Stonehenge, the mysterious Neolithic ring of stone slabs in Wiltshire, England, has baffled researchers for centuries. While many agree that the site was once a burial ground, how it was built – specifically how the stones were moved – still remains a mystery, especially since its builders didn’t have access to modern tools or even the wheel.
But was it as hard as we all think it was? That’s the question Barney Harris, a researcher from University College London in the UK, hoped to answer with a recent experiment that set out to see how many people it would take to move one of the 25-tonne stones into position.
First, let’s brush up on our Stonehenge research. The site’s construction started a whopping 5,000 years ago, and took a reported 1,500 years to complete.
The stones weigh about 25 tonnes on average, and measure about 30 feet (9.14 metres) long. Evidence suggests that the rhyolite bluestones used for the monument came from Wales, roughly 140 miles (225 kilometres) away. These stones form like natural pillars underground, which made them easy for ancient workers to cut them out.
Little else about the monument is agreed upon, and crazy hypotheses are always popping up to explain how ancient workers moved such large pieces of rock by hand. Maybe giants or aliens helped make it (when in doubt, blame aliens).
To put the debate to bed once and for all, Harris and his colleagues set out to answer a very simple question: how many people would it take to actually move one of Stonehenge’s gigantic boulders?
To figure this out, the team rounded up volunteers to move a stone that weighed roughly 1 tonne, about half the size of Stonehenge’s smallest stone. At first, Harris thought it would take about 15 people to move the stone and up to 50 to actually lift it, reports Talal Al-Khatib for Discovery News.
Surprisingly, only 10 people were needed to move the stone about 10 feet (3 metres) every 5 seconds, which rounds out to about 1 mile per hour (1.6 kilometres per hour). That’s not too bad!
Harris says this shows that a team of 20 could probably move the smallest chunk of Stonehenge with ease. There was no follow-up on how many it would take to actually lift one of the stones in the air, though ancient workers probably didn’t do that often anyway.
"We were expecting to need at least 15 people to move the stone so to find we could do it with 10 was quite interesting," Harris told The Telegraph’s Sarah Knapton. "It’s true that we did the experiment on flat ground, and there would have been steep slopes to navigate when going through the Preseli Mountains, but actually this kind of system works well on rough terrain."
It’s important to note that the team of volunteers did not pick up the stone and move it like a group of friends moving an extremely large couch. Instead, they used a sledge system that worked by placing logs on the ground and pulling the stone, which was also had logs attached to the bottom of it, over them.
This method reduces the amount of friction on the stone, allowing it to move easier and, therefore, faster. To get a better idea of this, here's the team in action:
"We know that pre-industrialised societies like the Maram Naga in India still use this kind of sledge to construct huge stone monuments," Harris told The Telegraph. "And similar 'y-shaped' sleighs have been found dating back to 2000 BC in Japan which we know were used to move megaliths."
The next step for Harris is to figure out how many people would have been needed in total to move the stones from Wales to its current site.
Though there is no word yet just how large that number will be when all the maths is complete, it seems like it was definitely feasible, especially if many communities came together to get the job done.
The experiment was conducted as part of University College London’s Festival of Culture. Harris' findings are yet to be published in a peer-reviewed journal, but we'll hopefully see that once the numbers are fully analysed.