Famed Viking 'sun-stone' did exist, say scientists
For centuries, it has been a crystal of legend locked in the verses
of Norse myth with little or no evidence that it was ever real. Now it
seems scientists at last have grounds for believing that the Viking
"sun-stone" used to navigate the seas did indeed exist.
Researchers who have spent three years poring over a cloudy crystal
discovered in the wreck of an Elizabethan ship sunk off the Channel
Islands believe they have proved that it could be the substance
described by the Norsemen as helping to locate the sun when obscured by
cloud.
The so-called sun-stone has long been the subject of scientific
intrigue after it was described in one Icelandic saga as a magical gem
which, when held up to sky, would reveal the position of the sun even
before dawn or after sunset.
Such a navigational aid could be one of the secrets behind the
Vikings' reputation as remarkable seafarers whose prowess at heading
into unexplored water means they may have beaten Christopher Columbus as
the first European visitors to America by hundreds of years.
Scientists based at the University of Rennes in Brittany have studied
the cigarette packet-shaped crystal found on board the wreck off
Alderney and today publish evidence which suggests Tudor sailors may
have used the stone to navigate in much the same way as their Viking
predecessors.
The stone, a calcite substance known as Iceland spar, was found by
divers next to a pair of dividers, leading investigators to wonder
whether it formed part of the navigational arsenal of the English
vessel, which sank in 1592, some four years after the Spanish Armada.
There is no reference to such stones being used by Elizabethan seamen
but the Icelandic sagas describe how the Viking king, Olaf, during snowy
weather, asked a vassal, Sigur, to point to where the sun would be. To
check the answer, "the King made them fetch the solar stone and held it
up and saw where light radiated from the stone and thus directly
verified Sigur's prediction".
Despite the literary references, no intact sun-stone has been found
on Viking sites.
But after carrying out a battery of tests, including an analysis to
prove its cloudy appearance is due to centuries of being abraded by sand
in the English Channel, the French-led team have concluded that shards
of Icelandic spar can act as a remarkably precise navigational aid Dr
Guy Ropars, writing in the journal Proceedings of the Royal Society,
said: "Alderney-like crystals could really have been used as an accurate
optical sun compass as an aid to ancient navigation.
"It permits the observer to follow the azimuth of the sun, far below
the horizon with an accuracy as great as plus or minus one degree. The
evolution of the Alderney crystal lends hope for identifying other
calcite crystals in Viking shipwrecks, burials or settlements."
The principle behind the sun-stone relies on its unusual property of
creating a double refraction of sunlight, even when it is obscured by
cloud or fog of the sort that would have been commonplace for the
Vikings.
By rotating the crystal against the human eye until the darkness of
the two shadows were equal, the sun's position can pinpointed with
remarkable accuracy, according to the researchers.
It is likely the stone, which would have provided a means of
navigating in daylight long before the arrival of the magnetic compass,
would be calibrated by taking a measurement on a sunny day or using
charts showing the position of the sun at different times of the year.
The Alderney crystal was most likely used by Elizabethan sailors to
fine tune their compass readings or overcome disturbance to a magnetic
instrument caused by the presence of large iron objects such as cannon.
- The Independent
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