How did sailors find their way in the sea?

In early times, sailors used to orient themselves to the stars. In order to calculate directions, they learnt to study the positions of the fixed stars, which, unlike other celestial bodies, appeared to be always present at the same point in the night sky. With the help of a simple geometric device called astrolabe, they would measure the angle between the horizon and the fixed stars at night, and the angle between the horizon and the sun during the day. With the help of their findings, they could calculate the distance to the north or the south of the equator. They also used a special navigator clock to determine how far they had come to the east or west of their home harbour. The astrolabes were replaced later by the modern sextants, and ships today navigate with the help of GPS devices that receive information regarding their position on the sea from satellites.

Production of money today-a real science

Experts are constantly devising new safety measures that are extremely difficult for anyone to bypass or to duplicate. It is due to some such measures that criminals nowadays find it difficult to forge money. The large Euro coins, for instance, have a magnetic core, which is surrounded by a non-magnetic ring. In currency notes, the safety features are much more complicated. These include water marks that one can see with the help of a backlight, a microprint that one can read only with a magnifying glass, and a shining silvery Cinegram, which is difficult to make. In addition, certain prints on bank notes can only be seen with a UV reader. For this reason, high-value bank notes are placed under a black light on the cash counters to check whether they are authentic.

How does tilt technology speed up a train?

Just a fast cars can often 'go off the curve' due to the impact of centrifugal force, trains too can lose contact with the tracks and get derailed while negotiating curves. Experts were long is search of a technology to prevent this danger which trains had to avoid by applying brakes strongly before entering curves. The solution was offered by tilt technology, by which engines and coaches could be slightly tilted towards the side. Due to the tilt, the centre of gravity got shifted around the curves in the tracks and the wheels thus remained connected with the rails. Tilt technology thus successfully countered centrifugal force. With the help of this technology, trains could now achieve high speeds even on stretches having lots of curves.

What is date line?

When the last ship of Magellan's expedition reached home after sailing around the world, there was an interesting discovery: the last entry made in the ship's log deviated from that of the people left behind by one day. After much speculation, scientists came to the conclusion that every time a person journeys around the Earth, the date upon return would be different form the one calculated according to standard time. They realised that it was necessary to fix a certain date line for such expeditions according to which the correct log date could be calculated. This 'line' was drawn through a stretch in the Pacific Ocean where it was not divided by any continuous landmass. It is an imaginary line, which goes zigzag from the North to the South Pole along the 180' longitude. The seafarer's watch had to be set backwards by 24 hours once the date line from west crossed, so that the same date would apply to 2 days.

Who was the first person to sail around the Earth?

The first expedition that went around the world was that of the Portuguese sailor Ferdinand Magellan. He had set out to find a new route to Southeast Asia. He had come to know that there was a passage from the Atlantic to the Pacific Ocean through the continent of South America. In 1519, he set sail towards the west with five ships, around 270 men, and a huge amount of supplies. At the coast of South America, they entered the broad mouth of a river, assuming that this was the passage they had heard of. In October 1520, they finally discovered the sought-after sea route between the island Tierradel Fuego and the southern tip of South America; this route later came to be known as the Magellan Route. When the expedition reached the Indonesian islands, Megellan started taking possession of them one by one by defeating the Spanish kings. When a small island protested against the rule of Spain, there was a fierce battle in which Magellan was killed. The Spaniard Juan Sebastian Del Cano now became the captian of the remaining ships. After a voyage lasting for 3 years, he managed to return to Spain with 17 surviving sailors. They were thus hailed as the first people to sail around the Earth in one go-and not in stages.

What is space debris?

Space debris implies the remains of all the past space travel missions, such as, old non-functional satellites, blasted rocket parts, tools used by astronauts, and engine dust, that are encircling the Earth in an orbit. Space authorities can observe the parts that are larger than 10 cm. There are about 10,000 such parts and about 15 times as many smaller parts encircling the Earth in an uncontrolled way. The debris poses a constant threat to future satellites and to the ISS. In case of a collision at high speed, vital parts of spaceships can get damaged.

How was the ISS built?

The ISS is the result of the collective effort of many countries and is the largest spaceship in orbit around the Earth. The construction commenced int 1998 and was scheduled to end in 2010. The ISS is composed of different components called 'modules'. The first was the drive module made by Russia, and this was followed by the living module and many other components, which were brought to the growing station by American space shuttles or by Russian proton rockets. As the ISS is constantly manned, supply flights carrying food, water, oxygen, and spare parts are sent to it frequently.

What are space probes?

Space probes are unmanned spacecraft, which are sent into space to investigate celestial phenomena. Unlike a satellite, a space probe leaves the orbit of the Earth and flies to a remote destination, like Mars or Venus. Thus, for instance, the Soviet Union sent space probes, named Venera, to Venus in the 70's and the 80s in order to study the unique features of the hot planet. Some of them reached the surface of Venus and sent back radio signals to the Earth for about an hour. Then they failed because the surrounding pressure and temperature were too high for them to withstand. Other probes, however, have remained functional for longer periods of time. Thus, the probes Voyager 1 and Voyager 2 sent into space in 1977 are still sending back images of the depths of space. Both have now travelled beyond the solar system.