June 2, 2025

Samantha Pradhan

12th Grade

Tak Nga Secondary School

Visualize this: You’re in the middle of the vast seven seas with no global positioning system (GPS) to guide you. How would you have found your way around? What would you have used as a compass?

Long before the advent of GPS, ancient navigators, seafarers, and explorers employed astronavigation, utilizing celestial bodies such as the sun, the moon, and constellations to determine their position during voyages. This feat was no miracle – it was the result of centuries of observation passed down through generations.

Constellations are groups of stars that form a recognizable pattern. The earliest reference to constellations appears in a poem, written in around 395-337 BCE by Eudoxus of Cnidus, titled Phaenomena. From multiple extrapolations, we can infer that the Greek constellations originated from the Babylonians and Sumerians. Today, there are 88 constellations officially recognized by the International Astronomical Union (IAU), 48 of which were recorded by ancient Alexandrian astronomer Ptolemy in 150 A.D. in his book The Almagest.

Discerning the constellations’ positions and arrangements throughout the months, voyagers could accurately ascertain their latitude and longitude. Latitude is your position in the north-south direction, while longitude is concerned with your east-west position. Using this information, voyagers calculated which trajectories to take. By the 15th century, celestial navigation instruments — such as the astrolabe, quadrant, and maritime astrolabe — became commonly used in wayfinding.

The North Star, also known as Polaris, was a critical tool in navigation. The star lies directly above the Earth’s north rotational axis, a point referred to as the north celestial pole. Consequently, it remains roughly stationary in the sky and indicates north, regardless of your location in the northern hemisphere. That is, if you are facing Polaris, you are indeed facing north.

Navigators found Polaris by locating the constellation Ursa Major. In Ursa Major, there’s an asterism—a smaller pattern of stars that can be part of a constellation—dubbed the Big Dipper, which looks like a large spoon. By connecting and extending the end stars of the Big Dipper, Polaris can be located in the Ursa Minor constellation, specifically in the asterism Little Dipper. Together, the Big Dipper and Little Dipper, akin to the yin and yang, symbolize balance in copious cultures.

In the southern latitudes, Polaris is not visible. Thus, the absence of a bright guiding star warranted reliance on the Southern Cross constellation. Observers drew an imaginary line from its longest arm, enlarging it about 4.5 times its length to find the south celestial pole. This method, with the patterns of sunrise and sunset, enabled them to deduce all four directions.

Orion, the Hunter in Greek mythology, was another prominent constellation on many voyages. Orion’s belt, composed of the 3 stars — Alnitak, Alnilam, and Mintaka — stretched more or less from east to west, while Orion’s sword pointed to the south.

Constellations weren’t just fruitful in navigation but in agriculture as well, since they allowed individuals to plan harvests ahead. In our era, we can hardly marvel over the wonders of the night sky due to light pollution, dampening out the light from stars. Despite having the convenience of GPS presently, our ancestors certainly one-up us in matters of casual stargazing.