What was an acropolis? An acropolis was actually a fort. In ancient times, Greek city-states comprised a walled city with an acropolis and an agora. The latter was a huge open space for meetings and markets. With the passage of time, the acropolis became a...
Is epilepsy a disease? During the Middle Ages, people who had epilepsy were believed to be mad. Epilepsy is a disease that affects the nervous system. Epileptic people suffer from sudden fits or convulsions. They may lose consciousness and become comatose too. Epilepsy is caused...
What is forestry? Forestry is the science of caring for forests. England passed laws about the cutting down of forests more than four centuries ago. Forests are very essential for our survival. For every tree that is cut down another must be planted. Forests provide...
Why does a top spin? The spinning of the top can be explained by the term ‘gyroscopic inertia’ A spinning body will continue to spin because of inertia Suppose there was an imaginary line through the centre of the top, it would point in the...
What is a hormone? Hormones are secretions of the endocrine or ductless glands. Organs like the liver and kidney also produce some hormones. The function of hormones is to regulate the internal activities of the body like growth, nutrition, use of food materials and reproduction.
Why do pipes crack when the water in them turns to ice? Most substances shrink when they change from liquid to solid state. But water is one exception. When water becomes solid or ice, it expands by around one ninth of its volume. So 9...
How is wind speed measured? The instrument used to measure the wind speed is called anemometer. It was discovered in 1667 by an Englishman called Robert Hooke. An anemometer usually consists of some aluminium cups on a spindle. The cups turn with the wind and...
How do zips work? Zips have two rows of teeth. These are joined together by a sliding key. The key locks the teeth together or pulls them apart. The zip fastener was first invented by an American, Whitcomb Judson, in the 1890s. But the interlocking...
Do winds have different names? Not all winds have names but some do have special names. Such names have been acquired for certain reasons. The doldrums are found near the equator. Here, there is a great belt of rising air and low pressure. Such winds...
When were bacteria discovered? The first high-powered microscope was made by Antoine van Leeuwenhoek, a Dutchman. It could magnify things up to 200 times. In 1683, he published some sketches of bacteria. These are tiny living organisms which can cause disease.
