Lighting of points in an OpenGL sphere

Hello friends,

I'm very new to OpenGL, so apologies if I'm missing something obvious (although I'm hoping it is obvious). I've tried and tried, and just can't figure it out :-/

I'm creating points around a sphere, and I'm wanting to use lighting to create depth as it rotates. But rather than the points at the back being darker than the ones in the front (or closest to the light source), it's just fading in and out.

Here's the patch, I've annotated what I'm trying to do.

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Thank you so much for any help you can provide!