Navigation
A look at the technology and tools that allowed early explorers to travel across vast oceans.
Imagine you are in the middle of the ocean with no land in sight, no GPS, and no phone. How would you know which way to go without getting lost forever?
Before modern maps, sailors used a magnetic compass to find their way. A compass has a tiny magnetized needle that balances on a pin. Because the Earth acts like a giant magnet, the needle always points toward the Magnetic North Pole. Even if it was pitch black or extremely foggy, a captain could look at the compass and know exactly which way was North. This allowed explorers to stay on course instead of sailing in circles. By knowing North was at , they could easily find East at , South at , and West at .
Quick Check
Which direction does a magnetic compass needle always point?
Answer
The needle always points toward the Magnetic North Pole.
While a compass told sailors which direction to go, the astrolabe told them where they were. An astrolabe is a circular tool that measures the height of the sun or the North Star above the horizon. Sailors would hold the tool up and align it with a star to find the angle. This angle helped them calculate their latitude, which is their distance north or south of the Equator. For example, if the North Star was at an angle of above the horizon, the sailors knew they were at a specific spot on the globe.
1. A sailor stands on the deck at night and finds the North Star. 2. He holds the astrolabe up to his eye. 3. He measures the angle from the flat ocean horizon up to the star. 4. If the measurement is , he looks at his chart to see which path stays on that line.
Quick Check
What does an astrolabe measure to help a sailor find their location?
Answer
It measures the angle (height) of the sun or stars above the horizon.
Early ships were big, heavy, and had square sails that only worked if the wind was blowing from behind. In the 1400s, the Portuguese designed the caravel. This ship was smaller, lighter, and faster. Most importantly, it used triangular sails (called lateen sails). These sails allowed the ship to catch the wind from the side, meaning it could sail into the wind! The caravel also had a rudder at the back, which made it much easier to steer through narrow waters or around dangerous rocks.
Imagine the wind is blowing directly from the North, but you need to travel North. 1. An old ship with square sails would be pushed backward. 2. A caravel tilts its triangular sails at an angle. 3. The ship zig-zags back and forth (called 'tacking'). 4. Because of the sail shape, the caravel moves forward even though the wind is pushing against it.
Quick Check
What was the main advantage of the caravel's triangular sails?
Answer
They allowed the ship to sail into or against the wind, rather than just with it.
A captain wants to reach a spice island. 1. He uses his compass to make sure he is heading East (). 2. At night, he uses his astrolabe to check that his latitude is still North of the Equator. 3. Suddenly, the wind changes direction. He uses the caravel's triangular sails to keep moving forward despite the wind change. 4. By combining all three technologies, he reaches the island safely.
Which tool would a sailor use to find which direction is North during a foggy day?
Why was the caravel better for long voyages than older ships?
An astrolabe uses the position of the sun or stars to help determine a ship's latitude.
Review Tomorrow
Tomorrow morning, try to name the three main tools we learned about and explain what each one does without looking at your notes.
Practice Activity
Draw a picture of a caravel ship. Label the triangular sails and draw a compass on the deck to show which way the ship is heading!