Who invented traffic signals? The first traffic controllers were foot patrolmen. Initially they directed traffic using their hands and later they used hand-operated traffic lights. In the early 1920s automatic traffic lights were used for the first time. In 1927, traffic-actuated controllers were patented. These...
What is the significance of April Fools’ Day? On April Fools’ Day we play practical jokes on friends and relatives. Some think the French started it. In 1564, Charles IX decreed that the New Year should begin on January 1st. Until then April 1st was...
What are bacteria? Bacteria are felt to be the lowest members of the plant kingdom. A bacterium is a single piece of living matter which has no nucleus. Bacteria have many roles to play. Some cause plants and animals to decay while others cause fermentation....
What makes a waterfall? Waterfalls are caused by a stream or river plunging over a wall of rock like a cliff or a precipice. A big size waterfall is called a cataract. If the rock wall is slanted, the flowing water is called a cascade....
Why are even-numbered pages always on the left? In a book, the first left hand page is the second side of the first right hand page. If that page is the first page, then it must be page 2 on its other side and every...
Why do our ears ring sometimes? The ringing sound in our ears we sometimes experience is called tinnitus. One reason for it is a bad connection between the inner ear and the brain. The inner ear contains hair cells. Damage to these cells makes them...
How is humidity measured? Humidity is the amount of water vapour in the atmosphere. If the relative humidity is 80%, it means that the air is holding 80% of the water vapour it can hold. A hygrometer is used to measure humidity.
What is a colour wheel? A colour wheel is often used by interior designers. This is done to choose colours which are in harmony with each other. If the intention is to create a more striking effect, contrasting colours are chosen. The colour wheel has...
How come spiders don’t get trapped in their own webs? A spider web has sticky threads to trap prey. But the spider avoids the threads while weaving the web. Some spiders like the orb spider use both dry and sticky threads for the web, using...
What is conservation? Conservation is the effort to preserve the earth’s natural resources so as to prevent them from being depleted. Natural resources include both renewable and non-renewable resources. Renewable resources are water, forests, farmland, and grazing land. Non-renewable resources are minerals like coal, oil...
