When they formed, Tyson tells us, Earth and Venus had similar amounts of carbon. As it is, the Venusian atmosphere is hot enough to melt lead.
In fact, Venus’s thick cover of clouds, mostly made of sulfuric acid, would actually make its surface ice-cold, were it not for the high levels of sunlight-trapping CO2. Heat from the sun was trapped in the atmosphere, and the planet grew hotter and hotter - and not merely because of its closer proximity to the Sun. Almost a paradise, until the planet’s atmosphere became too filed with carbon dioxide from volcanic eruptions, which eventually led to a runaway greenhouse effect. Tyson starts us out on Venus, explaining that for the first billion years or so of the planet’s existence, things were probably a lot like conditions on the early Earth - liquid seas, the occasional asteroid strike, maybe even the beginnings of life. And for the most part, it works impressively well.
Cosmos a spacetime odyssey the world set free how to#
This is the episode that you can tell has probably had the most editorial meetings behind it to plan out how to make the case, firmly and clearly, that climate change is real, it’s already here - not off in some distant future - and not only is the science not in dispute, but none of the “alternate” explanations hold water. You can pretty much bet that this week’s episode, The World Set Free, is going to be the one that gets talked about the most, and probably shown in more classrooms than any other, because after making passing mentions of it in several previous episodes, this is the one where Neil de Grasse Tyson brings out the Big Science guns and talks for the full hour about climate change. We are down to the last two episodes of Cosmos: A Spacetime Odyssey, already.