Where did Roman numerals come from? Despite their name, Roman numerals evolved from an Etruscan system of counting, which may possibly have come from Ancient Greece. The Romans popularized the system and left it for us to see, which is why we gave it their name. Here is a refresher course in Roman numerals. I […]
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Why did the first electrical plugs go into light sockets? The first electrical plugs screwed into light sockets because early homes were wired mainly for lighting, and the light socket was often the only convenient place to tap the electricity. These days, every house will have multiple electrical outlets in most rooms. We will be
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Why do screws tighten clockwise? Most screws tighten clockwise probably because the majority of people are right-handed. That might sound like something that must have been decided thousands of years ago, but the direction of screws has only really been standardized since the 19th century. That was when machining improved to the point where a
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Who invented the first eye chart? The first widely used eye chart was invented by a Dutch ophthalmologist called Herman Snellen. The earliest eye charts were invented in the early 19th century, but Snellen’s chart was the one that became the standard. The majority of people will have used an eye chart at some time.
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Why do some lakes have no fish? Some lakes have no fish because the environment they are in, or the composition of the water, is too harsh for the fish to survive. A related question is how some completely isolated lakes have fish. Most lakes contain fish. The few that don’t are usually too inhospitable
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What are the dark patches on the moon? The dark patches on the moon are called lunar mare, and they are large flat plains formed by ancient lava flows. The word mare comes from the Latin word for sea because the mare look like giant seas. A lot of people talk about the man in
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What was the Aberfan disaster? The Aberfan disaster was a terrible coal-waste landslide in 1966 that hit a school and killed 116 children and 28 adults. Aberfan is a small village in the area of Merthyr Vale in Wales, UK. The village was mostly a tiny hamlet until the Merthyr Vale Coal Mine was opened
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How do birds ride thermals? Birds ride thermals by flying in tight circles and by having specialized feathers and wings. Some birds, such as eagles, are able to make use of thermals and fly to great heights without using much energy. If a bird wanted to fly to a height of 3 km, it would
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Why are leaves different shapes? Leaves are different shapes because of the conditions they have evolved to survive in. That might be for catching more sunlight, for saving water, to not be eaten by predators, or for staying cool. Leaves on a plant or a tree are a constant tradeoff. The main purpose of a
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How were the Terracotta Warriors found? The Terracotta Warriors were found accidentally by farmers digging a well. The Terracotta Army was buried in 221 BC and it wasn’t uncovered again until it was found by farmers in 1974. There was a bad drought in the area, and Yang Zhifa and his five brothers were desperate
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