Navigatio Part II

 

The universe and the light of the stars come through me --- Rumi


Settling down with a second cup of grog, let's look at the whys and wherefores of how the Nautical Almanac serves us. 

Ptolemy

I've mentioned Ptolemy. Claudius Ptolemy (c. 100 - 170 C.E.) was the Chief Librarian at the Library of Alexandria. Alexandria was, unarguably, the greatest library ever assembled. Many of the painstakingly hand-copied texts in its rooms existed nowhere else.

Alexandria the city was founded on the Egyptian coast by Alexander The Great in 331 BCE, and it is still the second largest city in Egypt. In its prime, it not only was the largest city in Egypt, but it was by far the most cosmopolitan city in the world, playing host to visitors from Tokyo to Tara. Alexandria lay not far from the Silk Road trade route nexus in Judea, and served as a major port for seafaring traders, scholars, and tourists. Alexandria was famed for its lighthouse, the Pharos, and for the library. Tragically, neither proved to be fireproof over time, and much wisdom was lost, never to be regained. 

The Silk Road stretched from Reykjakvik to Edo

But while it flourished, Alexandria's library was a central repository for the world's knowledge and the Chief Librarian was considered the keeper of all that knowledge. Ptolemy himself was a scientist, and having pored over the available scientific texts and studied the night sky, he 

developed a theory of the heavens, that the solid and unmoving and flat Earth was at the center of the universe and that all else revolved around it. The rising and setting of the constellations he put down to the fact that the dome of heaven revolved above us. He noted that the stars in the constellations never seemed to move, so he called them fixed stars. 

He was completely wrong. 

In Ptolemy's own day, his geocentric view of the universe was not shared by everyone. Scholars from India and China debated with him,

pointing out that the motions of the planets didn't support his view. They argued for a heliocentric view of things, that the Earth and other planets revolved around the Sun. 

To deflate their arguments (because they were, admittedly, right that the planets seemed to move backward and forward and stop in space sometimes) Ptolemy added a wrinkle to his geocentric theory, that the planets not just circled the Earth but that their paths through the sky loop-de-looped in what he called epicycles.

Why things worked the way they worked was never a question he asked himself where anyone could hear. Brilliant Ptolemy may have been, but he suffered intensely from what scientists today call "confirmation bias" in that he ignored or explained away seeming contradictions in his hypothesis because he wanted it, and himself, to be right. His science, too, was based wholly on observation and not on measurement. Actual measurements would have disproved his mistaken ideas, or at least opened them to question. 

Ptolemy's model

      

Galileo

Copernicus

Since Ptolemy was more important than any visiting scholar and because he wrote in Greek which more Westerners understood than Urdu, and because he was Greek (or at least Hellenized) and spoke Greek, unlike any strange-eyed barbarians, and because Ptolemy's earth-centered theory seemed to fit with the idea that Man was the acme of God's creation, and because the geocentric theory worked for the arcane sciences of astrology and navigation, it became the accepted view in the West. His Almagest was the accepted science of the planets until Magellan proved the Earth is round.

Bruno

During the height of the power of the Catholic Church, questioning Ptolemy's view was made a capital crime: Galileo (1564-1642) was locked up in his own house. Nicholas Copernicus (d. 1543), a Polish monk, wrote a masterwork on the heliocentric theory, but refused to publish it until he lay dying in his own bed. The monk Giordano Bruno (1548-1600), who postulated not only that the Earth went around the Sun but that the other stars were suns with their own planets, was burned at the stake for preaching that God's creation was even more glorious than we understood.

Copernicus' model

It was not until the mid-17th Century that the astronomer Johannes Kepler (1571-1630) was able to, embracing Galileo and Copernicus and Bruno, publish "A New Astronomy" and not be broken on the rack for it. The Earth isn't flat, it revolves around the Sun, and everything in heaven and on Earth is in motion.

Kepler

Having stated actual scientific fact, let's step back now, and use Ptolemy's system to find out where the hell we are on the ocean . . .