The Journey
Before about 500 BC everybody on earth believed that the Earth was flat. There may have been a few people who wondered why ships disappeared over the horizon, but the conventional wisdom of the time was that they fell off the edge of the Earth. How they managed to rationalise the reappearance of these ships is not known, but when you consider that there are still Flat Earth Societies here in the 21st century, perhaps it’s not that surprising.
Although the people who lived before 500 BC were wrong, in one particular way they were also not wrong. Whatever point in history you pick, people can only give their understanding of the world their best shot with what they know. The knowledge held by people living before 500 BC excludes everything the human race has learned in the subsequent 2500 years. In other words they didn’t know all that much, especially about the shape of the world. People’s day-to-day existence gave them very little to contradict the natural assumption that the Earth is flat.
Shows how the 7 degree shadow at Alexandria is the same as the angle at the cetre of the Earth between the two places. Source - Wikimedia, David Monniaux
Until, that is, about 500 BC when Pythagoras, more famous for his triangles, suggested that the earth is a sphere. New ideas usually take some time to gain purchase with people, but we do know that an attempt was made to calculate the earth’s circumference about 260 years later. In 240 BC another Greek philosopher, Eratosthenes, noticed that at Syene (now Aswan) the sun was directly overhead and cast no shadow, yet at Alexandria a 7.2 degree shadow was cast at the same time of day. Eratosthenes knew the distance between these two cities (5000 stadia), and from that could work out the circumference of the Earth. There are several versions of the stadia, so it is not clear how close he got to the real figure (40,075km). It could have been anything between 1% and 31%.
But there’s a problem, because the Earth is not a sphere. Yes you heard me correctly; it’s not a sphere. The word ‘sphere’, like the word ‘cube’, describes a very specific shape. A cube is only a cube if all its edges are the same length and all the angles are right angles. Otherwise it’s not a cube, its cube-like or cuboid. A sphere is an object that has the same dimension in all directions from its centre, and this is not true of the Earth.
Even so it took more than 2000 years from the time of Pythagoras to pin this down. In 1687 Isaac Newton demonstrated that the Earth is an oblate spheroid, squashed between the poles and stretched out at the equator. The difference is about 42 kilometres.
65 years after Newton’s oblate spheroid the astronomer and geodesist Nicolas-Louis de la Caille discovered from detailed triangulation in South Africa that the Earth is slightly pear-shaped, with the southern hemisphere a bit fatter than the northern. This is a great example of research for one purpose revealing unexpected new knowledge about something else. La Caille wanted to measure the curvature of a suitable length of longitude in the southern hemisphere so that he could more accurately map the star fields of the southern skies. It is fortunate that La Caille was a practitioner of geodesy, the study of the Earth’s shape.
It doesn’t stop there either. A pure speroid has a smooth surface, and the Earth’s surface is all over the place. The difference between the deepest ocean trench and the highest mountain is about 20 kilometres. Tectonic plates are in perpetual movement and coastlines are constantly changing. There is practically no end to the level of detail we could reach in describing its shape, and we’d have to do it all again tomorrow because it’s a moveable feast.
In fact our knowledge of the changing face of the Earth is now so good that we can visualise how it changed over time and even project how it will change into the future. To see how cool this is the video left takes us forward by 250 million years. The video is from Tech Insider and they have 2 million subscribers. Worth checking out.
What I have described so far is essentially that knowledge is not a thing. Bits of knowledge don’t emerge at particular points in time and stay that way forever. Knowledge is a journey, a voyage of discovery in which we become, over time, progressively less wrong. The journey is hardly smooth, often feeling like three steps forward and two steps back. If we are in the midst of the two steps back phase it can feel hopeless, but over longer timescales the arrow of time is bound to increase our understanding. Practically all knowledge progresses this way.
I have described with this example five types of growth in our understanding. The most obvious is the correction of an error. The earth isn’t flat. The second is refinement. It’s spherical, but it’s flattened and pear shaped. The third is the filling of gaps, like the discovery of ocean trenches and the general mapping of the hitherto hidden ocean floors, especially the mid ocean ridges that force landmasses to move apart or crash into each other. The fourth is the accumulations of detail as the scales of our observations get smaller, and the fifth is our ability to project into the future. Theoretically there is no end to these last two. I like that because it means that the journey will never end.
All of the above describes the knowledge journey for the whole of the human race. It is the description of a collective journey with many participants and a lot of sharing. It will be just as illuminating though to describe it as a personal experience, a personal journey. It goes something like this:
I have no idea what I’m going to learn tomorrow. Nobody does. The one thing I can be sure of is that I will learn. It is impossible to pass through time and experience life without learning. Even if I shut myself away from all outside influence, my brain would still be recapitulating the things that are already in my head, making new connections and gaining new insights. I would also learn what it’s like to shut myself away from all external influence.
And here’s the thing: If I don’t know what I am going to learn tomorrow, I also don’t know what impact that new knowledge will have on the things that are already in my head. I would expect most of it to confirm and strengthen my understanding. This would include:
Filling gaps
Greater precision
New observations or experiments
But I would also expect to be challenged. New information can create contradictions that question the validity of current understandings and that need a resolution. It is this prospect, the opportunity to increase my understanding, to be less wrong, that gets me up each morning with an internal smile of anticipation for what the day will bring. And it also strengthens my conviction that certainty has no place in this journey. Anyone committed to learning the real truth about the real world needs to keep his or her mind open to the possibility of being wrong.
Posted by Soliloquy.
This video is about the history of our understanding about the shape of the Earth.
Knowledge as a journey is one of the main themes of these essays. Its essential quality is that we become progressively less wrong over time. most of the other essays include accounts of this process in illuminating other themes about knowledge, how we acquire it and what we do with it.