By Motti Sofer
Celestial Navigation on the High Seas from Polaris to GPS
Sailors are mostly G-d-fearing, say Chazal. The reason for this is, of course, the omnipresent perils of sea – famine, disease, piracy, and wreckage. But perhaps also because nautical navigators are always gazing upward, keenly attuned to the heavens, ever watching the sun, the stars for guidance. Seamen ride the seas but follow the pathways of the heavens.
The Gemara (Horiyos 10a) tells of a journey two Tanna’im took. Rabban Gamliel and Rabi Yehoshua had both packed food for the journey that was not expected to take long, but Rabi Yehoshua seemed to have packed excessively; sacks of flour supplemented his food rations. When Rabban Gamliel’s food ran out due to the unforeseen length of the trip, Rabi Yehoshua shared his food with his great colleague. When Rabban Gamliel inquired what had prompted him to prepare for the delay, Rabi Yehoshua said that he was aware of a star (perhaps a comet) that rises only once in 70 years and confuses sailors. Rabban Gamliel exclaimed in wonder over Rabi Yehoshua’s awareness of so obscure a celestial event, yet he lived in such poverty.
To understand how an unfamiliar object in the sky could cause a ship to be lost, we must become a bit more familiar with the how ships used to find their way on the high seas.
Charting the Seas
Though we may not realize it, man’s entire concept of space and time is inseparably intertwined with celestial phenomena. The stated purpose of creating the Great Illuminators was to “be for signs, and for festivals and for days and years.” A year represents the annual solar cycle and a month represents a complete cycle of the moon’s phases. Hours and minutes are subdivisions of the day, the mean time of the sun’s daily routine.
“The pathways of the heavens are as clear to me as the pathways of Nehardea,” Shmuel, the great Amora, once said. In a way, geography and cartography are actually both astronomy. Remember, Earth is a sphere, there is no top or bottom; you can choose any place on it as your equator or meridian. We have charted out the globe based on astronomical phenomena: the equator is the mean path of the sun, and the poles are the farthest points north and south respectively. The tropics of Cancer and Capricorn are the lines across which these constellations arc in the night sky.