How do scientists use carbon dating
As a rule, carbon dates are younger than calendar dates: a bone carbon-dated to 10,000 years is around 11,000 years old, and 20,000 carbon years roughly equates to 24,000 calendar years.The problem, says Bronk Ramsey, is that tree rings provide a direct record that only goes as far back as about 14,000 years.By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon-14 decay can be worked out, thereby giving an age for the specimen in question.But that assumes that the amount of carbon-14 in the atmosphere was constant — any variation would speed up or slow down the clock.The technique hinges on carbon-14, a radioactive isotope of the element that, unlike other more stable forms of carbon, decays away at a steady rate.Organisms capture a certain amount of carbon-14 from the atmosphere when they are alive. 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.
The recalibrated clock won’t force archaeologists to abandon old measurements wholesale, says Bronk Ramsey, but it could help to narrow the window of key events in human history.
Remember that the half-life of an isotope, such as C-14, means that it takes that many years for half of the isotope to decay. By calculating the percent remaining, scientists can determine how many "half-lives" have passed.
An isotope with a short half-life like Carbon-14 is more useful (and accurate) in estimating the age of formerly biotic matter such as fossil bones or petrified wood.
Two distinct sediment layers have formed in the lake every summer and winter over tens of thousands of years.
The researchers collected roughly 70-metre core samples from the lake and painstakingly counted the layers to come up with a direct record stretching back 52,000 years.
Meet paleoclimatologist Scott Stine, who uses radiocarbon dating to study changes in climate. What we think of as normal carbon is called carbon-12: six protons plus six neutrons. Several times a year, scientist Scott Stine travels to the shores of Mono Lake, near Yosemite National Park. He's studying the long history of droughts in California, trying to determine how frequently they occur and how long they last.