What is blood pressure? The heart pumps our blood so that it circulates throughout the body. The blood is forced out into the arteries which expand to receive the blood. But the arterial walls resist this pressure so that the blood is squeezed out into...
Who were the Mycenaeans? After the Minoans came the Mycenaeans from mainland Greece. They were both traders and warriors and built fortified towns. The walls around the city of Mycenae were built using huge stone blocks. They were good hunters too and used to hunt...
What is plasma? Fifty five percent of our blood is made up of plasma, a fluid which is clear and slightly yellowish. Many types of cells are found suspended in Plasma carries antibodies which make us immune to disease and hormones. It also transports digested...
Did the Babylonians know maths? Babylonians used cuneiform writing. Their mathematicians developed a system of counting based on the number 60. As 60 can be divided in various ways, the system proved to be very useful. It is still in use for recording time (60...
What is pitch? Loudness, pitch and tone quality distinguish one sound from another. Pitch is used to describe the high or low quality of sound. It depends on the speed of vibration of the object producing the sound. Pitch is directly proportional to the number...
Why do tidal waves occur? Tidal waves or tsunamis are caused by sudden movements of the earth under the se Such waves occur during an earthquake. Initially water is sucked away from the coast as if by a giant vaccum cleaner, followed by the tsunami...
What is the nitrogen cycle? Nitrogen is very important for the survival of plants, animals and humans. Plants take simple nitrogen compounds from the soil. Animals get nitrogen by eating plants. Nitrogen returns to the soil as waste. Bacteria convert the waste into simple nitrogen...
Why do plants make starch? Human beings get starch from plants where it is found as small grains. Plants make starch which serves as food for seedlings and new shoots until they are able to make their own food materials. Sunlight and chlorophyll, as well...
Can a porcupine shoot its quills? Porcupine quills are loosely fastened to the body of the porcupine. When an enemy attacks a porcupine, the latter swings its tail into the attacker’s face. This makes the quills fly out making it seem as if the quills...
What is cataract of the eye? In the old days, people believed that cataract of the eye was caused by an opaque film that came down like a cataract or waterfall over the lens of the eye. Cataracts are cloudy or opaque discolourations within the...
