From what I learned on a recent Youtube video on the sign of Cancer, there are signs associated with modernity (Cancer, Scorpio and Pisces), and the future (Capricorn, Aquarius and Pisces). They either tend to be water signs with feminine energies and natures, or in the case of Capricorn and Aquarius, ruled by Uranus (esp. Aquarius) and Saturn (esp. Capricorn), planets of science, planning and looking ahead. However, Cancer is the sign of history and the past (ruled by the Moon, "planet" of memory and emotions), opposite of Capricorn.