Cosmos: A Spacetime Odyssey, Episode 9, “The Lost Worlds of Planet Earth”
At the beginning of its run, Cosmos tended to alternate excellent episodes with mediocre ones, which made me wonder if that would be the pattern for the whole series. But I’m happy to say that the show has hit its stride: the last three episodes, including this one, have been outstanding, and in my opinion this was the best of the three.
We started out back on the Cosmic Calendar, this time in mid-December, the Carboniferous Period. This was the era when plants invented lignin, the stiff, strong molecule that allows trees to grow tall. Since fungi and bacteria couldn’t adapt to digest this tough new substance at first, vast numbers of trees died and were buried without decaying, eventually becoming the coal deposits we’re mining millions of years later to release their stored-up solar energy. I loved the scene on a Nova Scotia beach showing strata of petrified wood stacked one on top of another, a layer cake of fossilized ancient forests. (Ask a creationist how they think that formed during Noah’s flood.)
There were a lot of callbacks to episode 2, especially the return to the Halls of Extinction, still my favorite metaphor of the new series. In that earlier episode, Neil deGrasse Tyson spoke briefly about the Permian-Triassic mass dying, but here gave more detail about what we believe caused it. It was a chain reaction of cataclysms: the massive volcanic eruption of the Siberian Traps, which ignited vast subterranean coal deposits, belching toxic smoke and carbon dioxide into the air and acidifying and warming the planet. The heat melted ice clathrates on the sea floor, releasing huge amounts of methane, an even more potent greenhouse gas, that caused wild climactic swings.
In that era the world was just one continent, all the dry land united in Pangaea, and this was the episode’s jumping-off point to discuss continental drift. The jigsaw-puzzle fit of the continents had long been noticed by mapmakers, but Alfred Wegener was the first to put the idea on a scientific footing. He was roundly ridiculed by the scientific community (and to be fair, he had no explanation of how the continents could move), but never gave up, and in fact died on an Arctic expedition while seeking evidence for his ideas. The torch was handed on to other scientists, including Marie Tharp, who provided crucial proof of seafloor spreading by compiling the first map of the ocean floor. I was happy to see the scene with Tharp, which fulfilled my hope that the last episode wouldn’t be the only one to feature women in science. I also enjoyed the mention of the Zanclean flood that filled the Mediterranean, and surprised to learn how the closure of the Isthmus of Panama caused global climate shifts that may have played an important role in humanity’s evolution.
And it closed with a warning. We live in a warm, clement interglacial period, but we’re bending our whole industrial civilization toward making it hotter: digging up and burning those ancient fossil forests, spewing their carbon back into the atmosphere, bringing back the chaotic climate that last prevailed in the Carboniferous – even though the Sun pours down more free and clean energy than we could ever need. We know exactly what we need to do to get out of this trap, but inertia, denial and vested interests are obstructing progress and prolonging the switchover, while all the while we’re doing worse and worse damage (“The dinosaurs never saw that asteroid coming. What’s our excuse?”).
Tyson warned that the unmarked corridor in the Halls of Extinction, if we persist in acting unwisely, could well be ours. This episode closed with a monologue that was as powerful and as moving as anything Carl Sagan ever wrote:
No matter where we hail from, or who our parents were, we are descended from the hardy survivors of unimaginable catastrophes. Each of us is a runner in the longest and most dangerous relay race there ever was, and at this moment, we hold the baton in our hands…
Each of us is a tiny being riding on the outermost skin of one of the smaller planets for a few dozen trips around the local star… That we understand even a little of our origins is one of the great triumphs of human insight and courage. Who we are and why we are here can only be glimpsed by piercing together something of the full picture, which must encompass eons of time, millions of species, and a multitude of worlds.
In this perspective, it’s not surprising that we’re a mystery to ourselves and that, despite our manifest pretension, we are far from being masters of our own little house… What happens here, in countless ways both large and small, is being written by us. Right now.
Other posts in this series: