Scientists now know that the universe contains at least two trillion galaxies. It’s a mind-scrunchingly big place, very different to the conception of the universe we had when the world’s major religions were founded. So do the astronomical discoveries of the last few centuries have implications for religion?

Over the last few decades, a new way of arguing for atheism has emerged. Philosophers of religion such as Michael Martin and Nicholas Everitt have asked us to consider the kind of universe we would expect the Christian God to have created, and compare it with the universe we actually live in. They argue there is a mismatch. Everitt focuses on how big the universe is, and argues this gives us reason to believe the God of classical Christianity doesn’t exist.

To explain why, we need a little theology. Traditionally, the Christian God is held to be deeply concerned with human beings. Genesis (1:27) states: “God created mankind in his own image.” Psalms (8:1-5) says: “O Lord … What is man that You take thought of him … Yet You have made him a little lower than God, And You crown him with glory and majesty!” And, of course, John (3:16) explains God gave humans his son out of love for us.

These texts show that God is human-oriented: human beings are like God, and he values us highly. Although we’re focusing on Christianity, these claims can be found in other monotheistic religions, too.

Not a human-oriented universe

If God is human-oriented, wouldn’t you expect him to create a universe in which humans feature prominently? You’d expect humans to occupy most of the universe, existing across time. Yet that isn’t the kind of universe we live in. Humans are very small, and space, as Douglas Adams once put it, “is big, really really big”.

Scientists estimate that the observable universe, the part of it we can see, is around 93 billion light years across. The whole universe is at least 250 times as large as the observable universe.

Our own planet is 150m kilometres away from the sun. Earth’s nearest stars, the Alpha Centauri system, are four light years away (that’s around 40 trillion kilometres). Our galaxy, the Milky Way, contains anywhere from 100 to 400 billion stars. The observable universe contains around 300 sextillion stars. Humans occupy the tiniest fraction of it. The landmass of planet Earth is a drop in this ocean of space.

To paraphrase Adams, the universe is also really, really old. Perhaps over 13 billion years old. Earth is around four billion years old, and humans evolved around 200,000 years ago. Temporally speaking, humans have been around for an eye-blink.

Clearly, there is a discrepancy between the kind of universe we would expect a human-oriented God to create, and the universe we live in. How can we explain it? Surely the simplest explanation is that God doesn’t exist. The spatial and temporal size of the universe gives us reason to be atheists.

As Everitt puts it:

The findings of modern science significantly reduce the probability that theism is true, because the universe is turning out to be very unlike the sort of universe which we would have expected, had theism been true.

Other explanations?

The fact that atheism is the simplest reply to the mismatch doesn’t mean that other explanations aren’t possible. Perhaps God exists but his motives for not creating humans sooner, or on a bigger scale, are unknowable. The divine is, after all, mysterious.

Perhaps the swathes of space strung with gossamer nebulae serve some aesthetic purpose, beauty wrought on an inhuman scale. Or, perhaps, God exists but isn’t as human-oriented as we thought. Perhaps God values rocks and cosmic dust more highly than humans.

The problem with these rival explanations is that, as they stand, they are unsatisfying. They hint at reasons why God might create tiny humans in a gargantuan place but are a million miles away from fully explaining why. The weight of galaxies, and the press of years, seem to sweep us towards atheism.