Have you ever considered how to calculate the age of a fossil found after years in an archaeological dig? How do we know the age of a human body found in glaciers? The answer of all these questions is Carbon-14 Dating Method. What is Carbon 14 (14C) Dating? How is carbon 14 used dating? How carbon-14 dating works? What is the maximum limit on carbon 14 dating? Is carbon 14 dating reliable? You will find the answers to all these questions in this article.
What Is Carbon 14 Dating?
American Chemist Dr. Willard Libby could never have predicted that his article titled Radiocarbon from Cosmic Radiation, published in Science magazine in 1947, would be such an important breakthrough in the 21st century.
He won the Nobel Prize in Chemistry in 1960 with the carbon 14 (radiocarbon) dating method he developed following the period he wrote this article.
How is carbon 14 produced and where does it exist naturally?
Carbon is found in all living things.
But there are more than one type of carbon. Most carbon atoms consist of 6 protons and 6 neutrons. This carbon is called Carbon 12. Carbon 12 forms for 98.89% of all carbon on earth (including carbon dioxide in the atmosphere)
Carbon 14 is unstable element. In order for carbon 14 to form, some chemical events need to take place. The atoms in the air that interact with cosmic lights from space (the vast majority of which come from the sun) emit high-energy neutron particles. These neutrons collide with the highest amount of nitrogen (N) in the air (about 78%), causing a proton release from the nitrogen atoms.
The nitrogen atom that gains a neutron and loses a proton is transformed into a Carbon 14 atom.
Carbon 12 is stable element. Carbon 14 is unstable and combines with oxygen to form carbon dioxide.
Plants take carbon dioxide from the atmosphere by photosynthesis and use this carbon dioxide to form organic molecules. Thus, carbon 14 atoms are stored in plants.
Animals and humans continue to consume these plants or those who consume these plants and receive the carbon 14 atoms during their lifetime. In other words, because of the food chain, carbon 14 becomes present in the structure of all living things.
Carbon 12, Carbon 13 and Carbon 14 atoms are isotope atoms. Isotopes are atoms with the same number of protons, but differing numbers of neutrons. In other words, the have different atomic weights.
So isotopes are different forms of a single element.
What is Carbon 14 Dating Technique?
It is a dating method made by using the half-life of carbon 14 atoms because the carbon 14 atoms found in all living thing work like a nuclear clock.
As long as living things are alive, they get carbon 14 through the food chain. When they die, the intake of carbon 14 from outside stops and over time the amount of carbon 14 in the body begins to decrease.
What is the radioactive half-life of Carbon 14?
The radioactive half-life of carbon 14 is 5730 years. In other words, 5730 years after the death of a living thing, the amount of carbon 14 in his body is halved.
We can modeling the carbon 14 dating, with an hourglass. Let’s suppose that all of the sand at the top of the hourglass is carbon 14 atoms.
When we turn the hourglass, if we know how much sand is initially in the upper part and how much sand goes into the lower compartment, we can calculate at any time how much time has passed since we turned the clock.
If we know the initial amount of carbon 14 and that amount will be halved in 5730 years, we can also calculate how much time has passed since the creature’s death.
So how do we know the initial amount of carbon 14?
Here is the amount of carbon 12 helps us find the answer to this question. Even if livings die, the amount of carbon 12 in their bodies remains constant. In addition, since the ratio of carbon 14 to carbon 12 in livings is constant, we can determine the amount of carbon 14 initially.
What is the maximum limit on carbon 14 dating?
The maximum date for carbon 14 is up to 50.000 years with the current technology. Age determination by carbon 14 analysis is called radiocarbon dating.
Although this limit is mentioned as 60.000 years in the literature, it is the age limit found as a result of special research rather than the age limit reached in standard practices.
In Carbon 14 laboratories, Carbon 14 dating has been dated to the oldest 43,000-50,000 years ago. Carbon 14 dating does not give us exactly age. It gives us a age range. In technology that develops so fast, in the future, very accurate measurements can be made, and perhaps very close to the actual age.
What are some examples of radioactive dating?
The dating of Göbeklitepe‘s (Çatalhöyük) and many other settlements in Anatolia (Turkey), which is the greatest discovery in the field of archeology in recent years and shed light on the history of mankind, was performed with carbon 14 test.
Many Byzantine antiquity were found during excavations around Istanbul-Yenikapı as part of the Marmaray project and this event excited archaeologists. The excitement of the archaeologists was the result of the carbon 14 dating method. While the known date of Istanbul was 2,500 years, it was understood that it was 8,500 years with the archaeological excavations carried out in Marmaray project.
In 1991, two German climbers discovered the human body (called Iceman Otzi because of its presence in the glaciers) in the Tisenjoch region of the Alpine mountains on the Italian-Austrian border, and the age of the human body was determined by carbon 14 dating methods.
It was determined that there was a human being who lived approximately 3370-3100 BC.
The oldest known snowshoe was found in the same area in 2003. It was determined by the carbon 14 method that this shoe is approximately 5800 years old.
In Which Conditions Carbon 14 Method Causes Deviations?
As a result of some natural phenomena, the ratio of carbon 12 to carbon 14 which is constant may change. An example of this is the release of carbon dioxide containing large amounts of carbon 12 into the atmosphere as a result of volcano eruptions. Due to the abundant amount of carbon 12 released into the atmosphere, the carbon 14-carbon 12 ratio will affect, so age estimates in these areas can be based on earlier dates.
Another phenomenon that causes deviations of ratio carbon 14 / carbon 12 is solar flares. As a result of these explosions, the cosmic rays reaching the atmosphere increase the carbon 14 level.
One of the biggest factors affecting the carbon 14 carbon 12 ratio in the world is the nuclear weapons tests that started in the 1950s. Because of these nuclear weapons tests, the carbon 14 level in those years increased to about 2 times the natural level.
This unnatural increase in carbon 14 levels after 1955 caused serious uncertainty about dating at the time.
What is Suess Effect?
Apart from natural deviations, deviations can also occur due to human. The Suess Effect is a term which has come to signify the decrease in Carbon 14 in atmospheric carbon dioxide owing to admixture of carbon dioxide produced by the combustion of fossil fuels.
AMS-Accelarated Mass Spectrometer
The first carbon 14 dating laboratory was opened in the 1950s. With technological developments, measurement methods developed and the introduction of AMS-Accelarated Mass Spectrometer in some universities began a new era in the carbon 14 dating method.
Measurements with AMS showed that samples weighing milligrams were sufficient. This made it possible to date ants, pollen, even seeds with the carbon 14 method.
Because this test can be done with very small samples, the age of the priceless historical work is now easily dated.
Is Carbon 14 Dating Reliable?
One of the most important evidence that age determination with carbon 14 is a scientifically valid method is the results from tree analysis.
Trees produce a growth ring every year. With these growth rings, we can all guess how the age of the trees is calculated by looking at the trunk of a cut or broken tree.
This simple method, known by everyone, tested the carbon 14 dating method with trees that are known its age.
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