B. The Origin theory is a mystical problem. In our own solar system inside or around asteroid belt, there are four rocky planets close to the Sun, each formed in the way described follow – Mercury, Venus, Earth and Mars: The first stars which formed from primordial hydrogen and helium produced in the big bang, cannot have had any planets, because there were no heavy elements available from which they could be built up. Planetary systems are all second-generation (or later) systems. As the parent cloud of gas and dust from which our Solar System was being formed, began to shrink, any rotation it possessed made it spin faster and faster, and as the core of the cloud collapsed to form a star, some of the material from which it was forming was held out from the centre of the cloud by residual spin, and the material settled down into a dusty disc around the young star. Close to a young star, the lightest material in the disc, comprising mainly hydrogen and helium gas, is blown away by the heat of the star and solar radiation. The material left behind is made up of billions of tiny grains of dust that collide and stick together, building up larger lumps. The lumps of matter may be a few millimetres across and are settling into a thinner disc around the star. The process of accretion – lumps growing by sticking together carries on until the original dust grains have become lumps of rock about one kilometre across, similar to the asteroids that orbit in profusion between Mars and Jupiter today. Once the pieces of rock reach this size, they begin to tug on each other significantly through gravitation, pulling them into swarms that orbit around the star together, bumping into one another from time to time. Gravitation pulls the pieces more and more tightly together, with the largest lumps (which have the strongest gravitational pull) attracting more and more material, growing to become terrestrial planets and their satellites.