How do fish ladders work? Fish ladders have a series of stepped pools that allow fish to swim back up a river and climb over any human-built obstacles that might be in their way. The idea is to mimic the natural riverbed. Salmon are the most commonly known, but there are many different kinds of […]
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Why is someone who crosses a picket line called a scab? The insult goes back to the 1500s, when “scab” had come to mean a low, mean, rascally person—a scoundrel. Strikes themselves are far older than most people assume. One of the earliest recorded strikes happened in Ancient Egypt in 1152 BC, when artisans of
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How did John Harrison’s clock allow longitude to be used? John Harrison’s clocks were the first clocks that worked accurately on ships. To calculate longitude, it is necessary to know the time difference between where the ship is and the place it left from. That is only possible with a clock that can keep accurate
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What is a fly-by-wire system? A fly-by-wire system is a way of controlling a plane with electronics rather than with manual flight controls. It is called “fly-by-wire” because all of the pilot’s input is transmitted along electrical wires. The opposite of fly-by-wire controls is mechanical or hydraulic controls. These days, passenger planes and large planes
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How do supermarkets employ psychology? Supermarkets employ psychology by manipulating your senses, tracking your route through the store, understanding where you look, shaping how you feel, and knowing when you are most likely to buy something. Supermarkets appeared at the beginning of the 20th century. The very first supermarket was the Piggly Wiggly in Memphis,
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How does a building sprinkler system work? A building sprinkler system is a network of pipes and sprinkler heads that are activated by heat, not smoke. A sprinkler system is fairly straightforward. A network of water pipes is laid through the building, usually above the ceiling. At predetermined distances, a sprinkler head sticks through a
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What is Occam’s razor? Occam’s razor is a principle that says if you have two competing ideas to explain something, you should always prefer the simpler of the two. It is named after William of Ockham, but he never called it “Ockham’s razor” himself. The basic idea behind Occam’s razor is that if you have
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How does a vacuum cleaner create suction? A vacuum cleaner creates suction by making a pressure difference between the air in the vacuum cleaner and the air outside the vacuum cleaner. However, the dirt is not technically being sucked up into the vacuum cleaner but pushed up. There are two kinds of vacuum cleaners currently
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What causes cataracts? Cataracts are caused when proteins in the lens break down and clump together, making the lens cloudy. Cataracts form in the lens of the eye. As the lens becomes cloudy, it can look whitish, and vision can become hazy, blurred, or glary. If left untreated, the cloudiness can increase until the lens
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How do ants farm aphids? Ants farm aphids by herding them together, feeding them, and keeping them out of the sight of predators. Aphids are small insects that suck the sap out of plants. They are usually between one and three millimeters long, and they have specialized mouth parts for cutting into plants and drinking
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