Darvill said the excavation marks the first opportunity to bring the power of modern scientific archaeology to bear on a problem that has taxed the minds of experts since medieval times: Why were the bluestones so important to have warranted bringing them from so far away?
How Were the Stones Transported?
The goal is to find remnants of the original bluestones, or related materials, that can be subjected to modern radiocarbon dating techniques. This could establish a more precise time line for the construction of Stonehenge, said Dave Batchelor, an archaeologist with English Heritage, which oversees the Stonehenge site.
"We have to find the material that will give us a good date," Batchelor said.
"That's where the luck comes in. We could get an absolute blank, or we could get something magnificent, or we could get something in between."
He said bluestones have an "inky, bluey black" appearance. About 6 feet (180 centimeters) tall, they are the smaller of the stones at the monument. The larger stones are about twice as tall and were added later.
It is hoped that pinpointing Stonehenge's start date will shed light on how and why the monument was built.
The team may also learn more about how the stones were transported.
Research shows the bluestones—weighing an estimated five tons apiece—may have been dragged from the mountains in southern Wales to the sea, put on huge rafts, and floated up the River Avon.
Archaeologists believe that, before the bluestones were put in place, Stonehenge consisted of a circle of wooden posts and timbers built in approximately 3100 B.C.
The research began Monday with the digging of a trench. It marks the first time ground inside the inner stone circle has been excavated since 1964. The area is so sensitive that Cabinet approval was needed before the work could begin.
Renee Fok, a spokesperson with English Heritage, said the project was okayed only after experts were convinced of its potential value. She said the project represents "the logical next step" after the two professors located the source of the bluestones in Wales.
"It's the culmination of their work. It makes sense to go back to the stone circle and get a date," she said.
"We want to strike a balance. We want the best research, but we can't just say, Go ahead and dig as you like—it's a very fragile area. Even the Druids are happy with this project, we've spoken to them and they don't object."
She said tourists will be able to visit Stonehenge as usual and will also be able to watch live video coverage of the excavation in special tents at the site.