Why Apollo 17 is considered the last moon mission?
The Apollo 11 was the first manned mission that successfully landed on the Moon. Manned by three American astronauts, Apollo’s lunar module, the Eagle, landed on the face of the Moon on July 20th, 1969. Neil Armstrong and Edwin Aldrin were the first men to walk on the Moon. Three years later, Apollo 17 was the last Apollo Mission to land men on the Moon. It carried the only trained geologist to walk on the lunar surface – Harrison Schmitt. The Apollo 17 astronauts traversed the greatest distance on the Moon, using the lunar roving vehicle. They also returned the greatest amount of samples of rock and soil. The last human being to walk on the Moon was the Commander of Apollo 17, Eugene Cernan. No humans have visited the Moon since December 14th 1972.
Morse code was a system of communication in which letters and numbers were represented by dots and dashes that could be transmitted by telegraph in the form of sound, and also as flashes of light. The code was invented by Samuel Morse. The Morse code was used extensively by ships at sea. It was used in emergencies throughout the world. However, as technology advanced, the Morse code became obsolete.
Don’t you think a book is much more interesting if it has lots of pictures? Pictures or 
illustrations also make it easier to understand things. The manuscripts of ancient times which were decorated with elaborate initials, miniature illustrations and borders were called illuminated manuscripts. Sometimes, these decorations were even made with gold and silver!Very early printed books were sometimes produced with spaces left for miniatures, or were given illuminated initials or decorations in the margin. Illustrated printed books began to appear in the late 15th century, in Germany and Italy. In earlier times, some books had been published from woodcuts, with text and illustration all carved on a single block. Early type-printed books were illuminated by hand. However, this was very expensive. Although many early printed books, like the Gutenberg Bible, relied on hand-coloured illustrations, others quickly integrated the new printing, using moveable type for the letters, with the older woodcut traditions. Another early technique was etching, in which the lines of the picture were cut into a copper plate with acid. In either case, ink was spread over the carved illustration and applied to the paper
Typesetting is a presentation of text on paper or some other material, in a printed form. The word 
‘type’ is used to denote a small block of metal or wood, bearing a raised letter or number on the upper end that leaves a printed impression when inked and pressed on paper. We know that by the middle of the 15th century, movable type had been invented in Europe by the German printer, Johann Gutenberg. By 1462, Gutenberg’s invention became accepted and the use of it spread throughout Europe. Movable type is also called foundry type or hot type. In foundry type, each piece of type was cast into a precise size from metal which was an alloy of lead, tin, and antimony. Each piece contained a raised image of a single letter, number, or other character. In setting type, letters were selected one at a time, and lined up in what was called a composing stick until it was almost full. Then, by using pieces of type with no face on them, spaces between words were adjusted to bring the line to the required length. Each line of type was placed by hand in a larger box made especially for housing the type. The individually lines were laid out exactly like the page should look except that the type was backwards as if looking at it in a mirror. The type was then inked and copies made directly from the type. When printing was finished, the type was taken apart, cleaned, and returned to the distribution box to be used again another time
The ancient Phoenicians had an arrow-like symbol in their alphabet. It was the seventh letter, and called ‘zayin’. The ancient Greeks adopted this symbol from the Phoenicians as the sixth letter of their alphabet in 8000 BC. They called it ‘zeta’, and gave it its present form. The Romans adopted it from the Greek alphabet in 100 AD, and Z is the last letter of the Roman alphabet to this day. ‘Z’ is pronounced as ‘zed’ by the British and as ‘zee’ in America. If you are sending a Morse code, you will have to send two dashes and two dots to present ‘Z’! Another interesting fact about ‘Z’ is that it was used to represent the Roman number 2000 in medieval times.
The earlier flags of the Indian navy had the St. George’s Cross on them, and these were changed 
to an anchor within a frame surmounted by the state emblem, the Sarnath Lion.The navy blue Indian Naval Crest is also found in the flags of flag officers. Admirals fly a white flag with the red horizontal and vertical bars and the chakra in the middle. The flag of the vice admiral is similar to the Admiral’s flag with a red ball added. Rear Admirals, Commodores and senior officials all have their own flags too. The Navy also its different badges for different positions, gunner, radar plotter, torpedo and anti-submarine officers, survey records, etc.
Many political and social movements use flags to get noticed, to attract more people, and to unify its
members. The socialist movements use red flags to represent their cause. Anarchists use black flags to get attention.
While traveling by train, you might have seen railway men waving different colours flags at different times. Do you know what they mean? A red flag or a flag of any colour that is waved vigorously means only one thing…. STOP! A yellow flag tells the train driver to proceed with care, while a green, white or blue flag reassures him that it is okay to proceed. A blue flag stuck on the side of a train means that it should not be moved because someone is working on it. A blue flag on a track means that nothing on that track should be moved. At night, the flags are replaced by lights of the same colour
Sports flags, in some form or other have been used in sports for years. They are used by officials to signify to the fans, other players and officials that a rule has been broken. They are also use to communicate drivers during motor sports, and with participants of water sports. Soccer, rugby and football all have flags that are carried by the linesman and referees to signal when a rule has been broken. Other sports where flags are used are car racing, cycling and yachting rowing go –cart racing, and motorcycle racing. Fans of almost all sports wave flags in the stands to indicate support to their team. Many sports teams and organizations have their own flags. The most famous of these is the flag of the Olympic Games.
Flags have been in use since ancient times, and the oldest state flag still in use is that of 
Denmark. It has a white cross on a red background, and this cross was later adopted by other countries like Norway, Sweden, Finland and Iceland.The flag of Denmark is called the Dannenberg which means ‘the cloth of the Danes’ According to Danish legend, the flag fell from the sky on June 15, 1219, to the Danish king Valdemar ll. This makes it the oldest national flag in Europe still in use. The first recorded use of this flag was in the 1300s.
A flag in the air, and the word ‘flag ‘comes from an ancient Saxon word ‘flakken’ which means to fly or float in the air. The word came into use between the 15th to the 16th centuries in various northern European languages. It signified a piece of cloth, bunting, or similar material that displayed the insignia of a community, an armed force, an office, or an individual.
Semaphore is a flag signaling systems. In this system the letters of the alphabet are signaled by waving a pair of hand-held flags in a particular pattern. The flags are usually square. They are red and yellow in colour and divided diagonally with the red portion on top. The flags are held, arms extended, in various positions representing each of the letters of the alphabet. The pattern resembles a clock face divided into eight positions. Numbers are shown by special signals. Semaphore signals were used to exchange messages between other, but could see each other, but could not hear each other. They were used by railways to communicate with train drivers. Semaphore signals have generally given way to color light signals although there are still many places where semaphore signaling is in use.
Maritime flags are that flown at sea. A national flag flown at sea is called an ensign. There are strict rules and regulations for flying these flags.There is also a system for international maritime signal flags that represent numerals and letters of the alphabet. Each flag has a specific meaning when it is flown independently.
Cameras record images. Images that we see with our eyes are fleeting – one moment they are 
there, the next moment they are gone. These same images can be recorded and stored with cameras. But how is this done? A still film camera is made of three basic parts – an optical element which is the lens, a chemical element or the film, and a mechanical element that is the body of the camera itself. Photography is adjusting and combining these elements in such a way that they record a crisp, recognizable image.Most of the inside of a camera is an empty space. The empty space is dark, because it is sealed off from the light outside. Light can only get in when a little door at the front of the Camera, known as the shutter, is opened for a very short time.The light passes through a lens which is a type of glass. The lens bends the light and ends up marking an image on the film at the back of the camera. When the light hits the film, the chemicals on the film change to capture the image. The film is then taken out of the camera and treated with other chemicals to make the image visible and permanent.
Storm warning signals are symbols and flags that give us information about sudden, violent and strong wind which is approaching, or a storm that has already formed. Other symbols caution us that a port is threatened by a storm, and of danger from hurricanes and cyclones. Storm warning signals also show the direction that a storm is taking, so that boats and ships can avoid these areas. For people living in coastal areas, for fisherman and pilots, paying attention to storm warnings can save many lives. Storm warnings also play an important part in commerce, navigation and in farming