Given the tremendous variety and possibility of the world, we sometimes can not assume that something in particular will develop on and on. For example, one forecaster devised a Dyson Sphere-- a large metal orb surrounding the sun with a circumference the size of Earth-- and believed that one day humanity will actually build one. However, the amount of time needed for such a venture will be so great that in the interim there will be something else developed, which will cause the construction of the said Dyson Sphere to be cancelled. Another example can be seen in the "more power in the future" approach, modeled by bombs to nukes to a planet destroyer seen in Star Wars and Ender's Game. It is very unlikely that trends will remain THAT constant.