Radiocarbon dating Calibration Dating Ötzi Commentary

Willard Frank Libby physics

Radiocarbon dating

• The half-life of carbon-14
• is about 5,730 years.
• All living things
• gather carbon-14
• in known proportion
• to carbon-12; therefore,
• Willard Libby proposed
• that the proportion of carbons
• left in archeological artifacts
• can determine their ages.
• He used this idea
• to date wood from the tombs
• of two Egyptian kings,
• Zoser and Sneferu,
• finding these to be older
• than scholars had thought
• by nearly two thousand years.

Calibration

• The proportion of carbon-14
• has varied over time
• because of climate change,
• glaciation, volcanic activity,
• variations in earth’s magnetic field,
• human activities, and other factors,
• so it was necessary
• to correlate the results of radiocarbon dating
• with the dates of artifacts
• that could be independently established.
• Overlapping tree rings
• can be independently dated
• by counting the rings
• so this became the calibration
• standard for the first
• eleven thousand years
• before the present,
• and this range was extended
• using deep ocean sediment cores,
• lake sediment varves, coral samples,
• and speleothems.

Dating Ötzi

• Ötzi the Iceman, Europe’s
• oldest natural human mummy,
• is known to have lived
• about 3,300 BCE
• according to radiocarbon dating.
• He died of an arrow to his shoulder
• and a blow to his head,
• fell into a glacier,
• was discovered when it melted.
• Today his body is grotesquely
• on view at South Tyrol Museum
• of Archaeology.