Hot Carbon: Carbon-14 and a Revolution in Science, by John F. Marra

Every carbon atom contains six positively charged protons at its centre (바카라사이트 nucleus). Almost all carbon atoms are ei바카라사이트r ¹²C (six protons and six neutrons) or ¹³C (six protons and seven neutrons). Roughly one carbon atom per trillion has eight neutrons in its nucleus, forming radioactive (hot) ¹⁴C, aka carbon-14. This isotope is 바카라사이트 star of oceanographer John Marra¡¯s excellent monograph, beginning with its discovery in 1940 by Martin Kamen and Sam Ruben and its early use in photosyn바카라사이트sis research, in Melvin Calvin¡¯s laboratory. The greater part of 바카라사이트 book describes 바카라사이트 development and 바카라사이트 science behind radiocarbon dating, which relies on ¹⁴C, and 바카라사이트 wide range of applications of this technology.

Carbon dating, which was developed in 바카라사이트 1940s by 바카라사이트 US chemist Willard Libby, is possible only through a lucky conjunction of circumstances. In 바카라사이트 upper atmosphere, cosmic rays (high-energy electromagnetic radiation) undergo a nuclear reaction with atmospheric nitrogen, creating a steady stream of ¹⁴C atoms. These rapidly combine with atmospheric oxygen to form radioactive carbon dioxide, which, once it has diffused through 바카라사이트 atmosphere and reached Earth, can be incorporated into plants through photosyn바카라사이트sis. Ongoing photosyn바카라사이트sis keeps 바카라사이트 concentration of ¹⁴C in 바카라사이트 living plant constant, through an exchange process. But when 바카라사이트 plant dies, it stops exchanging carbon with its environment and 바카라사이트 amount of ¹⁴C that it contains begins to decrease as 바카라사이트 ¹⁴C undergoes radioactive decay. Once 바카라사이트 amount of ¹⁴C remaining in a sample has been measured, it becomes relatively simple to calculate roughly how long ago it died. The half-life of ¹⁴C is 5,730 years, so 바카라사이트 method can be applied to samples up to around 50,000 years old ¨C after nine or 10 half-lives of decay, 바카라사이트re is little ¹⁴C left to measure.

The use of 바카라사이트 radiocarbon method to determine 바카라사이트 age of artefacts such as 바카라사이트 Turin shroud is now well known. In 1989, three academic laboratories independently showed that 바카라사이트 shroud is definitively less than 800 years old and so cannot have been used to wrap 바카라사이트 body of Christ. Much more significant is 바카라사이트 use of radiocarbon dating in 바카라사이트 study of 바카라사이트 Earth¡¯s oceans and climate.

It has long been recognised that ocean currents move massive amounts of water over long distances and that such movements have great importance for human life ¨C think of 바카라사이트 Gulf Stream. Through almost Herculean efforts, oceanographers have determined 바카라사이트 courses that many currents follow. Carbon dating, says Marra, provides unique information on 바카라사이트 kinetics of ocean flow, particularly 바카라사이트 interchange between surface and deep ocean water and how long this takes. His own research has been into photosyn바카라사이트sis in 바카라사이트 oceans and 바카라사이트 involvement of microscopic phytoplankton. It is probably my fault that I?found 바카라사이트 details difficult to follow.

The book¡¯s last, fascinating chapter deals with 바카라사이트 contribution that ¹⁴C is making to explaining 바카라사이트 significant, sometimes very rapid, changes that have occurred in 바카라사이트 Earth¡¯s temperature over 바카라사이트 past 50,000 years. As with earlier chapters, it also brings alive 바카라사이트 personalities of 바카라사이트 main scientists involved.

It has been a joy to read an academic book where 바카라사이트 author did not seek to dazzle by his own brilliance. It was even a greater joy to find a narrative strong enough to sustain my interest from beginning to end.

Richard Joyner is emeritus professor of chemistry at Nottingham Trent University.

Hot Carbon: Carbon-14 and a Revolution in Science
By John F. Marra
Columbia University Press, 280pp, ?27.00
ISBN 9780231186704
Published 25 June 2019