The waves that break on the seashore are usually caused by winds blowing across the open sea. During storms, waves reach 12m (39 ft) or more in height. The highest wave recorded in the open sea was 34m (112ft) high. Other large and often destructive waves, called tsunamis, are triggered off by earthquakes or volcanic eruption. They are low, fast …

Bodies of ice, ranging from vast ice sheets to valley glaciers move downhill because of gravity. In Antarctica the ice sheet moves by only a metre (39in) or so a year, while most valley glaciers move the same distance in a day. Special circumstances can speed up the movement of the ice. In 1936-37, Alaska’s Black Rapids Glacier moved downhill …

Telescopes are like time machines. The father off in space they look, the farther back in history they go, because of the time that light takes to reach us from distant objects. The farthest galaxies and quasars visible in the Universe are so far away that their light has taken over 10,000 million years to reach us. Therefore we see …

Stars are too far away to use kilometers or miles to measure their distances, so astronomers use light-years instead. One light-year is nearly 10 million million km, and the nearest star, Proxima Centauri, is 4.25 light-years distant. The farthest heavenly bodies are at the unimaginahble distance of 8,000 million light-years! As the earth moves around the sun, the nearer stars …

The stars are so far away from us that astronomers do not normal measurements such as kilometers or miles. Instead, they have invented a unit called the light year. This is the distance traveled in one year by a beam of light, which moves at the fastest speed in the Universe, 300,000 km (187,000 miles) per second. A light year …

The Secretary bird prefer to walk around looking for its prey rather than to fly. As a result its feet are less adapted for killing. The Secretary bird strides around African grasslands on its long legs hoping to disturb its prey. It catches insects, small mammals and lizards, but it is best known for eating snakes. It attacks a snake …

In stormy weather, powerful waves hurl loose rocks at the shore, undercutting cliffs. While soft rocks are worn back to form bays, hard often survive as headlands in which waves then hollow out caves. If the roof of a cave collapses, a ‘blow hole’ is formed in the ground above. When waves break in the cave, clouds of spray burst …

Most people are familiar with the idea of the sea eroding or destroying land. For example, storm waves can remove rock from many coasts. Some loose rock is swept out to sea, but some is moved along the shore. Groynes, or sea walls, which jut out from the coast in many resorts, are built because of this movement. Without them, …

On hot days at the seaside, cool breezes blow inland from the sea. This is because lands warm up faster than water. Hot air over the land rises, and cool air from the sea is sucked in. At night, the reverse happens, because the land cools faster than water. In this way, the sea moderates the climate of coastlands. Ocean …

Hybrid engines use two or more power sources. They consist of a usual fuel engine, complemented by a pollution-free engine, an electric engine for example. The fuel engine and brakes are used to recharge the batteries for the electric engine, eliminating the need to plug in while unused. When brakes are applied, some of the energy being used to stop …