Category Science

Diamonds are very expensive because they occur at relatively few places in the world – like Russia and South Africa – and are very difficult to extract. They are made of carbon and are the hardest substance known to us, which is the result of the high pressure at their place of origin deep below the Earth’s surface. They are naturally thrown up on the Earth’s surface through volcanic eruptions. For this reason they are mined in the vents of the extinct volcanoes. Being very hard they have great industrial use for grinding tools. Diamonds can also be made artificially by creating the same conditions as found under the surface of the Earth, but these artificially made diamonds are not as valuable as natural diamonds. 

Windmills are machines that are driven by wind. Their blades have slightly diagonal surfaces. If the wind hits them from front, they deflect it to the side and in this way convert the wind pressure in a rotary movement. Initially, millers had to set the blades themselves in such a way that the wind came onto them from the front. The rotary movement of the blades gets transferred to the milling stones inside the mill through cogwheels. Windmills were traditionally used to mill corn to make flour and grate spices. They also acted as drive for oil presses and sawmills. 

Years ago people used wind only for running windmills, but today we have large wind power plants with triple-blade rotors. These power plants make electricity which can be used for residential as well as industrial purposes. The power of wind can be observed in nature too – it forms huge rocky arches or impressive sand dunes. We can feel it even while sailing, mainly while sailing at ‘high wind’. The importance of wind is also felt when sailors have to come to an involuntary stop in the windless areas of the subtropical calms. 

When compared with the two-blade rotors, the three-blade rotors are more stable and quieter. The disadvantage of the two-blade rotors is that they need a special ‘wobble’ motor to prevent the severe collision when the rotor passes the tower. When the rotor blade is on top, the wind presses against it with full force and bends it. At the same time, the opposite rotor blade is in front of the tower. Thus, it cannot counteract the high pressure at the upper blade which leads to a strong jerk which is compensated by the wobble motor. This problem does not occur in three-blade rotors because the blades are never exactly opposite to one another. In addition, the three blades form a kind of disc for the flowing wind and are hardly prone to faults. 

When we sail at ‘high wind’, we travel – as far as possible – against the wind. The wind, thus, comes diagonally from the front. The propulsion takes place when the wind sweeps quickly past the sails, which are possibly set up in the middle of the boat. In contrast, if the boat travels ‘before the wind’; the sails are diagonal to the boat. The wind comes from behind, blows into the sails, and pushes the boat forwards. 

The horse latitudes are the areas in the northern and southern hemispheres of the Earth, lying between the two big wind zones: between the trade wind and the westerly wind areas. In these areas, there is almost always no wind. Therefore, the sailboats of the early sailors were stalled often for weeks. The region of the subtropical high was given the name ‘horse latitudes’ because the sailors who transported horses on their sailboats threw their horses and cattle overboard to save on provisions during the long periods of calm. The areas were reported to be ‘strewn with bodies of horses’. This is supposed to be one of the reasons why these areas came to be known as horse latitudes.