Measuring Hollow Sphere Diameter with Compass & Ruler

[jmprada]

Using only a compass and a ruler, how can we measure the diameter of a hollow sphere?

 

[I like Serena]

Using only a compass and a ruler, how can we measure the diameter of a hollow sphere?

Hi jmprada! ;)

Here's my attempt.

Spoiler

We use the ruler to draw a straight line on the inside of the sphere.
The line will go all the way round and form a great circle.
Repeat and draw a second great circle.
Those 2 great circles will intersect each other in 2 points.
Measure the distance between those 2 points and we have the diameter.