What is the Great Barrier Reef?

-
The Great Barrier Reef is the longest coral reef in the world. It measures about 2000 km from end to end. The reef stands in the sea off the north-east coast of Australia. It is built of hard lime stone and most of it is produced by millions of tiny soft-bodied creatures called coral polyps. Most of the top of the reef lies just beneath the water and is a danger to ships. There are 10 safe passages where the ships can sail through. More than 340 varieties of coral have been identified on the reef. They display an astonishing array of colours and are home to a variety offish and other sea creatures. Part of the reef has been destroyed by crown-of-thorns starfish which feeds on the little reef builders.

Comments

Post a Comment

Popular Posts

How do Aircrafts Fly?

-
Image
T o fly in the air, aircrafts need power, which is provided by the engines. They need a lift to rise from the ground and stay in the air. This lift is provided by the wings. The aircraft wings have a special shape called an aerofoil . The top surface of the wing is curved, while the bottom is flat. As the plane cuts through the air , the air that flows over the wing has to travel greater distances than the air flowing underneath the wing, so it has to travel faster over the top. This reduces the pressure above the wing and creates lift At take-off, the engine provides the power to generate lift. The forward thrust of the engines balances the resistance or drag set up by the air.
Read more

Why is Venus so Hot?

-
Image
T he planet Venus is named after the Roman goddess of beauty and love. It is the brightest planet in the Solar System. It is visible as a star. Venus is much hotter, because it is much closer to the Sun. The atmosphere there is 90 times thicker than that of the Earth and the surface is hidden in a white cloudy cloak. This thick atmosphere acts like a blanket which holds back the heat of the Sun and turns the midday temperature to 4800C. The atmosphere on Venus consists mainly of the carbon dioxide gas which acts as a greenhouse roof , trapping the Sun's heat. The rocks on Venus are hotter than boiling water. Above the rocks, winds blow at a speed of 320 km/hour .
Read more

When were the First Spinning Machines Invented?

-
Image
People in the olden days used to spin thread by hand . They pulled fibres out of cotton and wool and twisted them together into thread. Spinning machines were invented in Britain in the 1700s. These machines had rollers turning at different speeds to twist the fibres into yarn. James Hargreaves in 1764 produced the first successful spinning machine. It was the hand-powered jenny which produced thin yarn. Richard Arkwright's water frame of 1769, powered by water wheels, gave a sturdy thread. Samuel Crompton combined these two spinning machines in 1779 , to make the spinning mule, which could spin many kinds of yarn. These machines were the precursors of the Industrial Revolution . 
Read more

When were the First Mechanical Clocks Made?

-
Image
The first mechanical clocks are believed to have been made in China in 1088 AD. Later in 1200s, they were first made in Europe. Such clocks made in Europe were driven by a weight on the end of a cord wound round a drum. As the drum rotated, it turned the hands of the clock. The earliest known clock was made in Spain in 1276 AD and the oldest mechanical clock that still works is in Salisbury cathedral in Britain. It was made in 1368. These clocks had devices called escapements to keep the hands turning at the correct rate, so that the clocks depicted the correct time.
Read more

What is a Geostationary Orbit?

-
Image
Artificial satellites sent from the Earth orbit around the earth. The ones near the Earth orbit faster than the ones far away. A satellite 35,900 Km above the Earth's surface, takes 24 hours to orbit once. The satellite is always above the same point on the Earth's surface as the planet rotates. Geostationary orbit is also called as geosynchronous ' orbit. Such satellites are used to receive telephone and television signals and retransmit them over long distances.
Read more