2010-02-23 [Sunrose]: "Build" stuff :P
2010-02-23 [Hedda]: Hey, that is complicated engineering! The old Egyptians and Greeks didn't know how to build arches!
2010-02-23 [Hedda]: And that is actually a hyperbolic cosine, which is post-Newton kind of math.
2010-02-23 [Sunrose]: Oh I thought they did know how :O
2010-02-24 [Hedda]: They did? But they didn't build any.
2010-02-24 [Sunrose]: Didn't Eqyptians carve into rocks and make caves that way, with an arch at the entrance?
2010-02-24 [Hedda]: No, there are no arches even there:
But carving a round hole isn't the same as building an arch out of stone. An arch might seem like an obvious way to build a roof, but if you have never seen one it isn't obvious at all that it's a better way to do it.