Ask Mr Brain...all will be explained

PUBLISHED : Monday, 20 December, 1999, 12:00am
UPDATED : Monday, 20 December, 1999, 12:00am

Which is the longest mountain range in the world? The Andes mountains, which stretch 7,200 kilometres along the entire west coast of South America from Tierra del Fuego to Panama and Colombia, form the world's longest range above sea level.

Beneath the waves, however, it is another story. The Mid-Atlantic Ridge, a submarine mountain range, snakes along the floor of the Atlantic Ocean for 16,000 kilometres from Iceland to near the Antarctic Circle. Some of its peaks rise more than 4,000 metres above the ocean floor.

What are the big spheres you see on top of hills around Hong Kong? PUPPY Chan Nam Chong Memorial College They are part of the weather radar system run by the Hong Kong Observatory. The radar equipment inside the protective spheres can detect rain in the atmosphere by sending out pulses of microwaves from its scanning antenna. When the pulses meet raindrops or ice, a certain amount of energy is lost and some is reflected back to the scanner. From the time delay and strength of the returning signals, information about distance of rain clouds and rain density can be worked out. Meteorologists can also track tropical cyclones, more commonly known as typhoons, with the radar system.

The first weather radar in Hong Kong was built in 1959 on Tate's Cairn and was in service until 1979.

Today, the radar images received in the SAR are exchanged with Guangdong Meteorological Bureau via a Beijing-Hong Kong circuit.

Is it true viruses cannot be killed because they are not alive? Viruses are very simple and extremely small particles consisting of a strand of DNA and a protective cover. They are the nearest thing to zombies - the living dead - in the natural world.

They do not carry out the usual functions of normal living cells. For example, they do need nutrients or oxygen and they do not grow. Since they cannot reproduce by themselves they fail one of the basic tests for life. They need to invade living cells and hijack the cell's system to turn it into a factory to produce more viruses.

Viruses are about 1,000 times smaller than a bacterium. They have chemical feelers that bond to the outside of the cell. Locking itself on, the virus injects its DNA into a cell, leaving the covering behind, and turns the cell into a factory to produce more viruses.

Once inside, the DNA can roam about freely. The cell starts to produce enzymes, new covers and components that the virus specifies. Eventually the cell becomes so full of new viruses that it bursts, spreading the disease further. The cell itself dies.

The body's immune system tries to fight back by producing proteins that bind to the viruses and prevent them from attaching to new cells.