This motion is far too slow to be seen with the naked eye. It's hard even to measure it because of how long it takes the sun to complete one full rotation around the heavens, more that twenty-five thousand years. Nevertheless, it is possible to ascertain precession if one carefully measures where the sun rises at equinoxes—an equinox ("equal night") occurs each spring and fall when the day and night last exactly the same time—and then compare the sun's position year to year. Still, it would take very premise calculations over a long period of time (centuries at least) to realize that the sun was moving against the background of the stars.