The Fine-Tuning of the Universe
From galaxies and stars down to atoms and subatomic particles, the very structure of our universe is determined by these numbers. They represent the fundamental constants and quantities of the universe. Scientists have reached the shocking conclusion that each of these numbers has been fine-tuned with astonishing precision, within an extremely narrow range that allows for the existence of life. If any of these numbers were altered by even a tiny fraction, no form of physical and interactive life could exist. There would be no stars, no life, no planets, and no chemistry.
Gravity
Take gravity as an example. The gravitational force is determined by the gravitational constant. If this constant varied by even one part in , we would not exist. To understand how extremely narrow this life-permitting range is, imagine a dial divided into steps. To realize how small these steps are, compare them to the number of cells in your body or the number of seconds that have passed since the beginning of time.
If the gravitational constant had been shifted by just one of these infinitely small divisions, the universe would have either expanded and thinned out so rapidly that stars could not form and life would not exist, or it would have collapsed upon itself, with the same result: no stars, no planets, no life.
Expansion
Or consider the expansion rate of the universe, determined by the cosmological constant. A change in its value by just one part in would have caused the universe to expand too rapidly or too slowly. In either case, the universe could not have sustained life.
Another example of fine-tuning: if the mass and energy of the early universe were not distributed evenly with an incomprehensible precision of one part in , the universe would have been hostile to any form of life.
The reality is that our universe allows for physical and interactive life only because these and many other numbers have been tuned independently and extremely precisely, as if on a razor's edge. Wherever physicists look, they find examples of fine-tuning.
The remarkable fact is that the values of these numbers seem carefully adjusted to allow for the development of life. If someone claims not to be surprised by these special characteristics of the universe, it means they are denying reality. These features are both surprising and improbable.
Possible Explanations
What is the best explanation for this breathtaking phenomenon? There are three viable options. The fine-tuning of the universe is caused either by physical necessity, chance, or design. Which of these options is the most plausible?
According to the first alternative, the universe must permit life. The precise values of these constants and quantities could not be otherwise. But is this a plausible hypothesis? Is a life-prohibiting universe impossible? Far from it. Not only is it possible, but it is much more likely than a life-permitting one. The constants and quantities are not determined by the laws of nature. There is no evidence that this fine-tuning is necessary.
What about chance? Did we just get incredibly lucky? No; the probabilities involved are so ridiculously small that the idea of accidental fine-tuning is excluded.
The Multiverse Hypothesis
To save this variant, some have moved beyond empirical science and proposed a speculative approach known as the multiverse. They imagine a universe generator that produces a vast number of universes, and statistically, a few of them would allow for life.
However, there is no scientific evidence for the existence of this multiverse. It cannot be detected, observed, measured, or proven, and the generator itself would require immense fine-tuning. Furthermore, small patches of order are much more likely than large ones; therefore, the most probable observable universe would be a small one, inhabited by a single simple observer.
But what we observe is the exact opposite of what we should expect: a vast, spectacularly complex, highly ordered universe, inhabited by billions of other observers. So, even if the multiverse existed—which is debatable—it would not explain the fine-tuning at all.
Conclusion
Given the improbability of physical necessity or chance, the best explanation for why the universe is tuned for life may be that it was designed that way.
A common-sense interpretation of the facts suggests that a super-intelligence has "monkeyed" with physics and that there are no blind forces worth speaking about in nature. The numbers one calculates from the facts are so overwhelming as to put this conclusion almost beyond question.
To me, there is strong evidence that something is behind it all... It seems as though someone has fine-tuned nature’s numbers to make the universe. The impression of design is overwhelming.
"The heavens declare the glory of God; the skies proclaim the work of his hands. Day after day they pour forth speech; night after night they reveal knowledge."
