Where was the wheel invented?

The earliest wheels discovered so far were found in graves at Kish and Susa, two ancient Mesopotamian cities. These wheels are believed to date from 3,500 B.C. They were made from three planks, clamped together with copper clasps. This kind of wheel also existed in ancient times in Europe and the Near East. No one is sure where the wheel was invented, but this archeological evidence suggests it was probably in ancient Mesopotamia.

A wheel with proper spokes was not invented until after 2,000 B.C. There are records of this wheel in northern Mesopotamia, central Turkey, and north east Persia. By the 15th Century B.C., spoke wheels were being used on chariots in Syria, Egypt, and the western Mediterranean.

The solid wheel was used mostly in farming. Tripartite wheels - wheels with three spokes - were being used in the Bronze Age in Denmark, Germany, and northern Italy for carts.

The invention of the wheel made it possible for people to transport heavy objects much more easily. It also enabled them to travel farther and trade with each other more easily, and so find out about other countries and customs.

What makes you feel dizzy?

Dizziness most commonly occurs when a person who has been moving around with speed stops suddenly. The sensitive liquid in the inner ear, which mainly controls balance, continues to move around for a time after the body has stopped. So the surroundings appear to be still in motion. However, it takes only a few seconds for the fluid and balance to settle.

This sensation, which is also called vertigo, may also occur to someone looking down from a height or on board ship. Here the cause is probably not so much physical as a nervous reaction which affects the fluid in the inner ear.

Why do we Become Sea Sick?

We become sea sick because our balancing organs, the labyrinthine portions of the inner ear, are disturbed by out of level movements, by sudden turning movements, and by sudden changes in movements in a straight line, either horizontal or vertical.

The three semicircular canals, filled with fluid are set on different planes in the ear. When sudden movements occur, each canal is affected differently. The nerve endings have no time to convey information to the brain so giddiness is likely to occur.

Nowadays, seasickness comes under the general heading of motion sickness, a name invented by Sir Frederick Banting in 1939, which includes the discomfort people feel while traveling in all kinds of vehicles.

Sea sickness may vary with individuals from slight uneasiness to complete transition. The symptoms are pallor, cold sweating, nausea and vomiting. People who have lost their ear labyrinths because of disease do not become sea sick. Others become resistant to it. We say they develop their "sea legs", but it would appear to be an adjustment of the central nervous system rather than the organs of balance. Some people find it helpful to keep their gaze firmly fixed on a steady object.

When did Mark Twain live?

Mark Twain was the pen-name of the American writer Samuel Langhorne Clemens who was born on November 30, 1835 in the village of Florida, Missouri. He was first apprenticed to a printer and worked on newspapers in New York and Philadelphia. He became apprenticed as a steamboat pilot in 1856 and stayed with the boats until 1861 when he went to Nevada to seek a fortune in mining. In this he was successful, but he soon obtained a job as a newspaper reporter signing his articles Mark Twain. He took the name from a phrase meaning, "two fathoms deep", which he had used to report river soundings during his steamboat career.

The rest of his working life was devoted to writing. He produced books about travel, such as A Tramp Abroad and Roughing It, but he is best remembered for Tom Sawyer (1876) and The Adventures of Huckleberry Finn (1884) which tell of amusing and hair-raising adventures of young boys in 1830s. The blend of romance, horror and humor in books has made them favorites with children and adults ever since. Mark Twain was still writing his autobiography when he died on April 21, 1910.

What is a Mandarin?

The word "mandarin" has several meanings which are all interconnected. Perhaps the most common use of it is as the name for the nine grades of Chinese administrations who were selected by a series of very difficult examinations.

In the T'ang dynasty (A.D. 618-906), this system of scholar officials was operating extremely effectively. This administration proved to be the backbone of the great Chinese Empire that persisted through about 20 successive dynasties.

The name mandarin is also given to the language spoken in China by officials and educated people and to a grotesque toy figure in Chinese costume which goes on nodding after it is shaken. The mandarin scholar-official wore yellow silk robes and so a dye obtained from a coal tar, a sweet, flattened, easily-skinned orange and a yellow liquor also have the name mandarin.

Where was the First Radio Signal sent from?

Guglielmo Marconi is usually credited with sending the first radio message. Marconi was born in Bologna, Italy. He came to England in 1896 and obtained a British patent for his wireless telegraphy system. In 1897 he established a radio transmitter on the roof of the Post Office at St. Martins-le-Grand in London, and sent a message a distance of a few hundred yards.

He continued to improve his apparatus and in 1898 radio was installed aboard a ship at sea, the East Goodwin lightship off the south-east coast of England. In the following year wireless messages were sent across the English Channel.

The first radio transmission across the Atlantic was on December 12, 1901 from a station on the cliffs at Poldhu, in Cornwall, and the message, three dots representing the letter S in the Morse code, was picked up at St. John's in Newfoundland.

The existence of radio waves was first demonstrated by Heinrich Hertz, a German professor, in 1887. Marconi based his experiments on Hertz's research.

Why does the Mediterranean Sea look blue and the Atlantic Ocean look green?

The blueness of the Mediterranean and the greenness of the Atlantic can be simply explained by the amount of sunlight reaching the water's surface. The more sunlight, the bluer the water.

However, in the case of the Atlantic, another factor helps to create the green effect and this is the coloring produced by plants decaying on the ocean bed. When these plants decay, yellow pigments are released, and this pigmentation added to the already duller blue waters of the Atlantic produces the characteristic greenish shade which distinguishes the Atlantic from the bright blue Mediterranean.

When does a Lizard shed its Tail?

A lizard is capable of shedding its tail at any time. If a lizard is attacked it may sacrifice its tail in an attempt to surprise and confuse the enemy.

When a lizard's tail is caught by an assailant or a trap, it will simply snap off and enable the reptile to escape.

Although some lizards' tails can be four times as long as the rest of their bodies, the loss in only temporary. A new tail can be grown quickly from the old stump.

Why do Bats make a high-pitched sound as they Fly?

Bats use high-pitched sounds to find their way about. The are nocturnal animals. That is they move about by night. So they have developed their hearing to such an extent that they can find their way by a method known as echo-location.

The blind-flying abilities of bats were first studied by Lazzaro Spallanzani (1729-1799). He surgically removed the eyeballs from several bats to prove that they did not need to see to fly.

In the 20th Century, biologists, using electronic instruments, have carried out experiments with bats. They have discovered that bats find out where to go by emitting high-frequency sounds and receiving the echoes as they bounce off objects. Most of the sounds have too high a frequency to be heard by the human ear.

Bats commonly fly together in groups, but apparently they are not confused by the sounds and echoes produced by each other. When hunting in woods and in the rain they are able to discriminate between the faint echoes bouncing off the ground, tree trunks, branches, twigs and raindrops.

These tiny flying mammals have been using the equivalent of our modern sonar device for millions of years.