Dating on the earth

And then only a little over 100 years ago was the discovery of radioactivity. That luckily, there are these things that decay at a very predictable rate.

And our best sense of when this happened the first time was by the Sumerians with cuneiform.

And this happened right around the third millennia BC, so around 5,000 years before the present time.

Jaejoong is a transferred student who have lost his parents when he was young and was brought up in an orphanage.

If we want to understand where we've come from, the stories that have led us to our present condition, if we want to understand our history, one of the prerequisites is to have a good sense of chronometry. And we take many, many things for granted these days.

So we can now look at evidence from our environment. It's radiation bombarding us from space that gives us clues as to not just the age of us, of humanity, the age of species, the age of the plant, but the age of the universe itself. Radioactivity is a big part of our chronometric revolution. So maybe this fossil of a fish that we're finding, or this primitive fish-like creature right over here, this would be between 100 and 150 million years old.

This is what allowed us for the first time, if we have layers on the Earth, people have known for a long time that if we assume that these layers haven't been jostled, that something at a lower layer, down here, is probably going to be older than at an upper layer. And the only way we're able to do this was with being able to date things using radioactivity. As I mentioned, we're getting better and better understanding of cosmology.

And the most important information that would get lost is how long ago did these stories start up?

And we weren't able, as a species, to really have a firm understanding of when things happened, and how long ago things happened until writing became mainstream, and until writing was done in a way that it became permanent.

Para complicar la situación entra Jaejoong, un nuevo estudiante implicado en la mafia y con un pasado dificil.

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