Why did early humans leave Africa? They were probably forced out by climate change, but they could have left because of their rising intelligence. Let’s look at the evidence for why paleontologists believe humans developed in Africa and then look at why they left. Humans probably separated from the common ancestor we share with other […]
#492 Why did early humans leave Africa? Read More »
Why do soldiers break stride on a bridge? So that the vibrations don’t make the bridge collapse. This rule was introduced by the British Army in 1831. On 12th April 1831, the 60th Rifle Corps were returning from a military exercise and they crossed over the Broughton Suspension Bridge, which had been built five years
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How does a canal lock work? By using gravity to increase the amount of water in the canal and rise the boat. There are two different reasons why canals need locks. The first is that canals are bodies of running water and so they have an upstream and a downstream, giving them a current. They
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What is cotton? Cotton is a fiber that grows around the seeds of the cotton plant. About 27 million tons of cotton is produced every year. India is the largest producer, with 6.1 million tons, and it is followed by China, the USA, Brazil, and Pakistan, in that order. A standard t-shirt requires approximately 226
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Why do we say “born to the purple”? What is Tyrian purple? We say that someone who is born into a royal or powerful family is “born to the purple” because Tyrian purple was an incredibly expensive color that only wealthy and powerful people could afford. The dye for Tyrian purple was made from the
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Is an Olympic gold medal really made of gold? The gold medal the winners at the Olympics get is only 7.5% gold. It is 92.5% silver with only a gold-plating of about 6g. With 6g of gold in a medal, the value of the medal would be about $800 if sold for its precious metals.
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Why is oil measured in barrels? Oil is measured in barrels because that was the size of a wine barrel in 1866. Nobody really knows when barrels were invented, but there is a picture of a wooden barrel made to measure wheat on the wall of the tomb of the Egyptian high official, Hesy-Ra, from about
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Why are katana blades curved? They are curved to make them more efficient at cutting. Katana are long, curved swords from Japan. Their name “katana” means one-sided blade. “Kata” means “side” and “na” means blade. Many swords are double-sided because it allows them to be more effective when thrust. They can also be used to
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What makes rain smell? A combination of plant oils, bacterial spores, and ozone. Everything always smells very fresh after a rainfall and there is a word for it. Merriam-Webster defines petrichor as, “a distinctive, earthy, usually pleasant odor that is associated with rainfall especially when following a warm, dry period”. The word was invented by
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How does dry cleaning work? Clothes are soaked in a water-free liquid solvent. Dry cleaning is a way of washing clothes without water. At home, all of us wash our clothes in the washing machine using some kind of detergent and water. Inside the washing machine is something called an agitator. This is a drum
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