On a clear night if you look in the sky towards true north, you’ll notice a star that seems to never change direction. If you’re able to find this star, it is called Polaris. Its position seems to be still while the rest of the sky rotates around it.
Polaris is one of the most known and common stars to humanity in this millennium. Some of us know this star as the North Star. When observing it, it seems permanent like it will always be there and never move. However, Polaris hasn’t always been in the same position in our night sky. We call it the North Star because when you look in the cardinal direction of true north, and the same altitude above the horizon as your latitude on Earth, this star will shine. Polaris hasn’t always been in the same position in our night sky, and it won’t always hold that exact spot over thousands of years.
Earth’s tilt and spin aren’t perfect nor exactly straight. Our planet has an axis tilt, and with that motion over long periods of time, that tilt slowly wobbles. Kind of like a coin as it wobbles to a stop on the ground. This slow wobble is called precession, and it takes almost 26,000 years or so to make one full circle. Because of that motion, the direction our planet points in space changes, and so the star closest to “true north” does as well.
If you were to turn back the clock when the ancient Egyptians were building the pyramids. Polaris wasn’t the star they used for directing north. The star that lined up much closer to the North Pole back then was a star called “Thuban”, which is located in the constellation Draco. Around 2500 BCE, Thuban would’ve looked almost perfectly steady in the sky. Many archaeologists think the Egyptians used stars like that to help line up the pyramids and other structures with amazing accuracy.
Over thousands of years, Earth’s wobble slowly moved the North Pole away from the direction of Thuban and eventually brought it closer to Polaris. Polaris has only been our North Star for a couple of thousand years, and it reached its closest point to true north just recently in Earth’s history, approximately in the early 2000s. The direction our planet is facing in rotation won’t stay the same forever. As Earth keeps wobbling slowly, Polaris will drift from our north sky, and in about 12,000 years, the bright star Vega will take its place as the closest star to Earth’s north pole.
So,if you look at Polaris tonight, you’re catching Earth’s direction of North pointing towards Polaris in just one moment of a very long cycle of which the star will seem to appear to never move. The sky looks steady to us as if it was circling one star, but it’s always changing “the star that our eyes are on” metaphorically speaking, little by little, across the ages. Civilizations may think the night sky never changes, but in fact the night sky will not stay the same..