Carbon 14 dating debate updating a year lease letter
A child mummy is found high in the Andes and the archaeologist says the child lived more than 2,000 years ago.How do scientists know how old an object or human remains are?Carbon dating is unreliable for objects older than about 30,000 years, but uranium-thorium dating may be possible for objects up to half a million years old, Dr. The method is less suitable, however, for land animals and plants than for marine organisms, because uranium is plentiful in sea water but less so in most soils.But even if the method is limited to marine organisms, it will be extremely useful for deciphering the history of Earth's climate, ice, oceans and rocks, Dr. ''But at earlier times, the carbon dates were substantially younger than the dates we estimated by uranium-thorium analysis,'' he said.''The largest deviation, 3,500 years, was obtained for samples that are about 20,000 years old.'' One reason the group believes the uranium-thorium estimates to be more accurate than carbon dating is that they produce better matches between known changes in the Earth's orbit and changes in global glaciation. Fairbanks, a member of the Lamont-Doherty group, said that if the dates of glaciation were determined using the uranium-thorium method, the delay - and the puzzle - disappeared.
Therefore they have sought ways to calibrate and correct the carbon dating method.
What methods do they use and how do these methods work?
In this article, we will examine the methods by which scientists use radioactivity to determine the age of objects, most notably carbon-14 dating.
Since 1947, scientists have reckoned the ages of many old objects by measuring the amounts of radioactive carbon they contain.
New research shows, however, that some estimates based on carbon may have erred by thousands of years.