If you can suspend the obvious question of why are you hiking from San Francisco to LA in the first place, the general analogy holds quite well: With software d

If you can suspend the obvious question of why are you hiking from San Francisco to LA in the first place, the general analogy holds quite well: With software development, you can not know how long it will take until you know exactly what you are building. You can not know exactly what you are building until you have fully described it. The act of describing it fully, precisely and with sufficient quality, is the act of coding. Hence the completion estimate has to be continuously refined as the details of implementation are continuously refined. Just like the slow zoom-in on the hike.