Don't understand what's happening

I’m trying to understand how transparency works in blender, and having a hard time with it. I have a green cube inside a red sphere. Half the sphere is transparent. I can see some of the cube but not the bit I should be able to see. I’ve used a ramp mapped to the alpha input of the material to create the half transparent part of the sphere (using material nodes). The sphere is a NURBS sphere but I don’t think that should make a difference. Blend file attached.

Turn on Z-transparency?.. I dont know anything about ramps… so I am not sure.

,Nik

I think the problem was that you have joined texture node’s ‘color’ with output ‘alpha’ directly. You should have mapped texture’s ‘color’ to ‘alpha’ of extended material node (look at the picture). And also unselect ‘col’ button under ‘map to’ tab.
http://www.quickfilepost.com/showimage.do?filename=trans.jpg&seed=b1aa9d8d0c0a3b04702863b454591397&code=53616c7465645f5f819f74ca457db527acbb9ea666e35d767862fc00977e49a8

And why you’re using nodes? You can simply select ‘alpha’ in the same ‘map to’ tab.

The picture somehow wasn’t added:
http://www.quickfilepost.com/download.do?get=b1aa9d8d0c0a3b04702863b454591397

krizas, thank you so much :D. I’m using nodes here mainly because I want to learn how to use them, as they can produce more complex results than ‘the old way’. I wasn’t really aware of the Extended Material Node until now (yes, it is in the menu, should have looked into it further). Also, it’s easier to follow tutorials written for Maya because they use node based shaders all the time.