Do you know why it does not pain cutting our nails?

Prof. Know Why answers:

In medical dictionary, nail is defined as “the horny epidermal derivative covering the dorsal aspect of the terminal phalanx of each finger and toe”. Well, in common man’s language, by fingernails and toenails, we understand hard scaley transparent structures that grow at the tip of our fingers and toes. Nails are part of our body. But the amazing thing is that it does not hurt when we cut them short, although it does not happen with other body parts (except hair).

A nail consists of:

• Eponychium or cuticle - the fold of skin at the proximal end of the nail.
• Paronychium - the fold of skin on the sides of the nail.
• Hyponychium - the attachment between the skin of the finger or toe and the distal end of the nail.
• Nail plate - the hard and translucent portion composed of keratin.
• Nail bed - the adherent connective tissue that underlies the nail.
• Lunula - the crescent shaped whitish area of the nail bed.
• Nail fold - a fold of hard skin overlapping the base and sides of a fingernail or toenail.

But, why it does not pain, cutting our nails? In common usage the word nail usually refers to the nail plate only. Nails are made of a tough protein called keratin and are produced from living skin cells in the fingers and toes. But they do not have nerve endings and pain receptors like the rest of our body. So the pain sensation does not reach our brain and we do not feel pain when they are cut.

But we do feel pain when a nail is plucked, because there are sensory nerves underlying the nail bed and pressure on it is transmitted to these nerves, which results in the sensation of pain. So as long as a nail is attached to the nail bed, harming or cutting it, creates pain. Actually it is the nail bed that causes the pain and not the nail. Thus, when we cut the tip of a nail, where it is detached from the nail bed, we are not hurt.

Usually, nails grow at an average rate of 0.03 centimeters a day (3 cm every 100 days). Fingernails require 3 to 6 months to re-grow completely. Toenails require 12 to 18 months. Precise growth rate of an individual is dependent on age, season, exercise level, and hereditary factors.

And, contrary to popular belief, nails do not continue to grow after death. Actually, the skin shrinks - giving the illusion that the nails grow.

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Do you know why we need to sleep?

Prof. Know Why answers:

There are conflicting theories about the “purpose of sleep” – that is, why do we need to sleep? But the fact that we spend about eight hours asleep of every 24 hours, suggests that there are powerful evolutionary reasons for its continuing existence. Most theories center on the beneficial effects that sleep has on the brain. This is because; there is little evidence of any direct physiological effects on the body. Some scientists believe that sleep is a time for the immune system to regenerate, while one theory suggests that sleep evolved as a way of coping with limited supplies of food.

The dominant theory is that sleep is a time for the brain to store memory. The idea is that during sleep the brain, in effect, goes offline to file the events of the day. Another theory is that the brain is a complex organ that needs the downtime provided by sleep to recover from the stresses of waking hours. “While we are awake, the higher centers of the brain are working flat out,” says Professor Jim Horne, who runs the sleep laboratory at Loughborough University. “Even when you are lying down, the brain is in a state of quiet readiness, ready to respond. The only time it can rest is during sleep.”

Neuroscientists argue that at least one vital function of sleep is bound up with learning and memory. A cascade of new findings, in animals and humans, suggest that sleep plays a critical role in flagging and storing important memories, both intellectual and physical, and perhaps in seeing subtle connections that were invisible during waking.

In a study which was published last year, the participants were given an exercise to study pairs of Easter eggs on a computer screen and memorize a day later, how the computer has arranged them. The researchers at Harvard and McGill Universities, who conducted the study, reported that participants who slept after playing this game scored significantly higher on a retest than those who did not sleep. While asleep they apparently figured out what they didn’t while awake - the structure of the simple hierarchy that linked the pairs.

“We think what’s happening during sleep is that you open the aperture of memory and are able to see this bigger picture,” said the study’s senior author, Matthew Walker, a neuroscientist who is now at the University of California, Berkeley. He added that many such insights occur “only when you enter this wonder-world of sleep”.

Researchers, who champion these brain theories, point to the fact that behavior changes significantly with sleeplessness. A person who is lacking sleep takes more risks, has slower mental processes and reacts to events with more emotion and less logic. One theory is that brain circuitry needs to be repaired and maintained regularly and that when this maintenance work is not carried out during sleep, the workings go awry, with communications slowing down or being wrongly routed, if you don’t get enough sleep.

So, how much sleep do you need? Some researches suggest that while seven to eight hours a night is healthy, under five hours or more than eight is unhealthy, and linked to disorders such as heart disease, depression, diabetes and high blood pressure.

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Do you know why the Great Wall of China was built?

Prof. Know Why answers:

The Great Wall of China is probably the China's best-known monument and one of its most popular tourist destinations. In 1987 it was designated a World Heritage Site by the United Nations Educational Scientific and Cultural Organization (UNESCO) and in 2007 it was elected one of the New 7 Wonders of the world.

Wonder! –It certainly is, stretching so many miles. But, contrary to the popular belief, the Great Wall of China is not a single, continuous structure. Rather, it consists of a network of walls with watch-towers at intervals that leave the frontier open in places. Estimates of the total length of the monument vary, depending on which sections are included and how they are measured. According to conservative estimates, the Great Wall of China is about 2,400 km long. While, other estimates cite a length of 6,400 km or even longer. From Hebei Province on the gulf of Bo Hai (a gulf of the Yellow Sea) in the east, the Great Wall of China stretches to Jiayuguan in Gansu Province in the west. The top of the walls have space, designed for soldiers to march. The Wall, at its most impressive site around Beijing, measures at least 7.6 m in height and up to 9 m in width, tapering from the base to the top. However, these dimensions vary greatly at other points.

But why was the Great Wall of China built? The natural answer that passes our mind at the first thought is protection or safe-guard from invaders and enemies. Well, that’s true! The Great Wall of China was the greatest manmade military defense structure in ancient China. The Great Wall was built mainly to protect China’s northern border from the Mongolians and other invaders.

But the Great Wall of China was not built at one time. It took several dynasties to complete the work. Based on the technology available at different dynasties, the Great Wall was usually built with local materials, mostly earth and stones. Natural terrain such as mountain ridges was often taken advantage of to form part of the wall.

There were two major periods of construction of the Great Wall, one during the Qin dynasty, and the second during the Ming dynasty. The construction first started more than 3000 years ago during the Warring States period, before China was unified. In 221 B.C., under the first emperor of China, Qin Shihuangdi, sections of earlier fortifications were joined together to form a united defense system against invasions from the north. It was called the “Chang Cheng” (long wall) of Shihuangdi. From then on, all successive Chinese dynasties had a hand in repairing, re-building, lengthening, modifying and preserving the Great Wall. The construction continued up to the Ming dynasty (1368–1644), when the Great Wall became the world's largest military structure. Most of the Great Wall that we see today was built in the Ming Dynasty.

There is a long-standing myth about the Great Wall of China that it is visible from outer space. But, actually, it is not visible with the naked eye from outer space. The astronauts have confirmed this. However, some of the wall is recognizable in special radar images, taken by satellites.

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Do you know why people are straight or gay?

Prof. Know Why answers:

There has always been a debate about the reasons of a person’s sexual orientation - Is sexual orientation something people are born with or a matter of choice? Well, in the latest study that is bound to re-ignite the debate, it is weighed more on the side of genetics.

So, why are people straight or gay? Researchers at McMaster University and Sunnybrook Health Sciences Centre in Toronto have found new evidence that shows that your genes are what make you straight or gay. Led by neuroscientist Sandra Witelson, the study scanned the brains of healthy, right-handed homosexual and heterosexual men using magnetic resonance imaging (MRI).

A decade back, Witelson had demonstrated that there are more left-handers in the homosexual population. Handedness is a sign of how the brain is organized to represent different aspects of intelligence. Language, for example, is usually on the left and music on the right. In other researches, Witelson had also found that left-handers have a larger posterior corpus callosum (the band of nerve fibres connecting the two hemispheres of the brain) than right-handers.

This raised the hypothesis for the current study - whether the anatomy of the brain of the sub-group of right-handed homosexual men is similar to that of left-handers. The researchers found that the posterior part of the corpus callosum is larger in homosexual than heterosexual men. As the size of the corpus callosum is largely inherited, it suggested a genetic factor in sexual orientation.

“Our results do not mean that heredity is destiny, but they do indicate that environment is not the only player in the field,” said Witelson. The finding may be one additional piece of information for individuals trying to determine their sexual orientation as “sometimes people aren't sure of their sexual orientation”, added Witelson.

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Do you know why we are humans?

Prof. Know Why answers:

This heading, “why we are humans” may sound weird, unless explained. There are so many different species living on earth, some, even being gigantic and physically immense powerful, but we, humans rule the planet Earth, in spite of being so tiny little beings! We have either tamed all the fierce and threatening species or put them in enclosures according to our whishes and requirements. And only we study them through various researches and it’s not the other way round. All these prove that we are the most powerful of the species. What makes us supreme? It’s sheer intelligence!

But why and how are we humans more intelligent than others? Researches have proved time and again, that it’s all in the brain. We humans have more advanced and bigger brain. When comparing different species, brain size does present a correlation with intelligence. For example the ratio of brain weight to body weight for fish is 1:5000; for reptiles it’s about 1:1500; for birds, 1:220; for most mammals, 1:180, and for humans, it’s 1:50. Modern studies among people, using brain scans have shown that brain size shows a rough correlation with IQ among adults of the same sex. The brain is also a metabolically expensive organ, and consumes about 25% of the body's energy.

Recently, scientists have identified a gene that controls the size of the brain, a finding that will give an insight into what it means to be human. The research team in Edinburgh has found that when the newly identified gene is faulty, the brain and body shrink as a result. Dr. Andrew Jackson and colleagues at the MRC Genome Damage and Stablity Centre studied families who have members with Seckel syndrome that retards growth in the womb, leading to short stature and a markedly reduced brain size (microcephaly).

The study noted that small brain size is linked to faults in a gene called PCNT. This gene works with another gene linked to the condition called ATR, which is again involved in DNA repair. The PCNT gene is responsible for the manufacture of a protein in the body called pericentrin, a component of the centrosome that is essential for the process of cell division that underpins growth. Other genes involved in the working of the centrosome have previously been found to be mutated in different forms of microcephaly, suggesting that it is essential for determining brain size.

So, it’s the size of the brain which is controlled by gene that makes us human, as larger brains and not bodies are associated with higher intelligence.

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Do you know why bats hang upside down?

Prof. Know Why answers:

There are nearly 1,000 species of bats, worldwide. They range from the tiny bumble-bee bats of Thailand, to the vulture size Fox bats. Their wingspans range from as short as 6 inches to as long as 6 feet in length. Their diet consists primarily of insects, though some species eat nectar and fruits. But, the vampire bats drink blood of other animals. And, remember for your general knowledge -bats are the only mammals that can fly.

The most amazing fact about the bats is that they spend most of their time by hanging upside down! Bats have special kind of feet joints that let them lock their feet in a tightly clasped position (without the use of any muscle), with the weight of the body keeping the foot locked. Bats roost this way by their hind feet. And special valves in their circulatory system keep blood from rushing to their heads as they hang upside down.

But why do the bats hang upside down? There are a few different reasons why bats roost this way. Bats have the ability to go into a form of hibernation at will. This is called torpor. When cold weather reduces feeding opportunities, the bats opt to sleep through the cold by hanging upside down. When a bat is in torpor, it uses little energy to maximize the use of its body fat for surviving through the cold period.

Again, hanging upside down is also a great way to hide from danger. During the day time when predators like “birds of prey” are active, bats huddle up at such secluded spots, like the roof of a cave, the underside of a bridge, the inside of a hollowed-out tree, etc, where enemies wouldn’t think to look or reach.. This allows them safety, until the night.

Another reason for hanging upside down is that it puts them in an ideal position for takeoff. Unlike birds, bats can't fly into the air from the ground. Their wings don't produce enough lift to take off from a dead stop, and their hind legs are so small and underdeveloped that they can't run to build up the necessary takeoff speed. So, they use their front claws to climb to a high spot, and then fall into a flight. By sleeping upside down in a high location, they stay ready to launch, if they need to escape the roost.

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Do you know why yawning is infectious?

Prof. Know Why answers:

Why is yawning infectious? First let’s see how we define a yawn. Yawning can be defined as a sudden, deep inhalation of air accompanied by an open mouth, tightened cheek muscles, eye closure, and tearing. Everybody yawns -from unborn babies to the oldest human being. Animals do it, too. And before you finish reading this, it's likely that you will end up yawning at least once, if not more. Why? I will come to that later.

But, why exactly do people and animals yawn? Science and researches haven’t yet reached a conclusion. But there are several theories or ideas about why people yawn. Here are the few most common theories. One theory says that our bodies induce yawning to draw in more oxygen or remove a build-up of carbon dioxide. According to another theory, which is also the most popular one, yawning is said to be caused by boredom, fatigue or drowsiness. Again there’s a theory which believes, yawning is a protective reflex to redistribute the oil-like substance called surfactant that helps in keeping lungs lubricated inside, saving them from collapsing. According to the evolution theory - yawning is something that began with our ancestors, who used yawning to show their teeth to intimidate others. An offshoot of this theory is the idea that yawning developed from early man, was a signal for others to change their activities.

But there is one idea about yawning that everyone knows to be true -yawning is contagious by nature. If you yawn in a meeting, you'll probably notice a few other people have started yawning, too. Even thinking about yawning can get you yawning. Scientists explain the "contagious" nature of yawning as, the power of suggestion, that is, when one person's yawn triggers another nearby to yawn.

How many times have you yawned while reading this article? Have I provoked a yawn out of you yet? If I have, it’s by the power of suggestion! Just as seeing or hearing someone else yawn makes you yawn, reading about yawning may also make you yawn. Honestly, even I have yawned a few times while writing this –such is the infectious nature of yawn!

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Do you know why does the wind blow?

Prof. Know Why answers:

What is wind? Why does the wind blow? How is wind different from air? Did any of these questions ever struck your mind? - If yes, just read on.

Wind is moving air and is caused by differences in air pressure within our atmosphere. Air, under high pressure, moves to the areas of low pressure. The greater the difference in pressure, the faster the air flows, and the stronger is the wind of that place. –That’s the simple explanation.

The atmosphere is composed of air which, is made up of tiny particles of different gases like nitrogen, hydrogen, oxygen, etc. The Sun shines on our atmosphere all the time. But, it heats the surface of the Earth unevenly. As a result, it’s warm in some places, while cold in other places. When air gets warmer, its particles spread out. This makes the air lighter, or less dense. So it rises. When air cools, it becomes heavier, or denser, and sinks. As warm air rises, air from cooler areas flows in to take the place of the heated air. This process is called convection and causes air to move. The differential heating of the Earth's surface and the resulting convection is what causes wind on this planet.

Have you ever wondered, how a hot air balloon floats in the air? Well, it applies the same science as that of the wind. Air is heated by a gas flame below the balloon. The air inside becomes hot and lighter or less dense than the cooler air outside the balloon. As the hot air rises, it carries the balloon upward. When the gas flame is turned down, the air cools and the balloon sinks back to the ground.

Wind also plays an important role in determining weather conditions.

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Do you know why flame is multicolored?

Prof. Know Why answers:

Flame color depends on several factors, mainly oxygen supply, generated heat, carbon particles and the burning material with the movement of electrons in the metal ions. Thus all flame colors are not the same and different flames have different colors, like the flame color of a candle is different from the flame colors of a burning wood or a gas burner.

Each flame is multicolored, being mostly blue at the bottom, then orange or yellow and finally black at the top. The blue color signifies the hottest temperature zone of any flame. Since fire needs oxygen to burn, and as the bottom of the flame does not get much oxygen, it is the hottest spot in the flame and is blue in color. The flame gradually cools and changes color as it moves away from its source, because it is exposed to more oxygen. The temperature change causes the color of the flame to turn from blue at the hottest lower portion, to the typical bright yellowish-orange or bright orange color at the upper part. The shade of orange at the upper portion of the flame (where the flame is the coolest) depends upon the material being burned. The product of the burnt carbon, when it has cooled, is black soot, and comprises the top part of the flame.

Now, if we get into a little bit of physics, we will understand the scientific reasoning behind the color of a flame. When a material is heated, the electrons gain energy and jump to a higher level. However, they jump back to their initial level to maintain the stability. For this, each of these electrons releases the excess energy. Each jump involves a specific amount of energy being released as light energy, and each corresponds to a particular color. As a result of all these jumps, a spectrum of colored lines is formed. The color you see is the combination of all these individual colors. The exact sizes of the possible jumps in terms of energy vary from one metal ion to another. This means each ion will have a different pattern of spectral lines, and thus a different flame color.

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Do you know why Eiffel Tower was built?

Prof. Know Why answers:

Eiffel Tower or “La Tour Eiffel” in French, situated in the city of Paris in France is one of the few greatest engineering amazements that the world has seen till date. It’s a beauty to watch the Eiffel Tower at night when it’s all illuminated with its lighting effects.

With a height of 324.00m (height with antenna) from the ground and 125m x 125m at the base, Eiffel Tower weighs about 10,000 tons (metal framework weight: 7,300 tons) in total. So what is this Eiffel Tower made up of and how was the foundation laid? Well, the foundation was constituted in stonework and is made of puddle iron. And, how much did it cost to build the Eiffel Tower? – A whopping 7,800,000 gold francs, way back in 1889. The tower was built by Gustave Eiffel, -the man behind the company “Gustave Eiffel & Cie” that got the contract.

Now let’s see, why was this huge structure which is one of the most desired tourist-spot in the world, was created! Eiffel Tower was built as the “theme structure” of the Universal Exposition of 1889, which was held in Paris. It was a huge international fair intended to show off France’s achievements to the world. There were dozens of other sculptures and buildings created also, but the Eiffel Tower was the only one to remain because the military discovered that it was a great antenna for the newly (then) invented technology of radio.

Today, the Eiffel Tower is one of the world's most recognized landmark and stands as an important symbol of Paris, of France, and of travel and exotic destinations in general.

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