Wednesday, January 6, 2010

The Moon's Birth

Time: 4.5 billion years ago.
Place: Earth.

It is hot, thousands of degrees hot. We float on red, molten rock. The entire planet is an ocean of molten heat. We look up to a black sky. There is no atmosphere, hence no sound. We are about to be hit by a planet the size of Mars.

If we had been alive and if we had a history to this point, this would seem like the end of time. For eons, we had dwelled in a nebula of gas and dust. Lost in legend were stories of a super nova, which originated our nebula. The nebula was comfortable and seemingly eternal. But gradually it had grown smaller. Gravity pulled it together.

When the gas at the center had ignited, that had seemed the end of time. Other bits of the nebula had formed around the center, angular momentum carrying them into orbits around the new star.

So, we float on the surface of this new thing, a planet and ponder our lost sanctuary. Wham! A giant meteor crashes. It must have been only a 100 miles away. Then another, and yet another. The semi-liquid rock beneath us shifts violently. The sky above is filled with falling objects.

In one corner of the sky, one star-like object catches our attention. It seems to be much bigger, than the last time we saw it. It was just a prick of light, like any star. Now it is a small disk. It seems to grow, even as we watch.

Now, it is the biggest object in the sky. We see parts of it are dark and other parts light. Almost no time at all has passed. Now it fills a quarter of the sky. We see a dark surface that bubbles towards us. Things seem distorted. We realize that our planet’s gravity is creating tidal effects on it. The violence around us tells us that our planet’s surface is being gravitationally pulled, too.

Now it fills half of the sky. It slowly blots out the rest of it. We wonder how liquid rock can appear to have a hurricane for it is not like water. A volcano erupts. It appears like we can reach out and touch it. The plume does not fall but seems to keep coming as the Earth’s gravity now pulls on the smaller planet as much as the planet’s own gravity does.

It is but an instant as we see an entire planet just 100 miles above us. Then it crashes.

If we had been anything but literary devices, and if we could have lived through this, we would be experiencing the most violent event in the history of the Earth, save possibly for the planet’s end, eons in the future. We, ourselves fly into space as the Earth’s surface breaks up. Down below, the Earth’s innards remain intact, though the other, smaller planet has broken up, entirely. Pieces of it remain on the surface; pieces vaporize; pieces bounce into suborbital paths that then land again in faraway regions throughout the globe. Over there is the planet’s heavier iron core. It falls to the Earth and gets buried in the goo. Eventually, it will join the Earth’s own core. In a short time, Planet Earth is 10% more massive than before.*

The rest of the debris stays in orbit. Gravity causes the smaller chunks of rock to fall into the larger chunks. Before a century has passed, a moon has formed. Billions of years later, people - real people - us, will look up at it and wonder how it got there.

More Information: Wikipedia,

* My 10% number comes from the History Channel's episode "The Moon" from their series "The Universe", season 1.