Why is the universe life-friendly?

A new book by James N. Gardner, BIOCOSM, offers a new theory as to why the universe is life-friendly (i.e. has physical constants and conditions that can and have given rise to life). He's written an article too, and here's my take on that.

Why is the universe life-friendly?

Probably the most common non-theistic answer is that there are lots of universes, maybe infinite universes, with varying physical laws and constants and numbers of dimensions, and so this universe just happened to be lucky in that it managed create Earth, where life could form.

One problem with this idea is that it violates the mediocrity principle.

The mediocrity principle, a mainstay of scientific theorizing since Copernicus, is a statistically based rule of thumb that, absent contrary evidence, a particular sample (Earth, for instance, or our particular universe) should be assumed to be a typical example of the ensemble of which it is a part.

How can we come up with an explanation for the life-friendliness of the universe that doesn't violate the mediocrity principle?

Suppose universes reproduce. To the best of my understanding, that's not so wild. Some scientists surmise that black holes spawn baby universes all the time. My brother's friend said he knew a black hole who had three universes while still in high school.

Suppose the physical properties of a parent universe are passed on to the baby universe, much like DNA is passed from parent to child in life reproduction. In that case, in any given group of universes, the kind of universes that reproduce most frequently will become more common than the infertile ones. What kind of universes reproduce the most? As I see it, there are two major factors that we know of (there are possibly a lot that we don't know of):

• how long the universe survives (i.e. the amount of time it has to reproduce)
• how often it reproduces

First, take how long the universe survives. There are a few ways for a universe to die: heat death, contraction, etc. (Dying, for a universe, might as well be defined as "not doing anything interesting, and certainly not reproducing"). If long-surviving universes are evolutionarily favored, we might expect to see lots of universes where the Big Bang's energy was just enough to avoid rapid collapse, but not so much as to blow everything so far apart that nothing interesting ever formed. And we do see lots of these universes, and by lots, I mean one. As Stephen Hawking said:

Why is the universe so close to the dividing line between collapsing again and expanding indefinitely? In order to be as close as we are now, the rate of expansion early on had to be chosen fantastically accurately.

The point is, this idea answers Hawking's question. The universe's rate of expansion is so fantastically tuned because it has been selected for over many generations of universes.

How often does a universe reproduce? As I understand it, there are two related theories as to how a universe reproduces. One is that black holes spawn baby universes. Another speculative idea is that extremely advanced, intelligent civilizations spawn baby universes, possibly with carefully designed black holes, which were built for experimental or recreational purposes, or some other purpose. And thus intelligent life is the means with which universes reproduce.

If universes reproduce with black holes, we might expect to see lots of black holes, because universes with black holes are selected for. And we know this universe does have some black holes, so that holds up. If universes reproduce with intelligent life, we might expect to see the conditions for intelligent life (which we do), and we might expect to see lots of intelligent life. We know of one form, and we're looking for more.

That's my ghetto take on Gardner's theory. You can read it in his words here.