Jonathan M. posted about the fine-tuning argument on the Apologetics UK blog.
Here’s the general argument:
The concept of cosmic fine tuning relates to a unique property of our universe whereby the physical constants and laws are observed to be balanced on a ‘razor’s edge’ for permitting the emergence of complex life. The degree to which the constants of physics must match precise criteria is such that a number of agnostic scientists have concluded that indeed there is some sort of transcendent purpose behind the cosmic arena. British astrophysicist Fred Hoyle writes: “A common sense interpretation of the facts suggests that a super intellect has monkeyed with physics, as well as with chemistry and biology, and that there are no blind forces worth speaking about in nature. The numbers one calculates from the facts seem to me so overwhelming as to put this conclusion almost beyond question.”
He goes into some detail about how the amount of mass of the universe has to be finely tuned to the volume of the universe, which is always expanding.
The mass density of the universe is finely balanced to permit life to a degree of one part in 10^59. If the universe were slightly more massive, an overabundance of deuterium from the big bang would cause stars to burn too rapidly for the formation of complex life. If the universe were slightly less massive, an insufficiency of helium would result in a shortage of the heavy elements — again, resulting in no life.
The density of protons and neutrons in the cosmos relates to the cosmic mass density. That density determines just how much hydrogen fuses into heavier elements during the first few moments after the origin of the universe. In turn, the amount of heavier elements determines how much additional heavy-element production occurs later in the nuclear furnaces or stars.
What would be the consequence if the respective density of neutrons and protons were significantly lower? Firstly, nuclear fusion would occur with less efficiency. Consequently, the heavier elements such as carbon, nitrogen, oxygen, phosphorous, sodium and potassium — all of which are essential for the emergence of physical life — would not be formed. Moreover, assuming no additional cosmic density factors such as dark energy, a cosmos which possesses less mass density would prohibit the formation of stars and planets. Why? The expansion rate would be so big that matter would expand too quickly for gravity to pull together the gas and dust to allow their formation. If that were not enough, with only a little extra mass, the cosmos would expand so slowly that all stars in the cosmos would quickly turn into black holes and neutron stars. The density near the surface of such bodies would be so enormous that molecules would be impossible. Therefore, life would not be possible. The radiation from the formed black holes and neutron stars would also render physical life an impossibility at any point in a universe with such a high density.
Conversely, what would be the effect if the density of protons and neutrons in the cosmos were to be significantly higher? Nuclear fusion would be too productive, meaning that all the hydrogen in the universe would rapidly fuse into elements heavier than iron. The ultimate result is the same — the life-essential elements would not exist. Moreover, if the cosmic mass density were to be greater, gas and dust would condense so effectively under gravity’s influence that all stars would be much more massive than the Sun. Thus, planets would not be life-permitting because of the intensity of the radiation of their respective star, and additionally because of the rapid changes in the stars’ temperature and radiation.
The mass of the universe exhibits cosmic fine tuning to simultaneously permit two features which are essential for permitting life: (1) the correct diversity and quantity of elements; and (2) the appropriate rate of cosmic expansion required to allow life. Such cosmic fine-tuning bespeaks foresight and planning — indicators of intelligent design.
You can read more examples of fine-tuning here in my previous post. That post includes a link to a secular science journal which talks about the fine-tuning of the gravitational force.