The fine-tuning of the universe is shown in the precise strengths of four basic forces. Gravity is the best known of these forces, and the weakest, with a relative strength of 1. Next comes the weak nuclear force that holds neutrons together inside an atom. It is 1034 times stronger than gravity but works only at subatomic distances. Electromagnetism is 1,000 times stronger than the weak nuclear force. The strong nuclear force—which keeps protons together in the nucleus of an atom—is 100 times stronger yet. If even one of these forces had a slightly different strength, the life-sustaining universe we know would be impossible.
If gravity were slightly stronger, all stars would be large, like the ones that produce iron and other heavier elements, but they would burn out too rapidly for the development of life. On the other hand, if gravity were weaker, the stars would endure, but none would produce the heavier elements necessary to form planets.
The weak nuclear force controls the decay of neutrons. If it were stronger, neutrons would decay more rapidly, and there would be nothing in the universe but hydrogen. However, if this force were weaker, all the hydrogen would turn into helium and other elements.
The electromagnetic force binds atoms to one another to form molecules. If it were either weaker or stronger, no chemical bonds would form, so no life could exist.
Finally, the strong nuclear force overcomes the electromagnetic force and allows the atomic nucleus to exist. Like the weak nuclear force, changing it would produce a universe with only hydrogen or with no hydrogen.
In sum, without planets, hydrogen, and chemical bonds, there would be no life as we know it. Besides these four factors, there are at least twenty-five others that require pinpoint precision to produce a universe that contains life. Getting each of them exactly right suggests the presence of an Intelligent Designer.