Carbon-14 decay - Astronomy News

Blobrana

L

Posts: 131433

Date: Feb 26 20:45 2014

Carbon-14	Permalink

Carbon-14 was discovered on 27 February 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley Read more __________________

Blobrana

L

Posts: 131433

Date: Oct 19 07:46 2012

Lake Suigetsu	Permalink

Lake yields new benchmark for dating older objects A new series of radiocarbon measurements from Japan's Lake Suigetsu will give scientists a more accurate benchmark for dating materials, especially for older objects, according to a research team that included Oxford University's Radiocarbon Accelerator Unit. The research team extracted cores of beautifully preserved layers of sediment, containing organic material (such as tree leaf and twig fossils), from the bottom of the Japanese lake where they had lain undisturbed for tens of thousands of years. Read more __________________

Blobrana

L

Posts: 131433

Date: Oct 19 01:53 2012

Radiocarbon dating	Permalink

Sediment from Japanese lake Suigetsu provides more accurate timeline for dating objects as far back as 50,000 years. The carbon clock is getting reset. Climate records from a Japanese lake are set to improve the accuracy of the dating technique, which could help to shed light on archaeological mysteries such as why Neanderthals became extinct. Read more __________________

Blobrana

L

Posts: 131433

Date: Jul 2 13:34 2012

Radiocarbon 14C	Permalink

Title: A new model of cosmogenic production of radiocarbon 14C in the atmosphere Authors: G. A. Kovaltsov, A. Mishev, I. G. Usoskin We present the results of full new calculation of radiocarbon 14C production in the Earth atmosphere, using a numerical Monte-Carlo model. We provide, for the first time, a tabulated 14C yield function for the energy of primary cosmic ray particles ranging from 0.1 to 1000 GeV/nucleon. We have calculated the global production rate of 14C, which is 1.64 and 1.88 atoms/cm²/s for the modern time and for the pre-industrial epoch, respectively. This is close to the values obtained from the carbon cycle reservoir inventory. We argue that earlier models overestimated the global 14C production rate because of outdated spectra of cosmic ray heavier nuclei. The mean contribution of solar energetic particles to the global 14C is calculated as about 0.25% for the modern epoch. Our model provides a new tool to calculate the 14C production in the Earth's atmosphere, which can be applied, e.g., to reconstructions of solar activity in the past. Read more (254kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Jan 16 01:06 2010

INTCAL09	Permalink

Title: IntCal09 and Marine09 Radiocarbon Age Calibration Curves, 050,000 Years cal BP Author(s): Reimer, PJ; Baillie, MGL; Bard, E; Bayliss, A; Beck, JW; Blackwell, PG; Bronk Ramsey, C; Buck, CE; Burr, GS; Edwards, RL; Friedrich, M; Grootes, PM; Guilderson, TP; Hajdas, I; Heaton, TJ; Hogg, AG; Hughen, KA; Kaiser, KF; Kromer, B; McCormac, FG; Manning, SW; Reimer, RW; Richards, DA; Southon, JR; Talamo, S; Turney, CSM; van der Plicht, J; Weyhenmeyer, CE The IntCal04 and Marine04 radiocarbon calibration curves have been updated from 12 cal kBP (cal kBP is here defined as thousands of calibrated years before AD 1950), and extended to 50 cal kBP, utilising newly available data sets that meet the IntCal Working Group criteria for pristine corals and other carbonates and for quantification of uncertainty in both the 14C and calendar timescales as established in 2002. No change was made to the curves from 012 cal kBP. The curves were constructed using a Markov chain Monte Carlo (MCMC) implementation of the random walk model used for IntCal04 and Marine04. The new curves were ratified at the 20th International Radiocarbon Conference in June 2009 Read more __________________

Blobrana

L

Posts: 131433

Date: Sep 12 18:55 2008

Carbon13/12 ratio	Permalink

The precise timing of the origin of life on Earth and the changes in life during the past 4.5 billion years has been a subject of great controversy for the past century. The principal indicator of the amount of organic carbon produced by biological activity traditionally used is the ratio of the less abundant isotope of carbon, 13C, to the more abundant isotope, 12C. As plants preferentially incorporate 12C, during periods of high production of organic material the 13C/12C ratio of carbonate material becomes elevated. Using this principle, the history of organic material has been interpreted by geologists using the 13C/12C ratio of carbonates and organics, wherever these materials can be sampled and dated. While this idea appears to be sound over the last 150 million years or so, prior to this time there are no open oceanic sediment records which record the 13C/12C ratio, and therefore, geologists are forced to use materials associated with carbonate platforms or epicontinental seas. In order to test whether platform-associated sediments are related to the global carbon cycle, a paper by University of Miami Professor Dr. Peter K. Swart appears in the Proceedings of the National Academy of Sciences. This paper examines changes over the past 10 million years at sites off the Bahamas (Atlantic Ocean), the Maldives (Indian Ocean), and Great Barrier Reef (Pacific Ocean). The variations in the 13C/12C ratio are synchronous at all of the sites studied, but are unrelated to the global change in the 13C/12C ratio. Read more __________________

Blobrana

L

Posts: 131433

Date: Jan 29 01:18 2008

Carbon-14 decay	Permalink

Researchers studying the labyrinthine nature of atomic nuclei say they have answered a question that has puzzled physicists for more than half a century: Why does the radioactive isotope known as carbon-14 decay so slowly? The discovery could lead to a better understanding of the workings of the strong nuclear force, one of the four fundamental forces of nature. Within the menagerie of common isotopes--such as carbon-11, nitrogen-13, and oxygen-15--carbon-14 is a tortoise among hares, and a painfully slow tortoise at that. Whereas its cousins take mere minutes or hours to decay, only half of the carbon-14 component of a given substance is gone after 5730 years, having become nitrogen-14. This long half-life has made the isotope invaluable to archaeologists as a tool to determine the age of organic matter, whether plant or animal. By analysing the ratio of carbon-14 to nitrogen-14, researchers can determine, within a narrow margin, when the sample in question last breathed or photosynthesised. That's because when an organism dies, it stops ingesting carbon, including carbon-14. Yet the reason carbon-14 decays much more slowly than other isotopes has remained elusive, and researchers have argued for decades about the mechanism. Source A New Calculation Explains the Mechanish Behind Carbon Dating In terms of the way the masses of mesons changes as they travel through an atomic nucleus. Mesons (particles such as pions, containing a quark and an antiquark) are thought to mediate the nuclear force between two nuclei. Radiocarbon dating began in 1949 when Willard Libby said that the amount of carbon-14 (the radioactive cousin of carbon-12) left in an object (such as a fossil tree) could provide an estimate of how old the object was. Read more __________________

* Astronomy