Transcript: Early in the Earth’s history, the first half billion years, it was a violent and inhospitable place. The crust had just formed; volcanism was extreme and very active. There was much lava flowing, and the surface was barely solid, certainly not hospitable for life. The primary...

Transcript: The Earth, the Sun, and all the planets were formed at the same time, 4.6 billion years ago. This time is estimated fairly accurately from radioactive decay in rocks from the Moon and the Earth added to the timescale for the collapse of the solar nebula. As the Sun formed, rocky...

Transcript: Charles Darwin was born into a wealthy family in England in 1809. He had two famous grandfathers. One, Erasmus Darwin, was a noted scientist, and the other, Josiah Wedgwood, was one of the first entrepreneurs of the industrial revolution. Darwin enrolled in medical school, but it...