Ray Laurence, Macquarie University

Roman concrete is pretty amazing stuff. It’s among the main reasons we know so much about Roman architecture today. So many structures built by the Romans still survive, in some form, thanks to their ingenious concrete and construction techniques.

However, there’s a lot we still don’t understand about exactly how the Romans made such strong concrete or built all those impressive buildings, houses, public baths, bridges and roads.

Scholars have long yearned for more physical evidence from Roman worksites to provide clues.

Now, a new study – led by researchers from the Massachusetts Institute of Technology (MIT) and published in the journal Nature Communications – sheds new light on Roman concrete and construction techniques.

That’s thanks to details sifted from partially constructed rooms in Pompeii – a worksite abandoned by workers as Mount Vesuvius erupted in 79 CE.

New clues about concrete making

The discovery of this particular building site hit the news early last year.

The builders were quite literally repairing a house in the middle of the city, when Mount Vesuvius blew up in the first century CE.

This unique find included tiles sorted for recycling and wine containers known as amphorae that had been re-used for transporting building materials.

Most importantly, though, it also included evidence of dry material being prepared ahead of mixing to produce concrete.

It is this dry material that is the focus of the new study. Having access to the actual materials ahead of mixing represents a unique opportunity to understand the process of concrete making and how these materials reacted when water was added.

This has re-written our understanding of Roman concrete manufacture.

Self-healing concrete

The researchers behind this new paper studied the chemical composition of materials found at the site and defined some key elements: incredibly tiny pieces of quicklime that change our understanding of how the concrete was made.

Quicklime is calcium oxide, which is created by heating high-purity limestone (calcium carbonate).

The process of mixing concrete, the authors of this study explain, took place in the atrium of this house. The workers mixed dry lime (ground up lime) with pozzolana (a volcanic ash).

When water was added, the chemical reaction produced heat. In other words, it was an exothermic reaction. This is known as “hot-mixing” and results in a very different type of concrete than what you get from a hardware store.

Adding water to the quicklime forms something called slaked lime, along with generating heat. Within the slaked lime, the researchers identified tiny undissolved “lime clasts” that retained the reactive properties of quicklime. If this concrete forms cracks, the lime clasts react with water to heal the crack.

In other words, this form of Roman concrete can quite literally heal itself.

Techniques old and new

However, it is hard to tell how widespread this method was in ancient Rome.

Much of our understanding of Roman concrete is based on the writings of the ancient Roman architect Vitruvius.

He had advised to use pozzolana mixed with lime, but it had been assumed that this text did not refer to hot-mixing.

Yet, if we look at another Roman author, Pliny the Elder, we find a clear account of the reaction of quicklime with water that is the basis for the exothermic reaction involved in hot-mixing concrete.

So the ancients had knowledge of hot-mixing but we know less about how widespread the technique was.

Maybe more important is the detail in the texts of experimentation with different blends of sand, pozzolana and lime, leading to the mix used by the builders in Pompeii.

The MIT research team had previously found lime clasts (those tiny little bits of quicklime) in Roman remains at Privernum, about 43 kilometres north of Pompeii.

It’s also worth noting the healing of cracks has been observed in the concrete of the tomb of noblewoman Caecilia Metella outside Rome on the Via Appia (a famous Roman road).

Now this new Pompeii study has established hot-mixing happened and how it helped improve Roman concrete, scholars can look for instances in which concrete cracks have been healed this way.

Questions remain

All in all, this new study is exciting – but we must resist the assumption all Roman construction was made to a high standard.

The ancient Romans could make exceptional concrete mortars but as Pliny the Elder notes, poor mortar was the cause of the collapse of buildings in Rome. So just because they could make good mortar, doesn’t mean they always did.

Questions, of course, remain.

Can we generalise from this new study’s single example from 79 CE Pompeii to interpret all forms of Roman concrete?

Does it show progression from Vitruvius, who wrote some time earlier?

Was the use of quicklime to make a stronger concrete in this 79 CE Pompeii house a reaction to the presence of earthquakes in the region and an expectation cracking would occur in the future?

To answer any of these questions, further research is needed to see how prevalent lime clasts are in Roman concrete more generally, and to identify where Roman concrete has healed itself.

Ray Laurence, Professor of Ancient History, Macquarie University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Jemima McPhee, Australian National University

Ancient scientists can be easy to dismiss.

Greek philosopher Thales of Miletus, often described as the West’s first scientist, believed the whole Earth was suspended on water. Roman encyclopaedist Pliny the Elder recommended entrails, chicken brains, and mice cut in two as topical remedies for snakebite.

The lone ancient Greek thinker who believed Earth orbits the Sun – Aristarchus of Samos – was universally dismissed by his contemporaries.

Because these scientific beliefs are so different from our own, it may seem we have nothing to learn from long-dead scientists. However, thinkers 2,500 years ago already faced many problems that are today amplified by social media and artificial intelligence (AI), such as how to tell truth from fiction.

Here are five lessons from ancient Greek and Roman science that ring surprisingly true in the face of misinformation in the modern world.

1. Start with observations

Almost every ancient scientific text offers advice about observing or collecting data before making a decision. For example, in a 1st century CE text about astronomy, author Marcus Manilius explains that his scientific predecessors learned via detailed, long-term observations. He says

they observed the appearance of the whole night sky and watched every star return to its original place […] by doing this repeatedly, they built up their knowledge.

Ancient astronomers, Manilius says, would look around and gather evidence before drawing any conclusions. Greek and Roman scientists wanted their readers to do the same, and to be suspicious of any claims that are not backed up by data.

2. Think critically

Ancient scientists insisted their readers think critically, encouraging us to analyse the claims made by other people.

The Aetna is an anonymous text that explains how volcanoes work. Its unknown author warns readers about two potential sources of misinformation: other authors and other people.

Whether these groups intend to mislead their audiences or are simply misinformed, the book urges us to scrutinise their claims carefully and think about whether they are consistent with the evidence of our own senses and ratio (the Latin term for the powers of reasoning).

Ancient scientists encourage us to think critically about information we read or hear, because even well-meaning sources are not always accurate. Writers like the Aetna author want us to think before accepting other people’s claims.

3. Acknowledge what you don’t know

Another skill ancient scientists encourage is acknowledging our limits. Even Greek and Roman scientists who claimed to be experts in their field frequently admitted they didn’t have all the answers.

In On the Nature of Things, Roman philosopher Lucretius proposed three different explanations for solar eclipses:

1. the Moon passing in front of the Sun
2. some other opaque body passing in front of the Sun, or
3. the Sun’s light temporarily growing dim for some reason.

Lucretius says he cannot determine which is more likely without additional evidence. In fact, he says it would be “unscientific” to eliminate any of these theories just for the sake of appearing more certain.

Multiple explanations seem unsatisfactory to us because they make ancient scientists’ theories seem less precise. Yet writers like Lucretius should be praised for their honesty in admitting they simply don’t have all the answers.

Greek and Roman scientists knew that people who claim they have no doubts can be very persuasive. However, as Lucretius demonstrates, a source that acknowledges its limits may actually be more trustworthy.

4. Science is part of culture

An ancient medical text from the school of Hippocrates called On the Sacred Disease sought to explain the causes of epilepsy. Contrary to what the title might lead us to expect, the author argues vehemently that there is nothing “sacred” about epilepsy or any other illness, and is determined to discover its physical causes.

Ancient Greek doctors were divided on the causes of disease, and on whether they were supernatural or not. A patient might be given very different answers and advice depending on the perspective of the person they consulted.

Ancient thinkers understood that science was part of culture rather than separate from it, and that an individual’s beliefs and values will have a significant impact on the information they promote as “factual” or “truthful”. Greek and Roman scientists remind us about this because they want readers to think about where information is coming from.

5. Science is for everyone

Our Roman astronomer Manilius says the only essential for students of science is “a teachable mind”. In other words, the ability to acquire new knowledge is all about interest and willingness to learn, rather than possessing any innate skill.

The anonymous Aetna author says something similar: “Science is no place for genius.”

Ancient scientists understood the importance of deferring to specialists and listening to expert advice. However, they were also keen for their readers to understand where scientists acquire knowledge and how scientific facts can be verified.

These hard-won lessons about how to figure what’s true and what’s not helped build the foundations of modern scientific knowledge – and they can still help us navigate a world where truth is just as slippery as it was for ancient Greeks and Romans.

Jemima McPhee, PhD Candidate (Classics), Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Konstantine Panegyres, The University of Western Australia

Parties in ancient Greece were wild, with evidence of copious alcohol and sex. That’s the popular idea that endures today.

But there were different types of parties at the time. Not all involved lots of alcohol and debauchery. Some featured moderate eating and drinking, and intellectual conversation.

So what actually went on at these parties? And how exactly do you party like an ancient Greek?

Different strokes for different folks

Ancient Greek historian Idomeneus of Lampsacus (4th–3rd century BCE) tells us the Greeks began partying in the 6th century BCE. He said that’s when two members of Athens’ ruling class started the trend:

Hippias and Hipparchus invented parties and wandering the streets drunk; this is why they were surrounded by a large number of horses and many friends.

The Greek writer Athenaeus (2nd century CE) provided more evidence for the role of alcohol at parties. He wrote that the Greek Macedonian nobleman Proteas (4th–3rd century BCE) declared at a party he once attended:

he who drinks most will be happiest.

There was also evidence of sexual debauchery at parties. Scenes of sex at parties, between male guests, and male or female prostitutes, appear on numerous vases.

Other parties were regarded as a good venue for debating ideas with friends. In fact, a few of the greatest works of ancient Greek philosophy supposedly stem from intellectual conversations at parties.

For example, in Plato’s Republic (written around 380 BCE), the intellectual debate about the nature of justice takes place at a party hosted at the house of a wealthy man named Cephalus.

Mate, you should have been there

There’s one detailed eyewitness account of a party from the ancient Greek world. Hippolochus of Macedon (4th–3rd century BCE) left behind a letter containing a lengthy description of a party he attended.

It was the wedding party of Caranus, a wealthy Macedonian nobleman. There were 20 guests, all male.

The walls of the room are lined with white linen curtains and the room filled with couches.

When the guests enter, they receive many gifts and lie down on the couches, rather than stand up, and start drinking from bowls:

The moment they lay down, each of them was given a silver libation bowl to keep. Even before they came in, he had garlanded them all with gold tiaras, each worth five gold coins. After they drank the contents of their libation bowls, each man was given a loaf of bread on a bronze platter of Corinthian workmanship (the loaf was as big as the platter).

After guests receive more gifts, a prominent member of the group gives a toast.

By this time, says Hippolochus, “we had now happily escaped sobriety”.

The next stage of the party involves musical entertainment:

Some pipe-girls, female singers, and Rhodian harp-girls came in – they looked naked to me, although some of the guests claimed that they were wearing tunics – and after playing a prelude, they went out again. Other girls came in after them, each carrying two perfume-flasks, one made of gold and the other of silver […] and they gave a pair to all of us.

After this comes the first main dish. A “huge roast piglet” is brought in.

This is followed by more gifts: baskets and bread trays made of strips of woven ivory, as well as flower garlands and an additional pair of gold and silver perfume flasks.

After these gifts, there are more performances, including from naked female acrobats:

who did tumbling tricks among swords and blew fire from their mouths.

As the drinking continues, a chorus of 100 men started singing a wedding hymn. Then there were more dancing girls, followed by:

the clown Mandrogenes [… who] made us break into laughter repeatedly; after that he danced with his wife, who was over 80 years old.

The party ends with the guests filled with wine and drink and amazed at the expensive gifts they have received:

Finally the after-dinner tables came in, and everyone was given […] snacks in ivory baskets, along with flat-cakes of every kind […] along with the special cake-containers for each. After this we got up and left.

Hippolochus doesn’t mention the guests at this party playing games. Some parties, however, included games such as kottabos. This involved throwing dregs of wine at targets on top of poles to try to dislodge them.

Some ideas for your next party

You now have a blueprint for your next party, whether it features bowls of alcohol, lavish gifts of gold and silver, naked fire-breathing acrobats, or intellectual conversation.

Just remember one rule: absolutely no togas. The ancient Greeks would’ve raised an eyebrow – and then sent you to Rome.

Greeks wore a chiton (a type of tunic) and himation (a mantle or wrap, sometimes worn over a chiton). None of these looked much like a bedsheet.

Konstantine Panegyres, Lecturer in Classics and Ancient History, The University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.