Fri 12 Feb, 2010 12:50 pm
This is interesting but is it a feasible explanation to the age old mystery of whether people could have navigated the oceans accurately long before Yorkshireman John Harrison perfected his timepiece in about 1770.
No it is not feasible to find longitude with such a device.
What this article seems to be describing is a primitive sextant
which can find your latitude (how far you are from the equator) but not your longitude (how far across the ocean from east to west. Of course, if these mariners were smart enough to use a sextant, why they would use a stone cross thing rather than a more precise metal (or even wood) version is an interesting question. Even this makes me very skeptical.
The problem with figuring out your longitude is that the earth is spinning in the east-west direction meaning that the stars that you would be pointing the device are at different points in the sky depending on the time of night. This means that if you don't have a way to know exactly what time it is, this method is completely useless.
The idea that the cross was used to find latitude is theoretically possible (but highly unlikely).
The idea that the cross was used to find longitude is simply impossible.
Brown is correct that such devices are intended to find latitude, not longitude. However, he is completely incorrect to suggest that it would not have been useful for finding latitude. In fact, the Norse simply used a notched stick to find latitude. All that is needed to find one's latitude is a fixed celestial point. By determining it's elevation above the horizon at a particular time of day, one can find one's latitude (relative to the point of departure from land). The evidence both from saga sources, and from the fact that the Norse routinely navigated out of sight of land and arrived reliably at their destinations is that the notched stick they used allowed them to be accurate to within a half of a degree (about 30 miles) or even a quarter of a degree (15 miles). So, they would only need to lay on their oars overnight, so as to approach the land safely in daylight. The Bjarni Herjolfsson voyage of 985 is evidence of the reliability of their ability to find latitude.
The link was hilarious, though. Them boys will believe anything.
In 984, Erik Raudi (Erik the Red) returned to Iceland after having been outlawed for three years for manslaughter (favorite Norse euphemism for bloody murder). He finally compounded a settlement with his enemies, but his life was screwed in Iceland. He convinced quite a few people to follow him to Greenland the following year, and among them was Herjolf Bardsson, an Icelandic merchant. Herjolf had long before abandoned sea-faring, and his son, Bjarni Herjolfsson, was the sea-going merchant in his family. Apparently, Herjolf left sailing directions for Bjarni. It was the custom in those days for Icelandic merchants to load a cargo, and sail to Norway, where they would overwinter, trading and filling a new cargo to take back to Iceland. (This was the custom adopted by those who traded to Greenland in later years, too.)
Bjarni arrived back in Iceland, and learned that his father had gone out to Greenland with Erik Thorvaldsson (i.e., Erik Raudi, or Erik the Red). He decided not to unload his cargo, and asked his crew to join him on a voyage to Greenland. However many agreed to go along (we can't know from the saga sources), it was enough to safely sail his knorr, the very fine trading vessels used by the Norse. A few days after they had left Iceland, in the track of Erik's expedition, they were hit by a storm which raged for days, and drove them far to the southwest.
Bjarni undoubtedly knew how far north he needed to be (as will become apparent shortly), but of course could not know how far west he needed to be, since they could not find longitude. When the weather finally cleared to the point where they could do more than just run before the storm, he started sailing west. They made landfall near what was very likely the Avalon peninsula in modern-day Newfoundland (based on the description of how long they sailed and the description of the shore they saw). Bjarni began sailing north by north-northwest, keeping the land in sight, but unwilling to sail very much farther west. They lost contact with the land, but made contact again in a few days, at a point which would coincide with the Great North Peninsula of Newfoundland--which they thought was probably a separate island. They lost contact again, but within a few days made contact with the land again, and based on the shore they saw, Bjarni called this new land Markland, meaning forest land--and southern Labrador was then (and mostly still is) covered by vast coniferous forests. Sailing on, they came to a land which was almost exclusively rock and glacier--but Bjarni was not confident that it matched the description of the land they were seeking, so he continued to the north. He called that new land Helluland, meaning land of stone, from hellur, meaning stone. His description matches perfectly a description of the Kaumajet peninsula of northern Labrador.
When Bjarni sailed out beyond Cape Chidley at the northern end of Labrador, he knew that this did not at all match the description he had been given. At that point, he turned and sailed due east. He would only have done this if he knew, or was sure to a moral certainty, that he had reached the proper latitude. Within five days, he made landfall at Herjolfness, the point for which he had been sailing when he left Iceland, and before he was blown off course. Bjarni could only have accomplished that feat if he knew his latitude, and was sufficiently confident of it to have sailed out of sight of land for several days--and his confidence was repaid to the extent that he made landfall at his father's settlement--his course was dead on the money.
In the book Westviking, Farley Mowat describes the husanotra, a device mentioned in saga sources many times, but the translation of which is disputed by Norse scholars. Mowat is convinced that this was the name of the notched stick which Norse sailors used to find latitude. Whether or not this is true, Bjarni was sufficiently confident that he had reached the proper latitude when he reached Cape Chidley that he was willing to turn ninety degrees and sail out of sight of land for several days, which was rewarded by making his landfall exactly. The tale of Bjarni's voyage can be found in the Short Saga (a fragment of the Erik the Red Saga, and derived from the earliest written versions), the Erik the Red Saga (a later version, separated more in time from the oral sagas than is the case with the Short Saga), the Thorfinn Karlsefni Saga and the Groenlendinga Saga (the Greenlander's Story). Mariners have been able to find latitude for literally thousands of years, and the evidence from the Norse is that it doesn't even require a very sophisticated device.
as long as we're reinventing the wheel try the
That was a very long writing. It is obvious that ancients did navigate the oceans without much ado, but using the celtic cross would be a limit to many of the more ancient societies, they, as we know used the stars.
and, despite what the guy says, it doesn't have a thing to do with Polynesian navigation, which was long-distance and accurate, but had nothing to do with latitude and longitude, but was rather based on a whole lot of empirical knowledge of prevailing winds, ocean currents, distance bird flight, and long0distance visiion of cloud formations over islands. they had map-analogues which consisted of reeds and counters (shells and stones representing specific things) arranged in the appropriate patterns to navigate between islands)--an equally valid, but completely conceptually different, means of navigation from Europeans.
A decent clock is the only way (other than gps which ancients probably lacked) to figure longitudes. Yeah, you COULD sail prior to 1770 or thereabouts, but a lot of guesswork went into it.
good god, what's happening to a2k? gungasnake is actually making sense. i suppose there has to be a first time for everything.