In 1978 my wife and I, with our two sons, then aged 2 and 4, were traveling home after a year in Connecticut. We had eight suitcases plus carry-on bags, and were flying from Hartford to New York on TWA, connecting to a flight to Toronto on Air Canada. There we planned to stay for a week before heading on to the UK. Air Canada had been on strike, but we were reliably informed that the strike had ended. No mobiles or internet in those days, and our phone had been disconnected because we were leaving. So, when we got to New York, it turned out that the strike was back on, and we were stranded. (Why TWA let us board the connecting flight I have no idea.) Our bags had also gone missing. Eventually, after I threw a tantrum, the airline found them. Not wanting to wait three days for a standby flight, we piled into a cab and headed to the Greyhound Terminal in downtown Manhattan. The cab dropped us at the wrong end of the terminal building, so we had to ferry all the bags, plus kids, a few hundred yards. Then wait six hours for a crowded Greyhound. After several other traumatic events, we finally got on the bus, and arrived in Toronto at 6 am, 12 hours late.

It worked, but all of our plans, carefully put in place over several weeks, had gone out the window. We live in an uncertain world, and even when you think you know what’s going to happen, the universe can bite you.

Basic Books Excerpted from Do Dice Play God: The Mathematics of Uncertainty, by Ian Stewart, emeritus professor of mathematics at the University of Warwick. Buy on Amazon.

On the other hand, uncertainty isn’t always bad. We like surprises, as long as they’re pleasant ones. Many of us enjoy a flutter on the horses, and most sports would be pointless if we knew at the start who was going to win. Some prospective parents are keen not to be told the sex of the baby. Most of us, I suspect, would prefer not to know in advance the date of their own death, let alone how it will occur. But those are exceptions. Life is a lottery. Uncertainty often breeds doubt, and doubt makes us feel uncomfortable, so we want to reduce, or better still eliminate, uncertainty. We worry about what will happen. We look out for the weather forecast, even though we know that weather is notoriously unpredictable and the forecast is often wrong.

Human affairs have always been messy, but even in science, the old idea of nature obeying exact laws has given way to a more flexible view. We can find rules and models that are approximately true (in some areas "approximate" means "to 10 decimal places"; in others it means "between 10 times as small and 10 times as large") but they’re always provisional, to be displaced if and when fresh evidence comes along. Chaos theory tells us that even when something does obey rigid rules, it may still be unpredictable. Quantum theory tells us that deep down at its smallest levels, the universe is inherently unpredictable.

Uncertainty isn’t just a sign of human ignorance; it’s what the world is made of.

And sometimes uncertainty can actually be useful. Many areas of technology deliberately create controlled amounts of uncertainty, in order to make devices and processes work better. Mathematical techniques for finding the best solution to an industrial problem use random disturbances to avoid getting stuck on strategies that are the best compared to near neighbors, but not as good as more distant ones. Random changes to recorded data improve the accuracy of weather forecasts. Space missions exploit chaos to save expensive fuel.

Random numbers—more precisely, the pseudorandom numbers that computers can be told to generate—can be really useful. SatNav uses streams of pseudorandom numbers to avoid problems with electrical interference. Medical trials use them to randomize patients and treatments, to avoid human bias. In fact, a bit of uncertainty can often act to our advantage. So although uncertainty is usually seen as a problem, it can also be a solution, though not always to the same problem.