Cosmological fine-tuning

Physics studies matter and the laws of nature. Natural events follow laws. A physical law describes a regular pattern in how nature behaves. Gravity, for example, pulls objects towards one another. But knowing this rule is not enough: we also need to know how strong this attraction is.

A physical constant is a value that physicists use to describe how nature works. Some concern the strength of attractions, others the properties of matter. Researchers measure them, then calculate what would happen if they had different values.

They find that some possibilities for life depend on very narrow ranges. Changing a value can prevent stars from forming or make the matter needed for life unavailable. So the issue goes beyond the features of our planet. It concerns the general conditions for a habitable world.

A comparison helps us understand. A device may work only if several settings stay within acceptable limits. The right temperature is not enough if there is no power supply. In the same way, one favourable physical value does not necessarily make up for another value that prevents structures essential to life.

This comparison shows how conditions can depend on one another. It does not prove that the universe is like a built machine in every way. The argument comes next: should we understand this combination of conditions as an accident, something required by the laws, or the result of an intention?

Cosmology studies the universe as a whole. Researchers gradually became aware of the problem. Robert Dicke drew attention to the link between the properties of the universe and the existence of observers. In 1973, Brandon Carter proposed the expression “anthropic principle”. An anthropic principle links what we can observe to the conditions that allow us to exist.^[1]

This finding does not rest only on authors who believe in God. Researchers Luke Barnes, who believes in God, and Geraint Lewis, who is an atheist, wrote A Fortunate Universe together. Philosophy examines fundamental questions through reasoning. Their philosophical conclusions differ, but both recognise the physical problem.

“The fundamental properties of the Universe appear to be fine-tuned for life.”

Luke Barnes and Geraint Lewis^[2]

A physical theory is a set of explanations and rules that help us understand natural events. Physicist Richard Feynman also expressed his amazement at the numbers used in physical theories:

“We use numbers in all our theories, but we do not understand them, what they are, or where they come from.”

Richard Feynman^[3]

These statements do not replace explanations. A great scientist can recognise a fact while refusing to see a Creator behind it. They do show, however, that the question deserves more than a dismissive smile: the fundamental values of nature call for serious thought.

Let us start with the matter we are made of. An atom is a small unit of matter made up of particles. A particle is a small component of matter.

The nucleus is the central part of an atom. An electron is a particle much lighter than the nucleus, found around it. A proton is a particle found in the nucleus. The properties of these components allow atoms to join together and form the substances found in living things.

An element is a category of matter defined by the type of atoms it contains.

The strong nuclear force holds the components of nuclei together. In the calculations presented by Bolloré and Bonnassies, a decrease of 9% would prevent elements heavier than hydrogen from forming. Hydrogen is an element of matter. We would not just be missing one particular flower. We would be missing some of the basic material needed for life.^[4]

Chemistry studies how substances form, combine and change. For living things, this organisation is essential: having matter is not enough. That matter must also be able to form stable combinations that can help an organism function.

The electromagnetic force is involved, among other things, in the bonds that hold atoms together. The weak nuclear force is involved in certain changes in particles. Along with gravity and the strong force, these forces help make stars and complex chemistry possible.

The ratio between the masses of particles also matters. A proton is about 1,836 times heavier than an electron. This ratio plays a part in the stability of the combinations needed for the chemistry of life. A small change in the ratio could therefore have major consequences for these combinations.^[5]

Another difficulty appears at the scale of the whole universe. Expansion means that the universe is spreading out. Gravity, by contrast, tends to pull matter together. According to the calculations examined here, an initial imbalance can lead to matter spreading out too quickly or collapsing too soon.

In both cases, the formation of galaxies is threatened. A galaxy is an enormous collection of stars. The question of the initial tuning therefore concerns whether these great collections can form at all. Matter present everywhere, but never forming stars, does not produce the same universe.

Density tells us how much matter there is in a given space. These calculations are made within the standard cosmological model. A model is a representation built to explain observations and make calculations from them.

To understand the precision involved, consider a calculation attributed to Robert Dicke. One second after the beginning described by this model, the expansion had to be adjusted to the fifteenth decimal place. A decimal place is a position after the decimal point in a number. This means that even tiny differences could already change the future of the universe.^[6]

The cosmological constant describes an aspect of the accelerating expansion of the universe and of vacuum energy. Vacuum energy is the energy that physical theories associate with space even when it seems empty. Theoretical calculations and observations reveal an enormous gap concerning this energy. Steven Weinberg describes a problem often expressed as a ratio of about 1 in 10¹²⁰.^[7]

The number 10¹²⁰ means a 1 followed by 120 zeros. It gives an idea of the scale of the problem. A probability expresses the chance that an event will happen. This ratio between calculation and observation is not, by itself, a measured probability of a random draw. Here, it expresses a precision that needs explaining within the calculations being discussed.

The starting state raises yet another question. Entropy is a measure related to the different ways matter can be arranged. To get an idea of it, think of a pack of cards. One precise arrangement corresponds to just one particular order. But the cards can be shuffled in a great many ways.

This comparison distinguishes one very particular arrangement from other, far more numerous arrangements. It does not reduce all the entropy of the universe to ordered or shuffled cards. The very low initial entropy studied here corresponds to an extremely particular starting state. This state makes the later formation of ordered structures possible.

Roger Penrose estimated the precision corresponding to this initial state. The result is 1 in 10^(10^123). Here, the symbol ^ means “raised to the power of”. The number 10^123 is a 1 followed by 123 zeros. The number after “in” would therefore be a 1 followed by 10^123 zeros.

This is an estimate concerning the initial state, not an observed frequency of universes being born. The main point is to understand that this difficulty concerns the beginning of the universe, not just the values of its constants.^[8]

We can compare these two questions to a board game. The rules determine which moves are possible. The starting position determines the game that will be played. So explaining the rules is not always enough to explain why the pieces are in precisely that position at the beginning.

Carbon: a concrete example

Carbon is an element of matter essential to the chemistry of life. Carbon makes possible combinations needed by the organisms we know. Understanding how it is produced in stars provides a particularly clear example of fine-tuning.

In stars, carbon can form when three helium nuclei join together. Helium is another element of matter. Fusion is the joining of atomic nuclei to form a different nucleus. But the general possibility of fusion does not guarantee that enough carbon will be produced.

This production depends on a very precise property of the carbon nucleus. Physicists call it a resonance. In this case, it means that a particular state of the nucleus makes the reaction easier at a precise energy. Without this possibility, the production of carbon needed for the chemistry of life would be seriously threatened.

In 1953, astronomer Fred Hoyle predicted the existence of this particular state. An experiment conducted by William Fowler later confirmed it. The conditions needed for life had therefore guided the research. A physical property was predicted, then found.^[9]

Hoyle, who held an atheist position at the time, drew a striking question from this. Here, the word “super-intellect” means an intelligence greater than our own.

“Would you not say to yourself: ‘A calculating super-intellect must have designed the properties of the carbon atom’?”

Fred Hoyle^[10]

This reaction does not turn a physics experiment into proof of the whole Christian faith. It shows why moving from precise physical conditions to the question of a creative intelligence can be reasonable.

The five examples examined are the strong force, initial density, the cosmological constant, initial entropy and carbon resonance.

The physical finding leads us to compare explanations. Under the hypothesis of chance, the values could have been different. They happened to produce conditions favourable to life without being chosen for that purpose. Physical necessity means that the laws would allow no other values. Intelligent design means that an intelligence would have intended a universe capable of supporting life.

A fourth answer appeals to the multiverse. This word refers to a collection of different universes whose properties could vary. If there were an immense number of them, some might allow life. According to supporters of this hypothesis, our presence in a favourable universe would then become less surprising.

Before examining these answers, one objection deserves our full attention. A very unlikely result does eventually occur when a draw is made. One particular hand of cards is unlikely. Yet once the cards have been dealt, no one is surprised that a specific hand is on the table.

Why should the universe be different? The critic thinks we find our result extraordinary simply because it is ours. Any other precise combination would have been just as unlikely. Presenting our combination as a miracle of luck could therefore be a way of judging the result after the event.

The reply distinguishes a particular result from a result belonging to a very small group. The argument does not say: this combination is ours, so it is special. It says: this combination belongs to those that allow structures needed for life. It is this property that calls for an explanation.

Catholic author Matthieu Lavagna offers a comparison with a bag of marbles. Just one red marble allows you to survive, while the others are deadly. Each individual marble may have the same chance of being drawn. But for the question we are asking, drawing the only marble that saves you is not the same as drawing just any marble.^[11]

Philosopher John Leslie uses another image: fifty marksmen aim at a person, then all miss. The survivor can point out that if the shots had succeeded, he would not be there to speak. Yet this does not answer his question: why did all the marksmen miss their target?^[12]

These comparisons do not calculate the actual chances of a universe. They explain why simply saying that an event is possible is not enough to explain it. Supporters of fine-tuning therefore consider chance insufficient. They seek an explanation that makes these favourable conditions more understandable.

The weak anthropic principle reminds us of something obvious: we can observe only a universe in which our existence is possible. This remark does not say that the universe was created for us. It says that observers cannot be found where no observer can exist.

Physicist Sean Carroll and biologist Richard Dawkins appeal to this idea against the fine-tuning argument. Since we are here, the conditions allowing us to exist must have been met. Why be surprised by a condition required for us to be able to ask the question? Their objection therefore concerns whether our surprise has any explanatory value.^[13][14]

The reply fully accepts this starting point. Yes, a universe without observers will never be observed. But two questions remain different: where can observers be found, and why does a place allowing them to exist actually exist? The first answer does not automatically provide the second.

In the marksmen analogy, surviving is necessary to tell the story. That is not enough to explain why the shots missed. In the same way, our presence sets certain conditions for the universe we observe. It does not produce these conditions or, by itself, explain why they come together.

The strong anthropic principle concerns the properties of the universe itself. According to this formulation, the universe must have properties that allow life to develop. This version therefore differs from simply reminding us of our position as observers.

Another objection concerns what we call life. Perhaps our idea of the forms it could take is too narrow. Organisms very different from ours might use other substances. A universe that rules out our way of living might then allow another kind of organisation, still unknown.

Physicist Victor Stenger defended this criticism. It asks us not to confuse the needs of life on Earth with every possibility of life. The reply must therefore concern more general conditions. Lasting structures and usable energy remain central to the problem being studied.

Luke Barnes criticises Stenger for not dealing correctly with the relationships between physical values. According to Barnes’s reply, changing one value while keeping the others fixed can hide the ways they depend on one another. He also accuses Stenger of changing his criteria for possible life from one passage to another.^[15]

Together with Geraint Lewis, Barnes concludes that favourable conditions remain very limited, even with a broader definition of life. So imagining other organisms is not enough: we still need to show how the laws would allow them to function.^[16]

A simple comparison helps put the reply in context. Replacing one material with another may solve a construction problem. It solves nothing if no structure can stay standing. The argument addresses this kind of fundamental difficulty, rather than a preference for only the forms of life we know.

Physicists do not yet have a complete explanation for the fundamental values of the universe. Some hope to discover a theory that would show why they must be exactly the values we observe. In that case, the constants would not be chosen from several possibilities. They would necessarily follow from deeper laws.

A theory of everything would seek to bring the fundamental laws together within a single framework. The hope of finding one therefore deserves serious consideration.

However, hoping for a discovery is not the same as making it. No theory presented in this debate has established that all the values favourable to life would be inevitable. So the explanation based on necessity remains unproven. It does not allow us to dismiss the question of fine-tuning today.

Stephen Hawking considered physical explanations that would avoid appealing to a Creator. Yet he acknowledged the starting point of the debate:

“The values of these numbers seem to have been very finely adjusted to make possible the development of life.”

Stephen Hawking^[17]

Even a perfectly successful theory would leave two questions to distinguish. Explaining how values follow from rules does not yet show why those rules describe a real universe. A detailed recipe explains how to prepare a meal. Its presence on a page does not make the meal appear.

This comparison does not prove that physical laws are recipes written by someone. It clarifies the difference between a description and what it describes. A mathematical rule can describe possibilities. The question remains why anything exists that actually corresponds to this description.^[18]

The other question concerns the initial state studied by Penrose. Laws can allow several starting situations. So explaining the constants does not automatically show why the universe began in such a particular state. As in the game mentioned earlier, knowing the rules does not necessarily fix the arrangement of the pieces.

The multiverse hypothesis also deserves a fair presentation. It does not simply assert a multitude of universes to avoid God. Researchers consider physical mechanisms capable of producing universes with different properties. Leonard Susskind supports this approach as a way to make sense of our presence in a habitable universe.^[19]

The idea is like increasing the number of attempts. If a favourable result is rare, more attempts can increase the chances of obtaining it. Observers would appear only in universes that allow them. We should therefore not be surprised to live in one of these favourable universes.

This proposal first faces a problem of observation. The other universes it appeals to are not directly accessible to our observations. We must therefore distinguish a mechanism considered within a theory from a multitude of universes actually observed. The hypothesis cannot be presented as a survey already completed.

We must then specify how to calculate the chances. Saying that there are an enormous number of universes does not tell us which ones are produced most often. To compare the possibilities, a rule for calculating is needed. Without one, simply multiplying universes does not let us measure the probability of obtaining favourable conditions.

A third difficulty concerns the mechanism that produces the universes. According to the critics presented here, this mechanism would itself have to meet precise physical conditions. Its laws would have to allow variations leading to habitable universes. These conditions would therefore need explaining, rather than assuming that the number of universes alone settles the whole question.^[20]

Some scenarios also face the problem of Boltzmann brains. This name refers to observers that would briefly appear through random fluctuations, with misleading impressions or memories. A fluctuation is a temporary change in a physical state. The problem arises when such observers become more likely than observers in an ordered universe.

In that case, the theory weakens confidence in the observations used to support it. This is a difficulty that the scenarios concerned need to resolve. Finally, multiplying universes does not automatically settle the question of their origin. If the whole collection has a beginning, that beginning still needs explaining.

Philosopher Richard Swinburne considers a single Creator a simpler explanation than a multitude of unobserved universes. His judgement does not rest only on counting. He compares what each explanation must assume to account for the facts. The multiverse therefore retains questions that its immensity does not make disappear.^[21]

Supporters of design put forward a positive idea. An intelligence can aim for a result and choose the conditions that make it possible. If life is intended, conditions favourable to its existence become understandable. They are no longer just a happy combination without intention.

Philosopher William Lane Craig sums up the approach as follows:

“The fine-tuning argument is based on what we know about physics, not on what we do not know”

William Lane Craig^[22]

A familiar objection, however, speaks of the God of the gaps. This expression criticises the use of God to fill a temporary gap in scientific knowledge. The danger is real: if a natural explanation is later found, the argument based on that ignorance collapses. The question is whether fine-tuning reasons in this way.

The reply is that it compares several explanations on the basis of known properties. It does not simply say that physicists do not know something. It asks why the measured values and initial conditions allow structures favourable to life. Natural mechanisms describe how things work; their existence and properties also remain questions.

Richard Dawkins raises another objection: an intelligence capable of designing the universe would be even harder to explain than the universe. In his view, a being of such complexity would also require an explanation. Adding a Creator would therefore move the problem rather than solve it.^[23]

Alvin Plantinga, a philosopher, and John Lennox, a mathematician, reply that this criticism assumes an intelligence made up of material parts. But that is not how Christian philosophy understands God. Divine simplicity means that God is not an assembly of parts. It does not mean that he lacks intelligence.^[24][25]

This reply does not prove the existence of God on its own. It shows that the objection must address the God actually being proposed. The richness of a result does not require its source to be made up of as many parts. A simple program can, for example, produce very rich patterns.

The question of the Creator’s origin remains. If God can exist without having been created, why not allow the same exception for the universe? Why not simply say that the universe exists without explanation?

A cause is what produces something or explains why it exists. The argument does not say that everything, without exception, must have a cause. It asks which explanation best accounts for a particular precision. Explaining a knife by a craftsperson remains relevant even before we know where the craftsperson came from.

A contingent being could fail to exist. A necessary being could not fail to exist. Catholic philosophy distinguishes these two ways of existing. It is not simply looking for somewhere to stop asking questions. It seeks a reality that does not receive its existence from another.

According to this reasoning, God exists without receiving existence from another. He would therefore not be one more object waiting for a maker of his own.

This distinction comes from reasoning that predates fine-tuning. Thomas Aquinas, a Catholic philosopher, was among those who developed it. His idea is that a series of beings receiving their existence is not explained simply by making the series longer. We must seek what does not depend on another. This reasoning complements the physical argument without being the same argument.

A habitable universe is not yet a living organism. We still need to explain how matter can form a being able to feed itself and reproduce. This second question concerns, among other things, biological information. These are the instructions recorded in organisms that help them function.

A cell is a small living unit that forms part of organisms. A molecule is a group of atoms bonded together. In cells, these instructions are carried by a large molecule. The order of the components in this carrier plays an essential role. A comparison with a text helps us understand: the same characters do not convey the same instructions in just any order.

Proteins are molecules that perform many tasks needed by organisms. They are made up of small units called amino acids. An amino acid is a component that can join with others to form these chains. Here too, the order of the units matters for how the whole thing works.

Michel-Yves Bolloré and Olivier Bonnassies examine the case of a protein containing about 150 amino acids. For the calculation of random assembly they present, they suggest a chance of roughly one in 10¹⁹⁵. This number concerns one specific calculation. By itself, it does not describe every imaginable stage in the emergence of life.^[26]

Researcher Hubert Yockey also studied the difficulty of producing a functional chain by chance.^[27] Philosopher of science Stephen Meyer offers a reason for recognising an intelligence here. He argues that, in known cases, complex information organised for a precise function comes from an intelligence. According to him, we have not observed such functional information arise spontaneously from chemical chance alone.

This comparison with the known origin of such information is the basis of his argument about living things. He connects this investigation with the study of the tuning of physical conditions. This proposed reason adds to the calculation of possibilities; it is not the same as that calculation.^[28]

Biologist Christian de Duve considers another answer: life could be built into the laws of the universe. This would mean that it does not depend only on an accidental meeting of substances. Bolloré and Bonnassies connect this idea with laws intended to allow life. This connection remains their interpretation.^[29]

The distinction between the two questions is important. Laws allowing stars and carbon to exist do not yet explain a functioning organism. In the same way, having paper and ink does not yet give us a text. This comparison illustrates a difference between questions; it does not replace the study of mechanisms.

For supporters of the argument, the two investigations point in the same direction. One studies the general conditions for a habitable world. The other studies the organisation needed for living things themselves. Answering a cosmological difficulty does not therefore automatically answer the second question. They invite us to consider this convergence rather than a single isolated number.

Fine-tuning offers a line of reasoning based on the observable world. It asks which explanation best accounts for certain precise properties of the universe. It does not require us to begin by believing the Bible. That is why it can support a discussion between believers and non-believers about the existence of God.

The conclusion defended is that a creative intelligence explains this combination better than chance without intention. Necessity remains to be established, and the multiverse retains difficulties of its own. This conclusion requires a thoughtful comparison of the answers. It cannot be reduced either to a sense of wonder or to the authority of a few great names.

The Catholic Church teaches that human reason can know the existence of God with certainty from the created world. A council is a gathering of bishops that exercises teaching authority in the Church. The First Vatican Council affirmed this in the text Dei Filius. This text speaks of our ability to know God through reason.^[30]

This does not mean that the Church has officially approved the fine-tuning argument. She has not settled this debate through a specific act of teaching. Catholic authors put forward this argument in keeping with the Church’s confidence in reason. Their judgement about its strength remains their own.

Priest and physicist Georges Lemaître warned against drawing connections too quickly between cosmology and faith. Recognising a convergence does not mean turning a physical theory into an article of faith. A scientific discovery can support reflection on God. It is not enough to establish the whole Christian faith. Revelation is what God makes known about himself to human beings.

This distinction also applies to accounts of the beginning. The calculations about the starting conditions mentioned here belong to the standard cosmological model. They are presented as results of that framework, with its assumptions.

Chronology is the order of events in time, with their dates. Here, Tradition means the teachings handed down within the Church. These calculations from the standard cosmological model do not change Ignispedia’s position. That position remains a young world, following the short chronology received from Tradition.

Finally, recognising a Creator does not yet establish God’s full Christian identity. The question of the historical existence of Jesus calls for a historical investigation. The resurrection of Jesus also requires us to examine its testimony and its own supporting reasons. Fine-tuning opens a path; other arguments allow the investigation to continue.

This progression does not weaken the argument. It allows us to ask of it exactly what it can offer. A first solid clue does not become useless because an investigation has further stages. Here, the universe appears understandable and favourable to life.

At the end of the comparison, intelligent design emerges as the most convincing explanation for these conditions coming together. It accounts for them through an intention, while the other answers leave the difficulties we have examined.

• Fine-tuning concerns the physical conditions that make a habitable universe possible.
• The forces, expansion and initial state all play a part in this question.
• A combination that allows life raises a different question from a combination that is merely particular.
• Our presence explains what we can observe, not why favourable conditions exist.
• Physical necessity remains unproven; the multiverse retains several difficulties.
• A creative intention offers a positive explanation for this set of conditions.
• The Church affirms reason’s ability to know God with certainty, without having defined this particular argument.

We are not simply looking at an immense sky. We are discovering a world whose properties allow organised matter, stars and life. Chance names a possibility, but it is not enough to make this combination satisfying. Fine-tuning invites us to recognise an intention behind the conditions that make our existence possible.

For the Catholic faith, this creative intelligence is God. Science describes the properties of the world; reason can ask what they mean. The universe then becomes more than a set of numbers that are hard to read. It offers a path of reflection towards the One who intended there to be beings capable of living and knowing him.