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Our Solar System

Less than 400 years ago, most people still believed the Earth was the centre of the universe. The turning point came when an Italian scientist, Galileo Galilei, constructed the first astronomical telescope in 1609. For the first time it was possible to see what the moon really looked like close up. Galileo’s studies of the night sky proved that the Earth, along with other planets in our solar system, rotates round the Sun.

We know now that our sun is just one of the millions of stars in the galaxy called the Milky Way. And the Milky Way is one of the countless galaxies in the universe.

The Chinese invented the explosive mixture that fired the first rockets more than 1,000 years ago. They concocted a black powder that exploded when lit and created bright sparks and a long bang. These were the world’s first fireworks.

Later, the Chinese used their secret recipe to fire arrows at their enemies. But it took hundreds of years before their important invention traveled west to Europe, where the once-guarded formula was copied to make gunpowder for weapons of war. It was the end of the nineteenth century before scientists realized for sure that rocket technology could be used to go to space.

To stay in orbit, spacecraft and satellites must reach the pheno­menal speed of 28,000 km per hour. So the rockets that launch them need to be extremely power­ful. Rockets don’t fly like airplanes, which rely on air rushing past their wings to lift them off the ground. Instead, they roar straight upward by pushing out vast amounts of hot gas with great force. This means they can also operate in the vacuum of space.

Rockets used for space laun­ches are usually made up of two or three separate sections, known as stages, to help provide enough power to reach orbit. Each stage fires in turn and then falls away after a few minutes when it runs out of fuel. In this way the rocket gets lighter and lighter, allowing it to reach great speed as it approaches the borders of space.

Rockets have become bigger and more powerful during the twen­tieth century. Most powerful of all is the Soviet “Energiya” which can lift a cargo of almost 200 tons into orbit.

The next era of space travel awaits a far more efficient way of getting off the ground. This may be some kind of space plane that flies to the borders of space like an airplane and only then switches to rocket power to blast into orbit.

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