Watch on YouTube How much wind does a wind turbine need? A wind speed of roughly 11 km/h. Wind power has been used for over 2000 years. The windmill was invented in the 7th century in Persia and wind power was harnessed to grind grain. The wind could do the work of a herd of […]
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Watch on YouTube How does an iron remove wrinkles from clothes? The heat forces the cellulose chains to lie straight. People started wearing clothes about 170,000 years ago. Scientists worked this out by looking at the evolution of lice that live on humans. Lice that live on clothes are different from the lice that live
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Watch on YouTube What makes things sticky? When the molecules in two substances are attracted to each other things become sticky. The stickiness of an adhesive and the stickiness of something like maple syrup are a little bit different from each other. Let’s look at the stickiness of glue, adhesive tape, and maple syrup. There
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Watch on YouTube Why is carbon-based life common? Because carbon can bond with many different elements to allow chemical reactions to happen. On our planet all living things contain carbon. There may be lifeforms on other planets that are made of different elements but on Earth, everything uses carbon in one way or another. Plants,
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How long do black holes last? Black holes will slowly dissolve, but it will take far longer than the length of our universe, so it has never been observed. There are two ways that black holes form. The first way is when a star collapses. As stars die, they burn up all of their hydrogen,
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How does an ion thruster work? It creates thrust by accelerating ions using electricity. An ion is a charged atom or molecule. Atoms always have an equal number of electrons and protons. Electrons have a negative charge and protons have a positive charge. Because there is an equal number of each, the charges balance themselves
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How does a breathalyzer work? The alcohol in a person’s breath reacts with a solution, creating an electrical current. The breathalyzer relies on the fact that when you drink alcohol, some of it gets into your lungs and you breathe it out. That’s why, when you take a late bus home on a Friday night,
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Why is lead poisonous? It settles in cells and interferes with many different enzymes, preventing the cells from working properly. Lead is a heavy metal that is very dense. It is also fairly soft. These days, a lot is known about lead poisoning, so lead is treated very carefully in factories and in devices that
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How long did it take for the sun to get hot? Approximately 10 million years for it to start burning. The sun is hot because of nuclear fusion, which is where hydrogen molecules are squashed together under great pressure to make a helium molecule. There is a difference in the atomic weight of the hydrogen
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When did oxygen appear on Earth? Oxygen appeared on Earth between 2.4 and 2.2 billion years ago. The air we breathe is not made up mostly of oxygen. It is 78.084% nitrogen, 20.934% oxygen, 0.934% argon, 0.035% carbon dioxide, and then a lot of other trace elements. Our bodies need the oxygen and the carbon
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