Jeff Tallon: Buses, probability and God

Dr Jeff Tallon. Photo / Supplied

Plans are afoot to mount a bus advert campaign with the message "There's probably no God - enjoy your life". It's a copy of a similar London campaign.

But is it a true statement? Is there in all probability no God? Can we account for the physical universe, the biological world and the nature of humankind without any recourse to a Creator? What is the likelihood that we are here merely by chance?

For the first time in our history we can start to quantify parts of this question in probabilistic terms. The result is surprising.

Let's start with the physical universe. The field of cosmology tells us that the universe is exquisitely finely balanced.

Its density, back at the first moments of the "big bang", was critically balanced to better than one part in one billion billion billion billion.

A fraction more dense and it all would have collapsed again. A fraction less dense and it all would have evaporated - no galaxies, no stars, no planets, no mother Earth.

All the known forces of nature are tightly balanced relative to each other. A little this way and protons do not form. A little that way and neutrons don't form. Tweak another way and no particles at all. Tweak another way and everything is hydrogen only.

Now if the universe were truly random this would not happen. It would be chaos with no structure. The only way around this is to postulate some unbelievably vast number of other universes that have somehow pulsed into existence, and ours is the only one that had the right values for molecules, life and humans to evolve. All the rest are the structureless chaos one would expect.

The bus slogan is tantamount to saying "Gazillions of other universes probably exist, so enjoy yourself." But the required number of universes is unimaginably huge for this to be the case.

Never mind, when we turn to biology there's no problem, thanks to Darwin ... or is there?

The biological world is constructed around amazingly complex molecules like proteins, DNA, RNA.

Each of these is like a sentence constructed of letters and words. It has been said that 1000 monkeys pecking randomly at 1000 typewriters will eventually type out all of Shakespeare's works and The Encyclopaedia Britannica. The comparison is clear: wait long enough and the precursor to a protein, albeit complex, would naturally self-assemble.

Well, look at the odds for just the three words "The Encyclopedia Britannica". It is easy to show that not even a billion monkeys typing on a billion typewriters for the lifetime of the universe will have a chance of coming up with just those three words.

Yet this problem is totally dwarfed by that of constructing a protein like nitrogenase. This is the catalyst that splits the bonds in a nitrogen gas molecule to make soluble nitrates.

It is the only route that the plant world has discovered to "fix" nitrogen. It comprises some 25,000 atoms with about 2000 amino acid residues. These are the letters in the metaphorical sentence for that particular protein.

The probability of random assembly in the required order for that protein is one part in 10 raised to the 2600th power.

Even if every cubic millimetre of the entire universe were crammed with the essential components, one of these molecules could not self-assemble over the lifetime of the universe - not even in a vast number of such universes.

That's just one protein. The human body uses about 100,000 proteins.

And then the machinery that makes these proteins is unbelievably complex. The human ribosome that does just part of the construction consists of more than 80 proteins.

The template for each protein is a gene structure in DNA. A code is used which translates genes to proteins. A vast number of codes are possible but computer simulations show that this code is apparently the least error-prone code of them all, at the very least better than one in 100 million.

DNA itself uses machinery to replicate and is reliant on both proteins and the cell to do the job and protect it from decomposing.

The cell in turn is a marvel of complexity - a miniature city, with information systems, power systems, transportation systems, refuse collection, factories, ambulances, police and gatekeepers.

Each human cell has half a million ribosomes, and to pick just one of the 100,000 proteins: haemoglobin is produced by ribosomes in bone marrow at a rate of 100 million million protein molecules every second.

The biological world is one improbability after another. Like the physical universe, it is unbelievably finely balanced and we have no idea how even the simplest elements came into existence. We can calculate probabilities for one component after another.

They are each totally improbable but when compounded one on another the prospects for the chance to play God fade beyond all possibility.

I could be wrong, but the bus slogan "There's probably no God" is probably, nay, almost certainly, incorrect. It is a purely dogmatic statement that is not informed by science. And we haven't even considered the nature of mind, mathematics, morals and mankind.

* Dr Jeff Tallon is a physicist specialising in the fields of superconductivity and nanotechnology.