Question: Why is the earth round?

Stuart Archer answered on 17 Jun 2013:

Before the Earth formed 4.5 billion years ago, the solar system was basically a large cloud of gas composed of many different chemical elements surrounding the sun. However, this cloud of gas wasn’t spread out evenly across the solar system, bits of it would have more gas, some bits less. The bits with more gas are heavier than the bits with less.

The heavier something gets, the more gravity it has, and it pulls lighter things towards it. This is the same force that keeps you on the Earth, and keeps the Earth in orbit round the Sun.

So, these heavier bits of gas started to pull the lighter bits towards themselves. Because gravity always attracts things towards the centre of an object, these heavier bits of gas would pull stuff from all directions around them forming a cloud of gas shaped like a ball. As it pulled in more and more stuff it got heavy enough to become solid, forming the planet Earth with the round shape it has today!