Episode 11 - Sailors and the Sky
In the early days of sailing and navigation, sailors had to stay close to the coast. They looked to the shore for landmarks to guide them. Hills, cliffs, churches, and windmills could all give a navigator key clues to his location. As local knowledge grew, and more people navigated coastal waters, books showcasing the horizon and specific landmarks regarding your route became available for purchase. A sailor knew as long as he could see land, he wasn’t truly lost. By keeping an eye on the coast, you had that rough idea of your location.
SHOW NOTES:
:58 Sir Cloudsley
In 1707 Admiral Sir Cloudsley Shovell was returning to England from a campaign in the Mediterranean with his fleet of warships. He lost track of his position and because of this his fleet ran aground - straight into the Sicillian Isles. Four of the finest ships in the Royal Navy and nearly two thousand men lost their lives.
1:40 Why Sailors Look Up
Keeping a weathered eye on the horizon, a wary view turned upwards, guides a sailor’s journey at night and at day. The heavens give insight to the weather from the shapes and colours of the clouds and to your position based on the angles and calculations from celestial bodies.
2:15 Red Sky at Night
One of the most enduring sayings of sailors, and one I have been personally saying since I was a kid is “red sky at night, sailors delight. Red sky at morning, sailors take warning”. It’s a saying every sailor will know and has passed into the vocabulary of amateur weather forecasters across the globe. The phrase even appears in the Bible, at Matthew Chapter sixteen, verses two to three.
Jesus said “When in evening, ye say, it will be fair weather - for the sky is red. And in the morning it will be foul weather today; for the sky is red and lowering”. But biblical prophecies aside, there is some science associated with this bit of lore. Colours we see in the sky are the effect of rays of sunlight being split into the colours of the spectrum as they pass through our atmosphere and ricochet off water vapour and particles.
4:05 Mackerel Sky & Mare’s Tails
Another one of my favourite sailor’s weather sayings is “Mackerel sky and mare’s tails make tall ships carry low sails.”
6:06 Dead Reckoning
The first method used to determine your position was known as dead reckoning. Now, dead reckoning is still taught in your nautical courses today. Using the compasses’ heading and the speed of the ship you could account for roughly how far you had travelled. This was the method used by many of the first voyagers across the ocean.
9:00 Celestial Navigation
Sailors used as many tactics as they could get their hands on to try and figure out their geographic location. While using time, distance, and heading was a good indicator - it wasn’t enough. This method didn’t account for currents, lee of the wind, or human error. In theory, sure, in practice, not so much. So to add on to their attempts, the sailors turned to the sky. On a clear day measuring the angle between the sun or certain stars and the horizon could give them a fix on their global position.
9:10 Astrolabe
One of the first instruments used in navigation was the astrolabe. This was a circular device with eyesights and measurements used to determine the altitude of the sun in the sky. This device dates back to ancient Greece - who’s astronomers used it. The astrolabe was first used by mariners, however, in the late fifteenth century. But astrolabes were expensive and challenging to use, so navigators crafted a much simpler tool known as a cross staff. With this increase of information and the abundance that soon followed the invention of the cross staff - nautical almanacks started publishing large tables of figures which eliminated mariner's needs for complicated mathematics.
9:35 Cross Staff
The issue with the cross staff though, was the cross staff forced the sailors to look directly into the sun, which even then we humans knew wasn’t the best of ideas.
10:00 Back Staff
To get around this - the back staff was invented - instead of measuring the angle of the sun from the horizon, you were now measuring the shadows of the sun.
10:20 Quadrants
Eventually variations of the astrolabe came around known as quadrants, and was first used by Arabic sailors trading along the east coast of Africa and often travelling out of sight of land.
10:30 Octant
The octant was much smaller and easier to use at sea than the now dated quadrant, and was soon adopated as the standard tool of navigation on board most ships of the time.
10:55 Sextant
The Octant was even further refined to the sextant we know today which replaced the octant almost entirely by the end of the eighteenth century.
11:20 Determining Longitude
Puzzling scientists and navigators for centuries - longitude was far harder to determine. There were of course vastly complicated calculations available But these were well above the knowledge of the average sailor. And these calculations wouldn’t do much good to even contemplate computing on the deck of a rolling ship.
11:40 Chronometer
This chronometer was essentially a highly accurate clock that enabled navigators to keep the time at a fixed position for months at sea. For British sailors this was known as Greenwich time. By comparing their fixed position with local time, based on the position of the sun, mariners were now enabled to quickly and accurately position themselves on the globe.
