Latitude, longitude, and the Greeks

Centuries ago, surviving at sea was largely a matter of luck. 

Sailors would take to the oceans without a complete navigation system – with very little, to point them in the right direction. It became even more unsafe when bad weather obscured landmarks or celestial markers.

It was the kind of risk that could cost time and money, or worse, lives, if ships got lost or crashed into rocks or reefs, they didn’t know existed. 

While sailors could work out their latitude – the distance from the Earth’s poles, using the Sun and the stars - there was little else to guide them until the ancient Greeks stepped in.

Fast-forward to the present and every single point on Earth can easily be found by using latitude and longitude coordinates.

More than two-thousand years ago, there was a Greek polymath who many believe changed the world.

Eratosthenes’ achievements include inventing geography and working out the planet’s circumference. 

He’s also widely credited with producing the first map of the world featuring meridian (longitude) lines and parallel (latitude) lines – one running from north to south and the other from east to west.

A few decades later, another Greek genius picked up where Eratosthenes had left off.

The astronomer, Hipparchus, became the first to use the lines as coordinates for specific locations. 

He used trigonometry to plot exact locations on the grid.  

To navigate effectively it’s critical to know the exact time at your reference (departure) point, so that you can calculate your longitude.

Centuries ago, sea farers navigated by relying on chronometers and the latitude found from the positions of the Sun, Moon, and brightest stars.

But the marine clocks were not accurate, often affected by the motion of the ship or weather extremes.

Astronomer and historian of science, Prof Richard de Grijs, says that changed in the 18^th century, when an English carpenter, John Harrison, revolutionised them.

‘Harrison’s prize-winning attempt to construct a working marine timepiece was like a big pocket watch, with a metal spring inside – spring-driven watches are still used today.

So, instead of the single metal coil, John Harrison put two different types of metal together, meaning any movement in one would be offset by the other.

Harrison’s spring-driven Marine Chronometer watch replica was called H4, which is on display at the Australian National Maritime Museum.

‘A carbon copy of H4 was used by Captain Cook and later on the First Fleet’, Prof de Grijs said. 

Over time, navigating the seas became easier and safer with each generation of timepieces. 

 

It took centuries to develop a precise way of measuring the earth using an invisible grid.

It now takes seconds to find where you are or how to get to where you’re going, thanks to the Global Positioning System or GPS which calculates latitude, longitude and even altitude.

Hundreds of years of studies have led to where we are now – a safer world in which we can even rely on devices such as mobile phones for accurate information.

Prof de Grijs says today, they’re just apps (on our devices), and we don’t even think about them.