Why pirates cover their one eye ?
Some assume pirates wore eye patches to cover a missing eye or an eye that was wounded in battle, but in fact, an eye patch was more likely to be used to condition the eye so the pirate could fight in the dark.
It takes an average human eye about 25 minutes to fully adapt from bright sunlight to seeing in complete darkness—if a pirate was fighting on deck in the light, then had to go under the deck to fight downstairs where it is usually pretty dark, that would be a long time to go without being able to see. The eye patch could be used to prepare one eye to see in the dark, so when they would go below deck they could swap over the eye patch from one eye to the other and see with the eye that has already adjusted to low light conditions. This would allow them to instantly in the dark.
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Can Rainbows be full circles?
Yes! Rainbows can be full circles.
However, the observer normally sees only an arc formed by illuminated droplets above the ground, and centred on a line from the sun to the observer's eye.
In a primary rainbow, the arc shows red on the outer part and violet on the inner side.
This rainbow is caused by light being refracted when entering a droplet of water, then reflected inside on the back of the droplet and refracted again when leaving it.
In a double rainbow, a second arc is seen outside the primary arc, and has the order of its colours reversed, with red on the inner side of the arc.
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How are bubbles formed in boiling water?
At room temperature, there is always some air dissolved in water.
The colder the water, the more air is dissolved. Air becomes less soluble in water as the temperature rises.
When the water boils the air is released in the form of bubbles. Two thousand years ago, an attempt was made to use the power of steam with Heron's ball, but the great breakthrough came only with the steam engines.
The steam engine improved by James Watt is the most well-known.
A little later the steam engines were used to drive locomotives and paddle steamers – the modern steam turbines followed later.
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Which is the shortest war ever fought?
The war between Zanzibar (presently part of Tanzania) and the imperial British is the shortest war ever fought.
It lasted for about 40 minutes. The immediate cause was the ascension of new sultan who was not ready to cooperate with the imperial power, thus British gave him an ultimatum to surrender which he rejected.
In the ensuing battle their defense failed pathetically before the mighty royal navy.
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Who invented the lock and key?
Linus Yale, Jr.
In 1861, Linus Yale, Jr. was inspired by the original 1840s pin-tumbler lock designed by his father, thus inventing and patenting a smaller flat key with serrated edges as well as pins of varying lengths within the lock itself, the same design of the pin-tumbler lock which still remains in use today.
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Which planet is the least dense?
If you're looking for a place a bit more airy, you could always visit Saturn.
The gas giant is the least dense planet in the solar system with an average density of a scant 0.70 grams per cubic centimeter.
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How do bats orient themselves with ultrasounds?
Bats cannot see very well. To orient themselves during their night flights, they emit ultrasounds.
We cannot hear these sounds. The ultrasonic waves falling on obstacles or preys get 'reflected' back and reach the sensitive ears of bats.
Thus, they come to know what all is present around them and where their prey is.
This concept is also used in shipping to determine the depth of the sea using a device called sonar.
It comprises a sound transmitter, a receiver, and a clock. The time difference between sending and receiving sound waves is measured, which is used to calculate the depth of the sea.
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Why is it difficult for the wandering albatross to take off?
Wandering albatrosses are quite heavy, and have to do a warm-up before lifting themselves up into the air-just like an aircraft that increases its speed on the runway.
They often have difficulty if the wind speed is below 12 km/h.
They usually glide when they are in the air because a lot of energy is consumed in flapping their wings.
Albatrosses, which have the largest wingspan of 3-5 m in the animal kingdom, cover thousands of kilometres in the air and are capable of remaining in the air without flapping their wings for several hours.
They mate for life and return to the small islands to the north of Antarctic for breeding.
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What did the Europeans gain by exploring Africa?
With the discovery of the sea route to India, the Europeans became increasingly familiar with the continent of Africa; explorers particularly took note of its extensive and diverse natural reserves. Gold and diamonds were found in plenty in the south of Africa. The British and the Boers fought here for a good bargain. Even the Churches began to take interest in this continent and sent their missionaries deep into interior of Africa. From all over Africa, especially Timbuktu, numerous tribal people were caught and forcibly sent over to America as slaves.
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How tattoo ink is made?
Manufacturers usually don't reveal their ingredients and recipes.
Commonly Professional tatto inks are made from iron oxides (rust), metal salts, plastics. Homemade or traditional tattoo inks are made from pen ink, soot, dirt, blood, or other ingredients.
Heavy metals used for colors include mercury (red); lead (yellow, green, white); cadmium (red, orange, yellow); nickel (black); zinc (yellow, white); chromium (green); cobalt (blue); aluminium (green, violet); titanium (white); copper (blue, green); iron (brown, red, black); and barium (white).
Metal oxides used include ferrocyanide and ferricyanide (yellow, red, green, blue). Organic chemicals used include azo-chemicals (orange, brown, yellow, green, violet) and naptha-derived chemicals (red). Carbon (soot or ash) is also used for black.
Other elements used as pigments include antimony, arsenic, beryllium, calcium, lithium, selenium, and sulphur.
Tattoo ink manufacturers typically blend the heavy metal pigments and/or use lightening agents (such as lead or titanium) to reduce production costs.
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Читать полностью…Where does the oxygen we breathe come from?
Gaseous oxygen was created on the Earth about 3.5 billion years ago.
At that time, the UV light of the sun decomposed the water vapour molecules present in the atmosphere, and released oxygen and hydrogen.
But a major part of the oxygen immediately reacted with other substances, so that it was no longer available in the atmosphere as gas.
Oxygen was also produced by the seas, where the 'blue algae' carried out photosynthesis.
These bacteria converted sunlight and carbon dioxide into energy.
In the process, gaseous oxygen was released as a 'waste product', which accumulated in the atmosphere.
About one billion years ago, about one-twentieth (4%) of the atmosphere consisted of oxygen.
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