Mystery Solved?
Ptolemy's map of the Nile. Source: The James Ford Bell Library, University of Minnesota (http://www.bell.lib.umn.edu/index.html)
The Greeks solve the mystery...?
By about 400 BC, the mystery seems to have been solved. Democritus of Abdera (460-357 BC) was a philosopher who asserted that space, or the Void, had an equal right with Reality to be considered existent. He conceived of the Void as a vacuum, an infinite space in which moved an infinite number of atoms that made up the physical world. These atoms are eternal and invisible; absolutely small, so small that their size cannot be diminished (hence the name atomon, or "indivisible"). With this as a basis to the physical world, he could explain all changes in the world as changes in motion of the atoms, or changes in the way that they were packed together. This was a remarkable theory which attempted to explain the whole of physics based on a small number of ideas and also brought mathematics into a fundamental physical role since the whole of the structure proposed by Democritus was quantitative and subject to mathematical laws. The theory proposed by Democritus was logical, scientific and accurate. His proposal that storm systems produced rain in central Africa that subsequently fed the Nile flood was far ahead of its time: the notion of storm systems was not accepted by the scientific community until the 18th century, over two thousand years later.
The next breakthrough in understanding the Nile began in earnest with Eratosthenes about 200 BC. He was the first to estimate accurately the diameter of the earth. For several decades, he served as the director of the famous library in Alexandria. He was highly regarded in the ancient world, but only fragments of his writing have survived. Eratosthenes died at an advanced age from voluntary starvation, induced by despair at his blindness. He mapped the Nile as far south as Khartoum through his own travels, and speculated at the presence of the equatorial lakes. This view echoed that of Democritus, but backed it up with research (in this case, in the form of travel).
Ptolemy's map (above) is remarkably accurate. (Click on the map image for a larger view.) It could be considered the pinnacle of Greek understanding. Unfortunately, this knowledge was about to disappear. It was lost for hundreds of years, victim to religious and political strife throughout Europe and North Africa.
The Romans reject (or lose) the findings
From 146 BC until 429 AD, the Nile River delta was governed by the Romans as part of their African empire. During this time, exploration took place west of the river (rather than upstream, or south) for the first time. There were political links to the west, as King Juba of Mauritania was defeated by Caesar in 46 BC. His son, Juba II, was raised in Caesar's court and - fiercely loyal to Caesar - returned to govern Mauritania in 25 BC on behalf of the Romans.
Why is this political story important? Juba II confused the Nile and Niger Rivers, and mapped the "Nile" as flowing eastward across the desert, disappearing beneath the sand for a great distance before resurfacing in Egypt. His map is wrong, of course, but it teaches us an important lesson: Knowledge has a societal context. The Greeks had solved the mystery of the Nile, and the Romans either lost or actively rejected their findings. This example shows us that just because something has been discovered or explained doesn't mean it will become integrated into societal knowledge. Truth is not always popular, nor is it always long-lived.
