bhauth

I was asked to respond to this comment by Eliezer Yudkowsky. This post is partly redundant with my previous post. > Why is flesh weaker than diamond? When trying to resolve disagreements, I find that precision is important. Tensile strength, compressive strength, and impact strength are different. Material microstructure matters. Poorly-sintered diamond crystals could crumble like sand, and a large diamond crystal has lower impact strength than some materials made of proteins. > Even when the load-bearing forces holding large molecular systems together are locally covalent bonds, as in lignin (what makes wood strong), if you've got larger molecules only held together by covalent bonds at interspersed points along their edges, that's like having 10cm-diameter steel beams held together by 1cm welds. > lignin (what makes wood strong) That's an odd way of putting things. The mechanical strength of wood is generally considered to come from it acting a composite of cellulose fibers in a lignin matrix, though that's obviously a simplification. If Yudkowsky meant "cellulose fibers" instead of "lignin", then yes, force transfers between cellulose fibers pass through non-covalent interactions, but because fibers have a large surface area relative to cross-section area, those non-covalent interactions collectively provide enough strength. The same is true with modern composites, such as carbon fibers in an epoxy matrix. Also, there generally are some covalent bonds between cellulose and lignin and hemicellulose. > Bone is stronger than wood; it runs on a relatively stronger structure of ionic bonds Bone has lower tensile strength than many woods, but has higher compressive strength than wood. Also, they're both partly air or water. Per dry mass, I'd say their strengths are similar. Saying bone is stronger than wood because "it runs on a relatively stronger structure of ionic bonds" indicates to me that Yudkowsky has some funda