Why does hair turn grey as we age?

Each hair on our heads is made up of two parts:

 -  shaft: the colored part we see growing out of our heads

 - root: the bottom part, which keeps the hair anchored under the scalp

The root of every strand of hair is surrounded by a tube of tissue under the skin that is called the hair follicle which contains a number of pigment cells. These pigment cells continuously produce a chemical called melanin which gives the growing shaft of hair its color of brown, blonde, red, and anything in between.

Hair turns gray as people age because the follicles at the base of the hair shaft cease to produce melanin. The darkness or lightness of the hair depends on how much melanin each strand contains. Genetics is the most common cause of gray hair, but other things can contribute to graying, including a poor nutrition.

Can birds fly backwards?

Most animals can walk backwards if they want to, even though they don’t choose to do it very often. There are a few birds who can move backwards in small amounts, but only hummingbird can actually fly backwards. 

The reason a hummingbird is so good at flying backwards (as well as sideways, up, down, or even just hovering in mid-air) is because of how they use their wings. While most birds flap their wings in an up-down fashion, hummingbirds use a stroke more similar to a circle made with a twisting motion. By using this special wing stroke and being able to fly so many ways, hummingbirds can successfully approach and feed from a flower in any number of directions!

What do B.C and A.D. (years) mean?

B.C. and A.D. are two abbreviations you usually see following years: 1,000 B.C., 1620 A.D., 2010 A.D.  Sometimes A.D. will come before the year: A.D. 400.

B.C. stands for "Before Christ".  Jesus Christ is the central figure of Christian religions. A.D. stands for the Latin term, "anno Domini" which means "in the year of the Lord". This term also refers to Jesus Christ. 1 A.D. was thought to be the year that he was born.  It was such an important and well-known event for Christians that it made sense as a starting point for a new calendar.  Any year before 1 A.D. is considered B.C.

Why do Analog Clocks show ten past ten (10:10) in advertising?

There are various speculations for setting the clock to ten past ten:

•  Clock and watch makers normally put their logo under the number 12. So placing the hands of the clock to 10 and 2, helps to frame and show the logo.
• Astrologers predicted that American President Mr. Abraham Lincon would die at the time of 10.15AM. So, entire Americans stopped their watches at 10.12AM 37sec in american clock tower. 
• 10:10 makes a resemblance to a smiley face and a "V" for victory.
• Clocks set on 10:10 time looks more symmetrical, therefore it is better for advertisement.
• In second world war American dropped their atom bomb on Hiroshima & Nagasaki . The first bomb was dropped at 10:10 AM. In remembrance of all the victims, all unused clocks or the clocks which are presented in show-cases have the same time of 10:10. 

Why do some people laugh when they are tickled?

When we are tickled by someone else, the sensation causes a form of anxiety or panic, as does not knowing where we will be touched or tickled next. Certain types of laughter stem from nervous reactions like anxiety and surprise. Hence, laughter is normally an involuntary, non-aggressive response in this situation. 

The surprise and tension happens when the tickler initially strikes and the laughter is an relief and reaction to that process. The reason we do not stop after the initial touch is because we do not know what is going to happen next, so the brain is tensed in anticipation of the tickler's next movement. Our body is actually in a state of panic & doesn't know what to do. The reason we squirm is because our body is trying to escape from whatever is tickling it, not knowing whether or not it is going to cause any harm. 

The reason we do not laugh when we tickle ourselves is because the brain is already aware of what is going to happen and where, thus there is no surprise and no need for tension.

Why Do Birds Fly in V-Formation?

The most accepted reason is that the flight formation plays an aerodynamic role. It conserves the energy of birds. Each bird flies slightly above the bird in front of him, resulting in a reduction of wind resistance. The birds take turns being in the front, falling back when they get tired. In this way, the birds can fly for a long time before they must stop for rest especially during migration. This formation also enables visual communication among members of the flock and reduces the possibility of collisions and of birds becoming separated from the flock. 

Why do stars twinkle?

We see the stars through the atmosphere. Their light passes through millions of miles of constantly moving pockets and streams of air, which distort the image of the stars. Even though many stars are much larger than planets, they're so far away from us that they seem smaller, like tiny dots. The distortions make it seem as if the shining lights are moving or blinking. Stars twinkle when we see them from the Earth's surface because we are viewing them through thick layers of turbulent (moving) air in the Earth's atmosphere. In outer space, where there is no atmosphere, stars don't twinkle.

Why are most people right-handed?

Handedness is the idea that one hand is better able to perform certain tasks than the other. The most common answer for people being right-handed is that handedness is determined by the structure of our brains, which are divided into two hemispheres. One theory suggests that it's more efficient for the brain to cluster control of these two major tasks in one hemisphere rather than having it spread throughout the brain. Since the vast majority of people have their language functions centered in the left hemisphere, it follows that most people's fine motor skills would be controlled by the left hemisphere too. Each hemisphere generally controls the opposite side of the body, so the end result is that most people are right-handed. In humans, the hemispheres tend to specialize: Nearly all righties process language in the left side of the brain, while many lefties process language on the right. Aga, thisis just a proposed theory, the reasons still being explored. :)

How are diamonds formed?

Diamonds are made of carbon. All carbon containing minerals do not turn into diamond. Diamonds were formed in the earth thousands of years ago under extreme heat and pressure. This extreme heat and pressure in the earth transformed the carbon into crystals and turned it colorless. Although diamonds formed deep in the earth, volcanic activity is what brought them to the surface. 

Most diamonds discovered on the surface in mining operations are at least one billion years old. When minerals mix with diamond in nature, it gives the diamond color. The raw diamond goes through a process of exploration, discovery and then cutting and polishing to appear in the shining state as seen in jewellery.

What is the difference between bacteria and virus?

Bacteria are tiny, one-celled living organisms that can only be seen with a microscope. They live and breed in warm, moist environments in the body and elsewhere, growing quickly and causing infection. They can reproduce independently, and inhabit virtually every environment on earth, including soil, water, hot springs, ice packs, and the bodies of plants and animals. Viruses are tiny geometric structures and cannot be seen with a microscope. They grow inside the body and produce toxins (poisons) that can cause rashes, aches and fevers. 

Bacteria carry all the machinery needed for their growth and multiplication, while Viruses carry mainly information. Viruses are not truly "living," but are essentially information that float around until they encounter a suitable living host. Outside of a living cell, a virus is dormant, but once inside, it takes over the resources of the host cell and begins the production of more virus particles. 

Why do I feel dizzy when I spin?

Within your inner ear you have a small organ system called the vestibular system. This system is basically made up of three tubular circles that contain fluid. The liquid moves when you move, telling your brain what position your body is in. When you spin, the liquid also spins and gains momentum. The liquid continues to spin after you stop. Imagine stirring a cup of coffee for a while - even when you stop stirring, the coffee keeps swirling around in the mug.

So while the fluid in our vestibular system keeps spinning, we keep on getting messages telling us we’re still turning around. Our eyes are trying to adjust for this movement but can’t, and are simultaneously noticing that actually, we’re standing (more or less) still. All these confusing and conflicting messages cause our muscles to move us off balance and our vision to get very mixed up - the combination of which gives us the feeling we know as dizziness! Your brain thinks you’re still spinning, so you continue to feel that everything is going in circles-until the liquid stops moving.

How is blood formed?

Blood consists of two basic components: the cellular components or the red and white blood cells. They are made in the bone marrow(a tissue in the central cavity inside almost all of the bones in the body) and some white cells in the lymph nodes. The bone marrow releases about 10-15 million red blood cells per second.  In children, the marrow of most of the bones produces blood. But in adults, only the marrow of certain bones -- the spine, ribs, pelvis, and some others -- continues to make blood. The other component is the watery part is the blood plasma and contains all the hormones, the water, the sugars, dissolved blood gasses, plasma proteins made in the bone marrow and liver and a host of other substances.

Red blood cells carry oxygen from the lungs to the tissues and carbon dioxide from the tissue to the lungs. Blood plasma transports antibodies, which protect the body from infection, carries food substances absorbed from the intestines and takes waste products to the kidneys for excretion. It also transports hormones, secreted by endocrine glands, to their sites of action.

Why do we cry when we are sad, angry or happy?

We have tear ducts to lubricate and protect our eyes from dust and other particles. The ducts are under the upper eyelids and produce a salty liquid(a tear)that gets spread throughout the eye after each blink. Three types of tears are generated by the human eye. Basal tears are very necessary as they keep the eyes well lubricated. Reflex tears flush out the eye when it becomes irritated. And emotional tears flow in response to sadness, distress, or physical pain.

People cry when they are feeling emotions that are beyond words. The emotion being felt can be extreme sadness, happiness, anger, frustration, resentment etc. When people are mildly happy or mildly sad, they don't usually cry. It's not WHICH emotion the person is feeling that causes crying, it's the LEVEL of emotion being felt that causes it. Emotional tears contain more manganese, an element that affects temperament, and more prolactin, a hormone that regulates milk production. Sobbing out manganese and prolactin is thought to relieve tension by balancing the body’s stress levels and eliminating build ups of the chemicals, making the crier feel better.

Why doesn't glue stick to its bottle?

Most glue in bottles consists of two components, some synthetic chemicals called polymers and a solvent that prevents the glue from drying or sticking. When glue is used to join two things together, the water in the glue evaporates, allowing the polymers to bond the items glued together. 

If we keep the glue bottle tightly closed, there is very little air captured in the bottle. Hence a very minute amount of water in the glue evaporates, which is not enough to dry up the whole bottle. The air in the bottle is usually insufficient for enough solvent to evaporate and dry out the complete glue. Hence glue bottles are recommended to be tightly closed. This is why, sometimes, a nearly-empty glue bottle might dry up. 

What are coral reefs and how are they formed?

Corals are small colony-forming marine invertebrate animals. Coral colonies are composed of these tiny, cup-shaped animals called polyps, which are related to jellyfish. Corals begin life in tropical waters as free-floating larvae. After a relatively short period of time, the larva eventually attaches itself to a hard surface and becomes a polyp. Polyps divide and form colonies.
Corals extract calcium and carbonate from seawater to build an inner skeleton that is external to the coral. This external skeleton lies underneath a thin layer of tissue. Over the years millions of coral polyps in colonies create the framework of the coral reef. Coral reefs grow very slowly.  These coral reef are very colourful and attractive. The colour, shape ordesign of coral reefs vary according to the coral-genus that produce the reef.
Deepwater and shallow water coral reef communities are rich in diversity and provide habitat for many species.

What causes waves?

The winds cause waves on the surface of the ocean (and on lakes). Winds blowing across the surface of the ocean push water through the friction forces and build up energy. Stronger winds (like storm surges) cause larger waves. As the wind blows over the water, it tries to drag the surface of the water with it. The surface water cannot move as fast as air, so the water rises. After it rises, the water is pulled back down by gravity. The falling water's momentum is carried below the surface, and water pressure from below pushes this swell back up again. This tug of war between gravity and water pressure creates wave motion.

As a wave approaches shore, friction between the bottom of the wave and the seafloor affects the wave's motion. The lower portion of the wave slows, while the upper portion continues to travel at the wave's speed in deep water. The wave rises with the slope of the sea bottom. Because the wave's top moves faster than its bottom, it begins to curl, break and collapse. Waves can travel thousands of miles from their sources of origin. But it's the wave energy that moves, not the water.

Waves are also caused sometimes by disturbances in sea by earthquake, volacnoes etc.

Why does coke fizz when you open a new bottle or shake it?

The key ingredient of coke or any other similar product is soda, which contains carbon dioxide (CO2). When Coke is purchased in a bottles, the drink is actually under very high pressure to keep the CO2 gas in a stable, liquid state. So, bubbles and fizz cannot be seen inside an unopened Coke bottle. Opening the bottle releases this pressutre and Co2 gas starts escaping, which causes the fizz.

When you shake a can, the carbon dioxide at the top of the can is spread throughout the liquid. Most of the air makes its way to the top of the can quickly, but some become bubbles that can stick to the sides and bottom of the can for a time. These bubbles can't escape when the can is opened, but the pressure is still there. So, instead of a pop of air escaping from the opened can, the pressure is relieved by the release of a burst of liquid.

Why is "I" always written with a capital letter?

Modern English ultimately derives from Old English, which is a Germanic language. Up until the 14th century, the first person pronoun in English was ich. When the old English "Ich" (like in German) became reduced to "i" it was thought to be too small and insignificant to be a real word and could easily get attached to the end or beginning of another word. So, "i" was capitalized to "I" to avoid misreading handwritten manuscripts. And now it is a grammar rule.

Why is it hot in summer and cold in winter?

This behavior is primarily because the earth's axis is tilted.

The earth revolves around the sun and completes one revolution each year, This causes various seasons. The earth is tilted on its axis, and in summer in the northern hemisphere, the northern hemisphere is tilted toward the sun. This makes the days longer, but more importantly, the suns rays hit the earth in the northern hemisphere more directly and therefore are more intense. This makes it warmer. 

When it's summer in the northern hemisphere, the southern hemisphere is tilted away from the summer, and it is winter there.During the summer, the sun's rays hit the Earth at a steep angle. The light does not spread out as much, thus increasing the amount of energy hitting any given spot. Also, the long daylight hours allow the Earth plenty of time to reach warm temperatures. During the winter, the sun's rays hit the Earth at a shallow angle. These rays are more spread out, which minimizes the amount of energy that hits any given spot. Also, the long nights and short days prevent the Earth from warming up. 

Do people who were born blind, see visuals in their dreams?

People who were born blind never saw anything, hence they wouldn't see dreams. They do not retain visual imagery because it was never acquired in the first place.  Dreams are not only visual in nature, its an amalgamation of one's senses. Blind people have heightened senses of hearing, touch, smell, and taste, because of their lack of sight. Their dreams are based around the senses they use most often, just as people with sight have dreams based on their sight (because we use that sense most often).  

Our dreams reflect our waking life experiences - conscious and unconscious. If someone has been totally blind since birth, they may only have auditory dreams. People whose vision has been blurred from birth dream of blurred images, people who have been deaf from birth do not hear in their dreams, and the colourblind are equally colourblind in their dreams.

How many senses do sharks have?

Sharks have 8 unique senses. They are hearing, smell, lateral line, pit organs, vision, Lorenzini, touch, and taste. The shark shares many sense that humans do such as taste and smell, but it has three senses that we do not have. The lateral line, pit organs and Lorenzini are senses that have been discovered over the past 10 to 20 years, and play an important role in how the shark functions when swimming around.

The six senses which shark use very effectively for searching and hunting their prey are - Smell, Eyesight, Electrosense, Water Pressure, Hearing and Taste. Two thirds of a shark’s brain is devoted to smell.  It can detect one drop of blood in a million drops of water, 1/4th of a mile away.  Water continually flows through their nostrils, giving them olfactory information. Sharks have colour vision and see well in dim light (because of a mirror-like layer in the back of the eye.) It is thought that sharks use the ampullae of Lorenzini as a navigational device to swim by the earth’s magnetic field. The lateral line is a sense organ used to detect movement and vibration in the surrounding water. The pit organs are used to sense temperature change.

Why do people need to sleep?

Sleep is vital to every mammal, bird, reptile, amphibian and fish on the planet. Scientists have explored the question of why we sleep from many different angles. Various reasons thought of are:

1 - Sleep enables the body to rest; in contrast to the highly active anabolic state that dominates during waking hours. It helps replenish fuel, which is burned while awake

2 - The primary function of sleep is to reduce an individual’s energy demand and expenditure

3 - During sleep, the body has a chance to clear adenosine (which is responsible for feeling of tiredness) from the system, and, as a result, we feel more alert when we wake up.

4 - Humans sleep to dream. Dreams allow the mind to file away important memories (including new skills) and discard unwanted information at the end of a busy day. Sleep might also be a time for your brain to do a little housekeeping.

5 -  Inactivity at night is an adaptation that served a survival function by keeping organisms out of harm’s way at times when they would be particularly vulnerable.

6 - Sleeping protects all animals from attack during the night, because they sleep in a safe, dark place out of reach from predators.

7- Sleep helps the body to heal, by dedicating energy to repairing the immune and nervous systems

The real reason for sleep could be any combination of these ideas :)

How Do Fish Get Their Oxygen?

Fish have gills. The gills work exactly the way human lungs work, except that oxygen is absorbed from water instead of air. When a fish opens and closes its mouth, it is actually pumping water back through the gills and is thus breathing. The fish allows water which contains dissolved oxygen, to pass into its mouth and over its gills. These are rich in blood vessels and also have a large surface area. The oxygen from the water passes into the blood of the fish by diffusion, and waste carbon dioxide passes out the same way.

As long as there is plenty of oxygen dissolved in the water, the fish can extract enough through its gills to gain enough oxygen for cellular respiration. Fish do get in trouble if the oxygen content of the water falls. When fishes are taken out of water, they suffocate, because their gills collapse and they are unable to absorb oxygen.

What causes hiccups?

A hiccup is an involuntary action involving a reflex arc over which we have no control. Hiccups are caused by a spasm in the diaphragm.The diaphragm is the muscle that separates the chest from the abdomen and has a key function in breathing.

The diaphragm almost always works perfectly. When you inhale, it pulls down to help pull air into the lungs. When you exhale, the diaphragm relaxes and air flows out of the lungs back out through the nose and mouth. But sometimes the diaphragm becomes irritated. When this happens, it pulls down in a jerky way, which makes you suck air into your throat suddenly. The sudden rush of air into the lungs causes the epiglottis to close, creating that hic sound.

How is bulletproof glass made bulletproof?

Bulletproof glass is a type of glass that is resistant to being struck by bullets. The correct term for "bulletproof" glass is bullet resistant. Basically it is layering of a polycarbonate material (usually consisting of products such as Armormax, Makroclear, Cyrolon, Lexan or Tuffak) between pieces of ordinary glass in a process called lamination. This process creates a glass-like material that is thicker than normal glass. The strength and durability of bullet-resistant glass depends on how it is made and the thickness of the final product. 

The use of plastic in the laminate provides impact-resistance. A bullet fired at a sheet of bullet-resistant glass will pierce the outside layer of the glass, but the layered polycarbonate-glass material is able to absorb the bullet's energy.  The ability of bullet-resistant glass to stop a bullet is determined by the thickness of the glass. A rifle bullet will collide with the glass with a lot more force than a bullet from a handgun, so a thicker piece of bullet-resistant glass would be needed to stop a rifle bullet as opposed to a handgun bullet.