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 is on an Egyptian vase dating from roughly 3500 BC. There is some evidence that sailing boats might have been used even as early as 6000 BC in Mesopotamia, but experts are divided. Some think that sailing boats were in use even earlier than this and some think later. The boat depicted on the Egyptian vase was a boat that had a square sail made of papyrus. It was used for sailing against the current up the River Nile. Before sailing boats, there were only oars to move a boat through the water and that depended on a lot of manpower. Oars can easily move a boat, but they are very limited in speed and distance, and you need to carry a large crew, which makes the boat much heavier and reduces the available space for trade. Sails improved boats because they could move under the power of the wind and they could go much faster and much further. The only problem with a sailing boat is that it relies on the wind.

Most places on Earth have wind almost all of the time. However, that wind is not always going in the same direction that the sailing ship wants to go in. As long as there is some wind, ships have a technique to keep moving. There is a belt near the equator called the doldrums, where winds can become very light or disappear for long periods. Sailing ships could become trapped there for days or weeks. These places are called the doldrums and if a sailing ship happens to get stuck here, the only thing they can do is use oars to get out. Ferdinand Magellan’s ship, the Victoria, was stranded in the doldrums for 20 days in 1521. Sir Walter Raleigh’s ship, the Destiny, was trapped there for 40 days on his expedition to South America. Ships stuck here have no idea when they will get out, and rations can often run out.

So long as there is wind, ships can move. Wind pushes a boat in two ways. The first way is simply through direct force. The wind pushes the fabric of the sail and forces the boat forwards. If the wind is blowing from behind the boat, this is the method used to move a sailboat in the direction of the wind. The second way is by using the sail as a wing and gaining lift. This is the method used when the wind is not blowing from behind the boat.

An airplane wing creates lift because its shape and angle change the speed and direction of the air flowing around it. This creates lower pressure on one side and higher pressure on the other. A sail can work in a similar way when the wind is coming from in front of the boat. Obviously, the boat cannot sail if the wind is coming directly at it, but if the boat sails across the wind at a 45 degree angle, the sail splits the wind into two. The back side of the sail is curved and this produces areas of low pressure and high pressure and produces lift, which pulls the boat horizontally. The boat can only sail at 45 degrees towards where it wants to go, so it sails across the point it is heading for, then turns and sails back in a zigzag. This is called tacking. They have to sail a lot further than if they could just go straight, but they can sail against the wind.

The problem with this method is that the wind strongly wants to push the boat sideways. To prevent this, boats have something called a keel. The keel is a piece of the boat at the very bottom that sticks out into the water. The keel helps to balance the boat and also keeps it stable when the wind is pushing the sails. It also acts to stop the boat from being pulled sideways when it is tacking. The keel has a shape like a knife. The blade of the knife easily cuts forward through the water, but the large surface area resists movement to either side. The sail tries to pull the boat sideways and forwards, but the keel blocks most of the sideways movement, so the boat moves forwards. This allows the boat to sail against the wind. Although, of course, the invention of the steam engine and then the combustion engine made sail boats a thing of the past. Today, sails are mostly used by hobbyists, for sport, for training, and on some traditional boats, although there is also renewed interest in using wind power to help cargo ships save fuel. And this is what I learned today.

Sources

https://en.wikipedia.org/wiki/Keel

https://en.wikipedia.org/wiki/Sail

https://www.boatsetter.com/boating-resources/how-to-sail-against-the-wind

Photo by K    : https://www.pexels.com/photo/sailboat-on-the-sea-10179159/

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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 not really true. An embassy can be owned or leased by the country that uses it, but that does not make it part of that country’s territory. The land is still under the sovereignty of the host country. However, the host country cannot treat it like an ordinary building. Embassies are protected by international law.

The most important modern agreement is the Vienna Convention on Diplomatic Relations, which was agreed in 1961. It sets out the basic rules for embassies, diplomats, and diplomatic immunity. Under this convention, the premises of a diplomatic mission are inviolable. That means the host country cannot enter the embassy grounds, search the embassy, or seize its documents without permission. The host country also has a duty to protect the embassy from intrusion, damage, or disturbance.

This is why embassies can seem as though they are foreign territory. The police of the host country cannot simply walk in. The tax authorities cannot raid the building. The government cannot seize the embassy’s files. The host country still has sovereignty over the land, but it has agreed to limit what it can do there so that diplomacy can function.

Diplomatic immunity also extends to many diplomats, though not every person working in an embassy has the same level of protection. Diplomatic agents have strong immunity from the criminal jurisdiction of the host country. This rule exists because it stops a host country from arresting a diplomat and using that person as a political pawn. If diplomats could be arrested every time relations became bad, diplomacy would collapse very quickly.

That does not mean diplomats are allowed to commit crimes freely. They are still expected to obey the laws of the country they are in. However, if a diplomat commits a crime, the host country usually cannot arrest or prosecute that person in the normal way. What it can do is declare the diplomat persona non grata, which means the diplomat is no longer welcome and must leave the country. The host country can also ask the sending country to waive diplomatic immunity so the diplomat can be prosecuted. That can happen, but it is not automatic.

The same idea explains why embassies often appear in spy stories and films. A person who reaches an embassy may be protected from immediate arrest because the host country cannot simply enter the building. However, that does not mean an embassy is a magic door to safety. The host country can refuse to let the person leave. It can surround the building. It can wait. International law does not give every embassy a simple right to shelter refugees or move them safely out of the country. Diplomatic asylum is complicated and is not accepted in the same way everywhere.

During war or a serious breakdown in relations, countries may close their embassies or withdraw their diplomats. Even then, the building and archives still have protection. A country can ask a third country to look after its interests. This is called a protecting power. Neutral countries such as Switzerland have often performed this role. The third country may help protect the embassy building, look after archives, or provide limited assistance to citizens.

Throughout this article, I have used the word embassy, but the wider term is diplomatic mission. A diplomatic mission is the official group of people sent by one country to represent it in another country. An embassy is a diplomatic mission headed by an ambassador. A consulate is different. Consulates usually focus more on helping citizens, issuing visas, supporting trade, and dealing with practical matters.

The idea of sending official representatives to foreign rulers is extremely old. As long as there have been organized states, rulers have needed messengers, negotiators, and envoys. In ancient times, these people could be treated very badly if relations turned sour, so rules gradually developed to protect them. In the ancient Greek world, foreign merchants and communities sometimes had special representatives or protected spaces. The Romans also had rules and customs for envoys. These were not modern embassies, but they were early steps toward the idea that representatives from another state should have some protection.

Permanent embassies developed much later. In medieval and Renaissance Europe, trading powers such as Venice began keeping representatives in important cities and courts. At first, envoys might be sent for one particular job, such as arranging a marriage, negotiating a treaty, or settling a trade dispute. Over time, it became useful to have someone stay permanently in another country. That way, both sides always had someone they could contact. This gradually developed into the modern embassy system.

These days, most countries maintain embassies in many other countries, although not every country has an embassy everywhere. Smaller countries may not be able to afford a large network. Some countries cover several countries from one embassy in a nearby capital. Some countries do not have embassies because they do not have formal diplomatic relations. For example, the United States does not have formal diplomatic relations with Bhutan, Iran, or North Korea. The U.S. Embassy in Syria is also closed, although that situation is slightly different because operations were suspended.

There are also a few unusual cases. Vatican City and Liechtenstein are so small that foreign embassies accredited to them are normally located outside their territory. Embassies to the Holy See are usually in Rome rather than inside Vatican City, and many embassies accredited to Liechtenstein are based in nearby countries such as Switzerland, Austria, or Germany.

So, an embassy is not foreign soil. It is not a little island of another country. It is a protected diplomatic space inside the host country. The host country still has sovereignty, but it has agreed not to enter, search, or interfere with the embassy so that diplomacy can continue even when countries disagree. And this is what I learned today.

Sources

https://history.state.gov/departmenthistory/short-history/diplomatictradition

https://www.sanfranciscopolice.org/your-sfpd/policies/general-orders/5-13

https://en.wikipedia.org/wiki/Diplomatic_immunity

https://en.wikipedia.org/wiki/Diplomatic_mission

Photo by Jean-Paul  Wright: https://www.pexels.com/photo/white-concrete-building-with-flag-7557294/

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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 numbered areas, and the strip of desert that became famous as Area 51 appears to have taken its name from that system. It was also called Watertown, Paradise Ranch, the Ranch, Groom Lake, Dreamland, and later Homey Airport.

Area 51 is in the Nevada desert, about 40 km south of the tiny town of Rachel, Nevada. It sits beside Groom Lake, a large, flat, dry lakebed. That flatness is one of the main reasons the place was useful. During World War 2, the area was used as an aerial gunnery range, and there was already an old airstrip near the salt flat. If you look at satellite images today, you can still see the runways and the huge pale shape of Groom Lake in the desert.

The area might have remained an almost forgotten piece of military land if the CIA had not needed somewhere extremely remote in the early Cold War. At that time, the United States was trying to develop spy planes that could fly higher than ordinary aircraft. These planes could stay above most danger and take photographs of Soviet military sites. Satellites can do that job now, but in the 1950s the spy satellite age had not really arrived, and aircraft were still very important.

The main plane the CIA needed to hide was the U-2. It was not invisible to radar, but it could fly so high that enemy fighters and missiles could not easily reach it at first. Richard Bissell, a senior CIA official, was involved in finding a place where the U-2 could be tested and pilots could be trained in secret. A group from the U-2 project flew over the Nevada desert and spotted the old strip beside Groom Lake. It was remote, flat, dry, and surrounded by restricted land. It was almost perfect.

There was one problem. Groom Lake was near the Atomic Energy Commission’s proving ground, but it was not actually part of it. The CIA asked the Atomic Energy Commission to add the area to its Nevada holdings, and President Eisenhower approved the arrangement. The Atomic Energy Commission had been set up after World War 2 to “foster and control the peacetime development of atomic science and technology”. One of the jobs they had was to manage nuclear testing across the US. After World War 2, there were hundreds of nuclear tests carried out on US land. The majority of those were in open deserts, such as the one in Nevada. The Atomic Energy Commission divided up the land that had been used in Nevada in Areas. The Areas they created go from Area 1 to Area 30 and each one contains between zero and 266 nuclear tests (Area 3). The Atomic Energy Commission designated the CIA’s land as Area 51, presumably because they never thought they would get as high as 51 nuclear test site areas.

Lockheed’s engineer Kelly Johnson gave the place a more attractive name, Paradise Ranch, because asking people to work in a place called Area 51 in the middle of the desert probably didn’t sound very appealing. The name was shortened to the Ranch, and people who worked there were sometimes called ranch hands.

Area 51 began its modern life as a secret testing site in 1955. The first U-2 accidentally became airborne during a taxi test there on August 1, 1955, and the first official test flight came a few days later. After that, Groom Lake became an important place for testing secret aircraft. The A-12 OXCART, which was the CIA’s very fast successor to the U-2, first flew there in 1962. It could fly at over Mach 3 and reach altitudes far above normal aircraft. Later, other secret aircraft were tested there as well, including stealth aircraft such as the F-117 Nighthawk.

So, why did Area 51 become as famous as it has? The obvious answer is aliens, but the real answer is secrecy. The CIA and the Air Force went to great lengths to hide what they were doing. The planes being tested there were far ahead of normal aircraft at the time. They flew higher, faster, and sometimes looked very different. When people saw strange lights or strange shapes in the sky, it was easy to imagine something from another world. And when the government refused to explain anything, the mystery grew.

That does not mean there was no conspiracy at all. There was definitely secrecy. There were cover stories. There were crashes of experimental aircraft. There were people told not to talk. The government really was hiding something, but what it was hiding was advanced aircraft technology, not alien bodies and flying saucers. The secrecy that was necessary for spy planes created exactly the kind of atmosphere in which alien stories could grow.

The U.S. government publicly acknowledged Area 51 much later than most people would expect. A heavily redacted CIA history of the U-2 program had been released in 1998, but the clearer public acknowledgment of Area 51 came in 2013, when more documents were declassified. Those documents confirmed the role of Groom Lake in testing aircraft such as the U-2 and the A-12. They did not confirm the existence of aliens.

Area 51 is still heavily guarded and closed to the public. That does not prove there are aliens there. It only proves that the United States government still has things it does not want people to see. That probably means aircraft, weapons, sensors, drones, or other military technology. If aliens had managed to cross the absolutely mind-boggling distances between stars, the chances of them reaching Earth and then crashing in a desert in Nevada are probably pretty slim.  And this is what I learned today.

Sources

https://edition.cnn.com/us/area-51-fast-facts

https://en.wikipedia.org/wiki/Area_51

https://en.wikipedia.org/wiki/Nevada_Test_Site

https://en.wikipedia.org/wiki/United_States_Atomic_Energy_Commission

https://www.google.com/maps/place/37%C2%B014’00.0%22N+115%C2%B048’30.0%22W/@37.2308464,-115.8139618,2114m/data=!3m1!1e3!4m4!3m3!8m2!3d37.233333!4d-115.808333?hl=en&entry=ttu&g_ep=EgoyMDI2MDUwNi4wIKXMDSoASAFQAw%3D%3D

https://www.dictionary.com/articles/area-51

https://en.wikipedia.org/wiki/Lockheed_U-2

https://www.nationalgeographic.com/history/article/us-nuclear-testings-devastating-legacy-lingers-30-years-later

https://en.wikipedia.org/wiki/Lockheed_A-12

Photo by Abhishek  Navlakha : https://www.pexels.com/photo/desert-landscape-with-no-trespassing-sign-in-arizona-33132626/

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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 weight. Let’s break that down. If an object is put in water, there are two main forces acting on it. The force of gravity pulls the object down, and the water below the object pushes it back up. This is called the upward buoyant force. If the upward buoyant force can balance the force of gravity before the object sinks completely, the object will float.

Let’s look at an example. Let’s take two objects that are both a cubic meter. We’ll use a cubic meter of wood and a cubic meter of gold. The weight of wood depends on the type of wood and how dry it is, but a cubic meter of wood is roughly 500 kg. A cubic meter of gold weighs about 19,320 kg. A cubic meter of water weighs a shade under 1,000 kg. So, for a cubic-meter object to float, it needs to weigh less than the 1,000 kg of water it could displace. Wood does, and floats. Gold does not, and would sink extremely quickly.

Ships float because they can spread out their weight and displace much more water. If that same cubic meter of gold was hammered into a large boat shape with a hollow in the middle, it would still weigh the same, but it would take up a much larger space and could displace much more water. If it displaced more than about 19 cubic meters of water, the upward buoyant force would be enough to hold it up and it would float. Then, if it filled with water, it would become much heavier for the same shape, and it would sink again. That is why boats float, and also why they sink when they are filled with water.

Pumice floats because it is not very dense. It has a large volume for its weight, and this is because it is full of holes. Pumice can sink eventually, but it often takes a while. When pumice falls into the sea, many of the holes are full of gas and they help keep the water out. Some of the holes are also tiny, so surface tension can stop water from entering them straight away. This lasts for a while, but over time, the gas is forced out and water moves into the holes. At a certain point, the buoyancy of the pumice declines enough that it no longer floats.

Pumice comes from volcanoes, and it is both rock and volcanic glass. That sounds confusing, but they can be the same thing. A rock is a natural solid material made of minerals, glass, or both. The difference is that most rocks have a crystalline structure, while glass has an amorphous structure. Rock is usually made of minerals, and those minerals have atoms that form in repeating patterns. In glass, the atoms are not in a neat order. They are frozen in a more random arrangement. This happens when molten material goes from a hot liquid state to a cold solid state so quickly that crystals do not have time to grow.

Pumice is made of gas-rich lava that cools extremely quickly. Inside the volcano, gases are dissolved in the molten rock because of the high pressure. Sometimes, this makes the magma very frothy. When the volcano erupts, the pressure suddenly drops. The dissolved gases expand, the lava foams up, and then it cools and solidifies before the bubbles can escape. Because it cools so rapidly, many of the minerals are not able to settle into a crystalline pattern, and much of the material becomes volcanic glass. The result is a light, hole-filled rock that is almost like hardened volcanic foam.

Pumice has many uses, and most people probably think of it as the rock in the bathroom used to scrape dead skin off feet. It is good for this because it is abrasive and soft at the same time. However, the biggest use of pumice is actually in concrete. It is also used in cinder blocks for building. Pumice is mined, but it is more environmentally friendly than some other forms of mining because it mostly sits on or near the surface. And this is what I learned today.

Sources

https://www.britannica.com/science/pumice

https://en.wikipedia.org/wiki/Pumice

https://www.geologyin.com/2024/02/why-pumice-floats-on-water.html

Photo by Jose Luis  Vanasco: https://www.pexels.com/photo/striking-white-rock-formations-in-desert-landscape-35406944/

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Why are there so many different types of electrical outlets? There are so many different types of electrical outlets because countries built their electrical networks independently, and they all made different choices based on their own technology, traditions, safety rules, and requirements.

There are 15 commonly listed styles of electrical plug and outlet around the world, and they are labeled from Type A to Type O. Type A is used in North and Central America and Japan. It has two flat parallel pins. Type B is similar, but it has a round earth pin as well. Type C is one of the most common types around the world and is used in many European countries. It has two round pins. Types E and F are also used in many parts of Europe, but they are not exactly the same because they handle grounding in different ways. Type G is used in the UK, Ireland, Malaysia, Singapore, and Hong Kong. It has three rectangular pins. Type H is used in Israel. Type I is used in Australia, New Zealand, Papua New Guinea, and Argentina. Type J is used in Switzerland and Liechtenstein. Type K is used in Denmark and Greenland. Type L is used in Italy. Type M is used in South Africa, Eswatini, and Lesotho. Type N is used in Brazil, and Type O is used in Thailand.

So, why is there no standardized outlet? The main reason is that each country built its electrical system independently of the others. By the time international travel and global trade became common enough for this to be annoying, the systems were already installed. Every house, every factory, every appliance, and every repair system had been built around the national standard. Changing all of that would be extremely expensive and very disruptive. Where countries share an outlet type, it is often because of history, trade, or colonial connections. The British Type G plug, for example, is used in the UK and in several countries that were once connected to the British Empire. North America uses the same basic system because the electrical network developed across the continent in a connected way. Japan uses a North American-style plug system, which is why Japanese plugs look so similar to American ones.

The difference is not just the shape of the outlet. It is also whether the plug has an earth connection, and what voltage the electrical system uses. All standard outlets have a live and a neutral connection. When a plug is connected to an outlet, electric current flows in through the live wire, passes through the device being used, and flows back out through the neutral wire. That completes the circuit. However, if there is a fault, the current could flow into the metal body of the device. If a person touched it, the current could pass through their body, which could be extremely dangerous.

This is why many plugs have a third pin, called the earth pin, or ground pin. The earth wire is connected to the body of the device and then to the ground through the building’s wiring system. It provides a low-resistance path for the current. If there is a fault, most of the current flows through the earth wire rather than through a person. Because the resistance is low, a large current flows, which should blow the fuse or trip the breaker. The important thing is not that the earth wire makes electricity harmless. It gives dangerous current a safer path and helps the safety system cut the power.

The voltage difference also comes from history. The USA was one of the first countries to build large electrical networks, starting in the 1880s. Early systems used around 110 volts, partly because lower voltage was seen as safer for electric lighting in homes. If electricity is compared to water, then voltage is like pressure. A higher voltage can push electrical energy more efficiently over distance, but it can also be more dangerous if something goes wrong.

When many European countries developed their systems, they eventually moved toward higher voltages, around 220 to 240 volts. This made it cheaper to deliver the same power because a higher voltage can provide the same amount of power with a lower current. Lower current means less energy is lost as heat in the wires, and the wires do not need to be as thick. That saves money, especially across a large electrical network.

By the time the USA realized the advantages of higher voltage, it was already too late to easily change everything. Homes, appliances, factories, wiring systems, and safety standards had all grown around 110 to 120 volts. Rebuilding the entire system would have cost far too much money. However, the US did not completely stay with only 120 volts. These days, most American homes receive split-phase power. Ordinary outlets provide about 120 volts for everyday devices, while larger appliances such as ovens, electric dryers, water heaters, and air conditioners can use 240 volts.

There will probably never be a single universal outlet because every country has different laws, different safety standards, different voltages, and millions or billions of devices already in use. A universal plug would be convenient for travelers, but it would not be convenient for the countries that had to replace their entire electrical infrastructure. The world is already too invested in the systems it has. That is why a small travel adapter can do what international governments probably never will. And this is what I learned today.

Sources

https://www.iec.ch/world-plugs

https://warrington.ufl.edu/news/why-do-different-countries-have-different-electric-outlet-plugs

https://www.kristechwire.com/electrical-outlets

https://www.bbc.co.uk/bitesize/guides/znvr4xs/revision/2

Image By ARTol – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=123266308

Photo by Castorly Stock : https://www.pexels.com/photo/black-wall-plugs-3639031/

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How do you dismantle a skyscraper? There are several ways to dismantle a skyscraper, but none of them are easy. The method depends on where the skyscraper is located, what it is made of, how tall it is, and what is standing around it.

The first skyscrapers were built in the 1880s. They were made possible by several inventions and improvements, including elevators, steel-frame construction, stronger foundations, and better fireproofing. The 42-meter-tall Home Insurance Building, built in Chicago in 1885, is often called the world’s first skyscraper, although historians still argue about the title. Forty-two meters was tall for the time, but these days it probably wouldn’t even qualify as a skyscraper. Since then, buildings have grown taller and taller, and the skylines of most major cities are dominated by them.

Many early skyscrapers have gone, but some famous old ones still remain. The Chrysler Building in New York, for example, was completed in 1930 and is about 319 meters tall. It is a beautiful building, but it also shows one of the problems with skyscrapers. They can last a very long time, but they do not stay modern forever. Elevators, plumbing, wiring, heating systems, windows, offices, and safety systems all age. At some point, an old skyscraper either has to be repaired and modernized, or, if that is not practical, taken down and replaced.

The easiest way to knock down a building is with explosives, but that does not mean it is simple. Controlled demolition is a very complex process. Engineers study the structure, remove parts of the building first, weaken certain columns, and place explosives very carefully. The goal is usually to make the building collapse inward, into its own footprint. It looks fast when it works, but it takes a huge amount of planning.

The problem is that skyscrapers are not ordinary buildings. They are exceedingly tall, they contain enormous amounts of steel, concrete, glass, pipes, wiring, and furniture, and they are often surrounded by other buildings. Even a controlled implosion produces dust, vibration, noise, and flying debris. A short building on an open site might be brought down with explosives, but a tall skyscraper in the middle of a city usually cannot be treated that way. There is too much around it to damage.

To avoid causing damage to nearby buildings, most skyscrapers have to be dismantled rather than simply demolished. There are two main ways this can be done. They can be taken apart from the top down, or, in some special cases, they can be taken apart from the bottom up.

The top-down method is the more straightforward idea. Workers start at the roof and remove the building floor by floor. First, the inside is stripped out. Furniture, walls, wiring, pipes, and non-structural parts are removed. Then machines, cranes, and workers break apart the concrete and steel structure in a carefully planned order. The pieces are lowered to the ground or carried down through the building. This can be slow and expensive, but it is safer than making the whole building fall at once.

There are still many problems. The building has to stay stable while it is being dismantled. Workers cannot accidentally remove a piece that is still supporting something important. They also have to stop debris from falling onto streets, neighboring buildings, cars, or people. Dust and noise have to be controlled as well. On a small building, this is difficult. On a skyscraper, it can take months or years.

The bottom-up method is stranger. In this method, the building is placed on extremely strong, computer-controlled hydraulic jacks. The lowest floor is dismantled, the waste is removed, and then the jacks lower the rest of the building by one floor. Then the next floor is removed. This is repeated again and again, so the building appears to sink into the ground. Kajima Corporation describes its Cut and Take Down method as starting at the bottom, removing one floor, and lowering the building on jacks one floor at a time.

The advantage of this method is that much of the work can be done near ground level. That makes it easier to remove waste and control noise and dust. The disadvantage is that the engineering has to be incredibly precise. The building must remain balanced while its lower structure is being removed. The jacks have to support enormous loads. The temporary supports have to be strong enough to survive wind, earthquakes, and uneven weight. This is not a normal method for every skyscraper. It is a clever solution for particular buildings in particular places.

Older skyscrapers can also be difficult because they were not designed to be taken apart. They were designed to stand. Many were built with huge amounts of steel, concrete, brick, and stone. They may also contain materials that are now considered dangerous, such as asbestos. Before the real demolition begins, workers often have to remove hazardous materials, disconnect utilities, protect nearby streets, and plan how every piece of waste will leave the site.

This raises an interesting problem. Architects and developers are always trying to build taller skyscrapers, but far less attention is given to how those skyscrapers will eventually be dismantled. The Burj Khalifa is 828 meters tall, which makes it the tallest building in the world. One day, it will also be old. It probably won’t be impossible to dismantle, but taking apart something that size would be one of the most difficult demolition projects ever attempted.

And that may be the future of skyscrapers. Building tall is only half of the challenge. The other half is maintaining, repairing, modernizing, and eventually taking those buildings down safely. A skyscraper looks permanent, but no building lasts forever. At some point, even the tallest building becomes a problem that has to be solved from the top down, from the bottom up, or one carefully planned piece at a time. And this is what I learned today.

Sources

Photo by Charles Parker: https://www.pexels.com/photo/residential-and-commerce-buildings-placed-in-downtown-of-megapolis-5847765/

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Do people actually live in igloos? People don’t usually live in snow igloos permanently, but some Inuit groups historically used them as winter homes or temporary hunting shelters.

The English word “igloo” comes from the Inuit word “iglu,” which means house or home. It does not necessarily mean a house made of snow. In some Inuit dialects, the more specific word for a snow house is “igluvijaq.” There are a few recorded uses of related words in early European writing about North America, but the word “igloo” seems to have become more widely known after 1824. This was when William Edward Parry, a famous Arctic explorer, published an account of his expedition in search of the Northwest Passage.

Parry and his crew spent a winter frozen in the bay near Igloolik Island. Temperatures dropped close to minus fifty, and there were months of darkness. Some of the crew developed scurvy, and they had to depend on the local Inuit people to survive. They spent a lot of time with them and picked up many of their words. Parry used many of these words in his book, including the word “igloo.” However, as with the Inuit people themselves, he used it to mean a house.

Over the next few decades, English speakers gradually narrowed the word. Instead of meaning any kind of house, “igloo” came to mean a snow house. Then, interestingly, it changed again. If the use of “igloo” is checked in Google’s Ngram graph, the word rises sharply around the 1940s before falling off again. This was not because people suddenly started making lots of snow houses during the war. It was because the US military started using the word “igloo” for earth-covered ammunition stores, which were similar in shape. This pushed the word into manuals, reports, and books, and it probably skewed the graph.

So, did people actually live in igloos? Yes and no. Snow igloos were not usually permanent homes in the way that modern houses are. However, some Inuit groups used them as winter dwellings, and smaller igloos were used as temporary shelters when people were hunting or traveling. Parry saw Inuit people building them near his ship while it was frozen in the ice, but these were temporary shelters rather than permanent settlements. An experienced Inuit builder could make a strong igloo in about one or two hours.

Why build an igloo at all? Hunter-gatherers in warmer climates can often have a base, maybe in a cave or a shelter, and travel out and back in a day. Prey is more plentiful, and sleeping outside is not usually deadly. The Arctic is different. Inuit hunters had to travel much farther to find prey because there were fewer animals, and many of those animals stayed in the sea, under the snow, or away from the worst of the wind. Hunters might be away from their settlement for an extended period, and they needed shelter.

They could take tents, and tents were used in some seasons, but tents have disadvantages. They have to be carried, they can be damaged by strong winds, and they do not always provide enough insulation in extreme cold. A snow igloo solves many of those problems because it uses material that is already there. The Arctic may not have many trees, but it has a lot of wind-packed snow.

An igloo is made by cutting hard-packed snow into blocks and arranging them in a spiral that rises into a dome. The best snow is not soft powder. It is dense snow that has been packed down by wind in very cold conditions. The builder cuts the blocks with a snow knife and places them so that each layer leans slightly inward. The structure is not a perfect half-circle. It is shaped to be strong, especially against wind.

The entrance is usually a low passageway, and inside the igloo there is often a raised sleeping platform. This is clever because cold air sinks. The coldest air collects near the entrance and lower passage, while the sleeping platform stays warmer. The entrance also helps block the wind from blowing directly into the living space. Inside, hides or furs could be used on the sleeping area, and sometimes on the walls, to make the shelter more comfortable.

The igloo works because snow is an exceptionally good insulator. That might sound strange because snow is cold, but snow contains a lot of trapped air. Air does not conduct heat very well, so the snow blocks slow the movement of heat from inside to outside. The igloo blocks the wind, traps body heat, and creates a small protected space. Even if the temperature outside is far below freezing, the inside can be much warmer.

A seal-oil lamp could also be used for light and heat. If the inside of the igloo warmed enough to melt the surface slightly, the water could refreeze into a thin layer of ice. This helped strengthen the structure and seal small gaps. The result was a shelter that was quick to build, strong in the wind, and much warmer than the open Arctic air.

So, people do not generally live in igloos permanently, and the idea that all Inuit people live in igloos is a stereotype. However, snow igloos were real, practical, and extremely clever. They were not primitive shelters. They were carefully designed survival technology, made from one of the few materials available in the Arctic. And this is what I learned today.

Sources

https://en.wikipedia.org/wiki/Igloo

https://en.wikipedia.org/wiki/Edward_Parry_(Royal_Navy_officer,_born_1790)

https://www.etymonline.com/word/igloo

https://language.chinadaily.com.cn/2004-11/15/content_531207.htm

Photo by Игорь Шабалин: https://www.pexels.com/photo/men-stacking-blocks-of-snow-10433610/

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How does a spring work? A spring works by storing mechanical energy when it is deformed and then releasing that energy when it returns to its original shape. Springs don’t have to be metal, but in human-made springs, metal is probably the most common material. There are natural springs as well. The tendons in a kangaroo’s legs work like natural springs because they stretch and recoil as the animal jumps.

Springs work by storing energy and then releasing it. There are generally three types of springs. There are springs that are compressed and then release the energy as they return to their original form. These are the types of springs you find in the suspension system of a car. Then there are springs that are stretched and release energy as they return to their original shape. These are the type of springs you will find on a trampoline, between the material and the frame. And then there are torsion springs, which are springs that are twisted or wound and then release energy as they try to return to their original shape. These are the type of springs you will find in many mechanical watches, clips, and wind-up mechanisms. The similarity between all of these springs is that they store energy when their shape is changed and then release that energy when they are allowed to return.

When you use a spring, you either pull it, compress it, or twist it, and you have to use energy to do this. If you pull a spring between your two hands, you can feel the force required to keep it in that position. The spring wants to return to its original shape. It is not really “wanting” anything, of course, but the forces inside the material are trying to pull everything back into balance.

When you stretch an extension spring, the wire in the spring is deformed. In a coiled spring, this does not simply mean that every atom is pulled straight away from every other atom. The wire is also bending and twisting slightly. However, at the atomic level, the basic idea is the same. The atoms in the metal are moved slightly away from their most comfortable positions. Metal atoms are held in place by strong electromagnetic forces. When the spring is stretched, those forces resist the change. The energy that was used to stretch the spring is stored in the strained arrangement of the atoms and their bonds. When the spring is released, those forces pull the atoms back toward their original arrangement, and the stored energy is released.

A compression spring works in a similar way, but in the opposite direction. When you compress the spring, the wire is deformed and the atoms are again shifted slightly away from their normal positions. Some parts of the structure are pushed into a slightly higher-energy arrangement. It takes energy to do that. When the spring is released, the electromagnetic forces in the material push and pull the atoms back toward their normal arrangement, and the spring returns to its original shape.

Springs are made of elastic materials, but any material has a point where it cannot return to its original position. You can try this with a spring that isn’t very strong. If you pull a weak spring between your two hands and keep pulling, you will pass the elastic limit of the spring, and it will stretch out of shape. At this point, the layers of atoms in the metal have slipped into a new arrangement. The spring is now permanently longer and weaker. If you keep pulling, the spring might snap because the structure has been damaged too much.

No matter the type of spring, it needs to be made of a material that resists being changed from its natural shape. It also needs to have a high elastic limit. This is how far the spring can be deformed before it won’t return properly. It needs to resist fatigue because it may be stretched, compressed, or twisted thousands or millions of times. Metals fit most of these conditions, but not all metals are good for springs. Copper and lead, for example, are too soft and deform too easily. Steel tends to be a very good spring material because it can be strong, elastic, and resistant to repeated stress when it is made and treated properly.

Springs weren’t invented by one person. They evolved over the centuries. The string in a bow and arrow acts like a type of extension spring, and bows have been used for tens of thousands of years. Many civilizations used different types of spring-like devices over the millennia. Ancient Egyptian chariots appear to have had suspension systems that absorbed shocks, and Roman vehicles also used spring-like suspension. However, these were not modern coiled springs. Coiled springs appeared much later, in medieval and early modern Europe, in devices such as locks, clocks, and weapons.

The scientific law behind many springs is called Hooke’s law. Robert Hooke first stated the idea in 1676 and published it more clearly in 1678. The law says that, within the elastic limit of a spring, the force needed to stretch or compress it is proportional to how far it is stretched or compressed. In simpler terms, the more you pull a spring, the harder it pulls back. The modern coiled spring was developed gradually, but Richard Tredwell patented an important coiled spring design for carriages in 1763. It was a revolutionary step that helped improve vehicles and machines. Springs are so simple that it is easy to overlook them, but we couldn’t live without them today. And this is what I learned today.

Sources

https://en.wikipedia.org/wiki/Robert_Hooke

https://www.explainthatstuff.com/how-springs-work.html

https://en.wikipedia.org/wiki/Spring_(device)

Photo by Brett Sayles: https://www.pexels.com/photo/close-up-shot-of-metal-pipes-11942508/

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How do storm drains work? Storm drains work by directing rainwater from roads, sidewalks, roofs, and streets into underground channels, where the water can be controlled and carried away.

Before there were cities, storm drains were obviously not necessary. When it rains in nature, the water hits the ground and either soaks into the soil, collects in low areas, or flows downhill toward streams and rivers. Rocks, plants, soil, roots, and slopes all help control where the water goes. If there is too much rain for the ground to absorb, the water runs over the surface until it reaches a river, a lake, or the sea. If the land is in a dip, it might flood for a while, and the water will stay there until it soaks into the ground or evaporates. This is natural. It only becomes a serious problem when we build cities.

The majority of a city is covered with hard surfaces, such as asphalt, concrete, roofs, sidewalks, and parking lots. These surfaces do not absorb water very well. Some cities have a lot of parks, trees, gardens, and open land, which helps because soil and plants can absorb some of the rain. However, the amount of green space varies enormously from city to city. In dense areas, most of the rain falls on surfaces that cannot soak it up. Unless there is a system to remove that water, it can flood streets, damage buildings, wash away roads, and make travel impossible.

With no storm drains, water would collect in low-lying parts of the city. Roads would become temporary streams and rivers because streets naturally guide water downhill. This would happen very quickly in heavy rain. If humans disappeared, storm drains would eventually become blocked with leaves, mud, trash, and broken pieces of the city itself. Over time, these uncontrolled streams would be one of the things that helped break cities apart.

Storm drains start with the inlets that can be seen at the side of many roads. These are the grates or openings where rainwater disappears from the street. The area around a storm drain is often slightly lower than the surrounding road, just like the plughole in a bathtub, so water naturally flows toward it. The location of storm drains is carefully planned. Engineers look at the slope of the land, the shape of the road, the nearby buildings, and how much rain the area is likely to receive.

A road that is in a dip needs more drainage than a road on a hill because water will naturally gather there. An area with many buildings may also need more drains because roofs and gutters send rainwater down to the street or directly into the drainage system. Modern buildings often have their own drainage pipes that connect to the stormwater system, so the water from the roof does not simply pour onto the sidewalk.

The drain inlet usually has a grate over it. This helps catch large pieces of debris, such as branches, leaves, plastic bottles, and trash, before they enter the underground pipes. The grate is also a safety feature because it stops people or animals from falling into the drain. However, the grate can also become blocked, especially in autumn or during heavy storms. This is why storm drains have to be cleared and maintained. A storm drain that is covered with leaves cannot do its job, no matter how good the pipes underneath it are.

Under many storm drain inlets is a catch basin. This is a small underground chamber with a deeper section at the bottom. Water flows into the catch basin first, and heavier material, such as sand, grit, leaves, and small pieces of trash, can settle in the lower part. The water then flows out through a pipe, while much of the heavier debris stays behind. This helps stop the underground pipe system from clogging too quickly. The catch basin has to be cleaned from time to time because, if it fills with debris, it will stop working properly.

From the catch basin, rainwater flows into a network of underground pipes. These pipes usually get larger as more water joins the system. Small pipes from individual streets connect to larger pipes, and those larger pipes may connect to culverts, channels, storage tanks, or open waterways. A culvert is basically a covered channel that carries water under a road, railway, or part of a city. In some places, these underground systems are like hidden rivers.

In many modern cities, stormwater is kept separate from sewage. Rainwater from the streets flows through one system, while wastewater from toilets, sinks, baths, and washing machines flows through another. The stormwater may be carried directly to a river, lake, or the sea. This is why water flowing out of a large pipe into a river is often rainwater, not sewage. However, this water is not always clean. As it runs along roads, it can pick up oil, dirt, rubber from tires, chemicals, and trash. That is why stormwater pollution is a problem.

Some older cities have combined sewer systems. In those places, rainwater and sewage travel through the same pipes. This can work in normal weather, but it becomes a problem during heavy rain. If too much rainwater enters the system, the pipes and treatment plants cannot handle it all. The system can overflow, and dirty water can be released into rivers or even back up into streets and buildings. This is one reason many cities try to separate stormwater from sewage when they upgrade old infrastructure.

Drainage systems have existed for almost as long as cities because water buildup is a problem wherever people build permanent settlements. Archaeologists have found drainage systems in ancient places such as Minoan Crete from around 2000 BC, and similar ideas probably existed even earlier. Early systems were often open channels in roads that carried water away, rather than underground networks like the ones used today. The technology has changed, but the basic problem has not. Cities are hard surfaces built in the path of rain. Without storm drains, our enormous cities would not be able to survive for long. And this is what I learned today.

Sources

https://www.treehugger.com/global-cities-most-and-least-public-green-space-4868715

https://en.wikipedia.org/wiki/Storm_drain

https://dem.ri.gov/sites/g/files/xkgbur861/files/ri-stormwater-solutions/documents/2.UnderstandingStormDrains.Factsheet.pdf

Photo by David McElwee: https://www.pexels.com/photo/drain-on-street-13319904/

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Why are British people called Limeys and Poms? British people are called Limeys because of the citrus juice British sailors drank to prevent scurvy, and they are probably called Poms because of Australian rhyming slang connected to the word immigrant.

There are many names for British people around the world. Some of them are affectionate and some of them are less so. Also, when people say “British” in this context, they often really mean English, rather than Welsh, Scottish, or Northern Irish. The two most famous terms are probably Limey, which is mostly used in the USA, and Pom, which is mostly used in Australia and New Zealand. Let’s look at where those two terms came from.

The term Limey comes from the practice of giving British sailors citrus juice to prevent scurvy. Scurvy was one of the great dangers of long sea voyages. It is caused by a lack of vitamin C. Without enough vitamin C, the body cannot make collagen properly, and that causes fatigue, swollen gums, joint pain, wounds that will not heal, bleeding, and eventually death. On long voyages, a ship could lose a huge number of its crew to scurvy.

People had known for a long time that fresh fruit and vegetables seemed to prevent scurvy, but they did not understand why. One of the first useful experiments was done by Sir James Lancaster in 1601. He commanded several ships and gave lemon juice to the crew of one of them. The men who received the lemon juice suffered far less from scurvy than the men on the other ships. However, the lesson was not immediately accepted by everyone.

A naval surgeon called James Lind carried out a more famous experiment in 1747 while he was on HMS Salisbury. He took twelve sailors who were suffering from scurvy and divided them into pairs. Each pair was given a different treatment. The pair who received oranges and lemons recovered most clearly. Lind had shown that citrus fruit could treat scurvy, although even after that, it took a long time for the British Navy to make citrus juice a regular part of life at sea.

When the Royal Navy finally did adopt citrus juice, it made an enormous difference. At first, lemon juice was commonly used, but later the Navy often used lime juice, partly because limes could be obtained from British colonies in the Caribbean. British sailors became associated with lime juice, and people began to call them “lime-juicers.” Over time, that was shortened to “Limeys.” The word originally referred to British sailors, but it later became a more general nickname for British people, especially in America.

The name Pom is more uncertain, but there is one explanation that has better evidence than the others. Pom, or Pommy, seems to come from pomegranate. That sounds strange at first, but the missing link is Australian rhyming slang. In Australia, immigrant was once turned into “Jimmy Grant,” because it rhymed. From there, the word seems to have moved toward “pomegranate” or “Pommy Grant,” and then it was shortened to Pom or Pommy. So, if this explanation is right, Pom is not really about pomegranates themselves. It is about wordplay.

There are other theories, but they are weaker. One theory says that English people were called pomegranates because they turned red in the Australian sun. That is possible as a folk explanation, but it is probably not the main origin. Another theory says that POM stood for “Prisoner of Mother England” or something similar, but there does not seem to be good evidence for that. It looks like one of those explanations people invented after the word already existed. Acronym explanations are often suspicious because many old slang words began in speech before anyone tried to explain them in writing.

Before Pom became common, new arrivals in Australia were sometimes called “new chums.” This meant people who had only recently arrived and did not yet understand life in Australia. The word chum originally came from chamber-fellow, meaning someone who shared a room. Over time, it came to mean a friend or companion. In Australia, a new chum was a newcomer, while an old chum was someone who had been there for longer.

British people have other nicknames as well. The French have called the British “les Rosbifs,” which means “the roast beefs.” This came from the stereotype that British people loved roast beef. In return, British people have called French people “frogs,” based on the stereotype that French people eat frog legs. These names are not especially kind, but they show how national nicknames often come from food, appearance, jokes, rivalry, or war.

That is what makes words like Limey and Pom interesting. They are not just random insults. They preserve little pieces of history. Limey carries the history of sailors, scurvy, long voyages, and the slow discovery that citrus fruit could save lives. Pom carries the history of migration, Australian slang, and the way a word can be twisted, rhymed, shortened, and passed around until almost nobody remembers where it came from. And this is what I learned today.

Sources

https://www.historyextra.com/period/20th-century/why-do-americans-call-british-limeys-history-meaning

https://www.economist.com/asia/1997/05/22/those-whingeing-poms

https://en.wikipedia.org/wiki/Scurvy

Photo by Marwan Marwan: https://www.pexels.com/photo/fresh-limes-selection-at-a-market-stall-35867157/

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