The positions of the equinoxes are determined by the position of the Earth's axis, and if this was constant in direction the equinoxes would remain fixed in position in relation to the fixed stars. Owing to a gyroscopic effect produced by the gravitational pulse of the moon and sun on the Earth's equatorial bulge, the Earth's axis, though remaining always at the same angle to the plane of its orbit, changes its direction, making one complete revolution in approximately 26,000 years. From the Earth, therefore, the equinox points in the heavens move slowly around the equinoctial or equatorial circle. The spring equinox in the early Christian era was in the constellation of Aries and was termed the 'first point of Aries'. It has now moved back into the constellation of Pisces, a movement of nearly 30?of Right Ascension.