Social Studies for class 8
Allah Almighty has created this Earth, the Sun, the Moon, and the planets for the benefit of mankind. His creation makes our belief in His existence still stronger.
This Universe is so large that it is almost impossible for the human mind to perceive it in its entirety. Everyone understands the Universe and its effects on us in a different way. But most of us would agree that humans have an innate need to understand their surroundings. While philosophers delve into the purpose of the Universe, scientists investigate its mechanism, pointing telescopes at massive objects which are far away at unimaginable distances or observing the behaviour of tiny drops of liquid in the laboratory. They strive to understand how the Universe is put together and how does it work. However, for our need and understanding we will be mainly looking at the Sun, the moon and the planets which together constitute the 'Solar System'. It is also interesting to know that our Solar System is one of the many such Systems in the Universe.
In our Solar System, the Sun is the only star. It is a mass of gas's undergoing nuclear fusion, which causes it to give off heat and light. The celestial bodies orbiting the Sun, including the nine planets and their satellites, the asteroids and the comets together make up the Solar System. The planets of the Solar System orbit around the Sun but do not give off heat and light. Some of these planets have moons orbiting them. Also moving about the Solar System are asteroids, meteoroids and comets. Asteroids and meteoroids are like rocks of various sizes travelling through space. Asteroids orbit the Sun like little planets while meteoroids usually have no specific orbit. Comets, on the other hand, are balls of ice and dust that orbit the Sun like asteroids. Both comets and asteroids usually follow very elliptical orbits.
Nine major planets are currently known. They are commonly divided into two groups: the inner planets (Mercury, Venus, Earth, and Mars) and the outer planets (Jupiter, Saturn, Uranus, and Neptune). The inner planets are small and are composed primarily of rock and iron. The outer planets are much larger and consist mainly of hydrogen and helium. Pluto does not belong to either group, and there is an ongoing debate as to whether Pluto should be counted as a major planet or not.