How do sailing ships sail against the wind? To sail against the wind, sailing ships use a combination of techniques. They angle themselves to increase aerodynamic lift, they use an underwater keel, and they use a zigzag motion called tacking. No one knows when sails were discovered, but the earliest known image of a sail […]
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Was there anything the Germans could have done after D-Day? Not to win the war. Short of producing a working nuclear bomb, and probably not even then, there was no realistic way for Germany to secure victory after the Allies entered Europe on D-Day. What they could have done was make the Allied advance slower,
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How does grass break concrete? Grass breaks concrete by widening existing cracks until the concrete falls apart. Grass can’t actually break solid concrete, but it can exploit cracks that are already there. This is due to a property of concrete. Concrete has incredible compressive strength, which means it can support an enormous amount of force
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How do fish farms work? Fish farms work by raising fish from eggs to full sized fish in a carefully controlled environment. There are different ways to farm fish, and they all have their benefits and problems, but they are all trying to overcome a situation that we have created ourselves. The situation is that
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What was the first hotel chain? It depends how you look at it, but the first hotel chain was either Fred Harvey’s Harvey Houses or Ellsworth M. Statler’s Statler Hotels. Conrad Hilton’s hotels later became the first coast-to-coast hotel chain in the United States and one of the first major international hotel chains. These days,
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Why do waterfalls move upstream? Waterfalls gradually move upstream because they erode the rock beneath them. You might think a waterfall will always stay where it is, but waterfalls can gradually move upstream, sometimes to the point where they disappear forever. Take Niagara Falls, for example. Niagara Falls is probably the most famous waterfall in
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How did people make the first scales accurate? They made them accurate by using simple physics, careful craftsmanship, and agreed standard weights. Weighing scales are incredibly simple when they are looked at from the outside. At their simplest, there are two dishes hanging from either end of a bar. In the center of the bar
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Is an embassy really foreign soil? No. An embassy is not foreign soil. It is still inside the country where it is located, but it is protected by special rules and immunities. The idea that countries own the land their embassy is on and that it becomes foreign soil is very common, but it is
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Why does jaundice turn people yellow? Jaundice turns people yellow because a yellow-orange pigment called bilirubin builds up in the blood and body tissues. The word jaundice came into English from French. In Old French, jaune meant yellow, and that came from a Latin word meaning greenish-yellow. That is why jaundice has always been connected
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Why is it called Area 51? The simple answer is that it was a map designation, but the exact reason why that number was chosen is not completely clear. The site at Groom Lake was near the Atomic Energy Commission’s Nevada Proving Ground, where nuclear testing was carried out. The land there was divided into
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