What is a photoelectric cell? A device that produces or increases the strength of an electric current when light falls on it is called a photoelectric cell. These cells are used for many purposes. The solar batteries in satellites and spacecraft are actually several photoelectric...
Were there libraries in ancient times? The people of Mesopotamia had libraries as early as 600 BC. Instead of books they had clay tablets which were arranged according to subject in temples and palaces. Egyptians too had libraries. Books were rolls made of papyrus. They...
What is a fireball? Many of the meteoroids that enter earth’s atmosphere are small specks. However, some are the size of pebbles. The larger, pebble-sized ones burn for a longer duration and more brightly than the others. This produces what we call fireballs.
Which birds cannot fly? Not all birds can fly. Flightless species of birds include ostrich, the rhea of South America, the emu of Australia and a few others. Large breast muscles are needed to fly but big birds do not have room for such muscles....
What makes hair curly or straight? A Our genes determine whether our hair will be curly or straight. Africans have tightly curled hair. Chinese have very straight hair. If one cuts across the shaft of a straight and curly hair and examines the two sections...
Why were Egyptian tombs robbed? The ancient Egyptians’ tombs were filled with treasures. Wealthy Egyptians were buried with things they would need in the afterlife, for the people believed in life after death. Food, clothes, jewellery, pets and even models of servants were among them....
Why is Venus so hot? Imagine an oven set on high. The average temperature on Venus is more than twice this temperature. Its atmosphere contains mostly carbon dioxide. It is a gas which traps heat. As the years pass it traps more and more heat...
Did dinosaurs sit on their eggs to hatch them? In 1993, there was another expedition to the Gobi desert. During this expedition, fossilized remains of an Oviraptor were found. It was sitting on a nest of eggs. This proved that some dinosaurs did sit on...
What makes sap go up a tree? One theory ascribes it to osmotic pressure. Liquids and dissolved substances pass through membranes in living things. This is called osmosis. Dissolved chemicals in contact with a membrane press against it. This is osmotic pressure. Yet another holds...
What causes the ‘pop’ in soda pop? Soda pop is a mixture of flavoured syrup, water and other ingredients. Carbon dioxide is also added under pressure. The mixture, still under pressure, is sealed in containers. Part of the carbon dioxide is trapped in the empty...
