Cosmic Origins 2
This is the story of a small planet in space called Earth. Today it has mighty oceans; scorched deserts; and frozen wildernesses. It supports a multitude of diverse creatures, and is home to more than 7 billion people and their technological civilization. But how did all this come about? Where do we come from? Until recently, Earth and its lifeforms were a mystery. Like a huge unpainted canvas, little was known about the origin of Earth and its inhabitants. But today, we have a rough idea of what happened. It began – with a bang. About 14 billion years ago, scientists think, an extraordinary event occurred. From a singular explosion, the universe was born. In those first moments, intensely hot hydrogen and helium raced outward – thinning, cooling, and clumping into vast, organized structures. Within a few billion years, countless galaxies had emerged, each one containing hundreds of billions of stars, constantly changing in cycles of birth, death and rebirth. In one of these galaxies, about 5 billion years ago, one average-sized star, our sun, captured in its gravitational field the gas and dust that would become 8 planets. One of these worlds, was Earth.