Why are polar bears white?

The polar bear lives in the Arctic, the region of the North Pole. Most of its environment is barren, covered year-round with ice and snow and not much else. A polar bear might eat what few plants it can find, but it feeds mostly on water animals like seals and small walruses, which share its frozen home. The polar bear’s yellowishwhite coat helps it blend into its snowy surroundings as it hunts its prey.

After all, there is not much in the Arctic to hide behind! The fur of a polar bear is also extremely thick, allowing it to withstand polar temperatures and swim in Arctic waters, where its prey is often found. Polar bears are excellent swimmers, and their unique paws—with hairy soles—allow them to run very quickly over ice and snow without slipping.

Why when suggesting an exhaustive search do we say,“Leave no stone unturned”?

The advice to “leave no stone unturned” comes from Greek mythology, Wherein the Oracle of Delphi, through his communication with the gods, had acquired great wisdom.

Euripides wrote that When the oracle was consulted about how to find a defeated general’s hidden treasure, he advised that the only way was “to leave no stone unturned.” The expression and the advice have been with us ever since.

Why do some people have freckles?

People with light skin and eyes are more likely to have freckles because they have less melanin, a chemical in the skin that protects it from sun damage by reflecting and absorbing ultraviolet (UV) rays. Instead of tanning, they freckle.

Some people’s freckles fade away almost completely in the winter, and then return in the summer, when the person is more likely to sunburn. Sunscreen can help protect everyone (freckled or not) from the Sun’s harmful rays.

What is the difference between bravery and courage?

Both bravery and courage are acts of valour and imply a certain strength and fearlessness. There is, however, a subtle difference in meaning between the two words. Courage comes from the French word coeur, meaning heart. It is a quality of character that allows someone to carry through with a difficult premeditated plan of action.

Bravery, on the other hand, comes from the Spanish word bravado, meaning a single or spontaneous act of valour. It is not planned, but rather a kneejerk reaction that often occurs within a crisis.

What is e-mail?

People can use the Internet to send electronic mail, known as e-mail, to one another in just a few seconds. Once you type a message into your computer to send to your cousin, let’s say, who lives miles from you across the country, it travels through the wires of your phone line as a series of electrical signals (or, for some people, the signals travel through the same cables that bring them cable television). These signals travel to a station run by your service provider, where a big computer sends them to an Internet routing center. Located all over the world, routing centers, which are linked to organizations and Internet providers, send the countless computer communications that come to them each second along the quickest possible routes to their destinations.

A giant computer there reads the address on your e-mail and sends it farther: depending on the distance it must travel, it may continue along phone lines, be changed into light signals that can travel with great speed along thin glass strands called fiber-optic cables, or be converted into equally speedy invisible bands of energy known as radio waves and transmitted to a communications satellite that will bounce it back to Earth, to a ground station located close to where your cousin lives. Once your message reaches the routing center nearest your cousin, it will be sent to the station of his or her service provider. From there it will be sent along regular phone lines to his or her computer. And all of this happens in a matter of moments.

When did people first use electric cars?

During the last decade of the nineteenth century, the electric vehicle became especially popular in cities across America. People had grown familiar with electric trolleys and railways, and technology had produced motors and batteries in a wide variety of sizes. The Edison Cell, a nickel-iron battery, became the leader in electric vehicle use. By 1900, electric vehicles were the most popular car. In that year, 4,200 automobiles were sold in the United States. Of these, 38 percent were powered by electricity, 22 percent by gasoline, and 40 percent by steam. By 1911, the automobile starter motor did away with handcranking gasoline cars, and Henry Ford had just begun to mass-produce his Model T’s. By 1924, not a single electric vehicle was exhibited at the National Automobile Show, and the Stanley Steamer was scrapped that year. Because of “Clean Air” legislation, the energy crises of the 1970s, and concern for the well-being of the environment, car manufacturers have again marketed several all-electric cars and “hybrid” vehicles.

Hybrid cars use two or more different power sources to propel them, such as a gasoline engine and an electric motor. General Motors sold the Impact, an electric vehicle. And Honda offered people two hybrids, the Insight and a Civic sedan. The Toyota Prius is a hybrid that first went on sale in Japan in 1997, making it the first mass-produced hybrid vehicle. According to the United States Environmental Protection Agency, the 2008 Prius is the most fuel-efficient car sold in the United States. Because of this, electric cars and hybrid vehicles may be the new cars of the future, eventually replacing all-gasoline-powered cars.

Which tree produces the largest nut?

The coco de mer tree, a palm that only grows today on two islands in the Seychelles, produces both the largest seed (each weighs about 44 pounds [20 kilograms]) and the largest nut in the world. The nut, which takes six to seven years to mature and another two years to germinate, is sometimes called the sea coconut or Seychelles nut. When early explorers first discovered the nut, they thought it came from a mythical tree at the bottom of the sea.

Sixteenth-century European nobles decorated the nut with jewels as collectibles for their private galleries. Today, the coco de mer is a rare protected species.

Why do I get sick?

When you get sick, part or all of your body is not working as it should. The cause of sickness can come from inside your body or from the outside world. Diseases that start on the inside are usually inherited in the genes that you receive from your parents, Which make up the master plan that determines how your body will grow and run. Abnormal development or functioning of different body systems is the cause of many chronic (long-lasting) diseases. Things in the outside world can cause sickness, too. Poisons in the environment can cause illnesses in people. Not eating the right foods, with their important nutrients, can also cause diseases. But the most common cause of sickness from the outside world is infectious agents. These agents are usually microscopic organisms (living things so small that they can only be seen with the help of microscopes) like bacteria and viruses, which we commonly refer to as germs.

Bacteria and viruses and other microscopic organisms live in the air, water, and soil that make up our world. They are on the things and people we touch and in the food we eat. Many of them are beneficial: bacteria are needed to make cheese, some bacteria help vegetables like peas and beans grow, and some bacteria clean the environment and enrich the soil by feeding on dead plants and animals. But there are other microscopic organisms that invade the bodies of plants and animals—and people—and cause diseases.

How long is each year?

Each calendar year is exactly 365 days, 5 hours, 48 minutes, and 46 seconds. This is the amount of time between two successive crossings of the celestial equator by the Sun at the vernal equinox (the first day of spring). The fact that the year is not a whole number of days has affected the development of calendars, which over time generate an error.

The current calendar we use, called the Gregorian calendar, attempts to fix this by adding an extra day to the month of February every four years. These years are called “leap years.”

Why do we say that someone looking for trouble has a “chip on his shoulder”?

In early England, one man would challenge another to a duel by slapping his face with a glove. The challenge was a serious matter of honour, and if the slapped man did not accept it, he would be branded a coward. Having a chip on your shoulder was kind of an early Wild West equivalent of the glove slap, though generally less mortal in nature.

Boys and men would place a woodchip on their shoulder, challenging anyone who dared knock it off to a fistfight. So, if a man had a “chip on his shoulder,” he was clearly in an aggressive mood and spoiling for a fight.