Ask Mr Brain... all will be explained

PUBLISHED : Wednesday, 16 August, 2000, 12:00am
UPDATED : Wednesday, 16 August, 2000, 12:00am

What and where is the Earth's ionosphere?

The ionosphere is a region in the Earth's atmosphere that has an effect on the transmission of radio waves. It has a high concentration of ions - electrically charged particles.

The ionosphere allows the transmission of radio signals to follow the curve of the Earth's surface.

The ionosphere begins at a height of about 50 kilometres above the Earth's surface but is most distinct at altitudes of above 80 km.

It has three layers. The lowest is called the D region and is most strongly ionised during the day. It reduces shortwave and broadcast- band radio signals but this effect largely disappears with nightfall.

The E layer, extending from 90 to 140 km, is a region of ionised molecules and strong electric currents.

The F region, from 140 km upwards, is characterised by ionised atoms and contains the layer in which ion concentration reaches a maximum.

Why do men have nipples?

In the first few weeks when a baby is developing in its mother's womb, nipples start to grow regardless of what sex the baby is. It is only in about the tenth week of development that a baby boy starts to grow testes.

The testes produce the male hormone testosterone that triggers male organs to grow and male characteristics to appear.

However, not all males of mammal species have nipples. Male horses for example, do not have them. In female horses, two teats are located near the hind legs.

It is thought that stallions do not have them because of a lack of space as their male organs are already located there.

What is a cafeteria?

It is a self-service restaurant in which customers select dishes from an open-counter display. The food is usually placed on a tray, paid for at a cashier's counter and carried to a dining table by the customer.

The modern cafeteria is designed to ensure a smooth flow of customers. It is particularly well-adapted to the needs of institutions such as schools, hospitals and big companies. It attempts to serve large numbers of people efficiently and inexpensively.

In addition to providing quick service, the cafeteria needs fewer employees than most other eating establishments.

Food industry historians consider the first cafeteria was established in 1891 in Kansas City in the United States by the Young Women's Christian Association.

What purpose does ear wax serve?

The purpose of ear wax is to stop dirt, dust and water from getting to and damaging the eardrum. Ear wax is secreted from glands in the ear canal. It is part of the ear's self-cleaning system, designed to dry up and fall out, taking dirt with it.

Removing ear wax with cotton- buds or by inserting anything into the ear are not recommended. Although some wax may be removed this way, you could push the rest deeper back into the ear canal where it could cause a blockage.