What makes us hungry or full? Hunger is driven by signals such as ghrelin, while fullness comes from a mix of stomach expansion, nerve signals, and hormones released by the digestive system. Ghrelin is known as the “hunger hormone” because it is released when the stomach is getting empty and it is one of the […]
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When and why did public libraries start? Public libraries started in the mid-19th century as a way to give democratic access to information and education to the working classes. A library is a purposefully assembled collection of books or manuscripts, and the first libraries were literally that. The Babylonians wrote on clay tablets, and these
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How can you save data in glass? Data can be saved in glass by using an ultrafast laser to write tiny permanent marks inside it. It is also called 5D storage. Those marks are far too small to see with the naked eye, but they can still be read later because they change the way
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How does a laxative work? There are several different types of laxative, and they all work in different ways. Some add bulk to the stool, some soften it by helping it hold more water, some lubricate it, some pull water into the bowel, and some stimulate the nerves and muscles in the intestine. There are
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How does a ship’s anchor work? A ship’s anchor works because the anchor digs into the seabed and the heavy chain creates a huge amount of resistance while keeping the pull on the anchor low and steady. Most people think that when ships rest at anchor, the only thing holding them in place is the
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Why do insects have such short lives? Many insects seem to have short lives because they have evolved to prioritize rapid reproduction over a long life. However, it only seems that way if we focus on certain kinds of insects, or if we only look at their adult stage. Not all insects have short lives.
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Why are some places windier than others? There are many reasons why some places might be windier than others. Some of those reasons are temperature differences, topography, the amount of surface friction, and wind funneling. Wind is caused when air moves from an area of high pressure to an area of low pressure. Air behaves
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Why does China only have one time zone? China only has one official time zone because that is what Chairman Mao decreed in 1949 to promote unity in the newly formed People’s Republic of China. The world is divided into time zones because of the speed at which the Earth rotates and the amount of
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What is a psychotic break? A psychotic break, more commonly called a psychotic episode, happens when a person loses touch with reality. Their thoughts and perceptions become disrupted to the point where they may struggle to tell what is real and what is not. The phrase “psychotic break” is informal, and although some episodes are
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When were streets first named? Nobody can pinpoint exactly when streets were first named, but, presumably, people started to give streets names from the very earliest cities. Among the world’s first cities were Jericho and Çatalhöyük. They were both formed in about 7500 BC and began as a collection of a few hundred people, before
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