4 ms·

> We may think we're at the height of human knowledge, but the ancients did possess precious knowledge that has been lost to time. I would love to hear why a c

> We may think we're at the height of human knowledge, but the ancients did possess precious knowledge that has been lost to time. I would love to hear why a chemical analysis doesn't solve the riddle here. Scientists were able to isolate a strain of the coronavirus and publish the entire genetic sequence in a matter of days, but we can't analyze a sample of concrete?

BiteCode_dev 7y ago
Available resources for the tasks are probably different.
deleted 7y ago
[deleted]
cmroanirgo 7y ago
Just as carbon ash from the fireplace has the same chemical makeup as a diamond, there's a bit more to it: namely the changing structure of the stuff itself. The CSH reaction (https://en.wikipedia.org/wiki/Calcium_silicate_hydrate https://en.wikipedia.org/wiki/Calcium_silicate_hydrate) is something that evolves over time, and even then the modern chemical reaction is not completely known in all its states (as far as I'm aware). > The [balanced chemical mass] of C-S-H in cement paste is variable and the state of chemically and physically bound water in its structure is not transparent, which is why "-" is used between C, S, and H The article actually misses how modern concrete (portland) get stronger over the first few years as the crystalline structures grow. So, I can well understand how it's a bit tricky to find out what the original roman mix was, just using observations 2000 years later: because a lot of things have happened from the original cake mix to what we see now.
- catalogia 7y ago
  > Just as carbon ash from the fireplace has the same chemical makeup as a diamond AFAIK wood ash is predominantly mineral oxides, particularly of calcium. The carbon in the wood is the fuel that burns up and goes out the chimney as carbon dioxide. When wood burns it first boils and burns off various volatile compounds, leaving behind black charcoal coals, made predominately of carbon. This charcoal also burns, leaving behind wood ash.
  - kragen 7y ago
    I think they meant charcoal.
blihp 7y ago
You can chemically analyze a piece of cake and know exactly what it's made of. You would still not know how to make one with that knowledge alone.
rnestler 7y ago
I guess some chemical reactions which happen over time are kind of like hash functions. So it's hard the find out what the input was just by observing the output.
b0rsuk 7y ago
I'm not a chemist, but perhaps a good analogy is making Mona Lisa with Game of Life? Recently posted on HN. Finding Mona Lisa in the Game of Life https://news.ycombinator.com/item?id=22552006 https://news.ycombinator.com/item?id=22552006 From the article: "This looks kinda cool, but what if we want to find a Life state that eventually, after following the rules of Life for a few rounds, reaches a state that looks like Mona Lisa? This requires working backwards instead of forwards from the target picture, which is a much more difficult problem. (...) We call Life state A the "parent" of state B if A turns into B by following the rules of Life. The reason that it's difficult to find the parent of a state is that the rules of Life are non-reversible. There's no direct way to go from a Life state to its parent, and in fact, it's possible for a state to have multiple parents or even no parents. "
lazyjones 7y ago
I'm sure they can analyze a sample of 2000 years old concrete, but it's not going to look the same as when it was built and it'll probably not be a simple mix of basic elements but very complex. The Romans might have used a mixture with actual lava or corals e.g. and it'd be hard to trace it back to such ingredients.

BiteCode_dev 7y ago

Available resources for the tasks are probably different.

deleted 7y ago

[deleted]

cmroanirgo 7y ago

Just as carbon ash from the fireplace has the same chemical makeup as a diamond, there's a bit more to it: namely the changing structure of the stuff itself. The CSH reaction (https://en.wikipedia.org/wiki/Calcium_silicate_hydrate https://en.wikipedia.org/wiki/Calcium_silicate_hydrate) is something that evolves over time, and even then the modern chemical reaction is not completely known in all its states (as far as I'm aware). > The [balanced chemical mass] of C-S-H in cement paste is variable and the state of chemically and physically bound water in its structure is not transparent, which is why "-" is used between C, S, and H The article actually misses how modern concrete (portland) get stronger over the first few years as the crystalline structures grow. So, I can well understand how it's a bit tricky to find out what the original roman mix was, just using observations 2000 years later: because a lot of things have happened from the original cake mix to what we see now.

catalogia 7y ago
> Just as carbon ash from the fireplace has the same chemical makeup as a diamond AFAIK wood ash is predominantly mineral oxides, particularly of calcium. The carbon in the wood is the fuel that burns up and goes out the chimney as carbon dioxide. When wood burns it first boils and burns off various volatile compounds, leaving behind black charcoal coals, made predominately of carbon. This charcoal also burns, leaving behind wood ash.
- kragen 7y ago
  I think they meant charcoal.

blihp 7y ago

You can chemically analyze a piece of cake and know exactly what it's made of. You would still not know how to make one with that knowledge alone.

rnestler 7y ago

I guess some chemical reactions which happen over time are kind of like hash functions. So it's hard the find out what the input was just by observing the output.

b0rsuk 7y ago

I'm not a chemist, but perhaps a good analogy is making Mona Lisa with Game of Life? Recently posted on HN. Finding Mona Lisa in the Game of Life https://news.ycombinator.com/item?id=22552006 https://news.ycombinator.com/item?id=22552006 From the article: "This looks kinda cool, but what if we want to find a Life state that eventually, after following the rules of Life for a few rounds, reaches a state that looks like Mona Lisa? This requires working backwards instead of forwards from the target picture, which is a much more difficult problem. (...) We call Life state A the "parent" of state B if A turns into B by following the rules of Life. The reason that it's difficult to find the parent of a state is that the rules of Life are non-reversible. There's no direct way to go from a Life state to its parent, and in fact, it's possible for a state to have multiple parents or even no parents. "

lazyjones 7y ago

I'm sure they can analyze a sample of 2000 years old concrete, but it's not going to look the same as when it was built and it'll probably not be a simple mix of basic elements but very complex. The Romans might have used a mixture with actual lava or corals e.g. and it'd be hard to trace it back to such ingredients.