BBC News Online science editor Dr David Whitehouse
The Vikings could have been using
a telescope hundreds of years before Dutch spectacle makers
supposedly invented the device in the late 16th century.
This remarkable possibility
has emerged from a study of sophisticated lenses just recognized
from a Viking site on the island of Gotland in the Baltic
Sea. They were initially thought to be merely ornaments.
"It seems that the
elliptical lens design was invented much earlier that we
thought and then the knowledge was lost," says Dr Olaf Schmidt,
of Aalen University in Germany.
lenses were initially thought to be ornaments
late Dr Karl-Heinz Wilms first heard of the so-called "Visby"
lens in 1990 when he was searching for exhibits for a Munich
museum. It was named after the major town on Gotland. Dr
Wilms found a picture of the lens in a book and planned
to examine the original.
it was not until 1997 that a team of three scientists went
to Gotland to take a close look at what were actually 10
lenses locked away in the storeroom of a local museum.
of the team, DR Olaf Schmidt, told BBC News Online: "I was
excited, of course. The polish of some of the lenses was
almost perfect. The second thing that caught our eye was
that their imaging was very good."
When the lenses were
put through their paces, the team was amazed. The lenses
passed a series of tests almost as well as modern optics.
lens was an almost perfect ellipsoid
from rock-crystal, the lenses have an accurate shape that
betrays the work of a master craftsman. The best example
of the lenses measures 50 mm (2 inches) in diameter and
30 mm (1 inch) thick at its center.
surface of some of the lenses have an almost perfect elliptical
shape," DR Schmidt said. "They were obviously made on a
lenses have a flattened central area that makes them excellent
could have been used as magnifiers, allowing fine carving
to be carried out, or they could have been used to start
fires or to burn wounds and cuts so that they did not get
intrigues the researchers is that the lenses are of such
high quality that they could have been used to make a telescope
some 500 years before the first known crude telescopes were
constructed in Europe in the last few years of the 16th
Gotland crystals provide the first evidence that sophisticated
lens-making techniques were being used by craftsmen over
a 1,000 years ago.
time, scientists had only just started to explore the laws
of light refraction.
to the researchers, it is clear that the craftsmen who figured
the lenses knew more about applied optics than did the scientists
of the time. They must have worked by trial and error because
the mathematics to calculate the best shape for a lens did
not become available for several hundred years.
researchers speculate that the knowledge to make such an
accurate lens was known to only a few craftsmen, perhaps
only one person.
it seems clear that the Vikings did not make the lenses
themselves. "There are hints that the lenses may have been
manufactured in [the ancient empire of] Byzantium or in
the region of Eastern Europe," DR Schmidt said.
of the lenses can be seen at Gotland's Fornsal, the historical
museum in Visby. Some are in the Swedish National Museum
in Stockholm. Others have been lost.