Why do many land animals naturally swim, but humans can’t
Many land animals have a natural instinct for swimming because they are mostly quadrupeds. For animals that walk on all fours, they don’t need to change their posture to swim, just like walking on land. They also have high nostril position, so if you raise your head slightly, the nostril can breathe out of the water, which makes swimming very easy. For example, the “doggy paddle” of a dog or horse, while not an effective or graceful swim, is enough to get a dog or horse across a river, while it is impossible for a human to swim upright. If you’ve ever seen someone who can’t swim at all fall into the water, they almost always deal with it in an upright manner: after bobbing up and down in the water for a while, they begin to sink, and if no one helps them, they become a victim. Compared to animals, humans need to learn to stay level in water, which requires learning to adapt to having their faces submerged. Humans need to learn how to control their breathing in the water and master specific breathing patterns while swimming. Without breath control, all humans can do is swim with their heads up, which is one of the least efficient ways to swim for a bipedal human. But even this way, humans must position their bodies in a more horizontal position, or they will drown. From a physical point of view, the most important thing in swimming is buoyancy, and in order for the body to achieve greater buoyancy, it must increase the surface area of contact with the water. Hands and feet grow from the sides and directly under the body, meaning that learning to float and swim fast requires learning to adjust the body to a horizontal position and to master proper breathing patterns. In short, swimming is not a skill that humans are born with.
How can people learn to swim
Why do people who can swim feel at home in water? In terms of the composition of the human body, although the human body is composed of bones and other materials with much higher density than water, it also has cavities such as intestines and stomach and lungs, which can store some air, making the average density of the human body only about 1.02 grams per cubic centimeter, slightly larger than pure fresh water (the density of pure water is 1 gram per cubic centimeter). In fact, the water in the natural water body or natatorium, because there are certain suspended particles, the density of water is slightly larger than pure fresh water, which can reach about 1.005 grams per cubic centimeter. According to Archimedes’s principle in physics, an object in the liquid more or less will be the buoyancy effect, the size of the buoyancy is the same as the object displaces the liquid by gravity, so the human body by buoyancy in the water also follows the law of the the volume of the human body into the water, the more the greater the buoyancy. Since the density of the human body is similar to that of water, it is theoretically possible to balance the buoyancy and gravity of the body only after it is almost completely submerged.
Because the density difference between the human body and the water is very small, so the human body by the gravity and buoyancy difference is not very big, people in the water motionless will slowly sink, and then as long as the hands and feet give a little force, will make the human body by the resultant greater than or equal to the gravity, which makes people can suspend or float on the water. People can learn to swim mainly by mastering the ability to exert force on water and breathe in water. People who can swim in the water is not panic, the force of arms and legs is more rhythmically, can assist people swimming on the water, can better use the power of water to float on the water, so that more body parts are exposed to the water for a long time, so it does not affect people’s breathing and breathing.
Swimming has a lot of skills, on this basis can be divided into swimming methods for underwater, breaststroke, freestyle, butterfly, backstroke and informal dog plane. Although swimming in the water of the human body movement is not the same, but are the use of inhalation and exhalation regulation, limbs and head action coordination: on the one hand because the density of air is far less than water, so through inhalation and exhalation to control the total amount of gas in the chest, to achieve the purpose of floating and sinking; On the other hand, it beats the surface of the water body or paddles inside the water body to disturb the direction of the water flow, so as to obtain the reaction force on the body and realize the body to move forward.
When people who cannot swim fall into the water, why the more they struggle, the more likely they are to drown
When people encounter danger in the water, their instinctive reaction is to trample on their lower limbs underwater, so that they can’t generate more upward momentum perpendicular to the center of gravity of the body, and the floating state may become sinking. Drowning, in order to their own safety, the upper body beat the water, trying to make the upper body as much as possible out of the water, such operation is also wrong. Because the buoyancy generated by water on human body will increase with the volume of liquid displaced, when people drown their head and upper limbs out of the water, the buoyancy generated by water is smaller than before. In this unstable state, people will float up and down in a larger range, and it is difficult to find a floating balance point in water, so it is easier to sink. And people in the drowning emergency, adrenaline secretion increases, the heart rate increases, muscle contraction leads to volume reduction, the whole person is in a tight state, and the body weight remains unchanged, so the human density will be slightly larger; And in the case of faster breathing, the lungs will contain less air, often choking water, the original air in the body is replaced by water, the density of the human body further increases, so people will sink into the water after drowning.
Why do drowning people float up after death
People sink to the bottom of the water, and after death, the body gradually rots, and the microbes inside the body decompose the body. Due to the variety and quantity of bacteria in the stomach and intestines of human body, methane, hydrogen sulfide and other gases generated by decomposition will make the upper part of the body swelling. Because the upper part of the body contains a large amount of gas, the density of the whole upper part of the body is less than that of water, and the body begins to float.
Therefore, we often see news reports of floating bodies, many of which are belly or upper body out of the water, the lower body immersed in water. Gas from decay is produced first in the chest and abdomen, and eventually in the lower limbs. If the whole body is floating on the water, it’s highly decomposed.
Why are there fewer black athletes in swimming
The NBA is definitely dominated by black athletes, Michael Jordan, Kobe Bryant, Lebron James and other superstars are all black. There was no denying the athletic talent of blacks, not only in basketball, but also in almost all track and field events. However, not all sports are black and there are almost no blacks in world-class swimming events. Many people don’t understand why, but the reason is not profound.
First, a very important factor comes from physiology. Black people have a higher muscle ratio than other races. The difference in muscle weight makes blacks feel much less buoyant in the water. In addition, the density of black bones is 5 to 10 percent higher than that of white bones. It also required a lot of effort in the water to deal with the problem of sinking. As a result, black people have lost their advantage in swimming.
Secondly, swimming is a sport with high requirements for training and competition venues, and the vast grasslands of Africa are obviously difficult to meet the conditions required for swimming. Relatively speaking, the wide field is better suited to sports like track and field and football. So in sports like track and field and football, many black sports stars emerged. In addition, water resources in Africa are scarce, and precious water is mainly used for living. The government will not invest much money in the construction of swimming venues and the purchase of equipment.