As many, many websites show, Back To The Future II got a few things right – and many things wrong. What I find most intriguing is not so much the stuff the movie projected into 2015 but failed to materialize (hoverboards, flying cars), as what the movie did *not* see coming (notably, the replacement of fax machines by the Internet). But it’s easy to ridicule such projections with what we know now – and let’s not forget it was an entertainment movie, not an academic study in futurology.

What’s more, if only Elsevier had waited one day, our VECTORS scenario paper would have been made available online exactly on the day Marty McFly arrives in the future! Actually, Back To The Future II is a perfect illustration of the merits and limits of scenario studies. When we developed the VECTORS scenarios I heard many responses like “it’s science fiction”, “we don’t know what the future will be like”, and so on. And it’s true: we don’t know what the future will be like, which is why you want to develop several scenarios in order to explore the bandwidth of possible outcomes. The variation in scenarios is more important than any (misguided) notion of accuracy or likelihood. In fact, it is better to ditch likelihood altogether and settle for ‘plausibility’. As we describe in the paper, this turned out to be a difficult thing for academics as you need to get out of your ivory comfort zone and speculate.

The reason I find the fax machines in the movie intriguing is that it shows how we tend to extrapolate current trends into the future: fax machines were becoming ubiquitous around 1980, just when the movie was made. So we can’t blame the movie makers for extrapolating that trend into a future where just about every street corner would have a fax machine. But then, what else can we do? Of course there are dangers to extrapolation, especially if you have good reasons to assume that a given trend will not hold outside your range of observations. Nevertheless, no matter how plausible (and probable) your extrapolation, the probability that it comes true exactly as you estimated is precisely zero. Again: it is the variation around that extrapolation that is much more interesting than the extrapolation itself.