But I regularly point out that when we arrive at the same celebration a year later we are not the same. So it is much more like a spiral, a helix, where we are looking from this year’s celebration back at last year’s.
Furthermore, the earth is not simply moving in a circle (ellipse) around the Sun. The Sun is moving around our galaxy, the Milky Way, so that we, on our planet, are journeying in the form of a helix, a spiral.
That gives the shape of the church’s year, a shape found constantly in nature, a dynamic shape. It is repetitive, certainly, but also moves as a journey, a pilgrimage, with each new generation picking up the pilgrimage from the previous one.
The Sun is moving upwards, out of the plane of the Milky Way, at a speed of 7 kilometers per second. Currently the Sun lies 50 light-years above the mid-plane of the galaxy, and its motion is steadily carrying it further away.
But the gravitational pull of the stars in the Galactic (Milky Way) plane is slowing down the Sun’s escape. The astronomer Frank Bash estimates that in 14 million years the sun will reach its maximum height above the Galactic disk. From that 250 light-year position, it will be pulled back towards the plane of the Galaxy. Passing through, it will travel to a point 250 light-years below the disk, then oscillate upwards again to reach its present position 66 million years from now. We crossed the plane 2 million years ago. We are currently in the thick of the galactic disk and our view of distant regions is largely blocked by dust but 10-20 million years from now, our motion will allow a full view of our starry galaxy.
Ps. If people start disputing this model with points about frames of reference/rest, remember I’ve got a maths degree and I’m not afraid to use it 🙂