Out of the million mysteries shrouding our planet earth, the most important is the fact that how it supports life forms. Even today, many questions revolve around the evolution of earth.
Earth is considered to be the only planet that supports life and it raises many questions, like why only earth? What makes it perfect for supporting life? To get all doubts and questions answered let’s get some idea about the evolutionary history of earth.
Time is the factor: The most fundamental thing that plays an important role in the evolution of earth is time. With time the universe has undergone many physical and biological changes, which ultimately led to the evolution of the solar system, planets, stars etc. The universe is considered to be 13-15 billion years old and the age of the Earth is around one third making it almost 4.6 billion years old. The gravitational collapse of the part of the giant molecular cloud or solar nebula led to the formation of Earth. Then a series of events occurred in the geographical time scale that gradually led to its evolution.
Some of the events to have taken place before the origin of life are:
- The formation of the solar system: Formation of the solar system took place from a large rotating gas cloud made mostly from hydrogen and helium called a solar nebula. Around 4.5 billion Years ago, the nebula began contraction which ultimately created a shock wave making the cloud gain momentum and inertia. After more contraction it ignited and a star evolved into the sun. The other outer parts clumped together to form planets. It took a total 10-20 million years in the formation of planet earth.
- Formation of Moon: Moon is the earth’s only natural satellite and the rocks brought from the moon after radio dating showed that the formation of moon took place around 30 million years after the formation of the solar system. It was thought that the moon and earth before the giant impact collision hypothesis basically had the same atmosphere. Due to this collision dinosaurs became extinct and the moon depleted a huge amount of metallic material creating an abnormal atmosphere. This made earth the only planet with oxygen and water.
After the formation of the moon, earth’s atmosphere changed with the formation of different continents and oceans. The creation of the continents took place when the earth’s crust started cooling and the tectonic plates divided leading to the formation of first continents. The only thing left that helped in the life sustaining process are the oceans rich in oxygen and the bacteria that produced oxygen.
All the processes ultimately played a major impact in the evolution of earth.
