The unraveling of the universe's mysteries certainly did not end with Albert Einstein, Edwin Hubble and the discovery of the Big Bang. It seems that the further scientists investigate the universe, the more evident it becomes that life as we know it could not exist in a universe that was even slightly different. This has come to be known as the "anthropic principle"-the fact that the universe appears to be finely tuned to support human life.
The late physicist Stephen Hawking made a rather startling admission of this fact in his famous book A Brief History of Time: "The laws of science, as we know them at present, contain many fundamental numbers, like the size of the electric charge of the electron and the ratio of the masses of the proton and the electron ... The remarkable fact is that the values of these numbers seem to have been very finely adjusted to make possible the development of life" (1996, p. 129, emphasis added).
How do these "fundamental numbers" influence the universe's potential for life? For one, it's noted the strength of various physical forces determined the rate of expansion of the universe. If it had expanded too quickly, we would have a universe sparsely scattered with gases but no stars or planets-and thus no life as we know it. If it expanded too slowly, the rate of formation of black holes would be much higher, again making the universe totally inhospitable.
Further, as stars burn hydrogen to produce light, nuclear fusion takes place to form carbon, nitrogen and oxygen, and all of the other elements that are essential to life as well as the foundations of a planet to host it. These fusion reactions intimately depend on the strength of the strong nuclear force-another fundamental number-and a small change in its value would mean that these reactions could not take place.
Scientists explain that these and many other physical constants-hundreds of them, by some assessments-all have to be set within very narrow ranges for this elaborate, ages-long process of planet formation to play out just the right way to provide a life-supporting environment.
We are then faced with the incredible number of ways that the universe could conceivably have formed that would not have supported the formation of stars and planets at all-let alone complex life! According to physicist Paul Davies, "There is now broad agreement among physicists and cosmologists that the universe is in several respects 'fine-tuned' for life" ("How Bio-Friendly Is the Universe?" International Journal of Astrobiology, April 2003).