# An excerpt from ‘Think Smart, Act Smart’/’Get It Done’

## Chapter Three: Analysing Options

Will this go on forever?

Estimating how long a situation will last can often affect how you view that situation and any decisions you take regarding it. If you knew, for example, that there was a better than even chance that your unpleasant new neighbours would move away within two years, that could affect how you decide to handle an ongoing dispute with them. But is it feasible to predict how long things will last?

An interesting perspective on this problem was devised by American physicist J. Richard Gott. In 1969, Gott visited the Berlin wall (built in 1961) and wondered how long it would remain standing. As there was nothing special about the time he’d picked to visit it, he reasoned that if he could divide the wall’s lifetime into four quarters, there was a 50 percent chance that he was somewhere within the middle two quarters. Based on this assumption, he reckoned that there was a 50 per cent chance that the wall would last from one-third to three times as long as it had already (more than two and two-thirds but less than 24 years). The wall was actually demolished 20 years later, in 1989.

Gott also estimated that there was a 95 per cent chance humanity would continue to exist for another 5,100 to 7.8 million years. The huge range results from his seeking such a high probability. The greater the certainty required, the wider the time span will need to be.

PICK A TIME, ANY TIME…

You can use the Duration Calculator (shown below), based on Gott’s formula, to predict approximately how long an object or situation will last, without needing to know anything other than its current age. For the calculation to work, there should be nothing special about the starting point. You can’t, for example, use it to predict the length of a friend’s marriage at the time of the wedding, because you are at a predetermined point: the start. Neither is it realistic for things that have a well-established average duration, such as a Human life. The calculation also works best on shorter time spans. With time-scales that run in to decades or even longer periods, you can only produce impractically broad estimates.

Some further examples for which this method can be applied include:

How much longer is your car likely to keep running?

How long might the company you work for last?

(and one for fun) How long will the current number 1 book/film/single stay at the top?

While not amazingly accurate, this technique can certainly provide a different view that could influence your decision-making.

THE DURATION CALCULATOR

This calculation will give you a quick estimate of how long an object or situation might last, with a 60 per cent chance of being correct – better than evens and without producing an unworkably broad time span.

Take the time (in weeks, months or years) that your object or situation has already been in existence.

Multiply by 4 to give the longest time probably left.

Divide by 4 to give the shortest time probably left.