SHADOWS

People have always been fascinated by shadows because, although they are always with us, we can never catch them or touch them. For this reason, shadows are often found in games and stories. Do you remember the story of Peter Pan losing his shadow?

But what is a shadow’ It is the dark area caused by an opaque object blocking light. It has the same shape as the opaque object. Shadows appear because light travels in a straight line and cannot go round obstacles.

Shadows can gradually change shape. They get longer when the angle between the light source and the opaque object increases. They get shorter when the angle decreases.

Try this experiment: darken a room by turning off all the lights and closing the curtains. Then, turn on a lamp or a torch and put your hands close to the light source. Move your hands farther away to see how their shadows change shape. 

PERPETUAL MOTION (Waterfall by M. Escher 1961)

All the machines we use need energy to function: a television needs electricity, a car needs petrol, a sailing boat needs wind, a bike needs a person to push the pedals.

Throughout history, people have tried to invent a machine that, once it was started, would not need more energy to keep functioning. This type of machine is called a perpetual motion machine.

Many people have tried to achieve fame by inventing a perpetual motion machine. However, all their machines eventually stopped because the energy ran out. If these inventions had worked, they would have changed the course of history.