Core sample sends carbon clock farther back in time

NATURE NEWS ^ | 18 October 2012 | Ewen Callaway

[neverdem]

Sediment from Japanese lake 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.

Carbon dating is used to work out the age of organic material — in effect, any living thing. 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. 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 clock was initially calibrated by dating objects of known age such as Egyptian mummies and bread from Pompeii; work that won Willard Libby the 1960 Nobel Prize in Chemistry. But even he “realized that there probably would be variation”, says Christopher Bronk Ramsey, a geochronologist at the University of Oxford, UK, who led the latest work, published today in Science1. Various geologic, atmospheric and solar processes can influence atmospheric carbon-14 levels.

Since the 1960s, scientists have started accounting for the variations by calibrating the clock against the known ages of tree rings. 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...

[neverdem]

Stress and the city: Urban decay - Scientists are testing the idea that the stress of modern city life is a breeding ground for psychosis.

Scientists uncover mystery of ball lightning

ExBox snares polycyclic aromatic hydrocarbons

Diabetes Study Ends Early With a Surprising Result

FReepmail me if you want on or off my health and science ping list.

[TXnMA]

GGG “Heads Up!”...

[I want the USA back]

Imagine, scientists using a “ruler” that was not calibrated properly.

[Condor51]

The carbon clock is getting reset ~~ which could help to shed light on archaeological mysteries such as why Neanderthals became extinct.

[SunkenCiv]

GGG managers are SunkenCiv, StayAt HomeMother & Ernest_at_the_Beach	join list or digest view topics view or post blog bookmark post a topic subscribe
Thanks TXnMA. Just adding to the catalog, not sending a general distribution. The Most Important Records For Dating Old Objects Were Just Found In A Japanese Lake To all -- please ping me to other topics which are appropriate for the GGG list.

[mlo]

"Imagine, scientists using a “ruler” that was not calibrated properly."

Imagine a process of disovering the true calibration by observation of the real world, and refining that knowledge over to time to be more and more accurate. That's how science works. It's not about being granted absolute precise knowledge up front.

[editor-surveyor]

The idea of the “extinction of the neanderthals” is a bit curious. Where does it come from?

[editor-surveyor]

‘Scientists’ calibrate their ruler by deciding what they wish the measure to be, and molding the ruler from there.

Works every time :o)

[Wonder Warthog]

"Imagine, scientists using a “ruler” that was not calibrated properly."

The calibration was as good as could be done with the available data and methodology of the day. Carbon-age dating technology has improve HUGELY from when I worked with it in grad school back in the 1970's.

Probably the most significant change was the switch from directly measuring the radioactive decay of C-14 to the mass spectral measurement of the total amount of C-14 isotope in the sample by using out-dated particle accelerators as ultra-high-resolution and ultra sensitive mass spectrometers. That extended the "carbon clock" further into the past than was possible before.

[tomkat]

Oddly, geochronologist never turned up on those aptitude thingies.

Perhaps things could've turned out differently . . .

nah

[SatinDoll]

The extinction of the Neanderthals could be something not present in the fossil records - like a devastating plague that killed them all.

[Balding_Eagle]

Imagine, scientists using a “ruler” that was not calibrated properly.

There is a Nobel prize awaiting you, or anyone else, who can provide absolute calibration.

I believe it comes with a large cash prize.