Over the past century, scientists have discovered that if certain properties of the universe were changed very slightly from what they are, we would not be here.  They have to be within a very narrow range for our universe to make life possible and be habitable. 

The universe is fine-tuned for the existence of intelligent life with a complexity and delicacy that literally defy human comprehension.  The sensitivity of the ‘habitability’ of the universe to small changes is called ‘fine-tuning.’

This was recognized about 60 years ago by Fred Hoyle who was not a religious person at the time he made the discovery.  Scientists like Paul Davies, Martin Rees, Max Tegmark, Bernard Carr, Frank Tipler, John Barrow, and Stephen Hawking, to name a few, believe in fine-tuning.  These are prominent names in cosmology as they are heard in the media whenever a news headline is made.

Types of Fine-Tuning

1.  Fine-tuning of the laws of nature.

2.  Fine-tuning of the constants of physics.

3.  Fine-tuning of the initial conditions of the universe.

We will explore each category below:

1.  Fine-Tuning of the Laws of Nature

There are two ways to look at this aspect of fine-tuning:

1.    Precisely the right laws are needed for highly complex life to exist.  If one of these were missing, such life would not be possible.  To say that the laws are fine-tuned means that the universe must have precisely the right set of laws in order for highly complex life to exist.  Perhaps this type of fine-tuning is the easiest of the three to understand.

Example 1: The law of gravity states that all masses attract each other.  What would the universe be like if gravity did not exist? There wouldn’t be any stars or planets.  Matter would be equally distributed around the universe with no place for life to form or energy sources like the sun that provide food to plants through photosynthesis that in turn become food for animals.

Example 2: One type of force can play multiple roles in this very well designed system.  For example, the electromagnetic force refers to the combination of electric and magnetic forces.  James Clerk Maxwell unified the two forces in 1800’s. 

If there were no electromagnetic force, there would be no atoms because there would be no force to hold the negatively charged electrons with the positively charged protons that allow for chemical bonds.  There would be no building blocks of life as there would be no chemical bonding, and therefore no life. 

The electromagnetic force plays another role in light which is a type of electromagnetic radiation.  It allows energy to transfer from the sun to our planet.  Without this energy we would not exist. 

2.    Harmony between nature and mathematics: Only in the 20th century have we come to understand that what we observe in nature can be described by only a few physical laws, each of which is described by simple mathematical equations.  Just the fact that these mathematical forms are so simple and few in number that they can all be written on one sheet of paper is amazing.

Table1.  The Fundamental Laws of Nature

·       Mechanics (Hamilton’s Equations)

·       Electrodynamics (Maxwell’s Equations)

·       Statistical Mechanics (Boltzmann’s Equations)

·       Quantum Mechanics (Schrödinger’s Equations)

·       General Relativity (Einstein’s Equation)

For life to exist, we need an orderly and intelligible universe.  Furthermore, order at many different levels is required. 

For instance, to have planets that circle their stars, we need Newtonian mechanics. 

For there to be multiple stable elements of the periodic table to provide a sufficient variety of atomic "building blocks" for life, we need the atomic structure given by the laws of quantum mechanics. 

We need the orderliness in chemical reactions that is the consequence of Boltzmann’s equation for the second law of thermodynamics. 

And for an energy source like the sun to transfer its life-giving energy to a habitat like Earth, we require the laws of electromagnetic radiation that Maxwell described.[1]

Physicist and Nobel Prize winner Eugene Wigner in his widely quoted paper, The Unreasonable Effectiveness of Mathematics in the Physical Sciences notes that scientists often take for granted the remarkable - even miraculous - effectiveness of mathematics in describing the real world.  He says:

"The enormous usefulness of mathematics is something bordering on the mysterious…There is no rational explanation for it…The miracle of the appropriateness of the language of mathematics for the formulation of the laws of physics is a wonderful gift which we neither understand nor deserve."[2]

What is a constant? What is meant are the constants of physics.  When the laws of nature are expressed as mathematical equations, like the force of gravity, the electromagnetic force, and the subatomic ‘weak’ force, you find certain symbols in them that stand for numbers that don’t change.  These unchanging numbers are called ‘constants’ that occur in the laws of physics. 

The laws of nature do not determine the value of these constants.  There could be a universe governed by the same laws, but with different values of these constants.  Therefore, the actual values of these constants are not determined by the laws of nature.  Depending on the values of those constants, a universe governed by the same laws of nature will look very different.

There are at least 20 independent constants and factors that are fine-tuned to a high degree of precision for life to be possible in the universe.  It is estimated that every year roughly another number is added to the list.[1]

G: Example of a Finely-Tuned Constant

An example of a constant is the Gravitational constant – designated by G – which determines the strength of gravity via Newton’s Law of Gravity. 

F is the force between two masses  and  that are at a distance r apart.  The actual value of G is 6.67 x 10^-11  N .  Increase or decrease G and the force of gravity will correspondingly increase or decrease. 

If one increased the strength of gravity by one part in 10³⁴, even single-celled organisms would be crushed and only planets less than around 100 feet in diameter would sustain life with our brain-size.  Such planets, however, could not sustain an ecosystem to support life of our level of intelligence. In fact even a basic ecosystem can barely be possible on such a place.

If fact, if G were increased by a mere 64-fold, the gravitational force of the surface of any planet that could retain an atmosphere would be at least 4 times as large.  A 400-fold increase in G would result in any such planet having a surface force at least 10 times as large.  Such a planet would be far less ideal than earth for humans.  On the other hand, a small decrease in G would negatively affect the planet’s hydrologic cycle, this also making any habitable planet less ideal.[2]

3.  Fine-Tuning of the Initial Conditions of the Universe

In addition to the constants, there are certain arbitrary quantities that are just put in as initial conditions on which the laws of nature operate.  Because these quantities are arbitrary, they are also not determined by the laws of nature. 

I will first give a simple example to explain what it means.  When I throw a ball, I throw it at a certain angle and with certain speed.  The angle and speed are the ‘initial conditions.’ After I throw it, the ball follows a certain course, and where the ball lands will depend on the ‘initial conditions.’ The course taken by the ball is calculated by using the law of gravity, which is one of the laws of physics.

Now, take an example of entropy (thermodynamic disorder) in early universe.  It is an ‘initial condition’ in the Big Bang model similar to the speed and angle for the ball in the example above.  Just like the example of the ball, after the Big Bang, the laws of physics take over and determine how the universe will develop from there on.  If the initial entropy (an initial condition) of the universe had been different, the laws would predict a very different universe.

Here is the amazing part.  Scientists have discovered that that these constants and initial conditions must fall into an extremely narrow range of values for the universe to exist.  This is what is meant by ‘the universe has been fine-tuned for life.’

1.  Fine-Tuning to Allow a Habitable Planet

When we think of the specific conditions that are needed nearer home in our solar system and on earth, we find that there are a host of parameters that must be just right in order for life to be possible.  A number of factors must be fine-tuned in order to have a planet that supports life:

·       It must be a single star solar system, in order to support stable planetary orbits. 

·       The sun must have the right mass.  If it was larger, its brightness would change too quickly and there would be too much high energy radiation.  If it was smaller, the range of planetary distances able to support life would be too narrow; the right distance would be so close to the star that tidal forces would disrupt the planet’s rotational period.  Ultraviolet radiation would also be inadequate for photosynthesis.

·       The distance from the earth to the sun must be just right.  Too near and water would evaporate, too far and the earth would be too cold for life.  A change of only 2% and all life would cease. 

·       Earth must have sufficient mass in order to retain an atmosphere. 

·       Surface gravity and temperature are also critical to within a few percent for the earth to have a life-sustaining atmosphere – retaining the right mix of gases necessary for life. 

·       Earth must rotate at the right speed: too slow and temperature differences between day and night would be too extreme, too fast and wind speeds would be disastrous. 

·       The earth’s gravity, axial tilt, rotation period, magnetic field, crust thickness, oxygen/nitrogen ratio, carbon dioxide, water vapor and ozone levels have to be just right.

Astrophysicist Hugh Ross[2]  lists many such parameters that have to be fine-tuned for life to be possible, and makes a rough but conservative calculation that the chance of one such planet existing in the universe is about 1 in 10³⁰.

2.  Fine-Tuning of Carbon ‘Resonance’

Life requires plenty of carbon that makes complex molecules.  Carbon is formed either by combining three helium nuclei or by combining nuclei of helium and beryllium.  Carbon is like the hub wheel in a tinker toy set: you can bind other elements together to more complicated molecules (carbon-based life), but the bonds are not so tight that they can’t be broken down again to make something else.

Eminent mathematician and astronomer Fred Hoyle, found that for this to happen, the nuclear ground state energy levels have to be fine-tuned with respect to each other.  This phenomenon is called ‘resonance.’

The carbon resonance level is determined by two constants: the ‘strong force’ and ‘electromagnetic force’.  If you mess with these forces even slightly, you either lose the carbon or the oxygen.  If the variation were more than 1% either way, the universe could not sustain life. 

Hoyle later confessed that nothing had shaken his atheism as much as this discovery.[3]

3.  Fine-Tuning of the Strong Nuclear Force

The "strong force" is the force that binds protons and neutrons together in nucleus.  If the strong force constant were 2% stronger, there would be no stable hydrogen, no long-lived stars, no hydrogen containing compounds.  This is because the single proton in hydrogen would want to stick to something else so badly that there would be no hydrogen left!

If the strong force constant were 5% weaker, there would be no stable stars and few elements besides hydrogen.  This is because you would not be able to build up the nuclei of the heavier elements, which contain more than 1 proton.

So, whether you adjust the strong force up or down, you lose stars that serve as source of energy or you lose complex chemistry which is necessary for life.

4.  Ratio of Strong Nuclear Force to Electromagnetic Force

If the ratio of the strong nuclear force to the electromagnetic force had been different by 1 part in 10¹⁶, no stars could have been formed.  Increase it by only 1 part in 10⁴⁰ and only small stars can exist, decrease it by the same amount and there will only be large stars.  You must have both large and small stars in the universe.  The large ones produce elements in their thermonuclear furnaces and it is only the small ones that burn long enough to sustain a planet with life.[4]

To put 10⁴⁰ in perspective, having a precision of one part in 10³⁰ (a much smaller number) is like firing a bullet and hitting an amoeba at the edge of the observable universe!

Arno Penzias, an American physicist and Nobel laureate who co-discovered the cosmic microwave background radiation which helped establish the Big Bang, sums up what he sees,

‘Astronomy leads us to a unique event, a universe which was created out of nothing, one with the very delicate balance needed to provide exactly the right conditions required to permit life, and one which has an underlying (one might say ‘supernatural’) plan.’[5]

First, physicists identify four fundamental forces of nature.  In terms of increasing strength, they are gravity (G₀), weak force (10³¹ G₀), electromagnetic force (10³⁷ G₀), and the strong nuclear force (10⁴⁰G₀).

Second, since extreme examples of fine-tuning deal with extraordinarily large numbers, we need to have an idea of just how big they are.  It will give us some perspective of how delicate fine-tuning is:

·       average number of cells in a human body is 10¹³ (i.e.  10 trillion)

·       age of the universe is roughly 10¹⁷s

·       number of sub-atomic particles in the known universe is estimated to be 10⁸⁰

Keeping these numbers in mind, consider the following three examples of fine-tuning:

1.  Weak Nuclear Force

One of them, the ‘weak nuclear force’ which works inside the nucleus of an atom is so sensitive (finely-tuned) that even an alteration of one part in 10¹⁰⁰ would prevent life in the universe![1]

2.  Cosmological Constant

The cosmological constant is a term in Einstein’s theory of gravity that has to do with acceleration of the universe’s expansion.  It is described as self-stretching property of space (or more accurately space-time).[2]  Unless it is within an extremely narrow range around zero, the universe will either collapse or it will expand too rapidly for galaxies and stars to form.  The constant is fine-tuned to an unimaginably precise degree.  If it were changed by as little as one part in 10¹²⁰, the universe would have no life![3]

3.  Penrose Number: The Most Extreme Example of Fine-Tuning

That is not it.  According to standard cosmology model, the accepted model of the universe today, if you were to go back some 14 billion years, you can think of the universe as condensed to less than the size of a golf ball.  The initial state of the space-time, and thus gravity, of the early universe had very low entropy[4].  This low entropy is required for a habitable universe in which high-entropy structures like stars are formed.  The ‘mass-energy’ of the initial universe had to be precise to get galaxies, planets, and for us to exist.  The most extreme example of fine-tuning has to do with the distribution of mass-energy at that time.

Just how precise?

Roger Penrose of Oxford University, and one of Britain’s leading theoretical physicists and cosmologists,  has calculated that the odds of a low-entropy state to exist by chance alone are one out of 10^{10^123} - the Penrose number.  He wrote in his book, ‘The Road to Reality,’ "Creation of the universe, a fanciful description! The Creator’s pin has to find a tiny box, just 1 part in 10^{10^123} of the entire phase-space volume, in order to create a universe with as special a Big Bang as that we actually find."[5]

In his other book, ‘The Emperor’s New Mind,’ he observed, "In order to produce a universe resembling the one in which we live, the Creator would have to aim for an absurdly tiny volume of the phase space of possible universes – about 1/10^{10^123} of the entire volume, for the situation under consideration."[6]

Let us try to get an idea of what type of a number are we talking about?

You don’t have enough particles in the universe (that we know of) to write down all the zeroes!  It is like a ten raised to an exponent of:

10000000000000000000000000000000000000000000000000000000000000


0000000000000000000000000000000000000000000000000000000000000. 

This number is so large, that if every zero were 10 point type, it will fill up a large portion of our universe![7]

That is why we will explain it with four illustrations. 

First, balancing a billion pencils all simultaneously positioned upright on their sharpened points on a smooth glass surface with no vertical supports does not even come close to describing an accuracy of one part in 10⁶⁰.[8]

Second, this is much more precision than would be required to toss a dart and hit a penny across the universe![9]

A third illustration suggested by astrophysicist Hugh Ross[10]  may help.  Cover America with coins in a column reaching to the moon (380,000 km or 236,000 miles away), then do the same for a billion other continents of the same size.  Paint one coin red and put it somewhere in one billion of the piles.  Blindfold a friend and ask her to pick the coin.  The odds of her picking it are 1 in 10³⁷.

All these numbers are extremely small when compared to the precise fine-tuning of the Penrose number, the most extreme example of fine-tuning that we know of.

In summary, the fine-tuning of many constants of physics must fall into an exceedingly narrow range of values for life to exist.  If they had slightly different values, no complex material systems could exist.  This is a widely recognized fact.