Scientists have come to the shocking realization that the fundamental constants and quantities of the universe have been carefully tweaked to an astonishingly precise value that falls within the smallest of life-permitting perimeters. If any one of these values were altered by the tiniest of margins, no physical life would exist in the universe and neither would there be stars, planets, or chemistry.
Consider gravity, for example. The force of gravity is determined by the gravitational constant. If this constant varied by just one in 1060 parts, none of us would exist. To understand how exceedingly narrow this life-permitting range is, imagine a dial divided into 1060 increments. To get a handle on how many tiny points on the dial this is, compare it to the number of cells in your body (1014) or the number of seconds that have ticked by since time began (1020). If the gravitational constant had been out of tune by just one of these infinitesimally small increments, the universe would either have expanded and thinned out so rapidly that no stars could form and life couldn’t exist, or it would have collapsed back on itself with the same result: no stars, no planets, no life.
Or consider the expansion rate of the universe. This is driven by the cosmological constant. A change in its value by a mere 1 part in 10120 parts would cause the universe to expand too rapidly or too slowly. In either case, the universe would, again, be life-prohibiting.
Or, another example of fine-tuning: If the mass and energy of the early universe were not evenly distributed to an incomprehensible precision of 1 part in 1010123, the universe would be hostile to life of any kind.
The fact is our universe permits physical, interactive life only because these, and many other numbers, have been independently and exquisitely balanced on a razor’s edge.