Curvature of a plane given a circumference I was skimming through a certain book when I came to an interesting passage.

And he made a molten sea, ten cubits from the one brim to the other: it was round all about, and his height was five cubits: and a line of thirty cubits did compass it round about.

On a flat plane, 10π≠30, so what radius of a globe would you need to have so that a diameter of 10 creates a circumference of 30?

Take $\alpha$ to be the (half) angle of a cone with apex at the center of the globe, and intersects the globe with a circle.
The relation between the diameter $d$ (arc distance) across this circle, the globe radius $r$, and $\alpha$ is $2 \alpha r = d.$
The relation describing the circumference of the circle is $2 \pi r \sin \alpha = 3d.$
Ten cubits is, let's say, $4.572$ meters (according to Google). So
$$r \alpha = 2.286 m; r \sin \alpha = 2.18296m.$$
The value of $\alpha$ that allows these equations to be consistent is around $0.5236$ radians, which means that the radius of the globe would need to be about $4.36 m$.
So, this gives strong evidence that $\pi \approx 3$ was used, rather than careful non-Euclidean geometry.
