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Art & Artifacts

Newscripts

Stonehenge secrets and paper cut physics

Newscripts plays rock, paper scissors

by Brianna Barbu
October 7, 2024 | A version of this story appeared in Volume 102, Issue 31

 

Rock

An aerial photo of Stonehenge.
Credit: Shutterstock
Rock and roll: Archaeologists believe the Altar Stone was dragged over land because wheeled technology hadn’t yet arrived in Britain.

Stonehenge’s Altar Stone, a 5 m long sandstone slab located in the middle of the Neolithic monument, continues to evade easy answers about its origins. The latest scientific evidence points toward northeast Scotland—though the islands of Orkney have now been ruled out a mere 2 weeks after a paper was published that appeared to imply that they were the stone’s most likely source.

Since the 1920s, experts have assumed that the Altar Stone came to Stonehenge from Wales in 3000 BCE alongside the bluestones of the site’s inner circle (the big standing rocks are locally sourced). But as scientists learned more about the geology and chemistry of the stones, that assumption didn’t stand up to scrutiny.

The Altar Stone “has a very peculiar chemistry”—unusually high in barium sulfate, says Nick J. G. Pearce, a geochemist at Aberystwyth University who has been studying the Altar Stone since 2009. When he and his colleagues found last year that the local sandstone of Wales and southern England is much lower in barium than the Altar Stone, they drew their attention 1,100 km northward to Orkney.

Orkney has sandstone with relatively high barium levels, its own collection of magnificent Neolithic standing stones, and other archaeological clues that the people living there 5,000 years ago had cultural contact with the people near Stonehenge. “You start thinking, two plus two—got to be Orkney,” Pearce tells Newscripts.

Pearce’s team struck up a collaboration with Anthony Clarke, a geology PhD student from Curtin University, to analyze zircon mineral grains in fragments from the Altar Stone. Clarke used uranium and lead isotopes to calculate the rock’s age and compared it to other sandstone deposits in the British Isles. The Altar Stone’s isotopic signature matched that of rock from the Orcadian Basin, where Orkney is located.

But further geochemical studies from the Aberystwyth team comparing the Altar Stone to Orkney’s standing stones showed that the Orkney stones’ mineral composition was consistent and local—and not the same as the Altar Stone.

In an attempt not to upstage Clarke’s thesis, Pearce says he and his colleagues waited until the zircon paper was accepted for publication in Nature (2024, DOI: 10.1038/s41586-024-07652-1) to submit a follow-up paper about the geochemical results to the Journal of Archaeological Science: Reports (2024, DOI: 10.1016/j.jasrep.2024.104738). They assumed the second paper would be published a few months after the zircon paper, Pearce says. But the follow-up flew through the review process with uncharacteristic swiftness and was published on August 30, 2024, two weeks after the Nature paper.

That timing did the exact thing they had been trying to prevent: it gave people the impression that the Nature paper was wrong, which it isn’t, Pearce says. The Orcadian Basin extends over a large swath of northeast Scotland, so there are plenty more places to look for a better chemical match.

 

Paper scissors

A teen with a bandage on his finger holding a copy of C&EN.
Credit: Bethany Halford/C&EN
Careful! C&EN’s pages are about 58 µm thick, very close to the paper-cut danger zone.

If you’ve ever gotten a paper cut and wondered why that particular misfortune befell you, science now has an answer. According to a paper from Kaare Jensen’s lab at the Technical University of Denmark, the question of whether or not a piece of paper is likely to slice you mainly comes down to how thick the paper is.

Though the topic seems mundane, Jensen tells Newscripts the science is broadly applicable—everyone gets paper cuts—and extremely fascinating. “Paper is about 100 times weaker, mechanically, than steel,” and yet it can slice into flesh, he says. That’s a fundamentally interesting physics question.

Using a robotic gadget to control the slicing angle, the researchers tested the cutting abilities of everyday paper products, including tissue-thin lens wipes, office paper, cardstock, and old issues of scientific journals. They found that if the paper is too thick, it won’t achieve the concentrated force necessary to cause damage; too thin, and the paper will simply buckle. Peak cuttability occurs at about 65 µm, just a little thinner than office paper.

The researchers also designed a “papermachete” using strips of scrap paper magnetically attached to a 3D-printed handle. The cellulosic scalpel successfully cut into fruits, vegetables, and meats.

Please send comments and suggestions to newscripts@acs.org.

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