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!]

In Latin, the writing on the Pantheon says “M.AGRIPPA.L.F.COS.TERTIUM.FECIT.”

The Latin is succinct but it translates to mean that Marcus Agrippa, son of Lucius, built this when he was consul for the third time.

[Alas Babylon!]

Dang! I meant to buy fish sauce today... Seriously (I have some Southeast Asian dishes to make...)

[SunkenCiv]

My pleasure. While compiling that list of pantheon / concrete topics, I realized, there are a lot of them, probably more than a third of them from me. At some point I should just break down and vacation there. 🙂

[GingisK]

After that, you get a glimpse of the Obama Library.

[telescope115]

👍🙂

[Liz]

I was there....it was stupendous to stand in it.

[telescope115]

I have not seen that movie yet….gotta do it.

[central_va]

Concrete does not dry - it cures. The water molecules in the mix form the chemical bond. Evaporation actually weakens the hardening concrete.

[central_va]

The 2nd Punic War is fascinating.

[ProtectOurFreedom]

Wow, never saw it or even heard of it before. Thanks. Just astonishing and breathtaking, isn’t it?

[central_va]

The Roman Arch was a popular technique used by the high denarius prostitutes.

[Governor Dinwiddie]

Yes, that's the thing that baffles me. Not an ounce of rebar anywhere.

[Rummyfan]

It is truly an amazing piece of architecture and construction. The front and entranceway opens on a large restaurant and cafe lined piazza. If you go to Rome it is a must-see building.

[Rummyfan]

[Rummyfan]

They also left a hole in the middle.

Interesting. I thought the oculus was mainly to provide light.

[Paal Gulli]

It definitely rains through the Pantheon's oculus. I've been in it on rainy days when the center was cordoned off to keep tourists out of the wet.

Here's a video of rain in progress:

https://www.youtube.com/watch?v=73vEsV9nvmw

FF to about 4 minutes for the rain.

The shape does create a 'mist' effect that tends to cause raindrops to break up as they fall but the building was engineered knowing the rain still would get through. The floor is slightly crowned from the center to the perimeter, causing water to run away from the middle of the building. And there are 20-odd discretely camouflaged drains around the perimeter so there's very little puddling.

There is a monument to the Yankee soldiers from Illinois in the Vicksburg National Military Park that is a scaled-down replica of the Pantheon. It has an oculus in its dome, and the locals there also perpetuate the myth that it doesn't rain through the hole, but it does there, too.

https://en.wikipedia.org/wiki/Illinois_Memorial

Summer is the driest part of the Roman year so there's limited opportunity for the bulk of tourists to see for themselves.

To me, a greater mystery than the self-healing concrete is why the pediment over the portico is 10 feet lower than intended.

On the wall above and behind the pediment you can see where it originally was intended to come to. It mirrors the pitch of the roof on the pediment but there's no roof there, so something's obviously not right.

All anyone knows for certain is the columns there now are about 10 feet too short. They're made from Egyptian marble that would have come by boat across the Mediterranean so theories range from a simple engineering foul-up to the ship carrying the original columns being lost at sea. In any case it would have taken months to get proper replacements so they might have grabbed whatever columns were handy and made do with 10 feet too short.

RE: the inscription on the portico, it reads: M⸱AGRIPPA⸱L⸱F⸱COS⸱TERTIVM⸱FECIT

As it means in highly abbreviated Latin: Marcus Agrippa Lucii filius consul tertium fecit

What it means in English: Marcus Agrippa, son of Lucius, [during his] third term [as] consul did [made] this

[Rummyfan]

It’s awe inspiring to visit Rome, Florence, Venice, etc. and see incredible architecture and engineering, craftsmanship and artistry. And then you look at the inscription of when these structures were dedicated…. and then consider context: what tools, what science, what resources, etc. was available to them.

Incredible.

Yes. Yes it is. Florence is my favorite city in the world.

[BradyLS]

It just proves it only takes a few to ruin the barrel leading to why we can’t have nice things.

[FLT-bird]

Interesting. I thought the oculus was mainly to provide light.

Well it did do that.....but it also took away weight. The Romans used concrete at the top that had these little jugs in it (creating air pockets and thus lightening the concrete). They were looking for any kind of way to save weight. Obviously their design worked. 2000 years later its still here.

[NFHale]

Absolutely amazing isn’t it?

They had some brilliant engineers for sure.