 | Libby first suspected the relationship between cosmic rays and carbon-14in 1946. Intrigued, he began to search for ways to measure its presence on Earth. He developed a sensitive Geiger counter to detect and measure the level of carbon-14 in any given sample. This device took Libby three years to perfect. One of the ways he tested his equipment was by trying to detect the presence of carbon-14 in ancient artifacts.
A Geiger counter is a device built to detect the presence ofradiation in a sample. It was invented by Hans Geiger, a German scientist,in the 1920s.
The first artifact studied was a sample of acacia wood from an Egyptianpyramid with a known date of construction. The radioactivity of the sample was then compared to a piece of modern wood. More studies of archaeological samples with known ages helped to calibrate the process. In 1949, scientists announced that they had been able to determine that the half-life of carbon-14 was 5,568 years.
Half-life: Carbon-14, like all radioactive elements, isunstable. It decays regularly by releasing electrons, meaning that after a certain amount of time, only half of the radioactive element remains.The rest of the element returns to its original state of nitrogen. This process is known as the element's "half-life." For example, if you find that the radioactive measurement of an ancient piece of wood is one quarter that of a modern piece of wood, you can set the age of the sample at two half-lives using the calculation 2 x 5,568 = 11,150 years. This is the amount of time that has passed since the death of the tree that produced the wood. Knowing the time when a tree died is important to scientists because this marks the time when the tree stopped absorbing carbon-14.
The discovery of carbon-14 dating set off a revolution in archaeology. Now, all you needed was a couple of ounces of charcoal, or some other organic material buried at the time in question, and science could do the rest.
Libby was awarded the Nobel Prize in chemistry in 1960. His citation read: "Seldom has such a single discovery in chemistry has such an impact on the thinking of so many fields of human endeavor. Seldom has a single discovery generated such wide public interest."
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