Lasers reveal invisible Stonehenge carvings

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Lasers reveal invisible Stonehenge carvings

NewScientist.com news service

The carvings are thought to portray bronze axe heads, which have

been found nearby (Image: Wessex Archaeology/Archaeoptics)

Laser scanning has revealed ancient carvings on the pillars of

Stonehenge that are invisible to the naked eye.

 

The experiment scanned just part of three of the 83 stones that make

up the famous prehistoric monument in Wiltshire, UK. The

archaeologists, from the Wessex Archaeology and Archaeoptics

companies, hope a full survey could provide compelling evidence that

Stonehenge was a memorial for the dead, at least at the time the

carvings were made.

 

The new-found carvings are just a couple of millimetres deep and

represent bronze axe heads. A few dozen visible carvings have been

reported before, the earliest in 1953. But the comparison of the 50-

year-old photographs with the new scans revealed that the carvings

seem to be wearing away.

 

"They have eroded quite a bit," says Tony Trueman, of Wessex

Archaeology. He estimates that a full survey would cost tens of

thousands of pounds.

 

Mike Pitts, an expert on Stonehenge, says: "It is extraordinary that

these carvings, the most significant art gallery from ancient

Britain, have still not been properly studied." Pitts is also the

editor of British Archaeology in which the results of the scanning

experiment are published.

 

 

Daggers and cups

 

 

Stonehenge was constructed in 2300BC, but the carvings are thought

to have been made after 1800BC, which is when bronze axe heads began

to be used.

 

 

The laser scanner generated nine million data points in 30 minutes

(Image: Wessex Archaeology/Archaeoptics)

 

Carving of axe heads, as well as daggers and cups, have been found

at burial sites all over the UK, Trueman told New Scientist: "They

seem in some sense to be commemorating the dead."

 

He thinks the same could be true at Stonehenge, especially as there

are hundreds of burial sites in the area around the monument. Other

theories of Stonehenge's purpose have centred on the fact that it

was designed to line up with the sunrise on the morning of the

summer solstice, and served as a calendar.

 

But the theories may not be mutually exclusive. The Sun could have

had a symbolic value and been part of the memorial, suggests

Trueman, or Stonehenge's use could have changed over time.

 

 

 

The team spent just 30 minutes scanning the stones, but gathered

nine million data points. These were converted into three-

dimensional images using triangulation, based on the fixed positions

of the laser and a camera.

 

Another laser scanning technique, which calculates distance by

measuring the time taken for the light to bounce of a surface, has a

resolution of about a centimetre and could not have revealed the

carvings.

 

"We have used scanning previously to enhance badly weathered

carvings on monuments, but never on details as fine as the

Stonehenge axe heads," says Alistair Carty of Archaeoptics. "The

possibility that other unknown carvings exist on the other stones is

very exciting and may hopefully lead to a more complete

interpretation of Stonehenge."

 

 

Damian Carrington

http://www.newscientist.com/news/news.jsp?id=ns99994849