Why there’s no such thing as coincidence

YOU meet someone at a party and you’re stunned to discover you share the same birthday.

Or perhaps you’re sitting in a beach bar in Bali when a neighbour from around the corner in the UK strolls past with a cocktail.

According to an American mathematician, these aren’t coincidences – it’s all down to simple numbers.

In his new book, Fluke: The Math and Myth of Coincidence, Joseph Mazur argues that chance happenings can be calculated, and the odds aren’t always as high as you’d think.

The ‘birthday problem,’ as it’s known among mathematicians, is easily explained, says Mr Mazur.

In a group of 366 people, there’s 100 per cent probability that two will have the same birthday because of the number of days in a year.

Conversely, with just two people the chances of them not sharing a birthday is 99.7 per cent.

With three people, the odds fall just barely to 99.18 per cent. But at 15 people, it’s down to 74.7 per cent and you need just 23 people in a room to get better than even odds that two of them were born on the same day.

For other random tests, the probability of achieving the unlikely can take much longer.

In 1931, mathematician Emile Borel asked whether a number of random events could amount to something meaningful. That question morphed into, ‘Could a monkey randomly hitting the keys of a keyboard type out a Shakespearean sonnet?’’

Mr Mazur said the answer is yes – but the probability of a monkey typing the word ‘shall’ – as in ‘Shall I compare thee to a summer’s day’ – is nearly 1 in 12million. The more it types, the better its chances. So, with 8.2 million tries, it has a better than even probability of typing ‘shall.’