Alokinn_N

The Romans built a 43 meter dome that should collapse but 2,000 years later, it's still standing. And it has no steel. They pulled it off because they made concrete lighter. The concrete at the bottom is heavy and dense. And as the masons built higher they mixed in lighter and lighter stone until at the very top they were using pumice. The dome also gets thinner as it rises, and those coffered squares carved inside took out tons of extra material. The oculus in the center is the whole trick. It's open sky where the heaviest stone should be. Inside you're standing inside a sphere. Same distance from floor to oculus as wall to wall. Hadrian's architects figured it out without anything we consider essential today and the result is still standing while so much of what we build falls apart in fifty years. Are we really that advanced?