Category Science

To understand exactly what lightning is, we must recall a fact we know about electricity. We know that things become electrically charged – either positively or negatively. A positive charge has a great attraction for a negative one. As the charges become greater, this attraction becomes stronger. A point is finally reached where the strain of being kept apart becomes too great for the charges. A discharge takes place to relieve the strain and make the two bodies electrically equal. This is exactly what happens in the case of lightning. This discharge follows the path which offers the least resistance. That is the reason why lightning often zigzags. Moist air is only a fair conductor of electricity which is why lightning often stops when it starts raining.

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It was the industrial revolution which brought about the introduction of metal bridges. In the past, bridges were constructed of stone and timber, which were available in large quantities. Iron was used because it was much stronger than either wood or stone, and was, on the whole, less expensive to produce. Bridges made from timber or stone become fewer and fewer.

The first ever metal bridge was built in England in 1779. The Coalbrookdale Bridge, which spanned the River Severn, was designed by Thomas Pritchard and built by Andrew Darby. This bridge, the first to be built solely of iron, spanned almost 100 feet across the river in an almost perfect semi-circular arrangement of cast-iron pieces.

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People have used canals to transport heavy goods for thousands of years. It is believed the first canals were built to join together existing rivers to make a transport route. Indeed, the city of Venice in Italy was built on a system of canals rather than roads; six thousand years ago the Aztec city of Tenochitlan was built with an impressive system of canals within it for transport.

However, the heyday of canal building was much more recent. The industrial revolution was responsible for the upsurge in canal building. There was a huge need during this era for cheap and easy ways to transport goods from factories to ports. Horse-drawn canal boats and steam-powered canal boats were faster than carrying cargo by horse-drawn carts along the road.

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The internet was created in 1983. The idea behind the internet came from the US Defence department who had a basic version of the internet set up as a secure system for their information.

The internet was born from a mainly academic origin, as a framework connecting numerous computer networks together. It has rapidly developed into a very popular commercial medium. By the mid-1990s, millions of computers all around the world were connected on the ‘world wide web’.

The limits of technology are always changing, and the internet tests the capabilities of modern developments to the full.

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The television was not ‘invented’ at one particular time by one particular person. The processes which enable a television to operate were developed over a period of time.

In 1875, G.R. Carey made the first basic television system using photoelectric cells. An object was focused through a lens onto a bank of photoelectric cells. Each cell controlled how much electricity would be passed on to a light bulb. Crude outlines of the object then appeared in lights.

1923 brought the first practical transmission of pictures over wires. There was also a great development in television camera technology.

By 1945 the television as we know it today had been developed.

Continuous technological developments have meant that the quality of television pictures has improved dramatically.

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Morse code is a messaging system which uses two kinds of signal, a short one called a dot, and a long one called a dash. The signals are sent via telegraphs. A transmitter sends a coded message in long and short bursts of radio waves along a wire; the receiver then translates the dots and dashes into their representative letters, numbers and words.

Samuel Morse (1791-1872) was an American engineer who developed this system. He conceived communication via telegraph in 1832. After several years of work on the idea, Morse perfected it in 1838.

However, at that time, telegraph lines did not exist across land, so there was no way Morse could put his code to use on a practical scale.

It was 1843 before the US government allocated a sum of money to construct a telegraph line between Washington and Baltimore. Morse sent the first Morse code message along the lines in 1844.

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