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Believe it or not: The battle over certainty
A POINT OF VIEW By Lisa Jardine
There is something attractive about absolute beliefs, but we cannot afford ourselves the luxury of waiting for evidence on some issues... Sometimes, if you're lucky as a historian, you find a bit of evidence which illuminates a big idea. That happened to me this week in the Pepys Library at Magdalene College, Cambridge.
The thought uppermost in my mind was how odd it is that non-scientists think of science as being about certainties and absolute truth. Whereas scientists are actually quite tentative - they simply try to arrive at the best fit between the experimental findings so far and a general principle.
The manuscript I found was a ship's journal kept by a 17th Century English sea captain, who had offered to carry some state-of-the-art scientific equipment on a voyage to the west coast of Africa and back - two new pendulum clocks.
The job he took on was to test the clocks to see if they kept accurate time in spite of being tossed up and down and generally shaken about at sea. I'll come back to how he got on in a moment.
This week John Mackay from Queensland Australia, a passionate advocate of Creationism, has been touring halls and chapels in the UK attacking Darwin's theory that the human race has evolved gradually from the apes over millions of years.
Mackay maintains that Genesis is literally true, that the earth is only a few thousand years old and that the exquisite organisation of nature is clear proof that God's hand lies behind all of creation. Mackay had hoped to debate the matter here in Britain with leading scientists. If evolution is "true", the Creationist challenges - step up and prove it.
Notorious rogue
There is something rather attractive about absolute beliefs. We all find them comforting: give up chocolate for Lent and you are taking a small step towards God's approval. Uncertainty is much more unsettling.
One of the reasons why we find it difficult to make up our minds about climate change and global warming is that the data is so complicated. Glaciers are melting, holes are detected in the ozone layer, emission of greenhouse gases is rising, yet we have just gone through an unusually cold winter and spring is unseasonably late arriving - it is hard to get alarmed.
Even a passionate advocate of the prospect of impending ecological disaster like the government's chief scientific advisor Sir David King, cannot go so far as to say: "It will be so, that is the absolute truth of the matter."
It is a basic requirement of scientific method that a tentative explanation has to be tested against observation of the natural world. And from the very beginning scientists have been suspicious whenever the data fits the hoped-for results too closely.
Which brings me back to my clock-testing sea-captain, and the ship's journal I was reading this week in Cambridge. I was looking for documents relating to attempts by the 17th Century Dutch scientist Christiaan Huygens to develop a pendulum clock which would enable mariners to find their longitude at sea (their precise east-west position on the globe).
In 1664, shortly after the first proper scientific research institute, the Royal Society, had been established in London its president, who was an admirer of Huygens's work, offered to organise a series of sea-trials to be conducted by the English navy, using two of his pioneering clocks.
Captain Robert Holmes, commander in charge of the Navy ship the Jersey, agreed to take the clocks along with him on a nine-month voyage down the west coast of Africa. He would keep the clocks wound and in working order, take regular measurements, make the necessary complex calculations and supply detailed documentation in support of his findings.
When he got back to London in 1665 Holmes presented his report to an expectant Royal Society. The clocks had performed spectacularly well. Indeed, he declared, they had actually saved the expedition from disaster.
Astonishing
On the return journey, Holmes had been obliged to sail several hundred nautical miles westwards in order to pick up a favourable wind. Having done so, the Jersey and the three ships accompanying her sailed several hundred more miles north-eastwards. At which point, the four captains found that water was running worryingly low on board.
Holmes's three fellow-captains produced three competing sets of calculations of their current position based on traditional reckoning, but all agreed they were dangerously far from any potential source of water.
Not so, declared Holmes. According to his calculations - based on the pendulum clocks - they were a mere 90 miles west of the island of Fuego, one of the Cape Verde islands. He persuaded the party to set their course due east whereupon, the very next day, around noon, they indeed made landfall on Fuego, exactly as predicted.
London was abuzz with excitement. The Fellows of the Royal Society were elated, and immediately rushed Holmes's account of how the pendulum clocks had saved the day into print. Orders began to be placed for the revolutionary new timekeepers.
But the inventor himself, Christiaan Huygens was not so sure. And his reason for being more cautious than his London colleagues was precisely the fact that the clocks had proved so astonishingly accurate.
"I have to confess", he wrote to the Royal Society. "That I had not expected such a spectacular result from these clocks. I beg you to tell me if the said Captain seems a sincere man whom one can absolutely trust. For it must be said that I am amazed that the clocks were sufficiently accurate to allow him by their means to locate such a tiny island."
Well, Robert Holmes was not 'a sincere man'. In fact, he was a rather notorious rogue. History remembers him as the man whose thuggish and piratical behaviour towards the Dutch merchants along the Guinea coast in the 1660s directly caused the second Anglo-Dutch war.
Tampering
So the Royal Society asked an official from the Navy Board, Samuel Pepys - the same Pepys who wrote the diary - to check the evidence Holmes had provided against the day-by-day entries in his ship's journal. Well, that was the journal I went to look at in Cambridge this week.
Lo and behold, it turns out that Holmes had falsified his evidence. The pendulum clocks had proved no more accurate for calculating longitude than conventional methods. The ships had been well and truly lost, the mariners had been extremely lucky to make landfall on the island of Saint Vincent before their water entirely ran out.
Holmes thought that by tampering with his evidence he would please the scientists at the Royal Society. Instead, the too-precise nature of the match between his data and the results they wanted alerted them to the fact that his testimony was unreliable.
And Huygens was right to be sceptical. His pendulum clocks never did prove accurate enough at sea to solve the problem of finding longitude. A scrupulous scientist like Huygens would rather be disappointed, than accept dubious evidence to provide pat confirmation of a pet theory.
That continues to be true in all areas of scientific investigation today. Which is why no scientist will take up the creationist Mackay's challenge to "prove" the truth of Darwin's theory of evolution in a public debate. They know they cannot present a strongly held view based on a body of supporting evidence with the absolute certainty of a revealed truth.
The most today's Royal Society is prepared to say is that a belief that all species on earth have always existed in their present form, and that the earth is "not consistent with the evidence from geology, astronomy and physics". And that is probably not enough to satisfy ordinary thoughtful citizens without a scientific training.
Because most of us want more certainty, we're on the side of the 17th Century's ship's captain, believing the experiments ought to prove the scientific theory once and for all. Unfortunately, where arguments about the ecology are concerned, time is not on our side.
We cannot afford ourselves the luxury of waiting for evidence which clinches the theory. We are going to have to learn how to participate in debates which are not about certainties. We have to decide right now whether we should sacrifice our right to cut-price air travel in order to cut carbon emissions. A public understanding of science has never been more important.
