Improved techniques now date the earliest stone structures at Stonehenge to about 2600 B. Sir Joseph Norman Lockyer, who co-discovered helium and founded the journal, Nature, wrote in 1901 that the Heel Stone section of Stonehenge "had been originally aligned with the summer solstice" and calculated that it was built in 1800 B. Further investigations have suggested that Stonehenge was an astronomical observatory, a place of worship and healing or perhaps a cemetery.
Whatever its exact history, origins or age, thousands each year flock to Stonehenge to welcome the sun on the summer solstice.
It is naturally unstable and so it will spontaneously decay back into N-14 after a period of time.
It takes about 5,730 years for half of a sample of radiocarbon to decay back into nitrogen.
This is how carbon dating works: Carbon is a naturally abundant element found in the atmosphere, in the earth, in the oceans, and in every living creature.
C-12 is by far the most common isotope, while only about one in a trillion carbon atoms is C-14.
The period of time that it takes for half of a sample to decay is called a "half-life." Radiocarbon oxidizes (that is, it combines with oxygen) and enters the biosphere through natural processes like breathing and eating.Correction: The original version of this post misstated the cause of inaccuracy in first-generation radiocarbon dating. It also linked to, and partially relied on, a website of dubious validity. Willard Libby (1908–1980), a professor of chemistry at the University of Chicago, began the research that led him to radiocarbon dating in 1945.He was inspired by physicist Serge Korff (1906–1989) of New York University, who in 1939 discovered that neutrons were produced during the bombardment of the atmosphere by cosmic rays.