Limits Of The Anthropic Principle

If the electromagnetic force were just slightly stronger, protons would repel each other with such gusto that fusion of hydrogen into heavier nuclei would be impossible and it would be a very boring, lifeless universe of pure hydrogen. If the electromagnetic force were just slightly weaker, fusion would be so easy that stars would burn up and explode in no time and it would be a universe far too exciting for life to survive.

This is only one of many such examples of the constants of nature being “fine-tuned” for life. This raises the question of why the constants are the way they are. Nobody knows. There are those that have suggested that this proves the existence of God, assuming that God created the universe with life and humanity in mind. Others point out instead that if the constants were different, we would not be here to ask the question, so it should surprise no one that we find ourselves in a universe with constants fine-tuned for life. They say, “Of course things are the way they are; if they weren’t you wouldn’t be here asking about it.” This is called the anthropic principle. As far as we know, there may be very many universes with random constants, and statistics predicts that at least one of them will be friendly to life simply by chance. Coupled with the anthropic principle, this explains much.

However, there are limits to the principle’s explanatory power. It only explains away those things that are absolutely necessary for sentient life to evolve. It does not explain the incredible complexity and redundancy of our ecosystem. In all the possible universes where life exists aware enough to pose the question “why these constants?” the fraction of them with ecosystems as complex as ours must still be very small – so where did it all come from?

Even if it turns out that evolving sentience requires conditions leading to the state of affairs we now see on Earth, it certainly does not require that life evolved anywhere else in the universe. Evolution is such an unlikely process to begin with that it would be far too unlikely to happen twice. If we ever meet aliens, we will know something more is going on.

Since we have already asked the question “why these constants?” there is no more reason that we must necessarily survive to ask other questions. There is nothing guaranteeing that the laws of nature will not change. There is nothing guaranteeing our surviving the next meteorite impact or gamma ray burst. Which is the more likely universe? One in which life survives just long enough to invoke the anthropic principle before dying? Or one in which life survives indefinitely? The longer we survive and the more we learn that can go wrong but doesn’t, the more we will know that something else is going on.

Of course, if humanity were to survive another ten billion years and meet trillions of other sentient species, one could always say, “Of course things are the way they are; if they weren’t you wouldn’t be here asking about it.”