Hint: It is the only known planet that harbours liquid water on its surface. In space, its orbit is located after Venus and before Mars. It has a satellite called ‘moon’. The Earth takes 365.25 days to go around the sun, along its elliptical orbit.
Complete answer: The Earth is a rocky planet that revolves around the sun in the third orbit, after Mercury and Venus. It is located at a distance from the Sun which provides it with the ‘just right’ temperature to harbour liquid water on its surface. It also has an atmosphere that contains Nitrogen and Oxygen in the majority. All these features enable Earth to sustain life on it. But Earth was not like this always.
Earth has formed 4.5 billion years ago, i.e. around 9 billion years after the universe itself was formed. When it was formed, the earth was extremely hot. Its atmosphere was formed by the outgassing of the planet and the oceans were huge craters with volcanic activities occurring throughout. Over the years of outgassing, the atmosphere was filled with water vapour. When the earth cooled down a little, all the water condensed and filled up the oceans. It was in these ocean beds that the first lifeform was born. That lifeform evolved over millions of years, giving rise to all different types of organism and ‘us’ humans.
Humans, being the most evolved species have explored and researched the entire planet and learnt a lot about it. We know that; - The earth is spherical in shape with three concentric layers; the Core, Mantle and Crust. The crust makes the surface of the earth and the beds of the oceans. - The highest point on earth is Mount Everest (which is 8.8 kilometres high) and the deepest point in the ocean is the Challenger Deep (which is 10.9 kilometres deep). - The hottest point on the earth's surface is called the Death Valley (but the highest temperatures are actually found at the core of the earth, which is 5,200 degrees Celsius hot). The coldest place on earth is Oymyakon (-67 degrees Celsius) in the Arctic Circle. - Its current atmosphere has 78% nitrogen and 20% oxygen.
Note: All these life-supporting features are present on earth because it is present in a very specific temperature zone in space. This temperature zone is known as the ‘Goldilocks’ Zone’. Scientists, while searching for life on other planets, look for these Goldilocks zones. Some planets have been found in this zone, but they still do not support life, because they either have a poisonous atmosphere or they do not have water and other minerals to support life.