Limitations and calibration: When Libby was first determining radiocarbon dates, he found that before 1000 BC his dates were earlier than calendar dates.

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In 1949, American chemist Willard Libby, who worked on the development of the atomic bomb, published the first set of radiocarbon dates.

His radiocarbon dating technique is the most important development in absolute dating in archaeology and remains the main tool for dating the past 50,000 years.

The extra neutrons in Carbon-14’s case make it radioactive (thus the term, radiocarbon).

Radiocarbon is produced in the upper atmosphere after Nitrogen-14 isotopes have been impacted by cosmic radiation.

How It Works: Carbon has 3 isotopic forms: Carbon-12, Carbon-13, and Carbon-14.

The numbers refer to the atomic weight, so Carbon-12 has 6 protons and 6 neutrons, Carbon-13 has 6 protons and 7 neutrons, and Carbon-14 has 6 protons and 8 neutrons.

The Mayan calendar used 3114 BC as their reference.

More recently is the radiocarbon date of 1950 AD or before present, BP.

When it comes to dating archaeological samples, several timescale problems arise.