Now, the period of time that was required for the evolution of intelligent life in the universe-if we are unique and we define ourselves immodestly as the carriers of intelligent life (a case could be made, you know, for other primates and dolphins, whales, and so on)-but for any of those cases it took something like 14,000 million years for intelligence to arrive. Well, how come? Why are those two numbers the same? Put another way: If we were at a much earlier stage or a much later stage in the expansion of the universe, would things be very different? If we were at a much earlier stage, then there would not be, according to this view, enough time for the random aspects of the evolutionary process to proceed, and so intelligent life would not be here, and so there would be nobody to make this argument or debate about it. Therefore the very fact that we can talk about this demonstrates, it is argued, that the universe must be a certain number of years old. So if only we had been wise enough to have thought of this argument before Edwin Hubble, we could have made this spectacular discovery about the expansion of the universe just by contemplating our navels.
There is to my mind a very curious ex post facto aspect of this argument. Let's take another example. Newtonian gravitation is an inverse square law. Take two self-gravitating objects, move them twice as far apart, the gravitational attraction is one-quarter; move them ten times farther apart, the gravitational attraction is one-hundredth, and so on. It turns out that virtually any deviation from an exact inverse square law produces planetary orbits that are, in one way or another, unstable. An inverse cube law, for example, and higher powers of the negative exponent mean that the planets would rapidly spiral into the Sun and be destroyed.
Imagine a device with a dial for changing the law of gravity (I wish there were such a device, but there isn't). We could dial in any exponent, including the number 2 for the universe we live in. And when we do this, we find that a large subset of possible exponents leads to a universe in which stable planetary orbits are impossible. And even a tiny deviation from 2-2.0001, for example-might, over the period of time of the history of the universe, be enough to make our existence today impossible.
So, one may ask, how is it that it's exactly an inverse square law? How did it come about? Here is a law that applies to the entire cosmos that we can see. Distant binary galaxies going around each other follow exactly an inverse square law. Why not some other sort of law? Is it just an accident, or is there an inverse square law so that we could be here?
In the same Newtonian equation, there is the gravitational coupling constant called "big G." It turns out that if big G were ten times larger (its value in the centimeter-gram-second system is about 6.67 x 10-8), if it were 10 times larger (6.67 x 10-7), then it turns out the only kind of stars we would have in the sky would be blue giant stars, which expend their nuclear fuel so rapidly that they would not persist long enough for life to evolve on any of their planets (that is, if the timescales for the evolution of life on our planet are typical).
Or if the Newtonian gravitational constant were ten times less, then we would have only red dwarf stars. What's wrong with a universe made with red dwarf stars? Well, it is argued, they're around for a long time because they burn their nuclear fuel slowly, but they are such feeble sources of light that to be warmed to the temperatures of liquid water, let's say, [2] then the planets would have to be very close to the star in order to be at this temperature. But if you put the planets very close to the star, there is a tidal pull that the star exerts on the planet so that the planet always keeps the same face to the star, and therefore, it is said, the near side will be too hot and the far side will be too cold and it's inconsistent with life. So isn't it remarkable that big G has the value it does? I'll come back to this.
Or consider the stability of atoms. An electron with something like one eighteen-hundredth the mass of a proton has precisely the same electrical charge. Precisely. If it were even a little different, the atoms would not be stable. How come the electrical charges are exactly the same? Is it so that 14 billion years later we, who are made of atoms, could be around?
Or if the strong nuclear force coupling constant were only a little weaker than it is, you can show that only hydrogen would be stable in the universe and all the other atoms, which surely are required for life, we would say, would never have been made.
Or if certain specific nuclear resonances in the nuclear physics of carbon and oxygen were a little different, then you could not build up in the interiors of red giant stars the heavier elements and again you would have only hydrogen and helium in the universe and life would be impossible. How is it that everything works out so well to permit life when it's possible to imagine quite different universes?
(What I'm about to say now is not an answer to the question I've just posed.) It is not difficult to see teleology hiding in this sequence of arguments. And, in fact, the very phrase "anthropic principle" is a giveaway as to at least the emotional if not the logical underpinnings of the argument. It says something central about us; we're the anthropos. And that's the reason I am saying that this is another ground, somewhat covert, on which the Copernican conflict is being worked out in our time. J. D. Barrow, one of the authors and promoters of the anthropic principle, is quite straightforward about it. He says that the universe is "designed with the goal of generating and sustaining observers"-namely, us.
Now, what can we say about this? Let me make, in conclusion, a few critical remarks. First of all, in at least parts of this argument there is a failure of the imagination. Let's take that red dwarf argument, in which if the gravitational constant were an order of magnitude less, then we would only have those red giants. Is it true that you could not have life in that situation for the reasons I mentioned? It turns out it isn't, for two different reasons. Let's look again at that tidal locking argument. Yes, for a close-in planet and the star, it seems possible that the net result would be the same kind of situation as for the Moon and the Earth, namely, that the secondary body makes one rotation per revolution, therefore always keeping the same face to the primary. That's why we always just see one Man in the Moon and not some Woman in the Moon on the back that we see as well. But if you look at Mercury and the Sun, you find a close-in planet not in a one-to-one resonance, but it's a three-to-two resonance. There are many more than just this one kind of resonance that are possible. What is more, if we're talking about planets that have life, we're talking about planets with atmospheres. A planet with an atmosphere carries the heat from the illuminated to the unilluminated hemisphere and redistributes the temperature. So it's not just the hot side and the cold side. It is much more moderate than that.
And then let's take a look at the more distant planets that you might imagine were too cold to support life. This neglects what is called the greenhouse effect, the keeping in of infrared emission by the atmospheres of the planet. Let's take Neptune, at thirty astronomical units from the Sun, so you would figure that it has almost a thousand times less sunlight. And yet there is a place we can see with radio waves in the atmosphere of Neptune that is as warm as it is in the cozy room I'm in. So what has happened here is that an argument has been put forward, but in insufficient detail. It has not been looked at closely enough. And I bet that will turn out to be the case in some of the other examples I present.
The second possibility is that there is some new principle hitherto undiscovered, which connects various apparently unconnected aspects of the universe in the same way that natural selection provided a wholly unexpected solution to a problem that seemed to have no conceivable solution whatever.