We stayed close to home tonight on Cosmos, traveling in time rather than in space. But as we heard, while it may be the same planet, there have been many Earths, each very different from our own. We started off with a lesson about plate tectonics. Looking back, it seems so obvious that the continents were once connected, the shape of the Atlantic Ocean and the coastline of the Americas against Europe and Africa get noticed by any observant elementary student who is presented with a map. The first cartographer to make a reasonably accurate map of the world back in the late 16th century noticed the same thing, but his observation remained only speculation, a footnote until the 20th century. The story of Alfred Wegener is well known, but the story of Marie Tharp and the discovery of the Mid-Atlantic Ridge is not, and it was a neat little bit of information.
Next we moved into the distant past, more than 300 million years ago. This was the Carboniferous period, a time when trees first appeared and giant insects roamed the Earth. This age is very important in our current time, because way back when, there were no organisms that could digest the lignin in the trees which is what made them grow, so instead of the tree being digested and its contents eventually returned to the environment, it was buried and eventually turned into coal. We also got a similar story about the Guadalupe Mountains in Texas, which was once a shallow tropical sea, full of life. As things died, they became buried under silt, and eventually turned into oil and gas. This is the era where we got our fossil fuels.
This episode featured a return to the Hall of Extinction, which we last visited in episode two. We learned about the Permian extinction, and how the Earth itself seemed to conspire against life. I think that brought home a valuable lesson. The Earth can support and nurture life, and then for no reason turn against it. Nature is a powerful force. We learned all about how plate tectonics has shaped our world, and I thought the story of the Mediterranean Sea was particularly interesting. I didn't know that it was so young, that it had been so inhospitable before it flooded, and that it was formed so quickly, over a span of just a year or two. Geologically speaking, that is remarkably quick.
We finished things off tonight with a warning. Our dependence on fossil fuel is pouring carbon dioxide into the atmosphere at a rate not seen in a very, very long time. There have been five mass extinctions in Earth's history, could we cause the sixth? If we're not careful, the Earth could be a much harsher place in the near future. I hope I'm not being optimistic here, but things are changing for the better. In ten years, I think we will be much further along in the road to clean energy then we think we will be. The tides are coming in, the slow march of progress in society is turning towards renewable energy. There might be plenty of fossil fuel left, but the costs of extracting it will become prohibitive long before they run out. Through government regulation, start-up energy companies, public opinion, things are slowly but definitely changing.
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