In recent years, physics has given this question a resounding answer that overthrows the principle of mediocrity and affirms man’s special place in the cosmos. It turns out that the vast size and great age of our universe are not coincidental. They are the indispensable conditions for the existence of life on earth. In other words, the universe has to be just as big as it is and just as old as it is in order to contain living inhabitants like you and me. The entire universe with all its laws appears to be a conspiracy to produce, well, us. Physicists call this incredible finding the anthropic principle, which states that the universe we perceive must be of precisely such a nature as will make possible living beings who can perceive it. The Copernican narrative has been reversed and man has been restored to his ancient pedestal as the favored son, and perhaps even the raison d’être, of creation.

Physicists stumbled upon the anthropic principle by asking a simple question: why does the universe operate according to the laws it does? Think about it: the universe seems to follow a very specific set of rules, and yet it didn’t have to have these rules. So why these rules and not other rules? To take a simple example, the various forces in nature, such as the force of gravity, operate in ways that can be measured. Why is the gravitational force just this strong, and not stronger or weaker? Or consider that the universe is approximately fifteen billion years old and at least fifteen billion light years in size. What would have happened if the universe was much older and bigger or much younger and smaller?

The physicists who asked these questions arrived at a remarkable conclusion. In order for life to exist—in order for the universe to have observers to take notice of it—the gravitational force has to be precisely what it is. The Big Bang had to occur exactly when it did. If the basic values and relationships of nature were even slightly different, our universe would not exist and neither would we. Fantastic though it seems, the universe is fine-tuned for human habitation. We live in a kind of Goldilocks universe in which the conditions are “just right” for life to emerge and thrive. As physicist Paul Davies puts it,”We have been written into the laws of nature in a deep and, I believe, meaningful way.” The anthropic principle is now widely accepted among physicists, and there are several good books that explain it in comprehensive detail. John Barrows and Frank Tipler’s The Anthropic Cosmological Principle is the most thorough and detailed exposition. In his introduction to that book, physicist John Wheeler writes that “a life-giving factor lies at the center of the whole machinery and design of the world.” If you want a shorter and more readable version of the same argument, try astronomer Martin Rees’s Just Six Numbers. Rees argues that six numbers underlie the fundamental physical properties of the universe, and that each is an exact value required for life to exist. If any one of the six (say the gravitational constant, or the strong nuclear force) were different “even to the tiniest degree:’ Rees says, “there would be no stars, no complex elements, no life.” Although he disavows the religious implications, Rees does not hesitate to call the values attached to the six numbers “providential.”

Astronomer Lee Smolin imagines God as a kind of master technician who is sitting at a control panel with a set of dials in front of Him. One dial sets the mass of the proton, another the charge of the electron, a third the gravitational constant, and so on. God spins the dials randomly. What, Smolin asks, is the probability that this random spinning would result in a universe with stars and planets and life? “The probability,” he answers, “is incredibly small.” How small? Smolin’s estimate is one chance in ten to the power of 229. Smolin’s point is reinforced by a single example from physicist Stephen Hawking: “If the rate of expansion one second after the Big Bang had been smaller by even one part in a hundred thousand million million, the universe would have recollapsed before it even reached its present size.” So the odds against us being here are, well, astronomical. And yet we are here. Who is responsible for this?