Introduction:
The interest of man in space has existed from ancient times when man employed the naked eyes to study and speculate on the moon, the stars, the sun, and other things which were imagined to be there in space. As time went by, man began to carry out more systematic studies of space. By the second century AD, a Greek mathematician called Ptolemy proposed that the earth moved in space. By the 16thcentury AD, some other scientists such as Tycho Brahe and Kepler had deducted the relationships between the motion of the earth round the sun and the motion of the moon round the earth. In the year 1686, Isaac Newton deduced and published the laws of mechanics. These included those governing the circular motion of the earth round the sun.
Tycho Brahe was one of those scientists who made very powerful telescopes for studying the details of very for objects such as those in space like the moon. The use of such powerful telescopes revealed that many more planets than just the earth existed. It also revealed that there were other smaller bodies which moved round some of the planets. These smaller bodies were then called moons.
Since scientists found that there were many planets which moved round the sun, man has been curious to find out whether:
- There was life on the moon and other planets
- Man could leave the earth and go to settle on any of the planets or the moon
By the end of World War II in 1945, powerful nations such as Russia (then USSR) and the United States of America began to think of establishing space stations on the moon. There were doubts however whether it was possible to establish such space stations. This was the origin of space exploration.
The Solar System
The solar system consists mainly of the sun and nine planets which move around it, with the sun at the centre. The planets are massive objects in the solar system and they are kept in their track around the sun as a result of a force of attraction from the sun. The distance of these planets to the sun determines how long it takes for the planets to complete one revolution round the sun. The time it takes for the planets to complete one revolution round the sun is known as the planet’s year. For earth, the planet year is 365 days or 3.2 x 107 seconds.
Apart from the planets, there are also several moons. A moon is a satellite of a planet. For example, the earth has only one moon which moves round it; mars has two moons; Jupiter has twelve moons; Saturn has nine and Uranus four…
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