Lesson 1: The Earth is a big, round ball

In the film “The Gods must be crazy”, the hero journeys to the end of the world and casts off into a sea of clouds an aggravating gift of the Gods. One should be careful about reifying film-fictional characters into reality, but I think it’s  OK here. Let’s just assume there are some people in the world who do not understand that the Earth is a big, round ball.

I will even assert to you that at some point early in your life, you did not understand this “theory”. At the stage in your life when you were solving the engineering problems of forward motion, you necessarily formed a theory that the Earth is a flat surface that extends indefinitely in all direction, that it is solid and unmoving beneath you, that “beneath” is an aspect of a fundamental distinction between Up-Down and Front-Back.

All of this “theory” you learned from your experience of leaving a place where there was no Up-Down, no hard surfaces, no awareness of Self-Other.

I am convinced that we all travel the same primal pathways of experience, which do diverge as we go along. But the early parts we share because we share the same growth patterns. The relics of those early experiences stay with us as things we think we already know about the world, and they are sometimes obstacles to learning new things about the world.  For example, Coriolis phenomena-turning to the right in the Northern Hemisphere- just don’t make sense in the  fixed, flat Earth theory of our infancy. It takes effort to change your mind about that.

So, how do we learn that the Earth is a big, round ball? Usually, we learn it in school, meaning some person in authority tells us to believe it, shows us some nice pictures or cartoon or a physical globe and usually that does it. But teachers can also be un-nice about it, making you feel stupid if you raise questions. Not good!

Much better, I believe, to show you the pathway from observation to the theory that the Earth is a big, round ball. It goes like this.

First, you have to travel some, or know what people who do travel  have learned.  Of course, as near as we can tell now, humans have always traveled a lot: out of Africa, around the world. But so long as there was no way to communicate back and forth, what one learned from traveling would not be known by someone else. Singing songs, telling stories was the way people communicated before we learned to write language down. Once that happened, all sorts of old theories had to go  out the window.

Traveling, it turns out, teaches you different things depending on whether its North-South travel or East-West travel. That  may strike your modern mind as a little weird. But you likely know the weather patterns change and the nature of the day-night cycle changes as you travel North-South. But if you live a city-life style, governed by clocks instead of hours of daylight, you treat these things like incidentals, sometimes pleasant or sometimes inconvenient. If your daily existence depended on integrating these things with a set of necessary tasks, you would be much more sharply aware of them.

Explaining these sorts of things with the flat-fixed Earth theory is certainly possible, but as more experience is accumulated by people traveling around and communicating about it, that theory gets to be pretty hard to maintain. Here’s the classic argument from observations.

Observation 1: The stars you see overhead at night  can be mapped into patterns and given names-constellations we call them. While the constellations of stars are the same in the night sky as you travel north and south, the position of them shifts according how far north or south you are. The whole pattern shifts together.

Observation 2: The constellations of stars you see at night move from the east toward the west, in the same way the Sun moves in the day. But they do not move in parallel straight lines. The move in circles, parallel to each other, so all the circles have a common center, which is a point in the northern sky very close to the star called Polaris- that’s how it got its name.

Observation 3: (actually, just 1 and 2 combined). As you travel north on the Earth, moving toward Polaris in the night sky, you don’t get any closer to Polaris, but it does get higher in the sky.

On a flat-fixed Earth, one could explain why you don’t any closer to Polaris by assuming that it is just too far away to tell the difference- which is actually correct. But you cannot explain how it gets higher in the sky. If the Earth were flat, whether Polaris were on a flat surface of a spherical surface, it should stay at the same angle above the horizon as you traveled north.

There may be a number of ways to explain how Polaris behaves, but the simplest way is to assume the Earth is round so as you travel around the curvature of the Earth, you look up at different angles. I use the simple word “round” rather than spherical to keep the terminology at the same level of precision of the observations.

The East-West business is a little more complicated. If the Earth is round in the East-West direction the same way it is in the North-South direction that would mean that the rise and set of  a star, or the Sun, should not occur at the same time in two places separated by a significant East-West amount. This is almost an acknowledged fact in the modern world. You know that, for example, the New Years moment, the stroke of midnight , is not the same in New York City as it is in San Francisco. In the ancient world, things were not so simple. The day started at sunrise in Rome and in Damascus, but how could you tell if those events were simultaneous? Well, they figured it out! Using a handy eclipse of the Sun, they observed that the Sun was not in the same position in the sky during the eclipse in the two different locations, which affirmed that the Earth was round in the East-West direction just like it is in the North-South direction. They guessed that the Earth was an example of their favorite shapes for an object-spherical.

If the Earth were spherical in shape, then , according to the geometry and algebra involved, traveling North-South a certain distance on the Earth should change the position of Polaris, as an example, by a specific amount. A chap by the name of Eratosthenes made the measurements-actually using the Sun-and calculated a size for Earth very close to the accepted modern value.

So it became known, at least to the educated people, that the Earth is a big, round ball. Big meaning so big that our common experience is typically that the Earth is flat, but that is just the limits of out perception. Standing at sea-level, the horizon is about 30 miles away. On the steppes of Mongolia, the grasslands rolling away toward the distant horizon, a succession mountains receding into the distance, I felt the curvature of the Earth was almost observable. It is measurable over much smaller distance. If you lay out a triangle several miles on a side and measure the angles precisely with a theodolite, they add up to more than 180°. But the intuition is rarely moved by mathematics.

Round means very close to spherical. But again, measurement shows that as an approximation. But that’s good enough for now.

In the process of going from observation to theory about the size and shape of the Earth, employing a little mathematical stuff along the way, we have also enlarged our scale of thinking. Our knowledge map has grown from a local map to a global map.

We have a partial answer to the question “How did the Earth get to be the way that it is?” Whenever we are working n this problem, we will have to begin with the part that answers the “way that it is” part.

A big round ball. That’s the way it is. How did it come to be that way?


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