Was Persia rich? Persia became a wealthy empire under Darius I. The palace he lived in was huge and was located in Persepolis. It had a great hall which could accommodate 10,000 people. During his invasion of Persia, Alexander the Great took 4,500 tonnes of...
Can echoes travel through water? Sound can travel through water. This means that echoes can travel through water too. The speed at which sound travels through water exceeds 1,430 metres a second. Ships have devices for sending and receiving signals under water. Such devices are...
What are scallops? A dish of scallops in restaurants resembles small squares. They are actually the muscles of certain molluscs. The muscles help to open and close the shells of the molluscs. Scallops are always wandering from place to place. They move by sucking water...
When did fish appear on earth? The first fish appeared in the seas around 500 million years ago. They did not have jaws or fins. Dunkleosteus was a fish that was a fearsome predator with razor-sharp bony cutters in its jaws. It had an armoured...
What is a Parthian shot? The Parthians lived in Persia in 1000 BC. After Alexander the Great died they took over Persia. One of the favourite tricks of Parthian archers during battle was to act as if they were retreating and then turn in their...
Did meteors kill dinosaurs? Scientists feel that dinosaurs and other species were wiped out because of the impact of a falling asteroid 65 million years ago. The asteroid formed a huge crater near the Mexican coast. The impact also changed the climate of the earth...
What shapes Mercury’s surface? Mercury has no atmosphere and thereby no weather. So the craters that formed on its surface many years ago by falling meteorites still remain as there is no weather to wear them away. The entire planet is covered with such craters....
When was ether first used in surgery? In 1818, an English scientist, Michael Faraday, suggested that ether could be used to relieve pain. In 1842, an American doctor named Crawford W. Long used ether to make a patient unconscious while he removed a cyst. In...
Who discovered hypnosis? Hypnosis is the ability to influence the behaviour and feelings of other people. Even primitive peoples have practised it as a form of medicine. A Viennese doctor, Franz Mesmer, used hypnosis to treat patients long ago. It came to be called mesmerism....
What is grafting? Grafting in plants is the process by which a twig from one plant is inserted into a slit made in the bark of another plant. In this manner, apples can be grafted on pear trees and peaches on apricot trees, etc. However...
