Dark energy apparently counteracts gravity by making space expand more energetically. If the amount of dark energy in the universe is, as astronomers think, proportional to the amount of space, then the continuing expansion of the universe means that the total amount of dark energy keeps increasing. Since the total amount of mass in the universe is not increasing, that means that the expansive effect of dark energy will ultimately overcome the contractive effect of dark matter. The more dark energy there is, the more open the geometry of the universe will tend to be, and the faster the expansion rate of the universe will increase over time.