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Blender 2.8.x / 2.9.x
Get it here: https://builder.blender.org/download
Spherecast (adds SubDiv level 4 + Cast as Sphere).
You can untick ‘Optimal Display’ to see the true wireframe.
Move negative Z.
Boolean > Inset / Outset
F9 > adjust thickness
F9 > tick “Inset Slice” to create a slice.
Uniquify the ‘cap’ so the cutter of the ‘cap’ slice is a duplicate e.g. ‘unique’.
If you now reduce the thickness of the Solidify, there will be an airgap between the cap and the sphere.
Start cutting to reveal the airgap. Cut out a strip. Cut away the front of the cap to see inside.