Science & Mathematics Questions & Answers

A flipbook is a small book with a series of printed images that create the illusion of motion when its pages are rapidly flipped. Typically, a flipbook is held in one hand while the thumb of the other flicks the pages and the user concentrates on the middle of each page. The flipbook relies on a basic optical principle known …

It is a type of wide-angle lens used in photography to capture extremely wide and hemispherical images. Its focus length varies between 8-10 mm for circular lenses and 15-16 mm for full frame lens. Originally developed for use in meteorology and astronomy, it is used in planetariums and dome theatres to show pictures on a broad canvas.

In Rail Terminology: A fishplate, splice bar or joint bar is a metal bar that is bolted to the ends of two rails to join them together in a track. The name is derived from fish, a wooden bar with a curved profile used to strengthen a ship’s mast. The top and bottom edges are tapered inwards so the device …

False vacuum and true vacuum form a metastable system. Metastable state is a state which does not change with time but is susceptible to falling into lower-energy states with only slight interaction. It is analogous to being at the bottom of a small valley when there is a deeper valley close by. True vacuum is the name applied to a …

It is an expanding bullet designed to grow on impact, increasing in diameter to limit penetration and/or produce a larger diameter wound. There are many expanding bullet designs though the most commonly encountered are hollow-point bullet and the soft-point bullet. Such bullets are sometimes known as ‘dum dum’ bullets. After an early British example produced in the Dum Dum arsenal, …

A dowser is another name for a water-diviner someone who can tell where there is water lying underground. The dowser uses a whole variety of tools to find the water, but one of the most common is the Y-shaped twig from a hazel tree. The dowser holds the twig by the two prongs of the Y, with the long stem …

There are about 500 active volcanoes around the world, not including those hidden by the sea. A few, such as Stromboli, a volcanic island off the north-eastern coast of Sicily, are active nearly all the time. But most undergo long periods when they are dormant, or sleeping. Some volcanoes stay dormant for so long that they are thought to be …

A digital pet (also known as a virtual pet or artificial pet) is a type of artificial human companion. They are usually kept for companionship or enjoyment. People may keep a digital pet in lieu of a real pet. Digital pets are distinct in that they have no concrete physical form other than the hardware they run on. Interaction with …

Look in any jeweller’s window, and you are bound to see diamonds, the white, glittering gems which are so valuable and so beautiful to look at. It’s hard to think that the diamonds which sparkle in the shop windows came out of the ground as lumps of dull rock, isn’t it? But this is how they are found. Diamonds are …

The word ‘dhow’ is used to describe any kind of Arab sailing vessel. They are the regular Arab trading craft, and make along voyages from the Red sea and Persian Gulf down to the African coast. The commonest are the small, square-sterned dhows known as ‘sambuks’. Then there are the smart ‘booms’, and the short, wide ‘bedeni’ from Muscat in …