So, the gist of this module is that life on earth evolved, it formed very early in the earth's history. Very soon after the earth formed but for most of its span 90 percent of the history of the earth it's very simple. So, what was happening that allowed life to become more complex, that allowed big things like Sequoia trees, and humans, and plants, and animals to evolve? Why did it take so long for that to happen on the earth? Then where's it headed? Where intelligent we've learned, the capability of actually altering our entire planet but that's relatively recent, just a couple of 100 years since we've been altering the planet. What if you play that forward? What would that look like? Has that happened elsewhere in the universe? Basically, this tree ring lab you know spun-off of Steward Observatory decades ago and was the world's first research unit for dendrochronology. Now, people come to this place from around the world to bring their samples to be inspected, to be analyzed, to store their samples, to have experts say what is learned or collaborations all around the world that evolves in the archives here are amazing. So, that's the story of life on earth more broadly, is that life is not just it didn't just start in a warm little pond like Darwin said and then just everything in the end went forward and got more complex. It's had enormous stresses and difficulties but it's a sample of how changeable the earth has been as a living planet. So, you know thinking about life in the universe means we have to think about the history of life on earth because, life perhaps could have been extinguished by a giant impact or by the snowball episode. All sorts of things have been really challenging to life on earth and if there's life in the universe elsewhere probably has similar challenges. So, here we are looking at one of the earth's oldest creatures. It's a Sequoia giant Sequoia tree. Just by counting tree rings we can see that it's essentially 2,000 years old. It's an example of a multi-celled organism, one of the biggest living creatures on the earth in fact. It also gives us a sense of the time span of life on earth because we can count these rings. So, a typical human life is basically this much. If I were going to projects here's a millennium. If I'm going to project to the age of the earth or the time that if life first started on the earth, we take this meter and multiply out to get 4.5 billion years. So, we're pointing down there 4,500 kilometers and that basically New York East Coast maybe into the Atlantic Ocean. So, think of all the things that might have occurred if we actually did happen in that fantastic span of time.