AK-47 stands for Russian Avtomat Kalashnikova 1947 (Automatic Kalashnikov 1947). Designed by Russian Mikhail Kalashnikov, it was the assault rifle used by most Eastern Bloc countries during the Cold War. The rifle was adopted and standardized in 1947, thus the name.

The Fog Index was developed by Robert Gunning, an American businessman, in 1952. It is a test designed to measure the readability of a sample of English writing. The resulting number is an indication of the number of years of formal education that a person requires in order to easily understand the text on the first reading. If a passage …

In physics, the fifth dimension is a hypothetical extra dimension beyond the usual three spatial and one-time dimensions. Some scientists have speculated that the graviton, a particle thought to carry the force of gravity, may leak into the fifth or higher dimensions, which would explain how gravity is significantly weaker than the other three fundamental forces. M-theory (the mother of …

The Fermi Problem, named after Italian physicist Enrico Fermi, is about a formula regarding how to think about what assumptions we make, how to make them as realistic as possible, how to estimate well, and how to put all these in the service of a straightforward mathematical calculation in order to come up with an answer.

Most of the world’s electricity is generated by oil, gas and coal in power stations. These fossils fuels are being used up quickly, and some experts have predicated that an energy crisis will occur before long. At the present rates at which we are using oil and natural gas, the known reserves will run out in the early 21st century. …

Making A Bird Table Many boys take a great interest in birds, and their especial delight is to see that those visit their gardens in winter are properly fed. To throw food on the ground for them is a kindly act; nevertheless, it often proves to be dangerous, as cats get to know where birds are likely to congregate. Pussy …

Southern Arabia contains one of the world’s bleakest deserts, which is visited only by the hardiest Bedouin nomads. Like all deserts, this is a place of extremes, and they must be prepared to risk hunger and thirst, and exposure to heat by day and bitter cold by night. The region is the Rub al Khali, or the Empty Quarter. Much …

Since World War II, many countries have joined common markets. These organizations try to develop the economies of the member countries, especially by removing all trade restrictions between them. The European Economic Community (EEC) was founded in 1957 by Italy, France, Belgium, Luxembourg, the Netherlands and West Germany. Six nations joined later: Denmark. Ireland and the UK in 1973; Greece …

The E layer is a region of the ionosphere, extending from about 90-150 kilometres above the Earth, which influences long-distance communications by strongly reflecting radio waves in the 1-3 megahertz. It is also called E region, Heaviside layer, or Kennelly-Heaviside layer. This region reflects radio waves of medium wavelength and allows their reception around the surface of the Earth. The …

Christian Johan Doppler (1803-1853) was an Australian scientist born in Salzburg who made and important discovery about the effects of sound and light when the sources are moving in relation to the observer. You may find the Doppler effect easier to understand if you consider what happens to the noise of a train as it approaches you and then fades …