Carbon 14 dating video
Everything from the fibres in the Shroud of Turin to Otzi the Iceman has had their birthday determined the carbon-14 way. There's plenty of hydrogen, oxygen and nitrogen in living things too, but carbon's got something none of them do — a radioactive isotope that can take thousands of years to decay.(You can read up on radioactivity and isotopes here).To understand how the C-14 clock works and what processes are involved, let us consider the egg-timer.By tipping the glass when the egg starts cooking, one learns when three minutes are up and the boiling should be stopped.
Radiocarbon dating is used to work out the age of things that died up to 50,000 years ago. As far as working out the age of long-dead things goes, carbon has got a few things going for it. The proteins, carbohydrates and fats that make up much of our tissues are all based on carbon.Carbon-14 has a half-life of about 5,600 years, so measuring the proportion of C-14 that's still present in dead organic matter, and comparing it to the known proportion of C-14 in living matter, will indicate the age of the sample. Libby assumed the ratio of C-14 to C-12 was constant, but the enormous amount of old carbon (from coal, petroleum and other fossil fuels) unearthed since the Industrial Revolution has changed the ratio.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.Once an organism dies, it stops taking in carbon-14.The carbon-14 it contained at the time of death decays over a long period of time, and the radioactivity of the material decreases.