Skip to content
Join us at Confident Faith 2024 on Saturday 13th July

I was once having a conversation with my late grandfather where he said to me that he found the idea of a personal creator God difficult to reconcile with the fact that the universe is so vast – much of it empty space – and we humans are so incredibly tiny in the grand scheme of things. In a way, I could understand where he was coming from. Thinking about the sheer size of the cosmos can almost induce in us a feeling of vertigo (a sense of disorientation). But I suggested to him that the biblical picture doesn’t actually lead us to expect a universe that’s only just big enough for us humans. The Book of Job, for example, talks at great length about how God delights in all sorts of aspects of the cosmos that are far removed from human concerns. As for the idea that the universe is unnecessarily big, well, that’s now very much open to question in light of a series of discoveries about the character of our universe – known as The Fine-Tuning of the Universe – which suggests that the universe couldn’t have contained life if it had been much different from the way it actually is.

In the past few decades, physicists have discovered that our universe appears to be fine-tuned for life, which is to say, various aspects of the fundamental structure and the laws of nature that govern our universe are balanced on a knife edge. If any of them had differed by only a really, really tiny amount, the universe wouldn’t have been able to contain life at all. Does this provide us with some kind of clue that points towards the designer who wanted to bring about life? Is God the best explanation for this intriguing discovery?

Now, there are lots of specific examples of fine-tuned features of the universe. To start with, let’s look at just a couple of examples. The first one has to do with the force of gravity. It’s been estimated by physicists that if the force of gravity had been either weaker or stronger by even a very tiny amount, there could be no stars and galaxies. If gravity had been just a tiny bit stronger, then all the matter in the universe would have collapsed back in on itself immediately. If gravity had been just a tiny bit weaker, then all the matter would have spread out too quickly for anything like galaxies or stars to be able to form. It’s been estimated that the chance of gravity having just the right strength for stars and galaxies to be able to form is about 1 in 1060 (that is one in ten followed by 60 zeros).

The second example of fine-tuning concerns something known as the cosmological constant, which determines how fast space itself expands or contracts. If the cosmological constant had been a tiny bit bigger, then the universe would have collapsed back in on itself. If it had been a tiny bit smaller, then the universe would have expanded too quickly for galaxies to be able to form. It’s been estimated that the chance of the cosmological constant being just right for that to be the possibility of life in the universe is about 1 in 1053 (that is one in ten followed by 53 zeros). The philosopher Robin Collins has suggested that the likelihood that all of these various fine-tuned features would fall into place by chance could be compared with the likelihood of trying to hit a bull’s eye on a dartboard whilst wearing a blindfold where the dartboard is the size of the entire observable universe.

Now, to be clear, it’s not just scientists with a religious worldview who accept the existence of these fine-tuned characteristics of our universe. Well-known atheist scientists, including Stephen Hawking, Lord Martin Rees (who is the British Astronomer Royal), and Fred Hoyle, all accept that the universe does indeed have these features that are finely balanced on a knife edge. And Martin Rees gives an excellent overview of several examples of fine tuning in his book, Just Six Numbers: The Deep Forces That Shape the Universe. Now, whilst physicists are broadly agreed on the fact that the universe displays fine tuning, they don’t agree on the interpretation of this fact. Is the best explanation that an intelligent mind stands behind the cosmos or does fine tuning even call out for explanation at all? These sorts of questions, I would suggest, are not questions of physics, but of philosophy.

Now, here’s one reason that someone might suggest that fine tuning doesn’t actually call out for any explanation at all. And the thought goes like this. If the universe hadn’t been fine tuned for life, then we wouldn’t be here to notice that fact. Indeed, there is no other kind of universe we could have observed other than a fine-tuned universe. And so, we shouldn’t be surprised to find ourselves in a fine-tuned universe. So, fine tuning doesn’t call out for explanation. The philosopher John Leslie has responded to this objection by way of an analogy. He asks you to imagine that you are about to be executed by a firing squad made up of 50 of the world’s finest marksmen. Each one of them has a live round in his rifle, and each of them has fantastic aim. They raise their rifles, take aim and fire. But to your amazement, you’re still alive. Every single one of them has missed. Understandably, you’d think this cries out for explanation. There must have been a set up. They must all have missed on purpose. But suppose someone said to you, actually, you shouldn’t be amazed. Because, after all, if the marksmen hadn’t all missed, then you wouldn’t be here to notice that fact. Well, that would be a flawed line of reasoning. It’s true that the only scenario you could witness is one in which the marksmen all miss. But the fact that they all missed it is very, very unlikely, given the hypothesis that they all intended to kill you. And so, you are right to look for another hypothesis to explain what happened, such as, the hypothesis that there was a set up. Similarly, it’s true that the only kind of universe we could observe is one which is fine tuned. But the existence of a fine-tuned universe is very, very unlikely, given the hypothesis of sheer chance. And so, we should look for another hypothesis. What are the hypotheses on the table?

Well, one is that the fine tuning of the universe is not the result of chance, but rather the deliberate choice of a rational mind who stands behind the universe. Let’s call this the design hypothesis. There’s also another hypothesis that has received a lot of attention recently, this is known as the multiverse hypothesis.

The multiverse hypothesis says that our universe isn’t the only one, but that instead there exists an enormous number of universes and they differ from one another in terms of their fundamental laws of physics. For example, these universes vary from each other in terms of how strong the force of gravity is in each of them. And so given enough universes, the thought goes, at least one of them will have just the right features to be able to contain galaxies, stars, and the possibility of life. The real contest seems to be between the design hypothesis and the multiverse hypothesis. So, what should we think of the multiverse hypothesis? Is it a good explanation for fine tuning? Well, a big problem with the multiverse hypothesis is that it needs to have some kind of mechanism that brings all of these universes into existence and that determines what these universes are like in terms of the laws of physics they contain (for example, the strength of the force of gravity in each of them). Let’s call this mechanism the universe generating machine. The issue is the universe generating machine would itself need to be fine-tuned to be able to have any chance at all of producing a universe with the right features to be able to contain life. For an analogy, think of a machine that produces loaves of bread. That machine needs to be set up in quite a precise way if it’s going to have any chance of producing even a single loaf of bread (let alone an edible loaf of bread). And so, the multiverse hypothesis actually just pushes the question back a stage; what explains the fine tuning of the universe generating machine?

Finally, it’s important to be aware of the limitations of the fine-tuning argument. Just taken on its own, the fine-tuning argument doesn’t show that the God of the Bible exists. But it does, arguably, give a fair amount of support to the idea that the universe is the product of a rational mind. And so, the fine-tuning argument can form part of a wider cumulative case, alongside other arguments for the truth of Christianity.

Let’s briefly summarize the ground we’ve covered:

Firstly, we looked at some examples of fine-tuned features of the universe, in particular, the strength of the force of gravity and the cosmological constant (which has to do with how far space itself expands). And there are lots of other examples, but what’s common to all of them is that if the feature in question had been different by even the tiniest amount, then there could be no life whatsoever.

Secondly, we considered the objection that says that fine tuning is unremarkable. It doesn’t cry out for explanation because the only kind of universe that conscious beings like us could observe is a fine tuned one. We saw that that isn’t a good objection. Just because we wouldn’t be around to see the alternative scenario, a universe that isn’t fine-tuned, that doesn’t detract in any way from the fact that the existence of a fine-tuned universe is very surprising and very unlikely on the hypothesis of sheer chance. So, we should look for a hypothesis that better make sense of the data. The design hypothesis which says that the universe is fine-tuned because an intelligent being with a mind wanted to bring about life would make sense of this fact.

Thirdly, we looked at the multiverse hypothesis, which says that there isn’t just one universe but a huge number of them and they vary in terms of things like how strong the force of gravity is in each of them. The thought being that if you have enough of these universes, at least one of them is bound to have the right features for life. But we considered the way that the multiverse hypothesis doesn’t really solve the problem. It just pushes it back.

So how might the fine-tuning argument be helpful to you in conversations with skeptical friends?

Well, let me first say that I think we really need to take the time to understand where our non-Christian friends are coming from so that we have a sense of what sorts of considerations are likely to connect with them. This argument won’t appeal to everyone, but in my experience it’s particularly with scientifically minded skeptics where this argument can be a useful conversation starter. As I’ve emphasized, the fine-tuning argument doesn’t take us all the way to Jesus, but it might help someone to see the idea of a God who created the universe as a live possibility. And that can open up the question: If there’s a God who fine-tuned the universe for life, might God have communicated with humanity? Might God have entered human history in order to reveal himself to us? And that’s where the conversation can begin to get into the question of whether a communication from God to humanity might look like the person of Jesus.

Hear from us