Figure 1. Orbital elements characterizing changes of the Earth's orbit and directions of its axis in the space. The elongation degree of the elliptic Earth orbit is expressed by eccentricity e = ((a2 - b2)1/2)/a where a and b are the lengths of the greater and smaller half-axes of the elliptic Earth orbit. With a circular orbit (a = b, the Sun (S) is in the center of the circle), e = 0. Elongation of the ellipse is achieved through reduction of the smaller half-axis b, the length of the greater half-axis remaining unchanged. In reality, the position of the Sun virtually does not change, the Sun remaining in the focus of the orbit, which shifts relative to the Sun. Over the last million years, the angle e changed from 22o to 24.5o. Arrow indicates precessional changes of the direction of the Earth's axis in the space.