©Illustration: Dan Durda
In the beginning, the earth was as hot as Venus is today, but it cooled down quickly because the young sun was much weaker then. Atmospheric water vapor fell as heavy rain and formed the oceans.
The earth was formed almost 4.6 billion years ago. It was very different from what it is today. And this strangeness lasted a long time: researchers on a journey through time to the primeval earth could not have taken a step without an oxygen mask 3.5 billion years ago. The air was not breathable, it contained a toxic cocktail of carbon dioxide and methane, possibly also ammonia and hydrocyanic acid - but no oxygen. The days were shorter, and the young
