BBC Radio 4 2016-01-28

BBC Radio 4 2016-01-28

Conspiracy theories: don’t we love ‘em? It’s said the US Government staged nine eleven. Or the Palace, Diana’s death. Or the Nevada desert is full of aliens.

We laugh them off. But belief in conspiracy can be serious. Mistrust in vaccines can have, quotes, “potentially lethal consequences.” Oxford physicist Dr David Grimes this week published his paper, On the Viability of Conspiratorial Beliefs, with an algorithm proving, he says, “how eye-wateringly unlikely some alleged conspiracies are,” to challenge our anti-science beliefs.

Conspiracy depends on secrecy. Obviously therefore, its viability is in inverse proportion to the number of people involved. Dr Grimes examines the belief, held by seven per cent of Americans, that the moon landing was a conspiracy by NASA, evidenced by the American flag blowing in a non-existent breeze. But at the time there were four hundred and eleven thousand people working at NASA. Given the probability of just one breaking silence, Dr Grimes’s calculations give the conspiracy a shelf life of three years and four months.

A fake lunar landing may not matter much. Belief in climate change conspiracy, in his words, “increases the risk of damaging-inertia.” Here, Dr Grimes’s maths is similar. The number of scientists involved would again number over four hundred thousand, so the conspiracy would fall apart within three years and nine months.

This is not to claim that all conspiracies are fake. Nor that they can be absolutely disproved by mathematics. Simply to demonstrate some staggering odds against.

I love probabilities. They help me make decisions. Will my children have a longer life-expectancy if I drive them to school, or teach them to ride a bike? Are they more at risk from strangers, or traffic?

Dr Grimes’s computation continues. For a plot to last five years, the maximum number colluding would be around two and a half thousand. For ten years, fewer than a thousand. A century-long deception would collapse with a hundred and twenty five collaborators. Clearly, to last twenty centuries, it wouldn’t take many.

Conspiracy theories abound about what happened to Jesus of Nazareth. He swooned during His execution and recovered in the tomb. The guards invented a bizarre fantasy to save their own skins after falling asleep. Odder, the authorities corroborated instead of producing the body, though they were trying to stamp the cult out. Most improbably of all, his friends made it up to cheer themselves and yet none cracked when faced with their own torture and execution.

Five hundred eye-witnesses were cited at the time. According to Dr Grimes’s model, this should indicate inevitable collapse of the conspiracy within decades. And yet it has lasted two millennia.

Along with several billion others, I regularly affirm my belief in the Resurrection. Not because it’s the only possible explanation of what happened. Of course it isn’t.

But because all the others seem quite eye-wateringly unlikely.