“Fine-tuning” refers to various features of the universe that are necessary conditions for the existence of complex life. Such features include the initial conditions and “brute facts” of the universe as a whole, the laws of nature or the numerical constants present in those laws (such as the gravitational force constant), and local features of habitable planets (such as a planet’s distance from its host star).Richards goes on to list and explain twenty two of those widely accepted examples of these precisely calibrated features.
The basic idea is that these features must fall within a very narrow range of possible values for chemical-based life to be possible. Some popular examples are subject to dispute, and there are some complicated philosophical debates about how to calculate probabilities.
Nevertheless, there are many well-established examples of fine-tuning, which are widely accepted even by scientists who are generally hostile to theism and design. For instance, Stephen Hawking has admitted: “The remarkable fact is that the values of these numbers [the constants of physics] seem to have been very finely adjusted to make possible the development of life.”
First, there are Cosmic Constants:
(1)Gravitational force constant
(2)Electromagnetic force constant
(3)Strong nuclear force constant
(4)Weak nuclear force constant
Then there are Initial Conditions and “Brute Facts”:
(6) Initial distribution of mass energy
(7) Ratio of masses for protons and electrons
(8) Velocity of light
(9) Mass excess of neutron over proton
And “Local” Planetary Conditions:
(10) Steady plate tectonics with right kind of geological interior
(11) Right amount of water in crust
(12) Large moon with right rotation period
(13) Proper concentration of sulfur
(14) Right planetary mass
(15) Near inner edge of circumstellar habitable zone
(16) Low-eccentricity orbit outside spin-orbit and giant planet resonances
(17) A few, large Jupiter-mass planetary neighbors in large circular orbits
(18) Outside spiral arm of galaxy
(19) Near co-rotation circle of galaxy, in circular orbit around galactic center
(20) Within the galactic habitable zone
(21) During the cosmic habitable age
Finally, Richards mentions the Effects of Primary Fine-Tuning Parameters:
(22) The polarity of the water molecule
Some of these examples express a balance of several features. A spectacular instance of this is the cosmological constant (#5) which is a relationship between the repulsive force of dark energy, which is causing the expansion of the universe to accelerate, and the force of gravity which causes the universe to tend toward collapse. This balance must be set with a precision of one part in 10^120. If the value of the cosmological constant were off by that much, an incomprehensibly tiny amount, the universe would either collapse or rip itself apart.
In talking about the gravitational force (#1) Richards creates a word picture to give us a mental image of the amazingly fine tolerances that physicists have discovered:
Imagine a measuring stick like a ruler that extends from one end of the universe to the other. Imagine that this ruler represents the range of force strengths from the weakest force (gravity) to the strongest (the strong nuclear force). If the force of gravity deviated from its actual value by the equivalent of about one inch on the ruler there would be no life-sustaining planets in the universe.No doubt the most remarkable example of fine-tuning is #6, the initial distribution of mass/energy in the nascent universe just after the Big Bang. Richards says:
One way of summarizing the initial conditions is to speak of the extremely low entropy (that is, a highly ordered) initial state of the universe. This refers to the initial distribution of mass/energy. In The Road to Reality, physicist Roger Penrose estimates that the odds of the initial low entropy state of our universe occurring by chance alone are on the order of 1 in 10^10^123. This ratio is vastly beyond our powers of comprehension. Since we know a life-bearing universe is intrinsically interesting, this ratio should be more than enough to raise the question: Why does such a universe exist?Good question. Here's another: Is this unimaginable degree of fine-tuning more likely on the assumption that theism is true or on the assumption that naturalism is true?
Richards gives a brief explanation of each of the twenty examples here.