Consider also the strength of gravity. When the Big Bang occurred billions of years ago, the matter in the universe was randomly distributed. There were no stars, planets or galaxiesjust atoms floating about in the dark void of space.
As the universe expanded outwards from the Big Bang, gravity pulled ever so gently on the atoms, gathering them into clumps that eventually became stars and galaxies. But gravity had to have just the right forceif it was a bit stronger, it would have pulled all the atoms together into one big ball.
The Big Bangand our prospectswould have ended quickly in a Big Crunch. And if gravity was a bit weaker, the expanding universe would have distributed the atoms so widely that they would never have been gathered into stars and galaxies.
The strength of gravity has to be exactly for stars to form. But what do we mean by exactly?
Well, it turns out that if we change gravity by even a tiny fraction of a percentenough so that you would be, say, one billionth of a gram heavier or lighterthe universe becomes so different that there are no stars, galaxies, or planets. And without planets, there would be no life. The other constants of nature possess this same feature. Change any of them, and the universe, like Robert Frosts traveler, moves along a very different path. And remarkably, every one of these different paths leads to a universe without life in it.
Our universe is friendly to life, but only because the past fifteen billion years have unfolded in a particular way that led to a habitable planet with liquid water and rich chemistry.
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The Questions | The BioLogos Foundation