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So, I was channel-surfing last night and skimmed by the History Channel. They were talking about the supercontinent Rodinia, which (it is believed) formed around a billion years ago. The History Channel program then presented as fact the idea that the entire Earth was covered in ice, a-la Hoth.
This snowball Earth theory is not without controversy, although it's believed to have happened at least twice - the first event being after the Oxygen Catastrophe of around 2 billion years ago. (Since I personally like oxygen, I was wondering what the 'catastrophe' was. Apparently free oxygen killed off most anaerobic bacteria, and CO2 levels fell to the point that Earth's greenhouse effect failed and we iced over.)
At any rate, I was struck by two thoughts. The first thought is that, as SF writers, we are taught to avoid the "it was raining on Planet Mongo" school of writing. This is the idea that a planet doesn't have just one ecosystem. Except, sometimes it will. Neither snowball Earth event proved stable long-term, but both events lasted for millions of years - periods of time longer than the human species has existed.
The second thought was Fermi's Paradox. During either of the snowball periods and a good chunk of time before and after, any visiting aliens would have found Earth uninhabitable, or certainly unattractive as a place to settle. Any evidence of their visitation would have been built on the top of an ice cap, and the remains washed away by melt-water. Space is big, and old too. We haven't found evidence of alien life yet because we've only been looking for an instant or so.
This snowball Earth theory is not without controversy, although it's believed to have happened at least twice - the first event being after the Oxygen Catastrophe of around 2 billion years ago. (Since I personally like oxygen, I was wondering what the 'catastrophe' was. Apparently free oxygen killed off most anaerobic bacteria, and CO2 levels fell to the point that Earth's greenhouse effect failed and we iced over.)
At any rate, I was struck by two thoughts. The first thought is that, as SF writers, we are taught to avoid the "it was raining on Planet Mongo" school of writing. This is the idea that a planet doesn't have just one ecosystem. Except, sometimes it will. Neither snowball Earth event proved stable long-term, but both events lasted for millions of years - periods of time longer than the human species has existed.
The second thought was Fermi's Paradox. During either of the snowball periods and a good chunk of time before and after, any visiting aliens would have found Earth uninhabitable, or certainly unattractive as a place to settle. Any evidence of their visitation would have been built on the top of an ice cap, and the remains washed away by melt-water. Space is big, and old too. We haven't found evidence of alien life yet because we've only been looking for an instant or so.
