How did people wake up before alarm clocks? Before alarm clocks, people woke up naturally or were woken by outside noises. In cities, they might have used candle clocks, been woken by church bells, or paid a professional knocker-upper. The idea of needing to be awakened by an alarm clock is a relatively recent problem. […]
#1653 How did people wake up before alarm clocks? Read More »
What is the rarest coin in the world? There are several possible candidates for the rarest coin in the world, but the most widely recognized contender is the 1933 Saint-Gaudens Double Eagle. This is a difficult question because there have been so many different coins over the thousands of years since coins were first used
#1652 What is the rarest coin in the world? Read More »
Why did it take so long for papermaking to reach Europe? It took so long for papermaking to reach Europe because they had materials that they thought were superior, they were resistant to Islamic influence, not many people could read or write, and the world was not as small then as it is now. Writing
#1651 Why did it take so long for papermaking to reach Europe? Read More »
Why don’t figure skaters get dizzy when they spin? Figure skaters do get dizzy when they spin, but they learn to manage it because they have trained their brains and vestibular systems to cope with the sensation. The sensation of dizziness comes about because of the way our balance system works. There are three parts
#1650 Why don’t figure skaters get dizzy when they spin? Read More »
How do cranes balance? Cranes balance by using a system of counterweights, a stable base, and computers that monitor the load and angle of the crane at all times. The idea behind counterweights is fairly simple to understand, and it can be tested on a desk with a ruler, a pencil, and some heavy objects.
#1649 How do cranes balance? Read More »
How can kangaroos hop so fast? Kangaroos can hop so fast because they have very large tendons in their legs that act like natural springs. Kangaroos are native to Australia and there are four species. Those are the red kangaroo, antilopine kangaroo, eastern grey kangaroo, and western grey kangaroo. The largest and the fastest species
#1648 How can kangaroos hop so fast? Read More »
What is the Janney coupler? The Janney coupler is a device that goes between train cars to join them together. It was a revolutionary jump in railroad technology and is still used today, over 150 years later. If you have ever ridden on a train and you have looked at the coupling that hold the
#1647 What is the Janney coupler? Read More »
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
#1646 What makes us hungry or full? Read More »
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
#1645 When and why did public libraries start? Read More »
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
#1644 How can you save data in glass? Read More »
