Why are leaves different shapes? Leaves are different shapes because of the conditions they have evolved to survive in. That might be for catching more sunlight, for saving water, to not be eaten by predators, or for staying cool. Leaves on a plant or a tree are a constant tradeoff. The main purpose of a […]
#1755 Why are leaves different shapes? Read More »
How can a bicycle freewheel? A bicycle can freewheel because of a ratchet and spring-loaded catches inside the gear hub. When you cycle on a bicycle, you use the pedals to apply energy to the chain, which transfers the energy to the wheels and makes you move forwards. You want that when you are on
#1739 How can a bicycle freewheel? Read More »
When did the modern census start? The modern census developed gradually between the late 17th and mid-19th centuries. Most civilizations have had some kind of census since the beginning of civilizations. It is always important to know how many people you have in your country because then you can tax them properly and you always
#1731 When did the modern census start? Read More »
How does the Netherlands reclaim land from the sea? They build a dike and then pump out the water. Before we look at how they do it, I thought it would be interesting to learn why Holland is called the Netherlands. Most of you probably know this, but I didn’t. The Netherlands is the official
#1727 How does the Netherlands reclaim land from the sea? Read More »
Why was the Erie Canal important? The Erie Canal was important because it connected the Atlantic Ocean to the Great Lakes. This cut down shipping time and costs, and it unlocked the American Midwest. The Erie Canal is 584 km long. It runs from the Hudson River in New York State to Lake Erie. The
#1725 Why was the Erie Canal important? Read More »
How does a revolving restaurant work? Only the outer dining platform rotates. The central core stays still. Revolving restaurants are usually located on the roof of buildings or at the top of towers. Diners can sit at tables around the outside of the restaurant and enjoy their meal as it slowly rotates. This allows them
#1716 How does a revolving restaurant work? Read More »
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
#1710 How do sailing ships sail against the wind? Read More »
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
#1703 Is an embassy really foreign soil? Read More »
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
#1701 Why is it called Area 51? Read More »
Why does pumice float? Pumice floats because it has a very low density. This is because of all the gas-filled holes inside it. Whether or not something floats depends on how much water it can displace. Objects float in water if they are positively buoyant, which means they can displace more water than their own
#1698 Why does pumice float? Read More »
