There’s an argument that many people make: that the natural world, and humanity’s existence in the Universe, point towards a divine creator that brought forth all of this into existence. To the best of our knowledge, Earth exists with a plethora of conditions that allowed for our existence, and does so in a way that no other world can match.
We live in a particularly privileged place. We live on a planet that has all the right ingredients for life, including:
- We’re at the right distance from our Sun so that temperatures are conducive to life.
- We have the right atmospheric pressure for liquid water at our surface.
- We have the right ingredients — the right balance of heavy elements and organic molecules — for life to arise.
- We have the right amount of water so that our world has both oceans and continents.
- And life started on our world very early, sustained itself for our planet’s entire history, and gave rise to us: sentient, self-aware creatures.
If you look at the other worlds we know of, the difference is striking.
The claim that’s often made isn’t merely that Earth is unlikely; it’s that our planet, with the confluence of circumstances that gave rise to us, is statistically impossible, even given all the stars and galaxies in the Universe. The emergence of intelligent life is so outlandishly unexpected, given all the factors that needed to occur in just the right particular order, that our Universe must have been designed specifically to give rise to us. Otherwise, the argument goes, the odds of us coming to be would be so infinitesimally small that it’s unreasonable to believe it could have happened by chance.
This is a very compelling argument for many people, but it’s important to ask ourselves three questions to make sure we’re approaching this honestly. We’ll go through them one at a time, but here are the three, so we know what we’re getting into.
- What are, scientifically, the conditions that we need for life to arise?
- How rare or common are these conditions elsewhere in the Universe?
- And finally, if we don’t find life in the places and under the conditions where we expect it, can that prove the existence of God?
These are all big questions, so let’s give them the care they deserve.
1.) What are, scientifically, the conditions that we need for life to arise?
In other words, things did occur in a very specific way here on Earth, but how many of them does life-as-we-know-it require, versus how many of them happened in a particular way here, but could have easily happened under different conditions elsewhere?
The things I listed earlier are based on the assumption that any life that’s out there is going to be like us in the sense that it will be based on the chemistry of atoms and molecules, occur with liquid water as a basic requirement of its functioning, and won’t be in an environment that we know to be toxic to all terrestrial life. For those criteria alone, we already know there are billions of planets in our galaxy alone that fit the bill.
Our studies of exoplanets — of worlds around stars beyond our own — have shown us that there’s a huge variety of rocky planets orbiting at the right distance from their central stars to have liquid water on their surfaces if they have anything akin to atmospheres like our own. We are starting to approach the technological capabilities of detecting exo-atmospheres and their compositions around worlds as small as our own; currently, we can get down to about Neptune-sized worlds, although the James Webb Space Telescope will advance that further in under a decade.
But aren’t there other things we need to worry about? What if we were too close to the galactic center; wouldn’t the high rate of supernovae fry us, and sterilize life? What if we didn’t have a planet like Jupiter to clear out the asteroid belt; wouldn’t the sheer number of asteroids flying our way wipe any life that manages to form out? And what about the fact that we’re here now, when the Universe is relatively young? Many stars will live for trillions of years, but we’ve only got about another billion or two before our Sun gets hot enough to boil our oceans. When the Universe was too young, there weren’t enough heavy elements. Did we come along at just the right time, to not only make it in our Universe, but to witness all the galaxies before dark energy pushes them away?…