A Stonehenge puzzle solved
Dr Karl Kruszelnicki
Dr Karl Kruszelnicki
The huge sandstone blocks known as sarsens in the prehistoric structure’s outer ring are each about 4m high, 2m wide, weigh about 25 tons, and came from about 26km away. The smaller bluestones of basalt in the inner ring, are each 1-3t in weight, up to about 2.5m tall and came from 240km away.
But the origin of the Altar Stone – 5m long and 6t in weight – has been a mystery. Due to modern sensitivities, it’s no longer possible to drill into the Altar Stone to fully analyse it. However, in the past, several pieces were chipped from various stones at Stonehenge.
Australian scientists from Perth’s Curtin University worked out a non-destructive method using X-ray fluorescence to identify which samples were identical to the Altar Stone. And bingo, a museum sample from 1884 was a perfect match!
The scientists were allowed to do intensive, and destructive, testing on a tiny amount of this sample. These tests found it perfectly matched rocks from a site in north-east Scotland, some 750km away.
Transporting it by land would have been difficult because of the terrain and its many forests, while a sea journey would have posed other problems. It’s not impossible to move these stones – just laborious and time-consuming. In 1995, a team of some 100 workers managed to push and pull a wooden sleigh carrying a 40t slab of stone some 29km cross-country, on a track greased with animal fat.
Unfortunately, the builders who made Stonehenge left behind no written or oral records. Maybe Stonehenge had a ritual or religious significance, or to worship an ancestor.
We do know that some of the stones are aligned to the sunset of the winter solstice and the sunrise of the summer solstice. Perhaps it was a way of declaring to farmers that the seasons were definitely on the turn and it was time to get planting. Maybe Stonehenge was just astronomy giving agricultural advice. After all, in contrast to Rene Descartes’ precept of “I think, therefore I am”, the motto of the scientist is “I think, therefore I get paid”.
