When the planets were born

How old is the earth?no one really knos but astromomers think that the solar system began about 45000 million years ago. In the vast darknes of space, a gigantic cloud of gas and dust once spun around like a huge flat wheel, millions of kilometres across the universe. Most of the gas in the cloud, or nebula, was hydrogen.
After millions of years, the space of the nebula was changed by gravity. This is a force which pulls things towards each other. The gravity of the spinning nebula pulled gas and dust into the centre, creating a tightly packed lump. This huge lump was shaped like a ball and waas the beginning of the stars we call the sun
As the new star grew larger and more larger and more tightly packed, the gas at its centre became very hot, aking the sun shine brightly. Far away from the shining sun, the force of gravity began to pull gas and dust into much smaller centres, like whirlpools in space. Over millions of years, these whirlpools also became tightly packed balls of gas and dust. Today, we know them as the nine planets of our solar system.