Regular readers of my column certainly know how to use the Big Dipper to find the North Star (aka Polaris). Some folks believe Polaris is important because it’s the brightest star in the heavens, and they are disappointed when they see it. It’s faint. Really faint.

If you listed the brightest stars in the sky, you’d discover that Polaris isn’t even in the top 10. It’s not in the top 20, the top 30 or the top 40. No, Polaris is the 49th brightest star in the night sky, and that means you’ll never find it when viewing from under the lights of a city.

So if it’s not the brightest star we see at night, why, then, is it so important? That’s because it happens to lie directly over the north pole of the Earth, and when you face it — no matter which season or time of night — you’re facing true north.

Over the centuries, writers and philosophers have recognized Polaris as a sign of constancy. Navigators have used it to safely guide their ships. Cultures throughout Asia long considered its prominent position as the pinnacle of the cosmic “Mountain of the World” or “Axis of the Universe.” In traditional Indian astronomy, its Sanskrit name is “dhruva tara,” which literally means “fixed star.”

So is there something magical about this star that aligns it almost perfectly with due north? Not at all; it’s simply a cosmic coincidence. As permanent a feature as Polaris might seem to us, it has not always occupied the role of our North Star. This is because our Earth doesn’t spin perfectly but rather wobbles a bit as we travel along our cosmic journey.

We can easily see this “precession” effect with a spinning top. As the top rotates on its axis, it eventually slows down and begins to wobble. The axis about which the top spins no longer points in a single direction but instead traces a much larger circle.

Our Earth behaves much the same, and over time, its rotational axis traces a giant circle among the stars. Rarely does anyone other than astronomers ever think about precession since a full cycle takes 25,800 years to complete.

For most of modern history, the northern pole of our Earth’s axis has pointed roughly toward Polaris. But this wasn’t always the case. Back when the ancient Egyptians were constructing the pyramids 50 centuries ago, they saw a different North Star. At that time, the star Thuban in the constellation of Draco, the dragon, appeared quite close to this “north celestial pole” and served this important function.

If you’re patient (and have really good longevity genes), you’ll see the pole star change gradually. Over the next few millennia, the sky will precess and Polaris will vacate this important position as other, fainter stars take over its role. In another 55 centuries, the star Alderamin in Cepheus, the king, will occupy that prominent position. And by 14,000 A.D. the bright star Vega will lie closest to the north celestial pole.

But fear not; Polaris will return to its starring role as our North Star. We’ll just have to wait 25,800 years!