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Carbon Dating
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CARBON DATING
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The earliest art that has been found dates from the Paleolithic or Old Stone Age period, (from about 35,000 B.C. to 10,000 B.C). This was during the last Ice Age, which lasted for thousands of years. It includes cave paintings, handprints and small statues. Paleolithic cave paintings were first discovered in France and Spain, though similar paintings have now been found in other parts of the world. Scientists who study the distant past date their finds in different ways, often using built-in atomic clocks. One of these clocks is called carbon 14. It is found in living and once living things. It forms in the atmosphere when atoms of carbon are bombarded by cosmic rays from Space. Carbon 14 atoms are radioactive, that is they keep breaking down and giving off tiny parts of themselves. When carbon 14 combines with oxygen, it forms radioactive carbon dioxide, which mixes with other carbon dioxide in the air. Plants take in carbon dioxide to make their food, and so each plant contains a tiny amount of carbon 14. The carbon 14 in plants and animals keeps breaking down, but more of it keeps being added. When an animal or plant dies, it stops taking in carbon 14. The carbon 14 already in its tissues goes on breaking down, but does so at a steady rate. After about 5,600 years half the carbon 14 atoms have broken down, half are left, after another 5,600 years, half of the half, a quarter, are left and so on. By measuring the amount of carbon 14 left, scientists can tell how long ago a plant or animal died. When the cave artists painted, they often rubbed their torches on the cave walls to make them burn brighter, this rubbing left charcoal on the wall. Charcoal comes from wood, so by dating the charcoal the scientists can learn when the tree died, so can show when the paintings were done. Carbon 14 dating is useful for dating material up to 40,000 years old. After that almost no carbon 14 remains. For earlier dates scientists can tell when hearth rocks were last heated or when flints fell into a fire and were heated.
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