Carbon dating is a well-calibrated radiometric dating system used for items generally younger than 50,000 years old (14 C has a half-life of 5730 years). A recently unearthed Viking burial mound contained a ship, a sample of which was found to have a C activity of 14.3 disintegrations per minute per gram of the sample. A nearby forest provided a living sample of wood with a 14C activity of 16.8 disintegrations per minute per gram of the sample.