Why We All Need a North Star

12/21/2023

Professor Harnett

On a clear night, put on a hat and a warm coat and peer straight up towards the darkness of the cosmos. Outside the world we focus almost entirely upon, are countless other celestial bodies that are solid, gaseous, or hot balls of plasma. Based on the technology we have today, there are an estimated 2 trillion galaxies and 700 quintillion planets. Indeed, these numbers are staggering and there is no way to verify if this is even close to accurate, but let’s just go on the assumption there’s a lot of stuff out there.

As you gaze directly overhead, you will see a very bright star that is at the tail of the Little Dipper. Depending on the amount of light pollution (which in the Ohio Valley we have plenty of) and the acuity of your peepers, you may need a vector to that tail. The Big Dipper is there to help and is easy to find. If you draw an imaginary line up from the outer edge of the Big Dipper’s… dipper [sic], that points directly to the tail of the Little Dipper, also known as Little Bear. Here, 433 light-years away, we find the star Polaris in the Ursa Minor constellation, more commonly known as the North Star. As a comparison, Proxima Centauri is the nearest star to earth, a scant 4.24 light-years away. Fun fact, one light-year is approximately 5.88 trillion miles.

The North Star has served as a beacon and reliable navigational reference for centuries due to its fixed position in the northern sky. Because it is positioned nearly in line with Earth's axis of rotation (the imaginary line that extends through the poles), Polaris remains relatively stationary while other stars appear to move throughout the night due to the earth’s daily rotation and annual path position around the sun. ‘Relatively’ means the earth's axis points within one degree of Polaris and varies over long periods of time due to earth’s precession in space.

Like a toy top that wobbles before it falls, the earth wobbles as it rotates on its axis. This wobbling motion is precession and is due to the slight bulge of the planet at the equator. If you extended the Earth's axis out into space, you would see this imaginary line slowly tracing a cone shape. That’s why Polaris moves slightly relative to a point on earth. But the wobble is very slow; it takes the earth 26,000 years to trace one complete conical shape. Because of precession, Polaris and another star called Vega alternate as the North Star hallway through that 360-degree cone, every 13,000 years or so. Right now, it is still Polaris.

Its consistent location above the northern horizon makes it a valuable celestial landmark in the Northern Hemisphere, where its angle above the horizon corresponds to the observer's latitude. This is what a sextant does. The North Star's brightness and unwavering position has made it a timeless and dependable guide for those navigating across land and sea. The North Star and its relation to other constellations was also used for timekeeping. Agriculture societies relied on the movement of the stars to keep track of time, which was crucial for planting and harvesting.

Obviously, Polaris is not visible from the southern hemisphere, but that side of the planet also has a point in space that does the same. While there is a near geometric opposite star in the Southern Hemisphere, Sigma Octantis isn’t very bright and is nearly impossible to find with the naked eye even though it is 153 light years closer than Polaris. Instead, the Southern Cross constellation was frequently used for navigation in much the same way that Polaris is used in the Northern Hemisphere, except to triangulate ‘due south’.

Humans have used the North Star as a guiding light throughout history to identify true north, aiding in orientation and navigation. And let’s not forget that true north is not the same as magnetic north. Magnetic north is based on the earth’s magnetic field driven by the planet’s molten core and not exactly aligned with the axis. Earth’s magnetic field lines emerge from the south magnetic pole of the earth and re-enter at the north magnetic pole, that is where a magnetic compass points. And more interesting, magnetic north is actually about 500 kilometers south of true north, currently in northern Canada. The difference is called magnetic inclination. Even more weird, magnetic north is always on the move, shifting west about 30 kilometers each year. Someday it will be in Siberia. This phenomenon is known as the Polar Shift Theory. It is a theory because we really don’t know why. The governing concept is because the molten core shifts in relation to the earth’s rotation, some point to the Coriolis Effect, like how weather patterns are dragged across the terrain and oceans because of the earth’s rotation. This is why low-pressure systems in the Northern Hemisphere spin counterclockwise and opposite in the south. Many believe the same thing happens on the inside of the planet, resulting in magnetic north’s slow westward migration. Incidentally, the classic compass including the one on your mobile phone points to that finicky magnetic north, but all GPS coordinates are based on true north, called Cartesian coordinates. How are we supposed to find our way?

The North Star has played a huge role in human history that goes beyond navigation and timekeeping. Many cultures use the North Star to symbolize guidance and direction. Despite changing seasons and other stars moving, Polaris’ constant position in the sky reflects a symbol of stability. People have used it as a guiding light for their own lives, providing hope, direction, and inspiration. It’s a reminder to stay true to oneself and follow one’s own path, no matter how hard or uncertain it may seem. When life gets dark, the North Star shines and reminds us that we’re not alone, and there’s always a light to follow.

We all need a North Star. We just need to know where to look.