Moving at 30 miles per second, it completes its orbit in 88 days and rotates on its axis once in the same period of time. As we look at Mercury from Earth, it is always within 28 degrees of the Sun, and appears to move backward in retrograde motion about three times a year when it is passing the Earth in its orbit. In a horoscope Mercury will always be in the same sign as the Sun or in the sign on either side. Its forward and backward motion symbolizes the mind's activity in past and future events and ideas. Mercury indicates how a person's mind will function in their thought processes, learning, and communication expression.
Mercury relates to youth who can learn so quickly, because they adapt and change continually.
Mercury expresses quickness, speed, and movement. Competition with fellow students or brothers and sisters often spurs them on to learn more, be best, or fastest, etc. They can learn quickly, but it takes perseverance and concentrated effort to develop a skill to a high potential. Mercury signifies the nervous system of the body, which sends and receives messages. Outer perception of the world and inner perception of the self, observation and understanding, are both clarified by the frequencies of yellow light, a vibration associated with Mercury.