Question about how root fills volumes with medium

Hello dear rooters,

I have a question and i think you can help me:

Suppose that i create a box as top volume (world), associated with a medium (air for example). In this box, i put a hollow tube in iron. Inside the tube, there is air or nothing (vacuum) ?

Thank you in advance

Hi Thomas,

Whatever empty space remains after adding a daughter volume has the same medium as the mother.