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How Did Egyptians Move Heavy Rocks For The Pyramids?

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The pyramids aren't just old, they're really really old: We are closer in time to Cleopatra than she was to the building of the first pyramids. That mind-boggling time-chasm might explain why the pyramids have proved to be a source of fascination and speculation for modern humans, who can't imagine how our ancient forefathers got anything done without technology, let alone building structures large enough to be seen from space.

Stacking the blocks into the towering iconic shape is often marveled at as a feat of mystery, but just assembling the necessary materials is equally miraculous.

For the Great Pyramid of Giza—which is thought to have been built over a span of two decades for fourth dynasty pharaoh Khufu—over 2,300,000 giant blocks of limestone and granite weighing an average of two and a half tons had to be transported to the site from quarries—some from places like Aswan, more than 500 miles away.

Archeological evidence suggests that the ancient Egyptians used crude wooden sleds to transport the heavy building blocks. But if you've ever dragged something through the sand, you can understand why these sleds might not have eased this task. The weight of the blocks would cause the sled to sink slightly and, as you dragged them, sand would accumulate in front of the sled, increasing the resistance.

A recent study in the journal Physical Review Letters proposes an explanation for how the Egyptians made use of the sleds that is based on a principle most people are familiar with: While dry sand is easily pushed around, wet sand is malleable but more rigid. This is why you need moist sand to give your sandcastles structural integrity at the beach. The correct ratio of water to sand—which is variable, but typically between 2 percent and 5 percent of the volume of sand—causes the water droplets to create capillary bridges that bind the individual grains of sand into a smoother, stronger surface.

In experiments, the force required to pull sleds across sand was reduced by a full 50 percent when the right amount of water was added. Not only would it make sense for the ancient Egyptians to have utilized this tactic, there's evidence to suggest that they did. A wall painting from the tomb of Djehutihotep shows a hoard of workers moving a statue of the Upper Egypt nomarch on a sled. While rows of workers are shown heaving heavy ropes attached to the statue, a single figure is painted perched atop the sled pouring what could certainly be water on to the ground in front of him.

"In fact, Egyptologists had been interpreting the water as part of a purification ritual, and had never sought a scientific explanation," Daniel Bonn, who led the study, told the Washington Post.

The science is sound, but that doesn't necessarily mean it overrules the Egyptologists' theories about Djehutihotep's wall painting or that it applies to the pyramids, which were built over 600 years before Djehutihotep lived. Most reports of the study have assumed that applying their findings to the pyramids is something of a foregone conclusion. Adding water to the sand to decrease friction certainly makes sense, but that doesn't necessarily mean it's what the Egyptians did.

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Stones, Bones, and Wrecks
8 New Ancient Ships Found at the 'Shipwreck Capital of the World'
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The number of wrecks discovered at the "shipwreck capital of the world" continues to grow. According to Haaretz, the latest find adds eight new wreck discoveries, bringing the total up to 53 sunken ships in a 17-mile stretch off the coast of Fourni, Greece.

As Mental Floss reported, in 2015 archaeologists working off the coast of Fourni identified 22 shipwrecks dating back to 700 BCE—already an historic find. But additional dives conducted by the Hellenic Ministry of Culture and the RPM Nautical Foundation have continued to yield new discoveries. Nine months later, in June 2016, the Fourni Underwater survey turned up 23 more ancient, Medieval, and post-Medieval shipwrecks in the area with the help of local fishermen and sponge divers. The latest expedition took place in June 2017.

Divers inspect and survey an ancient amphora near the shipwreck site.

The Fourni archipelago, consisting of 13 tiny islands, never hosted a sizable town, but it was an important stopping point for shipping routes between the Black Sea, the Aegean Sea, and on to Cyprus, the Levant, and Egypt. The area may have been a hotspot for ships seeking safe harbor from violent storms in that part of the Aegean Sea, as Peter Campbell of the RPM Nautical Foundation told Haaretz. It wasn’t an entirely safe destination for merchant ships, though; it was also a pirate haven.

Some of the latest wrecks found include a ship from the Greek Classical Period—around 500 BCE to 320 BCE—carrying Greek amphorae (ceramic jars), a Roman ship with origins in the Iberian Peninsula, and anchors dating back to the Archaic Period (800 to 479 BCE). Researchers found more stone, lead, and iron anchors all the way up to the Byzantine Empire, which lasted until the 15th century.

Two conservationists sit at a table working with shards of ancient pottery.

The ancient trade routes that crisscrossed the Mediterranean (and the dangers of ancient seafaring) have made the area a fertile ground for millennia-old shipwrecks even outside of Fourni. As recently as 2016, divers off the coast of Israel stumbled upon a 1600-year-old merchant ship filled with Roman artifacts. In 2015, Italian divers discovered the wreck of a 2000-year-old ship carrying terra cotta tiles in deep waters near Sardinia.

The Fourni project is still ongoing, and researchers plan to conduct a fourth season of underwater surveying in 2018. Once the project completes a full survey and documentation of the area, the researchers may consider excavating some of the wrecks.

[h/t Haaretz]

All photos by Vasilis Mentogianis courtesy the RPM Nautical Foundation

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J. P. Oleson
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science
Time Has Only Strengthened These Ancient Roman Walls
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J. P. Oleson

Any seaside structure will erode and eventually crumble into the water below. That’s how things work. Or at least that’s how they usually work. Scientists say the ancient Romans figured out a way to build seawalls that actually got tougher over time. They published their findings in the journal American Mineralogist.

The walls’ astonishing durability is not, itself, news. In the 1st century CE, Pliny the Elder described the phenomenon in his Naturalis Historia, writing that the swell-battered concrete walls became "a single stone mass, impregnable to the waves and every day stronger."

We know that Roman concrete involved a mixture of volcanic ash, lime, seawater, and chunks of volcanic rock—and that combining these ingredients produces a pozzolanic chemical reaction that makes the concrete stronger. But modern cement involves a similar reaction, and our seawalls fall apart like anything else beneath the ocean's corrosive battering ram.

Something else was clearly going on.

To find out what it was, geologists examined samples from walls built between 55 BCE and 115 CE. They used high-powered microscopes and X-ray scanners to peer into the concrete's basic structure, and a technique called raman spectroscopy to identify its ingredients.

Microscope image of crystals in ancient Roman concrete.
Courtesy of Marie Jackson

Their results showed that the pozzolanic reaction during the walls' creation was just one stage of the concrete toughening process. The real magic happened once the walls were built, as they sat soaking in the sea. The saltwater did indeed corrode elements of the concrete—but in doing so, it made room for new crystals to grow, creating even stronger bonds.

"We're looking at a system that's contrary to everything one would not want in cement-based concrete," lead author Marie Jackson, of the University of Utah, said in a statement. It's one "that thrives in open chemical exchange with seawater."

The goal now, Jackson says, is to reproduce the precise recipe and toughen our own building materials. But that might be harder than it sounds.

"Romans were fortunate in the type of rock they had to work with," she says. "They observed that volcanic ash grew cements to produce the tuff. We don't have those rocks in a lot of the world, so there would have to be substitutions made."

We still have a lot to learn from the ancient walls and their long-gone architects. Jackson and her colleagues will continue to pore through Roman texts and the concrete itself, looking for clues to its extraordinary strength.

"The Romans were concerned with this," Jackson says. "If we're going to build in the sea, we should be concerned with it too."

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