Have you ever played a game and you knew someone was cheating? They deal 5 Aces to themselves or they keep on getting royal flushes, or you keep on losing in Super Smash even though you’re playing Ganondorf on a small map with level 1 computers.[1] At what point do you suspect something is up? One royal flush might be explained away, but what if someone dealt themselves two in a row? 3 royal flushes? 4? 5? At what point does the unlikelihood of something happening cry out for an explanation? The way this universe is fine-tuned for human life to exist raises this exact question, because the unlikelihood of humans making their way onto the world stage is so staggeringly low. It’s not like the universe just dealt a couple royal flushes in a row… they dealt 20.[2] How do we explain that?

Biological life is an incredibly unlikely phenomenon, and humans are even more unlikely. Under the standard scientific view, the universe expanded from the singularity about 13.8 billion years ago, rapidly expanding at just the right rate while forming atoms, molecules, chemistry; all governed by fundamental physical forces that shaped the universe in precise, intricate ways as it expanded. Eventually the Earth formed roughly 4 billion years ago, probably out of left-over gas from the sun. Finally, just the right elements were combined with a precise level of gravity to allow the first biological life to emerge.

This is what we call the fine-tuning of the universe. It’s generally a pretty well accepted fact within the scientific community and there’s good reason for it. Here’s just a few examples of how the Earth is fine-tuned.

  • If the universe expanded in the slightest way faster, the universe would have spread out so far that particles wouldn’t interact with each other, and so no life would exist. If it had been the slightest bit slower, the universe would have collapsed back in on itself in a giant crunch. Slightly here means 10120, or 10 with a whole lot of zeroes.
  • If the Earth were just a couple hundred meters shorter in diameter, gravity would be 1000x stronger and human life wouldn’t be able to exist; nothing would rise off the ground because of how strong gravity would be.
  • If the strong nuclear force was long-range rather than short, all would instantaneously undergo nuclear fusion and explode (hint: not great for life occurring) or form a black hole (again, not great).
  • If the strong nuclear force (one of the laws that governs nature, it basically holds the elemental building blocks of nature together, like quarks, hadrons, protons and neutrons) were as little as 1% different, the total amount of carbon or oxygen formed would be really different, which would mean carbon-based life would have very little oxygen. You likely already know oxygen is kind of essential for human life.

That’s just four examples – there are many more. Even within these four examples we already see fine-tuning that defies belief. For example, the rate that the universe expanded at is finetuned to the level of 1 in 10120.

That number is so big it’s genuinely difficult to describe, but here are some visual pictures that may be helpful. Say you covered the entire North American continent in dimes all the way up to the moon, a height of about 239,000 miles. Next, pile dimes from here to the moon on a billion other continents the same size as North America. Paint one dime red and mix it into the billions of piles of dimes. Blindfold a friend and ask him to pick out one dime. The odds that he will pick the red dime are one in 1037.[3]

The odds of it are like winning the Jackpot for the Oz lotto 15x in a row,

So that’s some of the science. It’s certainly not exhaustive or detailed but it at least should give you a bit of an idea of how genuinely insane it is that we exist now. Bill Bryson’s A Short History of Nearly Everything covers some of these details in his typical witty way if you’d like to learn a little more. Luke Barnes and Geraint Lewis’ A Fortunate Universe is also a fantastic introduction and very accessible.

For these reasons the majority of the scientific community accept fine-tuning as a fairly well-settled fact.[4] For many Christians, this fine-tuning is evidence of an intelligent creator. The only thing that explains such wild improbability is that it was designed by an intelligent, rational mind that created order and natural laws to govern the universe.

So what do we make of all this? Obviously not all scientists believe in God (although certainly many do – see Ecklund et al.[5]), so how do they explain this fine-tuning?

There are four major naturalistic explanations put forward to explain why the universe is fine-tuned for human life:

1) The anthropic principle

2) The multiverse,

3) A more fundamental law

4) Luck

Explanations of Fine-Tuning:

  • The Anthropic Principle

The anthropic principle goes something like this: we look into the universe and observe the physical constants simply because we are the only observers capable of doing so. We exist because otherwise who would be around to do the observing? The anthropic principle has caught on in recent times as the in-vogue explanation of why the physical constants must allow life to exist. The problem is that the real anthropic principle does nothing of the sort. Under this view, humans caused the universe to exist – and it is precisely at this point we move from sophistry into nonsense.[6] Unfortunately this is an abuse of what the anthropic principle really means – as John Hawthorne points out “there are over 97 anthropic principles and they range from trivially true to obviously false.”[7]

Philosopher John Leslie points out how poor an explanation this is with his famous firing squad analogy. Say you have a prisoner due to be executed by a firing squad consisting of highly trained marksmen. They lead him out, blindfold him, and prepare to fire. The prisoner hears a couple dozen shots ring out. He prepares for his death, yet as the ringing in his ears fades he finds himself still alive. If he were to think ‘oh, of course I’m alive, otherwise I wouldn’t be around to observe that I’m alive’ one would think him strange indeed. Just because he is alive doesn’t explain why he is still alive. Just because we exist doesn’t explain why we exist, especially given how unlikely it is that human life would arise.

  • The Multi-Verse

By far the most worthy explanation capable of explaining why we are here is the idea we exist in a multi-verse of almost infinite universes. We just happen to be in the one capable of supporting life. While there are some reasons for believing in a multi-verse (the science is a little too long and complex for me to summarise here), I don’t think it fully explains away fine-tuning.

First, there’s an assumption hidden in the idea of the multi-verse that all of these universes in the multi-verse are going to be different. However that need not be the case. To maintain that these multi-verses are going to be generating universes with different sets of physical laws and forces (and different values for these forces) one needs to believe in some kind of universe generator – some kind of mechanism that generates and changes the physical laws and forces for each universe. But such a mechanism must itself be finely tuned; it merely pushes the question one step back.

The second issue is that the whole universe seems to be so tightly ordered. Rather, we’d expect only bits of pieces of order, rather than the entire universe being ordered. In the same way it is overwhelmingly more likely for a few letters on the scrabble-board randomly to form words than for all the letters throughout the board randomly to form words… or more simply, big flukes are much rarer than little flukes.

  • A more fundamental law

Some hold out hope for a deeper, more fundamental law that explains all of the laws above it, like a platform that grounds and explains all of the natural laws and forces that build upon it and govern this universe. The search for a theory of everything that explains the wide variety of different laws has obsessed physicists for much of the past century, however if anything we seem further away from that goal. The greatest hope of a grand unifying theory seems to be string theory. Even if this project succeeds (and the evidence certainly seems mixed on whether that will be the case), it still doesn’t explain away fine-tuning. Again, all it does is push the problem one step further back. A deeper, more fundamental law will still need an explanation of why it exists.

  • Luck

The numbers just defy this. If someone wins the Lotto jackpot 15x in a row or someone gets 20 royal flushes in a row, we don’t call them lucky. Some other explanation is required. Don’t play poker against the universe, it can deal itself a far better hand than you ever could.

A better explanation

In contrast to such complex and far-fetched explanations, the theistic one is surprisingly simple: a rational mind is responsible for designing and ordering the universe so that intelligent life would come about. This is a far simpler idea than a really complex fundamental law we haven’t found yet, insane luck, an infinitude of universes, or a mere observation. More importantly, it’s a better explanation.[8] It supposes fewer things (an intelligent creator and one universe) and it explains more of the data of what we see in the universe. Non-religious philosophers, whether agnostic, atheist, or otherwise, have recognized the force of the argument from fine-tuning. Given God, we should expect human life to exist; given naturalism (physical matter is all that exists) human life is jaw-droppingly improbable. Now it’s important to quickly say that we shouldn’t go further than what the evidence suggests – at best fine-tuning gets us to a creator God with an interest in Creation. But for me, fine-tuning gives evidence for an intuition I already had about the nature of the universe. When I read about the intricate physical laws that govern this universe, I get up early and see a beautiful sunset, when I have quiet moments in nature that restore my soul – these moments have design written all over them.


[1] Or maybe I’m just a really bad player… ok, that was probably too niche a joke. Back to your regularly scheduled programming.

[2] Odds are 1 in 649 74020, or 1 in 179 800 991 357 160 204 312 866 394 747 668 108 181 777 654 082 831 135 620 647 468 228 074 901 333 114 459 001 652 647 139 737 600 000 000 000 000 000 000. That’s just the fine-tuning of the expansion rate of the universe.

[3] Hugh Ross, The Creator and the Cosmos (1993), 115.

[4] For example: Barrow, Carr, Carter, Davies, Dawkins, Deutsch, Ellis, Greene, Guth, Harrison, Hawking, Linde, Page, Penrose, Polkinghorne, Rees, Sandage, Smolin, Susskind, Tegmark, Tipler, Vilenkin, Weinberg, Wheeler, Wilczek.

[5] Ecklund, E. H., Johnson, D. R., Scheitle, C. P., Matthews, K. R., & Lewis, S. W. (2016). Religion among scientists in international context: A new study of scientists in eight regions. Socius, 2, 2378023116664353.

[6] The anthropic principle has actually been really helpful for some scientific advances – unfortunately it is misused often. Some great discussions of the anthropic principle’s uses and abuses are found in Barnes and Geraint A Fortunate Universe, 274-278; https://www.forbes.com/sites/startswithabang/2017/01/26/how-the-anthropic-principle-became-the-most-abused-idea-in-science/#3d5398b57d69; and a more popular discussion here: https://medium.com/starts-with-a-bang/10-things-you-didnt-know-about-the-anthropic-principle-b46427f8a3a0

[7] Fine Tuning Fine-tuning, Hawthorne and Isaacs, 13.

[8] Simplicity should only be used as a tie-breaker when deciding between theories, and even that is controversial.