cave is now 36,500 years ago. This is almost 450 years older than previously thought ...
