When do cats purr? Purring is a kind of low continuous rattling hum. A mother cat uses purring to call her kittens to feed. At birth, kittens cannot see, …
When does hermit crab change its shell? A hermit crab changes its shell when it has grown large enough to need a bigger home. This type of crab is …
When was the pigeon post first used? The ancient Babylonians noted the habit of pigeons to fly back home. The ancient Egyptians built a network of pigeon towers watched …
When does a chameleon change colour? A chameleon changes colour when it senses danger. Being a member of the lizard family, the chameleon can change colour to match its …
When did Air Mail begin? Air Mail began in Italy, on the 20th May 1917, when during the First World war a mail was sent by air from Turin …
When does a car use overdrive? A car uses overdrive when it is travelling at high speed over long distances. Overdrive, or cruising gear, is a device which enables …
When was it proved that the Earth is round? On 20th September 1519, a Portugese explorer, Ferdinand Magellan left San Lucar in Spain with five ships and 237 men. …
When was the washing machine invented? The first washing machine was invented in 1782. It was a wooden tub filled with hot soapy water. In the 1800s, machines had …
