Our planet Earth is one of the eight planets in our solar system, which lies in the Milky Way Galaxy. A quick glance at Wikipedia reveals that the Milky Way is estimated to contain 100–400 billion stars and planets. Given there are billions of galaxies in the universe, we can skip the math on the possible number of planets out there.
Yet, Earth is the only planet known to harbor life. This makes Earth both stupendously insignificant in the vastness of the cosmos and remarkably significant for hosting life. Just like the origin of the Universe, the origin of Earth is a fascinating tale. But before we dive into that, it’s essential to understand how our solar system came to be.
Our solar system is estimated to have formed about 4.5 billion years ago from a dense cloud of gas and dust. This cloud collapsed, possibly due to shockwaves from a nearby exploding star (a supernova), forming a solar nebula, a swirling disk of material. As gravity pulled more material towards the center, hydrogen atoms began fusing to form helium atoms, releasing tremendous amounts of energy and creating our Sun.
Matter further out in the disk collided and coalesced, forming planets, dwarf planets, and moons. The smaller leftover pieces became asteroids, comets, and meteoroids. And that’s how Earth came into being, along with the other planets in our solar system.
When Earth first formed, it was a hot, burning mass of energy. Over time, this mass cooled and solidified, but it was still far from the habitable planet we know today. In fact, it was full of volcanic activity, lava, and hostile chemicals, enveloped in a thick atmosphere of methane, ammonia, and carbon dioxide — gases quite different from what we need to survive.
So, how did Earth transform from a lifeless, hostile environment to a planet capable of supporting hundreds of years of civilization and development? Next up, we will look at “how on earth” did life really start?
Nepali Wanderer 
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