Because the ship is lighter than water. Absurd? In part, yes. The problem is that no one accepts this very simplistic explanation very well. After all, everyone knows that a handful of the stainless steel that makes up the shell of any boat weighs much more than the same handful of water. Where is the secret then? It’s in the size of the ship, not its weight. To understand this better, let’s use a person as an example. Imagine if she decides to play the messiah and try to walk on water. It won’t work, of course, and it will eventually sink. But that same person, lying down instead of standing in the water, manages to float without major problems. And the body weight is exactly the same in both situations. The difference is in the concentration of that weight. In the first example, it is all concentrated on the person’s feet. Already in the second it is distributed throughout the area of \u200b\u200bthe body. Then, it’s like you become lighter, at least from the point of view of the water that supports you. For boats, exactly the same rule applies.
The secret of all this lies in the amount of water displaced by each material, be it a person’s body or a ship. If the volume of a material – the space occupied by its mass – is large, more water will be displaced, right? And the liquid reacts by trying to occupy that space again. The more water is taken from the place, the greater the reaction. This opposing force is what has the power to sustain a voluminous material submerged in water. “It is precisely its volume that allows this”, says naval engineer Cláudio Sampaio, from the University of São Paulo (USP). If the volume is reasonable enough, the amount of liquid displaced by it will have enough power to keep a body of enormous weight afloat. It is this principle that is behind the seaworthiness of all ships developed by man, from the first and relatively light galleys of ancient Egypt to modern nuclear aircraft carriers, true naval war machines, which can weigh approximately 100,000 tons.
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GUYS – HAND STRENGTH
Powered by dozens of oarsmen, sometimes aided by a rudimentary sail, galleys were the most important ships of antiquity. Primitive versions began to appear around the year 3000 BC, in Egypt. They were used in trade and, mainly, in war, as they were more maneuverable than boats powered by sail alone. They only disappeared for good in the 16th century of the Christian era.
CARAVELA – WIND IN FAVOR
The use of sails parallel to the hull, capable of taking advantage of crosswinds as propulsion, gave the boats autonomy, allowing for longer trips. Light merchant ships, like the Portuguese caravels, with 60 tons and 20 meters in length, could go from Europe to America in a month. In wars, Spanish galleons reigned, some weighing more than 700 tons.
STEAM SHIP – MOTORIZED TRIPS
In the second half of the 18th century, boats with steam-powered engines debuted. The first, slow and with rotating blades, became famous when crossing the Mississippi River, in the United States. The first such ocean liner appeared in 1838 in England. As these vessels were too heavy for wood, iron hulls appeared. Around 1860, paddle wheels were replaced by propellers.
AIRCRAFT CARRIERS – THE NUCLEAR AGE
The first aircraft carriers appeared in the 1920s. During World War II (1939-1945), they consolidated themselves as the most feared combat ships. But the great technological revolution came in the 1960s, with the debut of nuclear aircraft carriers. Powered by reactors, they don’t have to stop to refuel. A modern machine like this carries around 70 aircraft
Schooner – GIANT SAILS
With trade growing between distant countries, it was necessary to increase the speed of vessels. That’s why the schooners appeared, boats with a narrow hull, to reduce friction with the water, and very large sails. Ships like that, mainly the British and American ones, broke records non-stop. One of them went from Boston, in the United States, to Liverpool, in England, in just 12 days.
If a boat is a thousand tons, its volume has to be large enough to displace the same weight of water. The liquid will then react with a force equivalent to the thousand tons, only in the opposite direction to the weight of the ship. This counterlift force evens things out and floats the boat.