 Now it turns out that it didn't actually take long for the Earth to form after the Sun, at least not in astronomical terms, only in the order of tens to a few hundred billion years. Now one problem with trying to date the earliest history of the Earth is that it's a dynamic planet. It is constantly creating and destroying its own crust. And that means that we don't have a lot that's left from the very beginning. Now this dynamism is part of what makes the Earth special and a lively place. It brings up fresh nutrients for life and it distinguishes us from most of the other rocky bodies in the inner solar system like the Moon and Mars, which have frozen over and aren't really as active on their surfaces anymore. But this dynamism is again what makes things like volcanic soils fertile. They bring up nutrients from the inside and recycle them back in. This dynamism comes at the cost of losing the earliest history of the Earth. So the best we can do is go to the places that we know are the oldest. And that especially means Australia and in particular Western Australia. Now if you've seen a picture of the outback, you'll know that it's pretty flat. Part of the reason for this flatness is because it's so old. There used to be mountains out there, but most of them have been either polished flat by the wind in the rain and there's been no recent collisions to push new things up. So it's pretty much a polishing over hundreds of millions if not billions of years to make a flat landscape. Zircons are incredibly strong and unreactive. They also incorporate uranium, but don't include lead when they're forming as a crystal. And that makes them perfect as a chronometer, as something to tell the time with. The oldest zircon ever found was at a place called Jack Hills. And it's from a conglomerate or riverbed that itself is billions of years old. But the zircon was weathered away from mountains much older than that. The zircon formed 4.4 billion years ago. That's only 100 million years after our CAIs. Now the zircon as a mineral in particular doesn't just indicate that there was rock forming on the earth, but it indicates continental crust. This means that there was actually land as we know it beginning to form at this time. So with the earth forming only 100 million years after the sun. That makes our 4.4 billion year old planet almost a third the age of the universe. 13.8 billion years. We live on a very ancient planet. So to date anything younger than a million years we're going to need an isotope system with a much shorter half-life. And for that we can use carbon.