Length of the longest eclipse and peculiarities of solar and lunar eclipse

Q. How long is the longest eclipse?

A. A total solar eclipse can last at the most only 7 minutes and 40 seconds. A total lunar eclipse can last 1 hour and 40 minutes. But the longest known stellar eclipse (when a moving object such as a planet blocks the light coming from a distant star, it is called stellar eclipse or occultation) lasted 8 years!

The duration of a solar eclipse is set by the relative speeds of the Moon’s shadow, sweeping west to east at 3,200 km/h, and of the observer who is traveling west to east with the Earth’s spin. The Earth moves fastest at the equator: 1,600 km/h. The observer there is more nearly keeping up with the shadow than any other observer and sees the longest eclipse.

Similarly, a total eclipse of the Moon can last as long as it takes the Moon to pass through the widest part of the Earth’s shadow. Unlike a solar eclipse, which is visible only along a confined track across the Earth’s surface, a lunar eclipse can be seen by anyone who can see the Moon.

More reading:
Eclipse (Wikipedia)
Solar eclipse (Wikipedia)
Lunar eclipse (Wikipedia)

Dynamics behind total solar eclipse and its possibility on other planets

Q. Do other planets experience total solar eclipse like the one we are about to witness on July 22, 2009?

A. They don’t – and given the orbital dynamics of the planetary bodies, they never will. Total solar eclipses occur only on Earth, thanks to a remarkable coincidence. In essence, this involves two factors: Size and distance. The Sun and the Moon are apparently the same size in the sky, a fact that is hard to see for oneself, since the Sun should never be viewed directly. Rather than the actual size, it is this apparent size that matters and makes possible one of the most spectacular and awe-inspiring events in the natural world – the total solar eclipse, when the Moon’s disk almost perfectly covers the entire body of the Sun.

Two numbers are important in understanding this lucky relationship of size and distance: 400 and 108. The Sun has a diameter about 400 times that of the Moon; at the same time the Sun is about 400 times farther away from the Earth than the Moon. Both the Sun and the Moon are about 108 times their own diameters away from the viewer. No other planet and its natural satellites have the kind of relationship which the Earth and the Moon have with the Sun.

The maximum possible duration of an eclipse of the Sun is 7 minutes 40 seconds. However, from a supersonic Concorde aircraft traveling at the same speed as the moving shadow of the Moon (1,673 kilometers/hour) astronauts have observed it for 3.5 hours.

More reading:
Solar eclipse (Wikipedia)

Country and the man behind motorcycles

Q. From which country started a worldwide craze for motorcycles? And who was the man behind it?

A. The credit for creating a worldwide craze for motorcycle goes to Japan – especially to the Japanese engineer named Soichiro Honda (see photo). Just as scooter was innovated as an affordable vehicle for the common man in postwar Europe, Honda concentrated on the motorcycle. He inspired Kawasaki, Yamaha and Suzuki to follow him in this field.

At the end of the Second World War a large stock of two-stroke engines made for the use in various naval craft and submarines was laying idle unused. Soichiro Honda purchased these engines for the price of scrap. Thereafter making bicycles on stronger frames in his workshop and fitting two-stroke engines he converted them into motorcycles. From such a small beginning Honda Motor Company’s multi-national business commenced.

More reading:
Motorcycle (Wikipedia)
Soichiro Honda (Wikipedia)
Honda (Wikipedia)

Features of the world’s cheapest global car, Tata Nano

Q. Tata Motors of India has finally completed its mega project of the mini car. How is world’s cheapest car Tata Nano? What makes it different from the rest?

A. Generally when a motor car is embellished with the latest technology it becomes larger as well as more expansive, but the team of 500 engineers of Tata Motors has packed Nano with the latest technology without increasing either its price or its size. The age of small cars has dawned once again thanks to global warming and scarcity of petroleum. In such a situation it will not be surprising if Nano succeeds in capturing the Indian market as well as selling abroad as the world’s cheapest global car.

Young brains of Tata Motors have displaced many long extablished standards of automobile technology in their endeavors to curtail the size, weight and price of Nano. No other motor car’s engine has better power-to-weight ratio than Nano’s engine. It is made from aluminum instead of steel and seeing Nano’s low slung back seat one wonders how the engine was accommodated beneath it.

There is no room for battery in Nano’s engine compartment at the rear end of the car. If it were to be placed in the front under the bonnet a long length of copper wire would be required to connect it with the engine adding to the cost of the car. Hence, by placing the battery beneath the driver’s seat economy has been effected in both the cost of wire as well as space under the bonnet.

No part of Nano’s body has been welded because welding is not only expansive but also slows down production. Therefore, chemical adhesives have been used for the joints. Do not think that chemical joints are short-lived; framework components of giant airliners like Airbus-380 are also joined with adhesives.

Spare wheel in the luggage compartment beneath the bonnet is somewhat smaller than the regular wheels. The experts at Tata Motors thought that since spare wheel was going to be used only occasionally, a smaller wheel might serve just as well. By reducing its size the engineers also reduced the overall weight of the car to some extent which was their basic objective.

There is only one wiper and only one wing or side mirror on the driver’s side. Only three bolts hold the wheel together with axels instead the usual four. The fuel tank has only 15 liters capacity. There is no power steering because there is no engine in the front to press the wheels down with its weight.

More reading:
Tata Nano (Wikipedia)
Tata Motors (Wikipedia)

Methods used for making the machines talk like humans

Q. How do machines mimic speech?

A. Machines are learning to talk. Through the combined efforts of language scientists, acousticians and electronics experts, synthetic speech is allowing clocks to announce the time, machines to read to the blind and cars to warn their owners that it’s time to fill up.

In order to develop such chatty contraptions, linguists first had to learn what makes up a word. Linguists have broken down human language into a small number of identifiable sounds, or phonemes. All the words in Standard English are said to be composed of just 40 to 50 basic phonemes stung together and adjusted for syntax.

A computer is taught to recognize and synthesize words in one of two ways. In the first, known as synthesis by analysis, it takes recorded samplings of the human voice and analyses their sound waves every one-hundredth of a second. It then extracts and stores certain key attributes, such as predominant frequencies and energy levels. Later, the machine is able to mimic these impulses electrically and using filters, oscillators and noise generators, turn them into sounds. Since the computer monitors each tiny nuance, synthesis by analysis can produce extremely lifelike voices. Vocabulary, however, is limited to those words actually programmed into its memory.

The other method, synthesis by rule, allows enormous versatility because any word can be produced. The computer is programmed with the basic phonemes and the rules of pronunciation and stress, from which it assembles words. But what is gained in flexibility is lost in clarity, since it’s difficult to reduce all the permutations of pronunciation and inflection to a single set of rules. Regardless of the technique used, voice-synthesis systems are becoming ever more commonplace.

Reason why water-filled clouds float on the air

Q. Why do clouds float in the sky even though they have tons of water in them?

A. Clouds are the visible part of a continuous cycle in which water evaporates into the air, condenses and returns to Earth mostly as rain. The cycle starts when the Sun warms the Earth, which in turn, warms pockets of moist air. When an air pocket heats up, its molecules bounce around more actively and begin to take up more space. As a result, the air expands and becomes less dense. The surrounding heavier air then pushes its way underneath the warm pocket, which rises like a hot-sir balloon.

Only when the water condenses does it become visible, and when enough droplets condense, they form a cloud. Clouds can grow to vast proportions if enough air is heated. A thunderhead can tower up to 12 kilometers high, and half a million tons of water can be released in a single downpour. Clouds stay aloft because the droplets are so tiny that they remain suspended on air currents. Each mist particle is minuscule – only one millionth the mass of a final raindrop. They do not have any appreciable fall velocity and most of them continue to float with the surrounding air. Sometimes the larger particles drop out of the cloud, only to evaporate and be swept up again. At other times they leave the sides of the cloud to be replaced by water vapor from below, which condenses as tiny droplets. So there is no perceptible change in the cloud’s shape as well as size. The mass of water the cloud holds also remains more or less the same.

What makes this great mass float in the air is its relative lightness compared to the mass of air in which it resides. Take an example of a small cloud at an altitude of some 3,000 meters. Assume that it occupies a volume of 1 cubic kilometer and there is a 1 gram droplet per cubic meter. The total mass of these water particles would be about 1,000 tons, whereas the mass of the air in that same cubic kilometer would not be less than 1,00,000 tons. The heavier air keeps the cloud buoyant.

More reading:
Cloud (Wikipedia)

Harmfulness of overdose of vitamins

Q. Is overdose of vitamins harmful or the body just flushes out the excess substance?

A. When you go 10 times above the Recommended Dietary Allowance/RDA, a vitamin or mineral acts like a drug and may have side effects. For example, very high doses of vitamin A are extremely toxic, producing symptoms similar to brain tumor.

The fat soluble vitamins – A, D, E, and K – are the most dangerous in high doses because they are stored in the body. Two of these, A and D, have very clear toxicity. Large doses of vitamin K will cause clotting problems. With vitamin E, strangely enough, we have not seen any toxicity.

This is not to say that water soluble vitamins are safe at any dose. To be excreted in the urine, they must pass through the blood, and in that short time, they may have toxic effect. Vitamin B3 in very large doses causes palpitations, sweating and circulatory problems. And there’s evidence that excess of some vitamins, such as B6, may cause brain damage.

More reading
Vitamin (Wikipedia)
Vitamin poisoning (Wikipedia)
Hypervitaminosis A (Wikipedia)
Hypervitaminosis D (Wikipedia)
Hypervitaminosis E (Wikipedia)

Cause and cure of hiccups

Q. What causes hiccups and how they can be cured?

A. Hiccups are caused when our diaphragm – a large muscle across the chest – starts contracting in jerks, instead of moving smoothly up and down. To stop hiccups, one has to shock the diaphragm back to its normal movements. There is no sure-fire cure for hiccups, but some things that can work include a good scare, drinking water while someone plugs your ears, eating a spoonful of crushed ice, sucking a slice of lemon and holding your breath for a few seconds.

More reading:
Thoracic diaphragm (Wikipedia)

Dogs’ habit of going round and round before lying down

Q. Why does a dog go round and round before it lies down?

A. This behavioral trait has its origin in the evolutionary process and has been handed down for countless generations. The habit goes back to the ancient time when dogs were wild and lived in grasslands. To get a comfortable bed in such habitat, they had to turn round and round a few times so as to level the grass. Since those days, some of the species of dogs have been domesticated.

Today, these dogs sleep on a mat or the floor, but the old habit, possibly hardwired in their brain, still persists. Like their ancestors, they go round and round even though there is no longer any need to do so.

More reading:
Dog (Wikipedia)

Reason why astronauts are weightlessness in the space

Q. Why are astronauts weightless in orbit? Is it because they are beyond the pull of gravity?

A. Newton would not agree on this. Nor would anyone else, because the Earth’s gravity extends far out into the deep space. On the other hand, circling above the Earth spacecraft sometimes climbs no higher than 250 kilometers. At altitudes as low as this, the vehicle and its occupants are still very much held in the planet’s grip. Given this fact, why don’t they feel the pull of gravity which obviously is the source of weight?

The answer has a bit of surprise to offer. The fact is that orbiting spacecrafts don’t actually fly around the Earth. They fall – and continue to do so for days, months or years depending upon their altitude. Moving like a cricket ball that has been hit skyward for six, a spaceship no sooner reaches its apogee (highest point) in the space than it begins to drop back to the Earth. However, because of its speed and trajectory it never actually reaches the ground. The reason is that the Earth below constantly curves away from it. Hence, the spaceship’s circular or elliptical plunge never comes to an end. But why should this produce weightlessness?

Here’s why. The sensation of weight we experience daily is not only due to the tug of gravity but also to our constant resistance to its pull. Were you to remove the supporting ground or floor beneath your feet, you would feel your weight begin to disappear as you start falling. Assuming that air resistance did not retard your plunge, you would surrender completely to gravity’s pull and become weightless.

To get the feel of this condition during training, astronauts ride in airplanes that are flown in large ballistic arcs. These practice sessions are brief, but they do create – if only for a few seconds – the buoyancy the astronauts will feel when gliding through their orbits in the space.

More reading:
Weightlessness (Wikipedia)
Astronaut (Wikipedia)