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Jupiter has protected Earth from too many cataclysmic asteroid collisions, he explained -- but on the other hand, a neighbor much larger that Jupiter would not allow formation of an Earth-like planet in the first place. Similarly, our moon is just the right size to help stabilize Earth's spin axis and, as a consequence, the Earth's climate. With a bigger moon or no moon at all, a planet similar to Earth in other respects might not sustain life.

Looks like more evidence for the "anthropic principle."

"Rare Earth" mainly discusses the conditions for successful animal and bacterial life. Not just humans, but any higher animals. Other forms of life besides bacteria are left to the imagination. There could be replicating machines out there; they could be considered living by some definitions of life. There is probably teeming life everywhere, but it is all bacteria.

Jupiter has protected Earth from too many cataclysmic asteroid collisions, he explained -- but on the other hand, a neighbor much larger that Jupiter would not allow formation of an Earth-like planet in the first place. Similarly, our moon is just the right size to help stabilize Earth's spin axis and, as a consequence, the Earth's climate. With a bigger moon or no moon at all, a planet similar to Earth in other respects might not sustain life.
Looks like more evidence for the "anthropic principle."

I disagree. Or rather, I disagree that it's necessarily compelling evidence. It all hinges on qualifications. "a neighbor much larger that Jupiter", he says. Well, "How much larger?" I ask. Can this Jupiter-like planet be 10% larger & still be a net benefit? 1x10¹ bigger? 1x10² bigger? 1x10³ bigger? In astronomy, these numbers are always so big, it's easy to forget that the range between two numbers is often also very big - allowing for many possibilities - even though when that range gets distilled into conversational written English it sounds impressively small. Same thing with the size of the Moon, or with the ratios of subatomic particles & basic physical constants, etc.

The other, more basic problem I have with the Anthropic Principle is that it's a logical error right from the start. As we discover nature's regularities & relationships - how the world works - we naturally ask ourselves "why?". This means, "Why does it work this way instead of all the other ways I can imagine it 'could have' worked?"

The AP argument seems to be a more sophisticated sounding version of that question. But that question is invalid. Every time we study a natural phenomenon & discover why it works the way it does, we simultaneously discover why it could not have worked any other way. We discover the regularities that give rise to the regularities we seek to explain. It literally could not have worked any other way.

Here's an example: You live in a hot climate, & you have never seen what happens to water when it goes below 32^oF. I come along & tell you that water changes drastically at 32^oF. Now you start to wonder: What could water do at 32^oF? You start to list the possibilities:

The water gets colder.
The water shrinks to 1/2 its size.
The water turns color to {red|orange|yellow|green|blue|brown|purple|gray|opaque white|black}.
The water turns solid.
The water turns jiggly, like Jell-O.
The water jumps up & sings the Michigan Rag.
The water catches fire, but emits a cold instead of a hot flame.

As your imagination wanders, you go thru all possible combinations of the above "possibilities" & more, and if your imagination is big enough, you can generate an astronomical number of "possibilities" this way.

Then I show you an ice cube. Now, what are the odds that that would happen instead of something else? Well, it all depends on how big your imagination was! So in our example, the odds of it turning out this way were vanishingly small. And yet, as you learn about molecules, molecular bonds, thermal energy, & how light waves interact with molecules of different sizes, you begin to see why almost all of your possibilities were never "possible" in the first place.

Then, your curiosity piqued, you begin to wonder why the H atoms in H₂O have to stay at 110^o (?) instead of some other angle, etc. etc., & the cycle repeats - until we get to the question of why the charge of an electron is a certain ratio to the size of a graviton (or whatever). IOW, where we are today with AP.

So, IMO the wonder that AP writers express at how "fine tuned" the universe seems to be in order to produce the universe we see is nothing more than a misunderstanding of how the hypothetico-deductive reasoning process works.

(I always wanted to use the term "hypothetico-deductive" someday!)