Why we shiver when we are cold

Whenever we feel cold, our normal body processes begin to slow down and our body temperature drops.

However, before the body temperature drops to a critical level, the body tries to raise its own temperature by shivering.

The rapid contraction of muscles is shivering.

It is this contraction which helps generate heat within the body.

How X-rays got their name

The German Physicist Wilhelm Roentgen discovered X-rays in 1895. He was astonished by the way in which the rays could penetrate things and had no idea what they could be. Therefore he called them X-rays, because in science X is often used to represent something that is unknown.

X-rays were also called Roentgen rays for a time but the name X-ray stuck.

Roentgen's name is commemorated in science in the unit of X-ray dosage - which is the roentgen.

Who pioneered hang-gliding

Hang-gliding is not a modern invention. It was pioneered a century ago by the German inventor, Olto Lilienthal. He built several different kinds of hang-gliders to test aircraft design, managing to fly as far as 250m (820 ft). Lilienthal was killed in a crash in 1896.

How scallops get about

Scallops are a group of animals which belong to the family of molluscs. These particular molluscs are known as bivalves; in other words they have a shell composed of two halves or valves.

Most bivalves spend their time attached to rocks or hidden in the sand. If they are threatened, they dig deeper into the sand to escape. The scallops can also do the same but they have a more ingenious method of getting away. They vigorously clap their valves together to rise from the seabed and swim off to safety.

What dams have in common with eggs

The curved strength. High dams often consist of a slim concrete arch. The dam curves into the water so that as the water pushes against the dam, it compresses the whole structure. Compressed concrete is very strong, and the dam remains standing even though it is very thin.

Similarly a bird's egg has to be sufficiently strong to protect the growing bird inside. Yet it has to be weak enough to allow the bird to break out and hatch. Eggs are curved for this reason. A force applied to the outside compresses the egg making the shell stronger and preventing it from breaking (unless the force is extremely strong.)

The growing bird is thus protected inside. However, as the shell is not compressed when force is applied from the inside, the chick finds it easy to force its way out into the world.