Offspring of the Marriage of Cause and Chance
As much as physicists hate to admit it, not everything in nature happens as a result of natural law. Strange to tell, much of the universe is an accident.
Take the family of planets, for example. Johannes Kepler spent decades trying to figure out the harmonics behind the orbits of Earth and its neighbors. He tried to make them trace perfect, resonant patterns that would sing out the music of the spheres.
He failed because the planets didn’t fall into place according to plan. They just fell. When the solar system condensed from its primordial gas cloud, clumps of matter appeared here and there, by chance. One of them gave rise to us.
“We now understand that the planets and their orbits are the results of a sequence of historical accidents,” writes physicist Steven Weinberg in “Dreams of a Final Theory.”
He concludes: “The most extreme hope for science is that we will be able to trace the explanation of all natural phenomena to final laws and historical accidents.”
It’s often hard to tell which phenomena follow from law and which happen by happenstance, however. While Kepler spun his mental wheels trying to find reason in chance, other scientists dismissed important clues as “mere” accident. Geologists wrote off the almost perfect fit between the coasts of South America and West Africa as a funny coincidence. Only recently did they accept the idea that these continents used to be part of a single landform, that continents drift apart.
The distinction between law-abiding and accidental events is not merely a matter of curiosity. In general, phenomena that follow laws can be predicted, while accidental ones cannot.
Today, physicists would very much like to know whether or not the laws of physics are an accident. Or as Einstein put the question: Did God have a choice?
If the laws of physics are set in stone--if there’s only one possible mass for an electron or four possible dimensions for space-time or one possible strength for gravity--then God did not have a choice. Knowing the laws of physics would allow us to predict the universe as we know it.
Recent thinking suggests a more unsettling scenario: The universe could have evolved in many different ways out of the primordial chaos--all of them equally plausible. Just as ice can crystallize from water in just about any form, so the matter and energy in the universe could have crystallized in any number of ways.
The fact that things fell into place in a way that allows life to exist, according to this argument, is simply serendipity. Life got lucky.
On the other hand, maybe the universe we perceive is the way it is because it’s the only kind of universe we can perceive. Other kinds of universes may well be out there. But their laws would make the vast majority devoid of life.
Curiously, the evolution of life itself is ruled by a strange marriage of cause and chance. The genetic alterations that make changes in species possible are random events--stray cosmic rays zapping atomic bonds.
But biological imperatives ultimately determine the success of species. While chance plays a role, suitability to habitat plays a larger one.
In a new book, physicist Lee Smolin of Pennsylvania State University suggests that the universe itself evolved by a kind of natural selection. “The laws of nature themselves, like the biological species, may not be eternal categories,” he says, “but rather the creations of natural processes occurring in time.”
Roughly, Smolin says, our “accidental” universe evolved like this:
First, he assumes that multiple universes are continually sprouting into existence from the back side of black holes. (In essence, space-time gets pinched out of existence inside a black hole, but gets reborn out the other end into a new baby universe.) So universes that create many black holes give rise to more baby universes than universes without black holes.
Black holes are created by stars that explode and collapse under the weight of their own gravity. So universes with lots of stars are more “fit” to survive than others.
As it turns out, the same properties that produce stars make the universe a fit place for intelligent life forms.
So partly by plan, partly by accident, our universe (and perhaps others) evolved to produce beings like us. As Smolin explains it, the universe is more like a city than a clock. A clock needs a clockmaker to create it, and wind it up. But cities--like species--spring into existence seemingly of their own accord.
“If a city can make itself, without a maker,” he concludes, “why can the same not be true of the universe?”
The good news in all this is that the universe is not, as some people suspect, an accident waiting to happen. It’s an accident that happened 15 billion years ago.
