Lucky Planet: Why Earth is Exceptional, David Waltham
For the most part, I found Lucky Planet interesting enough, though at times there were gaps when it comes to the possibilities for life elsewhere — and no mention at all of the idea that there could be life somewhere else on Earth which uses molecules of the opposite chirality to us, suggesting more than one separate origin of life. There was nothing about the Viking biological experiments, which per Michael Brooks’ pop-science books are still thought by some to have shown evidence for life on Mars — the experimenter, Levin, still thinks so, and he’s not alone.
I think the problem with all these theories is that they rely on a gut feeling of how likely life is to arise and, once arisen, to become intelligent. Obviously, as Waltham points out repeatedly, because we exist, conditions are possible in which we can exist and observe (a condition called the anthropic principle). That tells us nothing in itself about how likely life is to arise, though. In fact, with everything that might indicate how likely life is to arise, we have a sample size of one.
It’s really impossible to scientifically judge, I think. It depends on whether you decide life is likely or unlikely, and follows from there. Waltham does discuss all the factors that make Earth a rarity, which may constrain life. But again, sample size of one, so how do we know that a planet’s satellites or seismic activity or atmosphere or predominant minerals are important or not? Life doesn’t have to look the same as us (but if it did, that would go a fair way to confirming Waltham’s point; we require very specific circumstances to have arisen, after all).
So, if you’re looking for an answer, I don’t think Waltham has one for you (though nor does anyone else, by the same logic).
