Why hasn't the Pantheon's dome collapsed? [13:33]

YouTube ^ | June 23, 2023 | Garrett Ryan, Ph.D (as toldinstone)

[SunkenCiv]

An in-depth look at the construction of Rome's Pantheon and its famous concrete dome. 

Why hasn't the Pantheon's dome collapsed? | 13:33 
toldinstone | 628K subscribers | 662,909 views | June 23, 2023

Chapters: 
0:00 Introduction 
0:28 The purpose of the Pantheon 
1:16 The design 
1:58 Roman concrete 
2:32 Quarries, contractors, and workforce 
4:02 Foundations 
4:44 Building the walls 
5:41 Relieving arches and buttresses 
6:35 Masterworks 
8:08 Building the dome 
9:51 The portico 
10:54 Decoration 
12:32 Insane Emperors, Sunken Cities, and Earthquake Machines

[Alas Babylon!]

True story.

When I was stationed in Italy, my wife and I took an ITT trip to Rome for Christmas.

We had free time in the evening, so we went to the massive Boun Natale (Christmas) market in the Plaza Navona, which used to be the Stadium of Domitian. Anyway, it started to sprinkle, so we headed back to the hotel. Just then a real gusher of rain exploded from the sky, we started to run and saw a lot people running into these massive dark doors, but well lit on the inside... We followed.

It was the Pantheon. So beautiful on the inside, and, despite the heavy rain, nothing was coming down the open roof! They say it was purposely designed to let in light, but kept rain out due to the natural lifting of the air from below!

At first I didn’t even know where we were; it was around 8:00 pm at nighttime, so not a lot of people in it, especially tourists. I had to wander around and then read the English language sign to see where we were!

[rlmorel]

"...They say it was purposely designed to let in light, but kept rain out due to the natural lifting of the air from below..."

That is fascinating! I didn't know that, and when I saw the picture, I briefly wondered about that-how no rain came in...thank you!

[Alas Babylon!]

Here's the view we saw while running in the rain. Massive door indeed!

I just ran in, didn't even read the inscription.

[rlmorel]

Thank you for posting these things that you do-fascinating subject matter!

[telescope115]

Here in Northern Illinois the roads need to be constantly patched or torn up and rebuilt. I guess the Romans didn’t have to deal with constant jobs programs for labor unions.

[Alas Babylon!]

No, they used bread and circuses!

[Lowell1775]

They have used a term for centuries......

The Roman Arch.
It is so stable that many are still standing in not only buildings, but aqueducts.

Their roads are another engineering marvel.

Of course African slaves were the source of this knowledge as well as the labor that built it while being raped by greasy Italians.

[rlmorel]

Hahahaha, made me think of this:

I used to take a highway into work, and it seemed like it was under construction for about ten years straight (I think it may have been 4-8 years, realistically) but I would get really aggravated like Michael Douglas in that movie "Falling Down" and rail that it had to be a jobs program, not something to actually fix anything!

[JeanLM]

...”Of course African slaves were the source of this knowledge as well as the labor that built it “
++++++++++++++++++++++++++++++++++++++++++++++++++
I hope this is sarcasm. The labor in the article was a mix of slaves and free men. Few Roman slaves were from Africa, certainly not Black Africa. They were conquered groups and Slavs were the reason we have the word slave.
An early Christian decided to preserve the Pantheon to honor all the saints. Otherwise it might have been destroyed like many other temples to pagan deities. If they could have demolished it.
The Caliphs would have converted iy into a mosque like the one in Constantinople.

[NFHale]

Yes, I knew that… Didn’t mean to imply that the Romans burned it. Just stating how much information was lost… God only knows what vanished.

[Liz]

Thx....enjoyed it.

[Locomotive Breath]

Concrete is strong in compression but has almost zero strength in tension. The rebars that we see in modern concrete are to add strength in tension.

Buildings such as the Pantheon are designed such that the concrete is always in compression. The dome is a perfect example. Thus reinforcement would have been redundant.

But they were still brilliant engineers.

[Locomotive Breath]

I’ll add that the concrete is porous so that moisture can penetrate. When the moisture gets to the rebar it rusts. When steel rusts it expands. This has the effect of popping off big chips of concrete in a process called “spalling”. The failure is not in the concrete but in the rebar.

[SunkenCiv]

Yeah, I want a slab of that for my grave marker. Not yet, but eventually.

[SunkenCiv]

Wow!

[j.havenfarm]

Have you seen “Nero’s bathtub”? From the same extinct quarry. Valued at $2 billion. The room where it sits at the Vatican was built around it. Just stunning
https://www.alamy.com/stock-photo-emperor-neros-marble-bathtub-16728626.html?imageid=2C6059FA-CAD6-4EB3-B71F-36DCFC699632&pn=1&searchId=1f4bc3ace49ba612a79ed3a858ee4b43&searchtype=0

[SunkenCiv]

There’s a bridge in Spain that, although it had some work done in the 20th c, was if memory serves set entirely without mortar. Still in use.

[citizen]

A very impressive structure. There are photos on Google Earth, tho not as many of the dome.

[SunkenCiv]

Not what I meant, but I appreciate your patience. The entire library contents were on papyrus, which started to get in bad shape, so the whole works was hand-copied onto parchment (animal skin) and the originals were disposed of. Given what has been dug up at Oxyrhynchus, I wonder if the fragments of the entire original library aren’t waiting in some forgotten public dump.

[SunkenCiv]

Circuses, bread, and garum spread.