Hadean Eon → Origin of Earth (4600 MA)

Where did the Earth come from? This is an important question. A question that helps us understand our own origin as a race of sentient, thinking beings. Did the Earth always exist? Has our planet spent eternity orbiting the Sun, quietly unchanging? Has the Earth always looked like it does today, with the same mountains, streams, lakes, forests, and oceans? Or does the Earth change over time? Was the Earth always a planet, or was it built or constructed at some point in the past? If it was built, what forces caused its creation, and from where did the materials to build it come?

Early in our universe’s history, the Earth – and other planets – was formed from dust, pieces of rock and gas orbiting the Sun. This material smashed together and began to heat up until the entire mass melted.

Some of the materials in this mass were heavier than others. The heavier metals fell to the center to become the Earth’s core. The rest of the materials became the mantle, crust and atmosphere.

Before the Earth existed, there were no people. This means that there was no one around to witness its creation. At least not any humans. However, scientists, like geographers, are able to make educated guesses about how the Earth came to be. These guesses are called theories. A theory is a guess based on evidence. These guesses are made by scientists who study clues to understand new things about the world and universe around us.

The best clues that scientists have come from the study of distant young stars, and the new planets forming around them. By studying these young suns, they can catch glimpses of the creation of their new baby planets, and of their young planetary systems.

These distant planets are so far away that they are too small for us to see them using modern technology. Secondly, planets do not form over night. They take millions, and even billions of years to develop. Thus, even if we could see these planets, all we would see is how they look today. Unless we watched them for many hundreds of millions of years, we would not be able to learn much about how they evolved.

In our Universe there are trillions and trillions of stars. Many of these stars have a family of planets orbiting them. Each of these planetary systems is a different age. Some of them are very old, and some of them are very young.

Today, our planet is neither young nor old. The Earth is a middle-aged planet. It has cooled sufficiently to allow liquid water to form, but has remained warm enough to sustain life, and to keep the water from freezing.

The mountains, valleys, hills, streams, rivers, and lakes that we see today are always changing. Over millions of years, new mountains form and older mountains get worn away. Lakes form, then disappear. Streams wander through the countryside, cutting deeper and deeper into the ground creating canyons, which eventually erode away.

The Earth has many billions of years left before it will be destroyed by the aging Sun. During these billions of years it will continue to change and evolve. The Earth we know today will not be the same Earth that others know millions of years in the future.