Why is the black box on an airplane called so, when it is actually painted orange?

Black boxes which usually hold the clues to a plane's crash, are built strong enough to survive bomb blasts, violent impacts and intense fires.  The black box records voice and flight data. The cockpit voice recorder continuously collects data. They are actually orange in color and a very high quality heat resistant paint is used, so that they can be spotted easily even at dimly lit crash sites. They are always placed in the tail end of the flight.

The term 'black box' is generally used to describe a thing/process which is not well understood by most people, but which produces something useful or well known. The term black box is used for the data recorder on airplane, in this context for similar reaso: the crash is the mystery process recorded by the black box - once you open up the black box, the process can be understood.

Why do bulls charge at red cloth?

Bulls are colour blind, so it's not the colour that attracts them, it is the swirling motion of the cape that agitates them. Bullfighters always use a red cape, but it is probably so the crowd can see it better. The color red really has no effect on a bull.

What is the use of gravel on railway tracks?

Gravel used on railway tracks is known as ballast. As rail tracks heats and cools, there is a lot of expansion and contraction, the ballast is there to hold the track from moving. Crushed rock works best as it has countless sharp edges form the broken rocks that actually dig into the sides and bottom of the ties and hold it in place. 

It is also used to dissipate the vibration produced by trains traveling at high speeds. In effect, the gravel layer acts as a cushion and damps the vibrations so that they do not travel long distances. If the rails are laid on a solid base, these vibrations can travel long distances and lead to cracks on the base as well as on nearby buildings.

Why do cut apples turn brown?

Apple is rich in iron. When an apple is uncut, the cells of apple are not exposed to the atmospheric oxygen and remain white. However, when it is cut, the iron particles in apple is oxidized by the oxygen in the atmosphere and hence turn brown.

Why are insects attracted towards lights?

Insect's attraction to artificial light is a cruel trick caused by our innovation moving faster than their evolution. Night flying insects evolved to navigate by the light of the moon. By keeping the moon's reflected light at a constant angle, the insects can maintain a steady flight path and a straight course. Artificial lights interfere with an insect's ability to detect the moonlight. They appear brighter, and radiate their light in multiple directions. The insect simply cannot keep the light source at a constant angle, as it does with the moon. It attempts to navigate a straight path, but ends up caught in an endless spiral dance around the bulb.

Why baldness pattern more common in men than women?

Baldness is related to the testosterone level which is naturally higher in males than in females. Baldness is caused by DHT, a testosterone derivative produced in the skin, and the degree of baldness depends on the hormon receptors present at the hair follicles. DHT tends to have a harmful impact on the hair follicles tending to slow down the hair regrowth process causing balding at a much earlier age in men than for women. 

Women do go bald, but that is more due to aging and or medical conditions.

Why do chefs wear tall hats?

The chef's hat is called a "toque blanche" (French for "white hat"). It is usually shortened to just "toque" . They are worn because the health department requires restaurant employees to wear a hat or hair restraint of some sort. This prevents hair from falling into the food. A hat also can absorb perspiration from the head before it reaches the plate. The tall hat allows room for air to circulate above the chef's head as well. he white hat has come to serve as a marker of a trained professional chef. The height of the hat represents the rank of the chef.

Why do the heels of feet crack?

The skin is normally dry and may have a thick callus which appears as yellow or dark brown discolored area of skin, especially along the inside border of the heel. The thickened dry skin around the heel that is more likely to crack is often due to mechanical factors that increase pressures in that area. 

Other factors that can be involved in the cause of cracked heels include:

 - prolonged standing

 - being overweight (this increases the pressure on the normal fat pad under the heel, causing it to expand sideways - if the skin is not supple and flexible, the pressures to 'crack' are high)

 - open back on the shoes (this allows the fat under the heel to expand sideways and increases the pressure to 'crack')

 - some medical conditions or skin conditions (eg psoriasis and eczema)

Why coastal areas are so humid?

Humidity is the presence of water vapor in the atmosphere. Due to day time heat in the sea, a lot of evaporation occurs on the surface of the water body. As humid air is heavier, it remains on the surface of the sea. During the day time, the land is warmer than the sea because of which the air is less dense in the land than at sea. Air moves from the region of higher density to a region of lower density and this causes the sea air to be blown towards the adjoining coastal regions thus bringing in a lot of water vapor and thereby increasing humidity.

Why does reading make some people sleepy?

It really depends on where your reading and what your reading.

Reading is action characterized by rhythmic eye movement, a relaxed physical position and a focused attention. When you’re in this state, your body becomes passive and your alertness decreases unless the topic that you’re reading requires you to use your mind like mathematical calculations, deductive thinking, reasoning etc. Reading is tiresome. When reading continuously, your body exerts a lot of energy from your eyes as magnetic waves. Mental work is three times more demanding than physical work.

Why do people have different blood groups?

Human blood types most likely came to exist to fend off infectious diseases. The reason individual humans have different blood types is that they inherit the trait of their blood having certain antigens on the outside of the blood cells from their parents. Antigens are molecules that trigger an immune response. 

Not all human blood types have always existed. In fact, they developed over time because of genetic changes and mutations. It's thought that type A is the oldest type of blood, which then mutated into type B about 3.5 million years ago. About a million years later, type O developed. Some people also have type AB blood, which has both A and B antigens. 

Red blood cells can have A or B antigens, or both A and B antigens, or neither. Blood with A antigens alone is classified as type A, while blood with only B antigens is type B. Blood with both A and B antigens is classified as type AB, and blood with neither antigen is type O. Type O blood is known as the "universal donor" and Type AB blood is likewise called the "universal recipient". 

What Do Astronauts Eat in Space?

The main challenge with eating and drinking in space is that there is no gravity. If you let go of a piece of food in a space craft, it will drift around, not falling to the floor. Water will not stay in a cup, it will float out and hang in the air. Food crumbs may float around the spacecraft causing harm to astronauts or the equipments.

Many types of space food are dehydrated, or freeze-dried, and sealed. When the astronaut is ready to eat the space food, he can add water to rehydrate the meal so that it will be edible. Space food is provided in disposable containers that can be attached to the astronaut's meal tray, which is strapped to his lap, so that the containers do not float freely through space. 

Astronauts expend a lot of energy and endure extreme stresses on their bodies. Their dietary requirements are therefore different from those of their gravity-bound counterparts on Earth. For example, they need extra calcium to compensate for bone loss.

Why do airplane seats have to be in an upright position during takeoff or landing?

Safety is the reason airplane seats must be upright for takeoff and landing. There are two main reasons why flight attendants pester people to keep those seats up—to keep injuries to a minimum during a crash and to clear the maximum amount of space for a quick exit. Since most aircraft emergencies occur during takeoff or landing, having the airplane seats up at this time is crucial. 

Why do some countries drive on the right and others on the left?

Which side of the road to drive on was decided long before the automobile. In the past, almost everybody traveled on the left side of the road because that was the most sensible option for feudal, violent societies. Since most people are right-handed, swordsmen preferred to keep to the left in order to have their right arm nearer to an opponent. Before automobiles, roads were meant for horse-drawn carriages. The coaches of these carriages have doors on the left side so they were driven on the left side so that alighting and embarking would be safer. During the time when the Horses were used to pull the Carriages the driver had to be situated on the right side of the carriage so that they won't hit their passengers on the rear when they use their whips. This technique was widely used in North America, and people may have started to naturally keep right because this was where the large carriages and wagons were, making riding on the opposite side rather dangerous. As postillion driving spread, more countries may have adopted the habit of keeping right for safety. No matter what side of the road one drives on, in most countries, cars are specifically engineered to drive on a specific side of the road. In countries with right side driving, the driver's seat is on the left, while left hand countries have drivers' seats on the right. In both cases, the seat positions the driver close to the middle of the road for better visibility. 

How many time-zones China has?

China is a vast country encompassing a geographic expanse of the equivalent of five time zones, yet it maintains only one time zone. This single time zone is China Standard Time, or Beijing Time, which is Greenwich Mean Time, plus 8 hours (GMT+8). China covers a range of 60 degrees longitude. It is traditional for every 15 degrees to be considered one time zone, with one-hour differentials. Northern China has an additional 15 degrees longitude, which accounts for the fifth time zone. 

The Chinese government promotes consistency, so the entire country has only one time zone. China does not observe daylight savings time. This can be inconvenient for the people living in the far eastern and western portions of the country as the sun rises and sets too early or too late.

Why does scratching gives releif to an itch?

Itching is an unpleasant sensation of damage to cells in our skin. As a result of the damage, substances like histamine are set free and irritate the nerve fibres in the skin. These send signals to the central nervous system which provokes an itch. Itch signals are received by the same part of the brain that receives pain signals. Scratching provides a "counterirritation" that distracts the brain from the original itch. Scratching interferes with the pain signals of itch by activating pain receptors in the same area where the itch occurred. However, the relief is usually temporary. Scratching sometimes releases pain-reducing endorphins. The pain neurons become temporarily overwhelmed, which masks the itching sensation and gives releif.

Why is the Hard Drive called "C" by default?

Originally, PCs had no hard drives.  Before bootable CD drives came along, floppy drives were provided with letters A and B. Now, either the bootable CD or floppy may take A. When The hard drive came along, and logically, its partition took the letter C. Hence default drive is called "C" by default.

Is Arithmetic and Mathematics different?

The most obvious difference is that arithmetic is all about numbers and mathematics is all about theory. Arithmetic is defined as the most basic and fundamental category of mathematics. It includes computations that involve adding, subtracting, dividing, and multiplying numbers that are real, rational, and complex. Mathematics involves studying numbers, shape, and quantity relationships. Mathematics also includes the use of not only signs and symbols, but also proofs.

How are seedless fruits and vegetables grown?

Seedless fruits and vegetables have been developed by scientists to improve existing varieties, to create new varieties and to meet consumer demands. 

Many plants put out what are known as runners or offsets. These shoots emerge from fully mature plants, and they are designed to spread the plant across a wider area. When a plant produces particularly tasty fruits and vegetables, these offsets can be encouraged to create a plantation which is actually just a series of clones from a single plant. It is also possible to grow seedless fruits through the use of cuttings, which produce clones of the parent tree. Cuttings are produced by snipping off sections of the plant and encouraging them to grow independently. Grafting can also be used to cultivate seedless crops. Grafting is a technique most notably used with fruit trees, in which a branch from one tree is cut and attached to another fruit tree. 

Why is 'money tree' plant called so?

The plant species that is employed for the money tree plant is the Pachira aquatica. It is a plant that is native in South America’s swamp lands. The concept of calling this plant a money tree caught on in Taiwan and  other Asian countries in 1980s.  The popularity of the money tree plant can be attributed to the belief that it brings good luck and fortune.

Do animals cry and shed tears?

All animals with mobile eyes are equipped with a tears system that keeps their eyes lubricated and protect their eyes. Tears serve to clean the cornea and keep it moist.

While animals do not cry in the way that humans do, they do produce tears. In animals, it is virtually impossible to tell if their tears are the result of emotions or merely caused by eye irritation. Most scientists agree, however, that humans are the only animals who produce emotional tears. Animals can suffer sadness etc., but most of them aren't capable of crying out of sadness like humans do.

How do pencil erasers work?

An eraser, called a rubber in some places, is an item used to remove the marks left by pencils and some types of pens.

A pencil mark consists of graphite particles that have peeled off from the pencil point onto the paper. Erasers pick up graphite particles, thus removing them from the surface of the paper. Basically, the molecules in erasers are 'stickier' than the paper, so when the eraser is rubbed onto the pencil mark, the graphite sticks to the eraser preferentially over the paper. A single rub using an eraser sufficiently soft to reach between the fibers will pick up most of the graphite particles. Looking at the eraser you can see undamaged graphite pieces sticking to the surface.

Where does magnetic compass point at north pole?

Magnetic compass is an instrument that uses a magnetic needle that points to the magnetic north. This instrument is used for navigation.

There are actually TWO North Poles - the one at the top of the earth (Physical North) and the other which is known as Magnetic North. Magnetic North is actually in northern Canada, and that is where compasses point to. If you were standing exactly on top of the magnetic north pole, your compass would point nowhere. The magnetic needle would spin or point in random direction because its natural inclination would be to move straight down.