For centuries, sailors navigated throughout the world using only the stars to guide them. Armed with only a sextant, they found their way through the Mediterranean Sea and even across the Atlantic Ocean with great accuracy.
Although the sextant has long sense been replaced with more modern technologies such as Global Positioning Systems (GPSs), we can still look to the stars for direction in a pinch.
The Big Dipper
In ancient times, men looked to the evening skies regularly. They observed that some stars appeared to form the basic outline of something recognizable: a lion, a fish, a swan. One of the most easily recognizable outlines is the Big Dipper.
As it’s name implies, it looks looks like, well, a large dipper used to scoop water from a barrel. Technically, the Big Dipper isn’t a constellation. It’s a asterism, an easily identifiable part of a larger constellation. In this case Ursa Major, also known as the Big Bear.
Like all heavenly bodies, the stars that make up the Big Dipper appear to rotate across the night sky. At different times of the year and evening, the Big Dipper will be at different locations. Sometimes it’s visible; at other times it’s below the horizon relative to us.
Identifying the Big Dipper, if it’s visible, allows to you to easily find Polaris, the North Star. Simply trace a line between the last to stars of the “cup” of the Big Dipper. Follow that line approximately 4 and 1/2 times the distance between the two stars and there you’ll find the North Star.
The North Star is sometimes called the Pole Star because it is located in line with the axis on which the Earth rotates. This means that no matter the time of night, the Pole Star can be found directly above the North Pole. It’s the only star in the sky that doesn’t appear to move as the night passes.
One really nice thing about the Big Dipper is that it is found almost directly opposite Cassiopeia, another constellation that may be used to locate Polaris. Due the rotation of the Earth, one if not both of these tell-tale constellations may be seen above the horizon, unless of course it’s a cloudy night.