You may know what your Mercury sign is, but do you know why? It’s only possible for Mercury to be in the same sign as the Sun, the one before, or the one after. Picture this inner circle as the one the sun seems to be making through the zodiac signs around Earth in one year. Then the outer circle is Mercury making the same moves through all the signs, but those little loop-de-loops are Mercury retrograde. When you calculate that out in an astrology chart, Mercury is never found more than 28 degrees away from the Sun, and because each sign takes up 30°, even if the Sun is at the furthest possible point of a single sign, Mercury can only be in an adjacent sign. If you superimpose it on the chart, it looks like this with Mercury retrograde backtracking ground that the sun already covered. Crunch that out and it looks like this. So you’ve got about a 50% chance of having Mercury in the same sign as the sun, 10 to 40% chance of the other two. Each sun sign has one cardinal, one mutable, one fixed Mercury choice. Fire suns can’t have air Mercuries, Earth suns can’t have water Mercuries.