Photo credit Patrick Doheny

Software development is a lot like sailing: unless you are sailing downwind you can’t get there directly and you have to tack; so you pick a tack and set off. You hold the tack for a ‘sprint’ and then you go ‘go about’ and head in a slightly different direction for another ‘sprint’ until you reach your destination. Just like sailing if you change direction too often you go nowhere (this is why agile insists no changes in direction during a sprint). Just like sailing, currents and wind can change during your trip causing you to adjust your tacking (sprints) to get there. Just like sailing, you can’t say exactly when you will arrive unless you know every single current and wind change that will happen during the trip.