What is a Leidenfrost droplet? A Leidenfrost droplet is something that you may have seen in your frying pan. It is a drop of liquid, often water, that hovers and glides over the solid surface beneath it. If you have a very hot, dry frying pan and you drop water into it, some of the
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Why can you hear the sea when you hold a seashell to your ear? Well, obviously, you cannot hear the sea through a seashell. What you are hearing is a mixture of ambient sounds that have been merged into a mix of frequencies, just like the sounds that waves hitting a beach produce. One thing
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Why do cut apples turn brown, but other fruits don’t? Cut apples turn brown because of an enzyme in their cells called polyphenol oxidase. However, apples are not the only fruits that go brown by a long way. There are many other fruits that also turn brown. Apples go brown when they are cut, and
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Why do cats have vertical pupils, but lions don’t? Cats have vertical pupils and lions don’t because of the different ways that they hunt. If you have ever looked at your cat, you will have noticed that it has vertical slit pupils. Cats are not the only animals that have vertical pupils. They can be
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Where did all the horses go when the car was invented? The car was invented and introduced overnight, so the number of horses in any country was slowly reduced over time. The number of horses in most countries peaked just before 1930 and then began a relatively rapid decline. Before cars were introduced, almost every
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Were the Dark Ages really dark? The Dark Ages were not dark in the way that we think. The Middle Ages lasted from roughly the 5th century to the 15th century. For centuries, much of this period was described as the Dark Ages, although modern historians generally avoid the term or restrict it to the
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How did Wilhelm Röntgen discover X-rays? He discovered that when he turned on a high-voltage electrical current in a cathode-ray tube, a nearby screen coated with barium platinocyanide began to glow with a green, fluorescent light. Wilhelm Röntgen was a German experimental physicist. He was born in Lennep, which was in Prussia at the time,
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How did ancient people move stone blocks? Ancient people had several methods to move enormous stone blocks. They could use water, wooden sledges, wooden rollers and levers, ramps and earthworks, scaffolding, machinery, or just by walking them. When we look at some of the monuments by people of the ancient world, it can make us
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What is a folly? A folly means something foolish, without lack of good judgment, foresight, or normal prudence. We are looking at architectural follies and they are the same, but with buildings. A folly is a building that was built solely for decoration rather than for purpose. Rich people have always built follies. If someone
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How did we discover viruses? Viruses were first theorized in the 1890s, but they wouldn’t be seen until electron microscopes were invented in the 1930s. The word virus comes from Latin and originally meant poison or poisonous liquid. It entered English in the late 14th century and was used by physicians to describe infectious or
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