статистика аудиторії Big Think

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Why is the Marathon distance 42,195 meters rather than exactly 42 or 43 kilometers? According to legend, a courier ran from Marathon to Athens (more than 30 km in a straight line) with the news of the Greeks' victory over the Persians in 490 BC. At the Olympics in Greece in 1896 the route from Marathon to Athens was a longer road (40 km). At the IV Olympics (Great Britain, 1908) it was decided to start the marathon race at the Royal Castle in Windsor and finish in London at the Great Stadium in front of the Royal Lodge. The route of exactly 26 miles (41,843 m) from Windsor Castle fell short of the Lodge by 385 yards (352 m), and they were added to the route. It was not until 1921 that the International Athletics Federation decided that the course should always be exactly 42,195 m (352 m) long, as it was in London.

Why does the skin renew itself, but the tattoos remain? They're too deep. The top layer of skin, the epidermis, regenerates in a couple of weeks. Its lower layers divide to form keratinocytes, which then slough off and new ones grow underneath. The dye that has penetrated the epidermis exfoliates along with the dying cells. However, below lies the dermis layer, renewing itself quite slowly. Besides, the space between its cells is filled with a network of collagen fibers — durable and chemically almost inert. Once in the dermis, the pigment grains remain there forever.

Why is the explosion of a grenade in water hazier than on land? In the air, a person is struck by flying grenade fragments. Under water, they quickly decelerate and water pressure serves as the main striking factor. The water set in motion by the explosion presses on the human body. Upon reaching the organs containing air, the pressure sharply squeezes and unclenches them, tearing the tissues. Death threatens the person at a distance of 6-7 meters from the explosion, and the obstacles are almost beyond saving.

Why does the cat invariably land on its feet? The ability to roll over in a fall is innate in cats and manifests itself as early as 3-4 weeks of age. When a cat falls, it instantly begins to level its body with the ground. In this, their highly flexible spine, the absence of collarbones, and well-developed vestibular apparatus contributes to it. It presses its paws and tail to its torso, speeding up the rotation. As soon as the cat gets its paws in a downward position, it immediately moves them aside and the rotation stops.

Why does one’s leg tingle when sit down? The leg "sits up" when the peripheral vessels in it are constricted. The nerve receptors in the limbs are sensitive to the lack of oxygen and respond by shutting down (stopping working). This can be felt as numbness. When the blood supply is restored, the receptors initially generate signals on their own, without external influence. These signals are felt as tingling or goose bumps.

Why cannot you wake up to a bad smell? Recent research from Brown University has revealed the function of smell sensation is altered by the brain during sleep. Although certain substances can affect body activity, we can't wake up from the smell itself. For those who thought of ammonia. It is one of those substances affecting the brain — it stimulates the respiratory and vasomotor centers of the brain and causes increased breathing and increased blood pressure, resulting in waking up.

Why is the whistling sound stronger when it's raining? The reason is that when it rains, the air is damp, i.e. its density is greater than in dry weather. That's why sounds are better transmitted. In rainy weather, for instance, you can hear a train driving on the railroad, especially at night, although at other times you cannot hear it. The molecular weight of water (H20) is smaller than that of the main components of the atmosphere: oxygen (O2) and nitrogen (N2). The lighter the molecule, the higher the speed of sound.

Why do the batteries in a flashlight run out on their own? There are wires running from the battery terminals to the flashlight switch. Even if the circuit is open, the distance between the switch pins is about a millimeter. A weak current can flow through this gap and discharge the batteries. To avoid this, insulate the battery from one of the contacts with a couple of layers of polyethylene or take them out of the flashlight when not in use.

Why does snow shine in the sun? Cause of the crystalline facets. Snowflakes are ice crystals with numerous flat facets that act as microscopic mirrors. Those that reflect sunlight directly into the eye provide a bright dot. As soon as one moves a little bit, the rays of other snowflakes fall into the eye. Therefore, when moving, the shiny spots replace each other. Freshly fallen snow is shinier than lain down, as the flat edges of snowflakes scratch, break, and melt with time.

Why do some animals have vertical pupils while others have horizontal ones? A vertical pupil allows predators to see vertically oriented objects, such as their prey, sharper. Herbivores, on the other hand, only need to view a wide horizon to spot a predator in time, so their pupils are frequently adapted to see horizontal lines more sharply.

Why are raw potatoes unpalatable? Due to the starch in their cells. Though it cannot be seen, you can easily obtain it if you grate the potatoes, pour water on them, and then strain and let them stand. A white sediment is sure to precipitate in the water. That is the very starch which makes raw potatoes bland.

Why do people pay for movie minutes in Germany? Cinema tickets in Germany are expensive, they can cost around €10. That's why it's a good deal for film lovers to buy a monthly pass for €23. Yet you have to pay for extra minutes of film: a subscription includes films of 120 minutes, and time over this limit is paid separately. There is even a special term for this phenomenon: Überlängenzuschlag.

Why cannot gasoline be put out with water? Why are ignited objects put out with water? The point is that combustion is the process of combining a substance with oxygen, so the main purpose of extinguishing fires is to limit the flow of air oxygen to the burning material. Extinguishing with water is the cutting off of oxygen to the burning object, since water, by wetting it, envelopes it (besides, water lowers its temperature). Gasoline isn’t mixed with water, and at the same time, is lighter than water, so it just floats up, while keep burning. In addition, it will begin to spread with the water, increasing the fire area.

Why do sharks not sleep? It used to be thought that sharks don't sleep at all as they need to be in constant motion to pass water through their gills to breathe. Therefore, it seems that a shark cannot sleep since it needs to swim all the time. Still some evidence from physiologists suggests that these sharks may be able to swim and sleep simultaneously. The nerve center responsible for contracting the muscles that move the body is located in the spinal cord, so theoretically they can turn off the brain and doze off on the go.

Why did the 7-up drink originally contain lithium citrate and was a cure for depression and hangover? 7-up was invented by Charles Leiper Grigg in 1920. He came up with the idea of adding lithium citrate to the drink, one of the drugs now prescribed for manic-depressive psychosis. Lithium citrate also helped relieve hangover syndrome. 7-up immediately became popular during the Great Depression and was called lithium-lemon soda at the time. The name was soon changed, but lithium was part of the drink until the 1950s, with 7-up officially considered a patented medicine. There are various versions of the drink's name origin. Some claim the initial recipe contained 7 components, while others recall the atomic mass of lithium, which is seven.

Why do the smells of food spread throughout the house? Due to the heated air. All odors sooner or later spread throughout the volume available to them. With cooking smells, though, this effect is amplified. The point is that the stove heats the air above it as it cooks. As it rises, it forms currents with which odorous substances from cooking and roasting foods are dispersed throughout the room.

Why is one crab's claw larger than the other? These claws have distinct functions. The larger claw, with its powerful teeth, is designed for crushing shells of mollusks and sea urchin carapaces, the prey of the crabs. The second claw has a cutting edge for dissecting soft tissues or bristles serving as a filtration device. In male semi-skinned beckoning crabs, one huge claw has turned into a "tournament weapon": it is used for mating demonstrations and in fights between males.

Why do trees not die in winter? Due to the peculiarities of the cell sap. The cell sap of trees accumulates sugars that lower the freezing point of the sap, preventing it from turning into ice. Besides, the plant's cellulose itself is a nice insulator. Though, severe frosts can lead to the death of the tree. And plants turn most vulnerable after an abundant harvest, since most of the minerals and sugars undergo the formation and growth of fruits, whereas in the trunk cells the latter are present in minimal quantities.

Why does a fly persist in hitting the glass when a section of the window is open nearby? The insect cannot see it. Even if a fly notices an open window, it will have no reason to fly there, as it cannot determine in advance whether there is glass or not. If you bring it close to an open window, it will fly into it at once.

Why doesn't it tickle when you tickle yourself? The brain decreases the sensitivity of the skin. Tickling is caused by irritation of the tactile receptors on the skin. Their sensitivity is controlled by the spinal cord and brain. If the irritation is caused by touching another part of your own body (which the receptors of the touched part tell the brain), the brain dulls the sensitivity of the receptors, preventing the tickle from occurring. Apparently, this mechanism serves to avoid "false alarms" in performing the main function of tickling — alerting us to the presence of foreign creatures on the skin, which may turn out to be parasites.

Why do the names of some currencies derive from measures of weight? The designations of many currencies are closely related to various measures of weight. A typical example is the British pound sterling: sterling was the name given to silver coins, and 240 such coins weighed one pound. Similar is the origin of the foreign currency in several countries called the lira, which is the Italian equivalent of the weight unit pound. In medieval Western Europe, a mark was used to measure the weight of silver, which was slightly lighter than the pound — from it came the Deutschmark.

Why does one's nose turn red and fingers bluish when cold? Vessels in our fingers narrow whereas those in our nose dilate In the cold, the lumen of the blood vessels in the fingers narrows, so the surface tissues turn pale to translucent, and blood stagnates in the deeper layers. By losing oxygen, the blood darkens and, shining through the skin, gives the fingers a bluish tint. The vessels of the nostril walls, on the contrary, expand in the cold: the upper airways, including the nasal cavity, warm the air supplied to the lungs. The colder it is outside, the stronger the heating must be. The increased blood supply to these tissues of the nose leads to its redness.

Why is Facebook designed in blue? In the mid-twenties, Facebook founder Mark Zuckerberg took a color-blindness test and realized that he was color blind. He had trouble distinguishing between shades of red and green. This is one of the reasons why Facebook, and now Meta, are designed in blue – all variations of blue are available to Zuckerberg. In this way, one man's peculiarity influenced the color scheme of the world's most visited site, and may have set a whole trend in social media design. Later VKontakte, Twitter, LinkedIn and Telegram used shades of blue and navy blue in their design.

Why doesn't the bottom button of a jacket get buttoned? This etiquette has been observed since the beginning of the XX century. Historians assume that the rule of wearing a jacket appeared thanks to the English King Edward VII (1841-1910), who was obese. He used to leave the bottom button undone so that a tight vest would fit better. As a sign of respect for his king, the British court, and after him all the inhabitants of England and the British colonies, no longer buttoned the bottom vest. This theory is not taken seriously by everyone, and some trendsetters have challenged it with other versions. Fashion designer Hardy Amies explained the single-breasted suit was first introduced in 1906 and was later called the "leisure suit". It became a casual garment, had a wide cut, and the three buttons gave the suit a proper fit. Over time, the jacket replaced traditional riding coats. And as the third button was below the waist, it was unbuttoned while sitting on a horse for comfort.

Why do all snowflakes appear different? The temperature of the cloud determines the shape of the ice crystal. Also, the amount of moisture in the cloud defines the size of the ice crystal. The more moisture, the larger the crystal. When several ice crystals stick together, they form a snowflake. As snowflakes fall into the air, twisting and swirling, each one goes its own way to the ground. Each single snowflake falls and floats through clouds with distinct temperatures and moisture levels. Thus forming each snowflake in a unique way. Two snowflakes from the same cloud will be of different sizes and shapes due to their separate travel conditions to Earth. Scientists say that the probability that two snowflakes would be exactly the same is about 1 in 1 million trillion. Meteorologists believe there are 1 trillion (with 36 zeros!) unique snowflakes.

Why is it better to breathe through the nose in the cold? The nasal cavity is capable of raising or lowering the temperature of inhaled air. As an example, if you run cold water through a hot pipe, after a while the water will warm up. It is the same with air. This nasal breathing makes the air temperature in the nasopharynx only 1-2 ° C deviates from the body temperature (36.6 ° C). Even when it is -25° C outside, the air in a person's nasal cavity heats up to +35°-36.6° C in a matter of seconds.

Why do sloths tend to hang upside down? That's how they relax. In strict terms, the sloth is not dangling with its head up, but with its back down. It may not grasp a branch, but passively hang on to it on powerful curved claws, like hooks. Sloths spend their entire lives in trees. Resting and sleeping in these conditions requires either a nesting device or anatomical adaptations to keep them from unclenching their paw and snapping off in their sleep. Suspended from a branch, the sloth remains in a completely relaxed state without the risk of falling. Besides, in this position it is less vulnerable to attacks of its main enemy — the monkey-eating eagle.

Why do store prices end at .99? Price ending at .99 is based on the theory that we are used to reading from left to right, with the first number sticking more into our brain than the next. That's why a person is more likely to buy a product that costs 4.99 rather than 5, since subconsciously we feel that 4 is less than 5, even though there's only a penny difference

Why might the electronic clock be lagging? It is due to temperature fluctuations. The "heart" of an electronic clock is a frequency oscillator, where the crystal quartz plate fluctuates. It is set so that the clock runs exactly at room temperature (about 25 °C). As the temperature deviates from this point, the oscillation frequency decreases and the watch lags (up to a few minutes per year). The more expensive models use a thermocompensated quartz, on which the error does not exceed a few seconds per year. Meanwhile, in smartphones and cars, clocks are corrected by precise time signals transmitted over the Internet, cellular networks, and radio.

Why does a giraffe need horns? Defending against predators with these horns is impossible: they are directed backwards, their ends are rounded and covered with skin and wool. Males use the horns for aggressive demonstrations and in ritual duels, but females never do that, although their horns are no less developed. The presence of horns in both sexes prevents them from being considered an ornament to attract sexual partners. So the mystery remains a mystery.