How long can a person go without sleep?

Sleep deprivation is more fatal than deprivation of food. It means that sleep is not only necessary but essential for life. In experiments done on rats in Chicago University in the US when the rats were deprived of sleep most of them gave way after 21 days. Even if the daily quota of sleep is cut down gradually it would prove harmful over a period of a few days. It would increase the chances of heart disease, diabetes, stroke attack, and as recent research shows, also cancer.

Let aside for days, if one is deprived of sleep even for 17 hours then one’s concentration, muscle energy, judgement, cognitive ability etc would reduce to a level that of a person under influence of alcohol. This condition is very common in present times, for which we should “blame” the inventor of light bulb, Thomas Edison. Before the invention of light bulb average person slept for 9 hours, whereas today owing to numerous factors like television, internet, 24x7 work culture etc, average person sleeps for about 7.5 hours.

Below are couple of examples of how deprivation of sleep can sometimes lead to grave consequences –

1) In 1986, at Chernobyl Nuclear Power Plant in Russia the experts conducting some important testing post-midnight were not in their best state because of their day-centric biological clock. As a result, due to their negligible inattention the nuclear plant exploded. A perfectly alert person would not have committed such an error.

2) In 1989, near the coast of Alaska state north of the US a giant oil vessel named Exxon Valdez was sailing. There was only one person operating it from the control room and he was on duty for over eighteen hours straight. Because of long stretch of wakefulness his concentration was wavering. As a result the giant vessel met with an accident and 40 million liters of oil was spilled over the ocean. For environmental harm as well as for negligence the vessel’s owner company had to pay 5.29 billion dollars in penalty.

Looking at the above two examples where hours of sleep deprivation caused gigantic disasters, one would find it hard to believe that the world record of wakefulness is in days. The record is official and unbroken for over fifty years. In the decade of 1960's a 17-year-old youngster named Randy Gardner spent 11 days staying awake. He started the marathon by waking up at 6 AM on December 28, 1963 and went back to sleep not before January 8, 1964, going without sleep for 264 hours.

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Why is it necessary to sleep every night?

This is an important question, because average person spends one-third of the time of their life sleeping. Sleep is so important that deprivation of it can kill a person just like deprivation of food can. Other animals and birds also sleep for long or short duration, so there must be some biological reason making sleep essential. However, we are still in the dark about the exact reason behind sleep. We can cite a few inferences drawn by researchers.

In the evolutionary past the very first organisms on earth were without a nervous system, so they did not have two states like sleep and wakefulness. Their descendants of about four billion year ago for the first time started adjusting their activity and inactivity with the light of day and the dark of night. This gave rise to the biological clock in their body, which in turn made some creatures nocturnal and some diurnal.

In case of diurnal humans the daily cycle set by the biological clock is of twenty-four hours – twelve hours for day and the same for night. Body temperature, blood pressure, heartbeats and many other processes in a human body increase or decrease according to this biological clock. The organ experiencing the highest change is the brain. With arrival of sleep the brain’s night-shift begins and it starts large-scale data-processing. Researchers have studied the brain and the processes taking place in it during night a good deal to understand that at night time sleep comes mainly to be of service to the brain. Another proof connecting sleep with the brain: vegetation don’t have brain, hence there is a no state of sleep for trees.

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Is it true that pupils dilate when we see something we like?

Pupil dilation has long held interest of many a psychologist. No one knows for sure what the changes in pupil size mean in different circumstances. It is certainly an involuntary result of our nervous system processing important information obtained from the various stimuli it comes in contact with. There are number of things that case pupils to dilate and it is impossible to figure out what it means each time. However, in context of this question, research has found links between liking something and dilation of pupils.

Pioneering study in this regard was done by a psychologist named Eckhard Hess at the University of Chicago who also coined the term pupillometrics in 1975 for the study of pupil size as an indicator of emotions. He was looking at photos of animals one night and his wife noticed that his pupils were expanded. She asked him if the light was not enough, and he said there was good enough light. This instance struck him as interesting enough to embark on research about what caused pupils to dilate.

Research shows that pupils dilate when we see or hear something in which we are interested. In order words, when something we see or hear interests us the pupils get bigger. In one study the subjects were given to listen to three excerpts from books. The first one was erotic, the second one involved mutilation and the third one was neutral. It was observed that the subjects’ pupils got bigger for all three passages but only in case of the first two – the erotic and the one involving mutilation – remained wide. It means that the pupils dilate when we hear or see something interesting but remain dilated only when it continues to be interesting.

The opposite is also true. Pupils are constricted when we see something which we find disgusting. This is also shown by a study in which the subjects were shown pictures of injured children. The results of the study were actually in line with what we learned from the above paragraph. In this study when the subjects were shown the pictures of injured children, their pupils got bigger at first (as their interest was piqued) but very soon they constricted because what they saw was disgusting. Unlike in the neutral case wherein the pupils become normal again due to the object not continuing to hold one’s interest, the opposite happens when the object holds negative interest.

Additional reading:
Pupillometry (Wikipedia)

In what atmospheric conditions is dew formed?

Moisture in the atmosphere turns into dew droplets when it comes in contact with any cold substance. Green grass, leaves, metal wires, threads of spider webs etc are substances that collect dew. These substances absorb heat in day-time when the sun is up, and during night they lose the heat and become cool. The condition for dew to form is that the temperature of the substance must reach the dew point. And to allow the temperature to fall thus the atmosphere must be free of clouds. Clouds store heat. So if the atmosphere is cloudy then the heat emitted from clouds would not allow the temperature to fall to the dew point during night, and dew would not form. It is also necessary for formation of dew that relative humidity of air is about 100%.

A thing to note here is that the dew point itself is not a constant like boiling point or melting point. The temperature at which dew is formed is called dew point. Albeit, it would always be greater than 0° Celsius which is the freezing point of water; or else instead of liquid droplets we would see ice crystals for dew.

Additional reading:
Dew (Wikipedia)

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What is the formula to calculate IQ? Is IQ of 100 good?

Intelligence is an abstract concept. It is difficult to measure intelligence level and express it in numbers. However, the term Intelligence Quotient is used for the purpose. This term became popular about a hundred years ago in 1916 when a Stanford University psychologist named Lewis Terman invented a formula to numerically measure the amount of intelligence in a human being. The formula was revised in 1937, then in 1960, and the last time in 1972 there were a few changes done to the formula. The formula used today to measure IQ is as follows:

IQ = Mental Age ÷ Physical Age x 100

In the formula, physical age is one's age from the date of birth, but mental age is a completely different matter. To explain with an example, if a 10-year-old correctly answers questions which can normally only be answered by a 13-year-old, then even though his physical age is 10 years, his mental age is considered to be 13 years. Thus, according to the formula, his IQ would be 13 ÷ 10 x 100 = 130. On the other hand, if a 10-year-old answers questions which can normally only be answered by a 10-year-old (and he can't answer tougher questions), then his IQ would be 10 ÷ 10 x 100 = 100. It means his mental and physical age are the same.

IQ Distribution

A person with IQ of 100 can not be said to have a sharp mind, because the IQ figure of 100 is normal. It also means that majority of the people the in world have an IQ of 100. Refer above the distribution of Intelligence Quotient.

To tell the truth, human intelligence level can not be determined mathematically with accuracy, intelligence being an abstract concept. Therefore, the formula for measuring IQ is not very reliable. According to this formula a woman named Marilyn vos Savant has IQ of 228, whereas Albert Einstein's IQ is said to be 160.

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How does polygraph test work? Is it accurate in detecting lies?

Polygraph is a scientific term for what is popularly known as lie detector. It is an instrument used in criminal investigations to find out if the person being prosecuted is telling the truth. Many employers, too, use lie detectors during job interviews to check veracity of job applicants' answers to the interview questions.

Polygraph test involves attaching multiple (hence the prefix poly) sensors (usually four to six) on a subject's body to measure physiological functions like breathing, pulse rate, blood pressure, perspiration etc while the subject is ran through a series of questions. Some polygraph tests record bodily movements such as movement of hands and legs. These sensors send signals to a computer which records them as a horizontally moving graph (see, picture below). The idea behind polygraph test is this: Lying puts stress on the person lying. And this stress is detected though physiological functions, e.g. increased breathing and pulse rate, high blood pressure, sweating,.. At a point where any of these stress signals is detected in the subject the graph would capture that as a spike.

Polygraph Test

An examiner in a polygraph test starts with very simple questions ("What is your name?", "Do you reside at..?",..) and moves on to slightly stress inducing questions such as those involving personal details. This is necessary to establish the baseline of physiological responses in the subject, because different people experience different level of stress while answering a particular type of question. By running this routine of escalating questioning the examiner would know what is the normal level of stress experienced by the subject being examined, which is then compared with the unusual spikes in the polygraph.

Accuracy of polygraph tests is still a subject of debate as the opinions are widely divided. There are ways in which polygraph can be "fooled". These involve 1) using of drugs while under the test to neutralize emotions, 2) biofeedback training, 3) "nail-in-the-shoe" technique in which the subject would press his foot against a sharp nail hidden in the shoe to cause pain which would skew the polygraph results, etc. Not to mention that polygraph test is completely ineffective on psychopaths (people with inability to feel emotions). Polygraph's accuracy also varies by the type of equipment used and proficiency level and subjectivity of the examiner. When conducted without manipulation on the subject's part, polygraph tests are fairly accurate. According to American Polygraph Association (APA) the accuracy rate of polygraph tests is 80-90%.

Here is a real world example of effectiveness of polygraph test: A private investigator in the US, named Scott Lewis (of Scott Lewis Private Investigation), took a polygraph test to test its accuracy. The test was conducted by Neil Myres who runs the company called Forensic Polygraph Services. Myres asked Lewis to choose a number between 1 to 7, and then he would ask him, one-by-one, whether the number chosen is 1, or 2, or 3, and so on. Lewis was asked to say "no" each time. This means he would be lying to one of the questions. It was a simple test, involving inconsequential questions. Lewis expected to pass the test as he did not think the questions would be stressful. Moreover, he already knew the questions. However, he was surprised by the results of the test. The number he had mentally chosen was 5. He saw on the graph paper that as Myres asked if it was the number 4 the graph showed an upward movement; and it peaked on the fifth question when he was asked if it was the number 5 and Lewis had to lie.

Additional reading:
Polygraph (Wikipedia)

How long is the life of passenger planes like Boeing-747 (Jumbo Jet) and Airbus?

There are three ways of ascertaining the life of an aircraft based on about a dozen factors like its frame construction, weight, engine strength, average flight time, etc. The first unit of measuring longevity of an aircraft is year. A passenger aircraft like Boeing-747 or Airbus 300 is normally considered "aged" after 20 years of service. However, it is inadequate to ascertain the age of an airplane in years alone. It is also important to take into account the number of take-offs and landings by an aircraft within a span of time, which is called usage cycle.

At the time of landing an aircraft endures a mild collision vertically, whereas during take-off the entire frame endures a horizontal pull. Aircraft's metal then "tires" just like human muscles after physical hard work, and gradually becomes weak. To talk in the language of engineering, an aircraft experiences metal fatigue. The most memorable example for this is of Boeing-737 of Aloha Airlines in Hawaii. Flying between various islands this plane took off from the runway for a similar flight on April 1988, and when it was at the height of thousands of feet all of a sudden its roof went off. One air-hostess and a passenger were thrown out with the wind, while the other passengers had their seat-belts on, hence they remained safe with minor injuries. Eventually the plane landed on the airport, but in the below picture you can see the condition it is in. After this accident Boeing declared the life of Boeing-737 to be 75000 cycles. It means once the aircraft completes 75000 take-offs and landings its life is over.

Aloha Airlines' Boeing-737 Accident

The third unit of measuring an aircraft's life is hours of flight. At the latitude of 32000-33000 feet the air temperature is about minus 48° Celsius. Plane's metal is contracted at that low temperature. After beginning to land, within 15 minutes as the plane hits the ground the air temperature is much higher, possibly around 30° Celsius. Such a difference in temperature within 15 minutes is no small matter. As a result of this an aircraft experiences another kind of metal fatigue which diminishes its strength. By this measure, the life of Boeing-737 is 51000 hours of flight. Whereas the life of the supersonic Concord is 45000 hours of flight. For more information about different planes refer to the table below. As shown in the table there are three parameters of longevity. A take-off and landing equals one cycle. Boeing-747 (Jumbo Jet) is meant for International travel, hence it does fewer take-offs and landings and has higher hours of flight compared to the planes used for domestic flights.

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