Why are pocket knives called penknives? Detailed answer

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Why are pocket knives called penknives? Detailed answer

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Why are pocket knives called penknives?

Steel fountain pens became widely used in the middle of the 19th century, and before that they wrote mainly with goose quills. Such feathers needed to be sharpened periodically, which was called sharpening. Accordingly, a special knife for this procedure was called a penknife. Later, the word "pencil" was applied to all pocket knives.

Authors: Jimmy Wales, Larry Sanger

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How is carbon-14 used to determine the age of objects?

All living things contain carbon. They also contain small amounts of carbon-14, a radioactive form of carbon. Using carbon-14, scientists can determine the age of trees, clothing, and anything that was once alive. The use of carbon-14 for this purpose is called radioactive aging. Radioactive carbon helps determine the age of objects that are up to 50 years old. The rate at which radioactive elements decay is called the half-life.

The half-life is the time it takes for half the atoms of an element to decay. The half-life of carbon-14 is about 5500 years. This means that 5500 years after the death of an animal or plant, only half of the carbon-14 atoms that were originally in them will remain in the dead organisms. After 11 years, only a quarter, after 000 years - an eighth of the original amount, and so on.

Suppose a piece of old wood is found in an ancient tomb. In the laboratory, it can be heated and turned into carbon, or burned to release various gases containing carbon dioxide. Carbon or carbon dioxide contains several carbon-14 atoms. These atoms decay. When decaying, tiny particles leave the atom at high speed. Carbon or carbon dioxide is placed in a very sensitive instrument called a Geiger counter. It takes into account particles given off by carbon-14 atoms. Based on the number of these particles, scientists make a conclusion about the amount of carbon-14 in the sample.

Scientists know how much carbon-14 is contained in the same amount of living wood. Comparing this number with the amount of carbon-14 left in the ancient sample, scientists give the age of the tree. For example, if an ancient tree found contains half the number of carbon-14 atoms contained in a living tree, then the sample is about 5500 years old.

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