How it happens !
 

[CENTER][B]Why Lips Are Red?[/B][/CENTER]

Did you know that the outline or the border of your lips (called the vermillion border) is a special feature of humans only? This transition line from your skin to the pinkish-red part of your lips is found only in humans—no one knows why.

The lips appear red because of the underlying blood vessels. Arteries are blood vessels that carry blood back to the heart. The arteries and veins are connected through a series of blood vessels called the capillaries.

These red-colored blood filled capillaries are close to the thin skin on your lips, so your lips appear red.


[B][CENTER]How Does the Brain Memorize Information?[/CENTER][/B]

Memory is an associative brain function, meaning a function in which one object is associated with another by a relationship. Everything we experience is stored in the brain subconsciously, but storing information is not the problem that most of us have, retaining it, in a way that we can recall it is. The more association one has with a memory or experience the easier it is to retrieve.

The brain stores information and experiences like a computer, first it encodes the information, that it stores it in a place for retrieval at a later time. But just as a computer needs its brain defrag, meaning to bring like, and associated things together, so does the human brain.

Naturally the brain stores information based on association. In the short term memory things are based on the current experience and our senses. What we see, hear, smell, taste, and feel. If this information is used once and never recalled again, it is discarded, like a phone number we just got from 411. If this information is recalled frequently it is than processed into the long-term memory.

Information in the short term memory only last a few seconds and decays to make room for new information. So I guess it may be safe to say that short-term memory is not for memory at all, but simply information. Information we are currently experiencing, long enough to experience the moment.

But if there is an association to that information based on a previous experience that information is than placed in the long-term memory right along with that previous experience. If it is a new memory, it will be easier to recall it once it is recalled a few times, which creates new information to be stores with this new long term memory.

[B]Why do we have eyebrows?[/B]

Eyebrows are a very significant aspect of our appearance. They are one of the most distinctive features that make up our faces, and we pay a lot of attention to them. We think of some types of eyebrows as attractive and some as unattractive, and many people spend as much time preening their eyebrows as they do applying makeup to their eyelashes or lips. Eyebrows are also one of our most expressive facial features. One of the clearest ways to tell somebody what you're thinking is to simply move your eyebrows up or down -- we all know what different eyebrow positions mean.

So, eyebrows obviously serve a lot of functions in our culture today -- beauty, nonverbal communication, distinctive appearance. But why are they there in the first place? As we evolved and lost most of the thick hair on our bodies, why did we keep that little bit over the eyes?
Scientists aren't entirely sure why we kept this hair, but they have a pretty good guess. We know that eyebrows help keep moisture out of our eyes when we sweat or walk around in the rain. The arch shape diverts the rain or sweat around to the sides of our face, keeping our eyes relatively dry. The most obvious advantage of this is that it lets us see clearly when we're sweating a lot or out in the rain. Without eyebrows, getting around in these conditions is a little more difficult. The shape of your brow itself diverts a certain amount of moisture, but eyebrows make a significant difference in your ability to see. Diverting the sweat away is also good because the salt in sweat irritates the eyes, making them sting a little.


Regards

Can Fish Hear?
 

Fish don't have ears that we can see, but they do have ear parts inside their heads. They pick up sounds in the water through their bodies and in the ear, according to the National Wildlife Federation.

A fish also senses movement in the water with the lateral lines that runs down each side of its body. Sharks, which are fish, have a keen ability to sense electricity. Oddly the genes that contribute to this ability are responsible for the head and facial features in humans, linking sharks and humans to a common ancestor way back in time.

[B][U]Human ears, interestingly, evolved from fish gills.[/U][/B].....:blink:

Your ability to hear relies on a structure that got its start as a gill opening in fish, a new study reveals.

Humans and other land animals have special bones in their ears that are crucial to hearing. Ancient fish used similar structures to breathe underwater.

Scientists had thought the evolutionary change occurred after animals had established themselves on land, but a new look at an old fossil suggests ear development was set into motion before any creatures crawled out of the water.

[B]The transition[/B]

Researchers examined the ear bones of a close cousin of the first land animals, a 370-million-year-old fossil fish called Panderichthys. They compared these structures to those of another lobe-finned fish and to an early land animal and determined that Panderichthys displays a transitional form.

In the other fish, Eusthenopteron, a small bone called the hyomandibula developed a kink and obstructed the gill opening, called a spiracle.

However, in early land animals such as the tetrapod Acanthostega, this bone has receded, creating a larger cavity in what is now part of the middle ear in humans and other animals.

[B]Missing link[/B]

The new examination of the Panderichthys fossil provides scientists with a critical "missing link" between fish gill openings and ears.

"In Panderichthys, it is much more like in tetrapods where there is no longer such a 'kink' and the spiracle has widened and opened up," study co-author Martin Brazeau of Uppsala University in Sweden told LiveScience. "[The hyomandibula] is quite a bit shorter, but still fairly rod-like like in Eusthenopteron. It's like a combination of fish and tetrapods."

However, it's unclear if early tetrapods used these structures to hear. Panderichthys most likely used their spiracles for ventilation of either water or air. Early tetrapods probably passed air through the opening. Scientists would need preserved soft tissue to say for sure.

"That's the question that we're starting to investigate, whether early tetrapods used it for some ventilation function as well," Brazeau said. Whether it was for the exhalation of water or air, it's not really clear. We can infer that it's quite expanded and improved from fish."

[I]This research is detailed in the Jan. 19 issue of the journal Nature.[/I]

[SIZE="4"][B]Why do we yawn when we see others yawning???[/B][/SIZE]
No one really knows why we yawn, maybe it has some useful purpose - it does allow us to take in more oxygen and expel carbon dioxide, it also increases heart rate a bit. Yawning could keep the brain aroused in situations where sleep is unwanted - like first period maths lessons or 9 am meetings.

Why we yawn when we see others yawning has baffled scientists for ages and a number of suggestions have been put forward to explain this phenomenon. What we do know is that yawning is an involuntary action - our brain does it without us thinking about it. Even very young babies yawn, showing that it's a built in action (Chimps do it too by the way). Just thinking about yawning can trigger the bit of the brain that causes a yawn and, chances are, when reading this, you will end up yawning at least once!

My favorite explanation for why we yawn when we see others yawn is that it's a throw back to the days of our ancestors, when we lived in groups. Yawning could have been a sign that it was time for the group to go to sleep or change activities. It's important, after all, that all group members were ready to do the same thing at the same time.

It appears that there is some relationship between yawning and our ability to 'put ourselves in other peoples shoes'. Not all people can 'catch' a yawn when they see someone else yawning and these people also appear to be less able to understand things from other people's points of view. This is an important skill for being able to get along with other people - it lets you sympathize with them and understand how they feel. So yawning is maybe just a by-product of us being able to use our own experience to understand how others are feeling. Maybe it's due to accidental 'cross-wiring' in the brain that occurs when the 'thinking about others' part of the brain is stimulated or could serve some other purpose that no one knows yet.

Another theory is that yawning is a way of baring our teeth at potential enemies - something along the lines of "I may be sleepy but you'd be stupid to attack me - just look at my vicious teeth!". Could it be that the reason a yawn is contagious is that a whole group of sleepy primates showing teeth together is less likely to be the target of a predator?

How Identity Theft Happens
 

How Identity Theft Happens

At the core, identity theft and credit card fraud are both results of the same actions. It starts when a criminal gains access to your personal information. That information includes your full name, date of birth, Social Security Number, address, telephone number, and the names of your family including parents and children.
In today’s world, a lot of that information can be gained with little more than digging through your trash and even engaging you in conversation in the grocery store line. For example, identity thieves will go through your trash and gather credit card statements, bank statements, and personal correspondence. This documents usually contain nearly everything they need.

To get the last few bits of information, a conversation at the grocery store or even a telephone call to your home usually works. These criminals are great con artists. They know what questions to ask and how to phrase those questions to get you to spill your guts. Before you know it, you’ve told someone you don’t even know your whole life story.

After that, all that’s left is to begin the process of creating another you on paper. They create new accounts, order copies of your Social Security card and birth certificate, and secure a new job in another state. And it’s done. Someone else who looks nothing like in you in real life is your exact duplicate in the paper and cyber world.

Of course, that’s not the only way to get your information. Phishing emails, spoofed web sites, telephone surveys, and even old-fashioned breaking and entering or purse/wallet snatching are also methods that identity thieves use. Even your medical records and employee records at your place of employment put you at risk.

Most concerning is the places that aren’t obvious where your identity can be snatched without notice. Remember the news anchor from Nashville? After a lot of investigating on his own, he eventually learned that his identity had been stolen when he applied for a private pilot’s license.

Others have learned that family or friends sold their identifying information. And many never figure out what happened. The one consistent factor in every case of identity theft is that it happens when you least expect it, usually in a place where you feel safe.:ph34r: :ph34r: :ph34r:

What is the urban heat island effect?
 

How it Happens: The Physics Behind the Urban Heat Island Effect

To understand the urban heat island effect, we first need to understand a few simple rules of physics. Most importantly, we should understand that objects can absorb and reflect light. In fact, the color of an object depends on what kind of light it reflects. For example, a green object reflects green light and absorbs all the other visible colors of light. When we see a green object, we perceive it as green because it reflects the green wavelength of color back to our eyes. Darker colored objects are excellent absorbers of light. In fact, black surfaces absorb almost all light. On the other hand, lighter colored surfaces do not absorb much light at all -- rather they reflect almost all of it.
So what does the absorption of light have to do with heat? When an object absorbs light, it converts that light to thermal energy, and emits it back out as heat. So, because black objects absorb more light, they also emit more heat. That's why wearing a black shirt on a hot, sunny day will only make you hotter. The black shirt absorbs light and emits it as heat onto your skin. Wearing a white shirt, on the other hand, will help reflect the sunlight and keep you cooler.

The rate at which an object can reflect solar radiation is called its albedo [source: Budikova]. The bigger the albedo something has, the better it reflects radiation. Traditional asphalt has a low albedo, which means it reflects radiation poorly and instead absorbs it.

When we build and expand cities, we tend to erect buildings with dark surfaces and lay down asphalt pavement. The buildings and the pavement absorb a significant amount of light and radiation and emit it as heat, warming the city. Because more than half of the surfaces in cities are man-made, cities heat up more than rural areas, where structures are less concentrated [source: EPA]. This heat absorption is why the temperature difference between cities and rural areas is highest a few hours after sunset. Cities hold on to more heat for a longer period of time than rural areas do [source: EPA].
But that's not the only thing that causes the urban heat island effect. Scientists believe that vegetation plays a large part in keeping an area cool through a process called evaporative cooling. Evaporation is when liquid turns into gas. Plants take in water through their roots and depend on it to live. But after the plant is done with it, dry air absorbs that water by turning it into gaseous water vapor. The air provides the heat that drives this process, so during the process, the air loses heat and becomes cooler. We experience the same type of thing when we sweat -- when air hits your sweaty skin, it absorbs the moisture and cools the air around you [source: Asimakopoulos]. Because building a city means replacing vegetation with structures, the city loses the evaporative cooling advantages of vegetation.

Other factors also contribute to the effect. For instance, cars and air conditioners, which are ubiquitous in urban areas, convert energy to heat and release this heat into the air.

Now that we know what's causing this phenomenon, let's learn the steps to reduce it.

Techniques to Reduce the Urban Heat Island Effect

Luckily, since we know what causes the urban heat island effect, we can control it to a significant extent. Certain techniques reduce the demand for air conditioning and reduce energy bills.

Because the dark surfaces and low albedo of urban structures heat the area, the logical solution would be to reverse this trend. Urban planners may do this by painting structures white, or other light colors. This basic technique goes a long way in reversing the urban heat island effect.[
QUOTE]The Hypothetical Little Black Dress of Physics
To talk about the movement of heat and energy, scientists use a theoretical object that is a perfect absorber (and hence perfect emitter) of heat and energy. They call this a blackbody because it absorbs all light and would appear completely black to us. It is one of the fundamental tools for students of thermodynamics.[/QUOTE]

Solar eclipse: how it happens
 

Solar eclipse: how it happens

The solar eclipse that plunged Asia into darkness for over six minutes this morning brought stargazers flocking from around the world. Here's how it happened.


By Heidi Blake
Published: 12:00PM BST 21 Jul 2009

[IMG]http://i.telegraph.co.uk/telegraph/multimedia/archive/01447/Untitled-1_1447206c.jpg[/IMG]
During an eclipse, only the solar corona is visible: a much fainter white ring 600,000 miles from the Sun's surface Photo: GETTY

A total solar eclipse occurs when the Moon passes between the Earth and the Sun during New Moon, replacing the intensely bright solar disk with a lunar silhouette. Though New Moon occurs every 29 and a half days, eclipses only occur when the angle of the Moon is such that it obscures part or all of the Sun.

This morning's eclipse was part of series 136 in the Saros cycle, which governs the recurrence of eclipses over periods of around 6,585 days.
Only the solar corona was visible during the eclipse: a much fainter white ring 600,000 miles from the Sun's surface.

Between two and five solar eclipses occur each year across the world, with each existing only along a narrow corridor in the relatively small area of the Moon's shadow.

Although they occur somewhere on Earth around every 18 months, it has been estimated that total eclipses recur at any given place only once every 370 years on average.

During this morning's eclipse, the Moon's shadow moved from west to east across the Earth at over 1500mph.

Its exceptional duration of six minutes and 39 seconds at its maximum point was a result of the Moon being near perigee – its closest position to the earth.

It is impossible for an eclipse to last more than seven minutes and 40 seconds at its maximum point, and is usually much shorter: during each millennium there are typically fewer than 10 total solar eclipses exceeding seven minutes. The last was in 1973.

The longest total solar eclipse during the 8,000-year period from 3000BC to 5000AD will occur on July 16, 2186, when "totality" will last seven minutes and 29 seconds.

Due to tidal acceleration, the orbit of the Moon around the Earth becomes approximately 3.8cm more distant each year. It is estimated that in 600 million years, the distance from the Earth to the Moon will have increased by 23,500km, meaning that total eclipses will no longer be possible.

[B][CENTER][SIZE="5"]How do we see our dreams?[/SIZE][/CENTER][/B]

neurologicals says:

According to the biological approach, our dreams are a result of random neurons firing in our brain. You see when you're asleep your brain sorts out the information you gained during the day. As it is doing this neurons from that day and your past memories and experiences are fired and randomly collide, resulting in the dreams that you see. This is why sometimes dreams don't make any sense at all! This is also why experts insist on the fact that sleep is very very important.

Psychologicals says:

According to Freud and the psychodynamic approach, people have repressed thoughts and feelings in their subconscious which we do not have any conscious access to. You see we have 3 parts in our personality, the Id, the ego and the superego. The Id is the child in us, it is the part of you that always says "I want I want" this part of you doesnt care about consequences. The superego is the voice that tells you not to do something because it is wrong. The superego, is your morals, rules, integrity and so on. Now the ego is what creates a balance between your Id and your superego. When they are in conflict the ego just takes the "issue" represses it in your unconscious mind.

Moving on...Dreams are referred to as the royal pathway to our unconscious. Because it is through dreams that our unconscious tries to give us a message about what is repressed. You see our body is clever, because what is repressed is usually unaccepted it stores it away to protect us (however this produces negative energy and affects your life without you being aware of this...for example, maybe you have an unreasonable fear of brushing your teeth).

Anyway, in our dreams, symbols are used to protect us from the truth. Each and every person uses their OWN and personal symbols, so if I see a snake it can mean something good but if YOU see a snake it can be something bad. Therefore in order to analyze your dreams, you try and see what these symbols are and what they mean to you...We dream because our subconscious is sending us messages about what is affecting us and what we need to deal with...

[QUOTE=Qaiserks]Very interesting & useful sharing by all the members.

Here I want to ask that [B]"Why our mouth opens when we yawn?"[/B]

Plz someone must reply.



[B]BR[/B][/QUOTE]
[B][CENTER][SIZE="3"]Why do we open our mouths to yawn properly?[/SIZE][/CENTER][/B]
The involuntary act of yawning usually includes opening the mouth very wide while slowly taking in a deep breath. This contortion of the mouth puts pressure on the salivary glands causing the eyes to sometimes tear-up, causes the throat to better open, and tightens the muscles around the mouth making sure the yawn is better accomplished.

[COLOR="Indigo"]A yawn is a reflex of simultaneous inhalation of air and stretching of the eardrums, followed by exhalation of breath. Pandiculation is the term for the act of stretching and yawning simultaneously.[/COLOR]
Yawning is associated with tiredness, stress, overwork, lack of stimulation, or boredom. Yawning can also be a powerful non-verbal message with several possible meanings, depending on the circumstances. In humans, yawning has an infectious quality (i.e., seeing a person yawning or just thinking of yawning, can trigger yawning) which is a typical example of positive feedback.

[SIZE="3"][B]Hypothesized causes of yawning[/B][/SIZE]
1.The shallow inhalation during a yawn is a means of preventing alveolar collapse.
2.The deep inhalation while yawning stretches type II alveolar pneumocytes, which release the surfactant dipalmitoylphosphatidylcholine (DPPC) into the layer of fluid on the alveolar surface.
3.A means of cooling the brain.
4.An action used as an unconscious communication of psychological decompression and stress after a state of high alert.
5.An excess of carbon dioxide and lack of oxygen in the blood.
6.A way of displaying (or indicative of) apathy or arousal.
7.Tiredness.
8.A means of equalizing middle ear pressure.
9.Need of food/drink or hunger/appetite due to reduced level of glucose supplied to the brain.
10.To cool the body, such as after repeated exercise.
11.To moisten and lubricate the sclera and cornea of the eye, or stimulate the tear ducts.
12.To purge the lymphatic system before or after sleep.

What makes us yawn?
 

What's behind this mysterious epidemic of yawning? First, let's look at what a yawn is. Yawning is an involuntary action that causes us to open our mouths wide and breathe in deeply. We know it's involuntary because we do it even before we are born. Research shows that 11-week-old fetuses yawn.

*There are many parts of the body that are in action when you yawn. First, your mouth opens and jaw drops, allowing as much air to be taken in as possible. When you inhale, the air taken in is filling your lungs. Your abdominal muscles flex and your diaphragm is pushed down. The air you breath in expands the lungs to capacity and then some of the air is blown back out.

[B]Common Yawning Theories[/B]

While the dictionary tells us that yawning is caused by being fatigued, drowsy or bored, scientists are discovering that there is more to yawning than what most people think. Not much is known about why we yawn or if it serves any useful function, and very little research has been done on the subject. However, there are several theories about why we yawn. Here are the three most common theories:

[IMG]http://static.howstuffworks.com/gif/yawn-2.jpg[/IMG]
[B][B]The simple truth is that even though humans have been
yawning for possibly as long as they have existed, we have no
clue as to why we do it.[/B][/B]


1.[B]The Physiological Theory[/B] -- Our bodies induce yawning to drawn in more oxygen or remove a build-up of carbon dioxide. This theory helps explain why we yawn in groups. Larger groups produce more carbon dioxide, which means our bodies would act to draw in more oxygen and get rid of the excess carbon dioxide. However, if our bodies make us yawn to drawn in needed oxygen, wouldn't we yawn during exercise? Robert Provine, a psychologist at the University of Maryland, Baltimore County, and a leading expert on yawning, has tested this theory. Giving people additional oxygen didn't decrease yawning and decreasing the amount of carbon dioxide in a subject's environment also didn't prevent yawning.

2. [B]The Evolution Theory [/B]-- Some think that yawning is something that began with our ancestors, who used yawning to show their teeth and intimidate others. An offshoot of this theory is the idea that yawning developed from early man as a signal for us to change activities.

3. [B]The Boredom Theory[/B] -- In the dictionary, yawning is said to be caused by boredom, fatigue or drowsiness. Although we do tend to yawn when bored or tired, this theory doesn't explain why Olympic athletes yawn right before they compete in their event. It's doubtful that they are bored with the world watching them.

The simple truth is that even though humans have been yawning for possibly as long as they have existed, we have no clue as to why we do it. Maybe it serves some healthful purpose. It does cause us to draw in more air and our hearts to race faster than normal, but so does exercise. There's still much we don't understand about our own brains, so maybe yawning is triggered by some area of the brain we have yet to discover. We do know that yawning is not limited to man. Cats, dogs, even fish yawn, which leads us back to the idea that yawning is some form of communication.

Have we provoked a yawn out of you yet? If we have, hopefully it's not out of boredom, but by the power of suggestion.

[B][SIZE="4"]Interesting Yawning Facts[/SIZE][/B]

* The average yawn lasts about six seconds.
* Your heart rate can rise as much as 30 percent during a yawn.
* 55 percent of people will yawn within five minutes of seeing someone
else yawn.
* Blind people yawn more after hearing an audio tape of people yawning.
* Reading about yawning will make you yawn.
* Olympic athletes often yawn before competition.

REGARDS

Is the human skull made up of one bone or two?
 

Is the human skull made up of one bone or two?



It surprises many to learn that the human skull is not one solid bone as is usually thought. Nor does it consist of just two bones---the top of the head and everything underneath. The skull (cranium) is actually composed of (count them!) twenty-two separate bones. There are eight cranial bones around the brain and fourteen facial and jaw bones in the human skull. Just one of these bones moves - the jaw bone (mandible). In infants and very small children, the cranial bones are disconnected segments held together by connective tissue stripes called sutures. At certain sites, these sutures are especially weak, creating the so-called “soft spots” (fontanels) in an infant’s head. The most prominent of these is a little way up from the infant’s forehead. When growing is complete, the bones of the skull fuse together along the suture lines. These unions contain small amounts of fibrous connective tissue similar to those of the joints of arms and legs. Although the skull may structurally appear to be one piece when fully developed, it is still composed of separate bones. Many fossil skeletal remains that anthropologists find often appear to have cracked or broken skulls. But these skulls are actually just missing some of their pieces. The softer connective tissue having decomposed, little support is left between the individual pieces in the skull. This causes them to fall out and perhaps get left behind over thousands and thousands of years.

How Sleep Works?
 

Sleep is one of those funny things about being a human being -- you just have to do it. Have you ever wondered why? And what about the crazy dreams, like the one where a bad person is chasing you and you can't run or yell. Does that make any sense?

[CENTER][IMG]http://i235.photobucket.com/albums/ee182/Dangerous_deviant/sleep-stages.gif[/IMG]
[B]Dreaming occurs in the fifth stage of sleep.[/B] [/CENTER]

If you have ever wondered about why people have to sleep or what causes dreams, then read on. In this article, you'll find out all about sleep and what it does for you.

[B]Characteristics of Sleep[/B]

We all know how sleep looks -- when we see someone sleeping, we recognize the following characteristics:

* If possible, the person will lie down to go to sleep.

* The person's eyes are closed.

* The person doesn't hear anything unless it is a loud noise.

* The person breathes in a slow, rhythmic pattern.

* The person's muscles are completely relaxed. If sitting up, the person may fall out of his or her chair as sleep deepens.

* During sleep, the person occasionally rolls over or rearranges his or her body. This happens approximately once or twice an hour. This may be the body's way of making sure that no part of the body or skin has its circulation cut off for too long a period of time.

In addition to these outward signs, the heart slows down and the brain does some pretty funky things (we'll get to this later).

In other words, a sleeping person is unconscious to most things happening in the environment. The biggest difference between someone who is asleep and someone who has fainted or gone into a coma is the fact that a sleeping person can be aroused if the stimulus is strong enough. If you shake the person, yell loudly or flash a bright light, a sleeping person will wake up.

For any animal living in the wild, it just doesn't seem very smart to design in a mandatory eight-hour period of near-total unconsciousness every day. Yet that is exactly what evolution has done. So there must be a pretty good reason for it!

**Reptiles, birds and mammals all sleep. That is, they become unconscious to their surroundings for periods of time. Some fish and amphibians reduce their awareness but do not ever become unconscious like the higher vertebrates do. Insects do not appear to sleep, although they may become inactive in daylight or darkness.

By studying brainwaves, it is known that reptiles do not dream. Birds dream a little. Mammals all dream during sleep.

Different animals sleep in different ways. Some animals, like humans, prefer to sleep in one long session. Other animals (dogs, for example) like to sleep in many short bursts. Some sleep at night, while others sleep during t*he day.

[B]Sleep and the Brain[/B]

*If you attach an electroencephalograph to a person's head, you can record the person's brainwave activity. An awake and relaxed person generates alpha waves, which are consistent oscillations at about 10 cycles per second. An alert person generates beta waves, which are about twice as fast.

During sleep, two slower patterns called theta waves and delta waves take over. Theta waves have oscillations in the range of 3.5 to 7 cycles per second, and delta waves have oscillations of less than 3.5 cycles per second. As a person falls asleep and sleep deepens, the brainwave patterns slow down. The slower the brainwave patterns, the deeper the sleep -- a person deep in delta wave sleep is hardest to wake up.

At several points during the night, something unexpected happens -- rapid eye movement (REM) sleep occurs. Most people experience three to five intervals of REM sleep per night, and brainwaves during this period speed up to awake levels. If you ever watch a person or a dog experiencing REM sleep, you will see their eyes flickering back and forth rapidly. In many dogs and some people, arms, legs and facial muscles will twitch during REM sleep. Periods of sleep other than REM sleep are known as NREM (non-REM) sleep.

REM sleep is when you dream. If you wake up a person during REM sleep, the person can vividly recall dreams. If you wake up a person during NREM sleep, generally the person will not be dreaming.

You must have both REM and NREM sleep to get a good night's sleep. A normal person will spend about 25 percent of the night in REM sleep, and the rest in NREM. A REM session -- a dream -- lasts five to 30 minutes.

Medicine can hamper your ability to get a good night's sleep. Many medicines, including most sleeping medicines, change the quality of sleep and the REM component of it.

REFARDS

How Sleep Works
 

[B]Missing Sleep[/B]

One way to understand why we sleep is to look at what happens when we don't get enough:

* As you know if you have ever pulled an all-nighter, missing one night of sleep is not fatal. A person will generally be irritable during the next day and will either slow down (become tired easily) or will be totally wired because of adrenalin.

* If a person misses two nights of sleep, it gets worse. Concentration is difficult, and attention span falls by the wayside. Mistakes increase.

* After three days, a person will start to hallucinate and clear thinking is impossible. With continued wakefulness a person can lose grasp of reality. Rats forced to stay awake continuously will eventually die, proving that sleep is essential.

A person who gets just a few hours of sleep per night can experience many of the same problems over time.

Two other things are known to happen during sleep. Growth hormone in children is secreted during sleep, and chemicals important to the immune system are secreted during sleep. You can become more prone to disease if you don't get enough sleep, and a child's growth can be stunted by sleep deprivation.

But the question remains -- why do we need to sleep? No one really knows, but there are all kinds of theories, including these:

* Sleep gives the body a chance to repair muscles and other tissues, replace aging or dead cells, etc.

* Sleep gives the brain a chance to organize and archive memories. Dreams are thought by some to be part of this process.

* Sleep lowers our energy consumption, so we need three meals a day rather than four or five. Since we can't do anything in the dark anyway, we might as well "turn off" and save the energy.

* According to ScienceNewsOnline: Napless cats awaken interest in adenosine, sleep may be a way of recharging the brain, using adenosine as a signal that the brain needs to rest: "Since adenosine secretion reflects brain cell activity, rising concentrations of this chemical may be how the organ gauges that it has been burning up its energy reserves and needs to shut down for a while." Adenosine levels in the brain rise during wakefulness and decline during sleep.

*What we all know is that, with a good night's sleep, everything looks and feels better in the morning. Both the brain and the body are refreshed and ready for a new day.

Dreams and Improving Sleep Habits

* Why do we have such crazy, kooky dreams? Why do we dream at all for that matter? According to Joel Achenbach in his book Why Things Are:

*The brain creates dreams through random electrical activity. Random is the key word here. About every 90 minutes the brain stem sends electrical impulses throughout the brain, in no particular order or fashion. The analytic portion of the brain -- the forebrain -- then desperately tries to make sense of these signals. It is like looking at a Rorschach test, a random splash of ink on paper. The only way of comprehending it is by viewing the dream (or the inkblot) metaphorically, symbolically, since there's no literal message.

This doesn't mean that dreams are meaningless or should be ignored. How our forebrains choose to "analyze" the random and discontinuous images may tell us something about ourselves, just as what we see in an inkblot can be revelatory. And perhaps there is a purpose to the craziness: Our minds may be working on deep-seated problems through these circuitous and less threatening metaphorical dreams.

Here are some other things you may have noticed about your dreams:

* Dreams tell a story. They are like a TV show, with scenes, characters and props.

* Dreams are egocentric. They almost always involve you.

* Dreams incorporate things that have happened to you recently. They can also incorporate deep wishes and fears.

* A noise in the environment is often worked in to a dream in some way, giving some credibility to the idea that dreams are simply the brain's response to random impulses.

* You usually cannot control a dream -- in fact, many dreams emphasize your lack of control by making it impossible to run or yell. (However, proponents of lucid dreaming try to help you gain control.)

Dreaming is important. In sleep experiments where a person is woken up every time he/she enters REM sleep, the person becomes increasingly impatient and uncomfortable over time.

To learn more, check out How Dreams Work.

How Much Sleep Do I Need?
Most adult people seem to need seven to nine hours of sleep a night. This is an average, and it is also subjective. You, for example, probably know how much sleep you need in an average night to feel your best.

The amount of sleep you need decreases with age. A newborn baby might sleep 20 hours a day. By age four, the average is 12 hours a day. By age 10, the average falls to 10 hours a day. Senior citizens can often get by with six or seven hours a day.

Tips to Improve Your Sleep

* Exercise regularly. Exercise helps tire and relax your body.
* Don't consume caffeine after 4:00 p.m. or so. Avoid other stimulants like cigarettes as well.
* Avoid alcohol before bedtime. Alcohol disrupts the brain's normal patterns during sleep.
* Try to stay in a pattern with a regular bedtime and wakeup time, even on weekends.

Regards

black hole?
 

[B][CENTER][SIZE="3"]What is a black hole?[/SIZE][/CENTER][/B]

A black hole is an object with such powerful gravity that nothing can escape from it, including light. The black hole's mass is concentrated in a point of almost infinite density called a singularity. At the singularity itself, gravity is almost infinitely strong, so it crushes normal space-time out of existence. As the distance from the singularity increases, its gravitational influence lessens. At a certain distance, which depends on the singularity's mass, the speed needed to escape from the black hole equals the speed of light. This distance marks the black hole's "horizon," which is like its surface. Anything that passes through the horizon is trapped inside the black hole. Black holes come in several varieties, depending on mass.

[B]How does a black hole form?[/B]

A black hole forms when any object reaches a certain critical density, and its gravity causes it to collapse to an almost infinitely small pinpoint. Stellar-mass black holes form when a massive star can no longer produce energy in its core. With the radiation from its nuclear reactions to keep the star "puffed up," gravity causes the core to collapse. The star's outer layers may blast away into space, or they may fall into the black hole to make it heavier. Astronomers aren't certain how supermassive black holes form. They may form from the collapse of large clouds of gas, or from the mergers of many smaller black holes, or a combination of events.

[B]Are any black holes close to Earth?[/B]

The closest black holes yet discovered are several thousand light-years away. They are so far that they have no effect on Earth or its environment. A super massive black hole appears to inhabit the center of the Milky Way galaxy, about 27,000 light-years away. Although it is several million times the mass of the Sun, its great distance insures that it won't affect our solar system.

[B]Will our Sun become a black hole?[/B]

No. Stars like the Sun just aren't massive enough to become black holes. Instead, in several billion years, the Sun will cast off its outer layers, and its core will form a white dwarf - a dense ball of carbon and oxygen that no longer produces nuclear energy, but that shines because it is very hot. A typical white dwarf is about as massive as the Sun, but only as big as Earth, which is one percent of the Sun's present diameter.

[B]Will our universe become a black hole?[/B]

Unlikely. Recent developments that show our universe is expanding at an ever-increasing rate. The cause of the expansion, called dark energy, is not understood, but it appears that the universe is destined to undergo a slow and cold death. If there were enough mass in the universe, and if dark energy did not exist, then it might have been possible for the universe to collapse in on itself, condensing all matter and energy to an almost infinitely small point, like a black hole.

How Tornadoes Work ?
 

What Your Bathtub Can Teach You About Tornadoes

If you've ever watched a whirlpool form in your bathtub or sink while draining the water, then you've witnessed the fundamentals of a tornado at work. A drain's whirlpool, also known as a vortex, forms because of the downdraft that the drain creates in the body of water. The downward flow of the water into the drain begins to rotate, and as the rotation speeds up, a vortex forms.
Why does the water start rotating? There are many explanations, but here's one way to think about it. Imagine yourself as a particle in the water, suddenly pulled toward the suction that the drain creates. At first, you'd find yourself accelerating toward the drain. Then, quite literally, there's a twist. Because of your previous momentum and the number of other particles rushing toward the drain at the same time, chances are that you're going to be pushed off to one side of the point of suction when you arrive. That deflection sets you on a spiraling path into the point of suction, like a moth spiraling in toward a light. Once the spiral has started in one direction, it tends to influence all the other particles as they arrive. A very strong spiraling tendency is created. Eventually, there's enough spiraling energy to create a vortex.

Vortices are obviously a common phenomenon. After all, you see them in tubs and sinks all the time. Small dust devils sometimes form when winds flow over hot deserts, and wildfires have been known to produce climbing vortices of flame and ash called fire whirls. Scientists have even observed dust devils on Mars and spotted solar tornadoes whipping out from the sun.

In a tornado, the same sort of thing happens as with our bathtub example, except with air instead of water. A great deal of the Earth's wind patterns are dictated by low-pressure centers, which draw in cooler, high-pressure air from the surrounding area. This airflow pushes the low-pressure air up to higher altitudes, but then the air heats up and is pushed upward as well by all the air behind it. The air pressure inside a tornado is as much as 10 percent lower than that of the surrounding air, causing the surrounding air to rush in even faster.

H*ow do weather conditions pull the plug on atmospheric conditions? Skip to the next page to find out how tornadoes form.

Tornadoes and Thunderstorms

*Tornadoes don't just pop into existence -- they develop out of thunderstorms, where there's already a steady, upward flow of warm, low-pressure air to get things started. It's kind of like when a rock concert erupts into a riot. Conditions were already volatile; they merely escalated into something even more dangerous.
[CENTER][IMG]http://static.howstuffworks.com/gif/tornado-5.jpg[/IMG]
A tornado descends from the mesocyclone of a thunderstorm over New Mexico. [/CENTER]
Thunderstorms themselves form like many other clouds: A warm, moist air mass rises and cools, causing the water vapor to condense into clouds. However, if the updraft continues, this cloud mass will continue to grow and rise 40,000 feet (12,192 m) or more up into the troposphere, the bottommost layer of the atmosphere that we live in. A typical thunderstorm cloud can accumulate an enormous amount of energy. If the conditions are right, this energy creates a huge updraft into the cloud, but where does the energy come from?

Clouds are formed when water vapor condenses in the air. This change in physical state releases heat, and heat is a form of energy. A good deal of a thunderstorm's energy is a result of the condensation that forms the cloud. Every gram of water condensed results in about 600 calories of heat -- and another 80 calories of heat per gram of water results from freezing in the upper atmosphere. This energy increases the updraft temperature, as well as the kinetic energy of upward and downward air movement. The average thunderstorm releases around 10,000,000 kilowatt-hours of energy -- the equivalent of a 20-kiloton nuclear warhead [source: Britannica].

In supercell thunderstorms, the updrafts are particularly strong. If they are strong enough, a vortex of air can develop just like a vortex of water forms in a sink. This precursor to the tornado is called a mesocyclone, and is typically 2 to 6 miles (3 to 10 kilometers) wide. One a mesocyclone forms, there's a roughly 50 percent chance that the storm will escalate into a tornado in around 30 minutes.

Some tornadoes consist of a single vortex, but other times multiple suction vortices revolve around a tornado's center. These storms-within-a-storm may be smaller, with a diameter of around 30 feet (9 meters), but they experience extremely powerful rotation speeds.

The tornado reaches down out of a thundercloud as a huge, swirling rope of air. Wind speeds in the range of 200 to 300 mph (322 to 483 kph) aren't uncommon. If the vortex touches ground, the speed of the whirling wind (as well as the updraft and the pressure differences) can cause tremendous damage, tearing apart homes and flinging potentially lethal debris.

The tornado follows a path that is controlled by the route of its parent thundercloud, and it will often appear to hop. The hops occur when the vortex is disturbed. You've probably seen that it is easy to disturb a vortex in the tub, but then it will reform. The same thing can happen to a tornado's vortex, causing it to collapse and reform along its path.

Smaller tornadoes may only thrive for a matter of minutes, covering less than a mile of ground. Larger storms, however, can remain on the ground for hours, covering more than 90 miles (150 km) and inflicting near continuous damage along the way.

At this point, you might be wondering just how tornadoes eventually dissipate. Scientists still debate exactly how these deadly storms die, but one of the prime suspects is none other than the parent thunderstorm: the rotating mesocyclone. Tornadoes need instability and rotation. Disrupt the airflow, take away its moisture or destroy its unstable balance of hot and cold air, and it can't function. Often, a tornado will die because the cold outflow of air from falling precipitation upsets the balance.

[B][SIZE="4"][COLOR="Olive"]What produces Thunder?[/COLOR][/SIZE][/B]

Thunder is the sound made by lightning. Depending on the nature of the lightning and distance of the listener, it can range from a sharp, loud crack to a long, low rumble (brontide). The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within a bolt of lightning. In turn, this expansion of air creates a sonic shock wave which produces the sound of thunder.

The cause of thunder has been the subject of centuries of speculation and scientific inquiry. The first recorded theory is attributed to the Greek philosopher Aristotle in the third century BC, and an early speculation was that it was caused by the collision of clouds. Subsequently, numerous other theories have been proposed. By the mid-19th century, the accepted theory was that lightning produced a vacuum. In the 20th century a consensus evolved that thunder must begin with a shock wave in the air due to the sudden thermal expansion of the plasma in the lightning channel. In a fraction of a second the air is heated to a temperature approaching 28,000 °C (50,000 °F). This heating causes it to expand outward, plowing into the surrounding cooler air at a speed faster than sound would travel in that cooler air. The outward-moving pulse that results is a shock wave, similar in principle to the shock wave formed by an explosion, or at the front of a supersonic aircraft. More recently, this consensus has been eroded by the observation that measured overpressures in simulated lightning are greater than what could be achieved by the amount of heating found. Alternative proposals rely on electrodynamic effects of the massive current acting on the plasma in the bolt of lightning.

[QUOTE=Ms. Lily][CENTER][B]Why Lips Are Red?[/B][/CENTER]

Arteries are blood vessels that carry blood back to the heart. [/QUOTE]




Arteries are blood vessels that carry blood away from the heart. All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.