Why does entropy happen? Entropy happens because there are vastly more ways a system can be in disorder than it can be in order. Entropy is explained in the second law of thermodynamics. It says that the state of entropy of an isolated system will always increase over time. It has been rewritten since it […]
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When did exams start? Exams started in China in 605 AD. Modern schools, universities, and other educational institutions have complex systems of examinations. The purpose of them is to rank students, decide if people pass or fail, see if schools are teaching successfully, see if students are learning successfully, and many other reasons. There are
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Why are coconut crabs so big? Coconut crabs are big because they need enough power to be able to crack coconuts. Coconut crabs live on islands in the Indian and Pacific Ocean. They are enormous. They weigh about 4 kg and they have a leg span that can be over 1 m. They are not
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Which came first, the chicken or the egg? It depends on how you think about it, but the egg came first evolutionarily. Chickens were domesticated about 10,000 years ago and eggs evolved about 350 million years ago. This is one of those questions where the point is not the answer, but the thought process along
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Why is carbon dioxide the main greenhouse gas? Carbon dioxide is the main greenhouse gas because it absorbs more heat than other gases. When we think of greenhouse gases and climate change, we think of carbon dioxide, but it is not the only greenhouse gas. All of these gases are obviously produced naturally, but human
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What is pneumonia? Pneumonia is an infection that causes the air sacs in the lungs to become inflamed and sometimes full of liquid. The word pneumonia was coined in 1603 and it comes from the Greek “pneumon”, which means lung. Pneumonia is caused when viruses, bacteria, or other microorganisms infect the lungs. It is a
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Why didn’t French decimal time last? It was too hard to alter the way people already told the time to introduce a system of decimal time and too expensive to remake all the clocks. France began to use decimal time on 5th October 1793, just after the French Revolution. The point of the revolution wasn’t
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What are tails for? Animals have tails for several different reasons. They use them for balance, to grip things, for motion, as weapons, to lose heat, to communicate, and to keep flies off. The majority of mammals, birds, and reptiles have tails, but not all do. Some insects have tails as well. Out of the
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When was the wheel invented? The wheel was invented in roughly 4200 BC, over 6,700 years ago. I have toyed with whether “invented” might be the wrong word to use here. “Discovered” might be better because there are many round things that naturally exist in the world. However, I think we can safely go with
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Why is Mexico City sinking? Mexico City is sinking because they are pumping more water out of the underground aquifer than can be replaced. Mexico City is the capital of Mexico, and it has a population of almost 22 million people, which is over 17% of the population of Mexico. Since the beginning of the
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