Ask Mr Brain...all will be explained

How do people take the caffeine out of coffee? Regular raw (green) coffee beans are soaked in hot water or steamed for about five hours. This softens the beans and helps open their pores. The beans are then treated with solvents made of chlorine, for example.

Carbon dioxide is also used in the process. The beans are then reheated, so the solvents can take the caffeine with them in the steam.

Once the beans are decaffeinated, with 97 per cent of the caffeine removed, the beans are dried. Then they go through the regular roasting process.

Are sugar and salt made up of the same crystals? Sugar and salt do not look alike close-up. If you took a magnifying glass and looked at both salt and sugar, they wouldn't look the same. Sugar is made up of large, hard-to- define crystals, while salt is made of tiny cubed crystals.

When salt and sugar are in large pieces they are clear because they reflect light. When they are broken into tiny pieces, they scatter some of the light, while also reflecting some of it. This makes both look like white powders.

If you'd like to make a giant salt crystal, fill a glass with warm water, and put as much salt in the water as it can absorb and cover it with a tissue. In about a week, you'll have big salt crystals! Do flies have a sense of taste? Flies don't have anything that we would call a tongue, but they do have sensory organs. Flies have mouth parts they use mostly to suck up liquids.

The major structure of the mouth part is the labellum, which has lots of tubules that make it spongy. The labellum has sensory organs that can help the fly taste. But a fly's feet also help out. That means the fly can taste something by walking on it! Flies generally don't chew; they suck liquids from their prey. But the sensory organs tell them if they should continue eating what they've tasted.

How did Stonehenge originate? Stonehenge, in south-western England, means 'hanging stones'. It began as a ditch and an earthen wall that circled about the site. Experts say it probably was begun by prehistoric people around 5,000 years ago.

A ring of large grey sandstone and two circles of blue stones were added over the course of hundreds of years. Even the smaller stones weighed several tonnes. People believe that Stonehenge was a religious site, and that the people who built it used the cycles of the sun and moon in their worship.

How does a map-maker make sure he has the right distance? Map-makers are officially called cartographers. To measure distances for maps, cartographers use one of three ways. They can measure the ground, use geometry and the science of angles, or use photos from aircraft or satellites.

Many of the calculations are done by computer these days. Once the real distances are established, scale is developed.