I just built this mob spawner, one of my first, and while I was headed back up to check on it the light glitched out and went from completely dark to completely lit. I've attached a video and some stills to demonstrate the problem.
When I first entered the room and sealed myself in.
A minute later, when the sun had begun to set.
This is a free standing, above ground structure. I made sure that even the entrance I used to get in was completely closed.
As you can see, the light from the sun is shining through the stone, despite completely closing myself off. It even responds to the sun's setting.
I've had something like this happen before. A small area of grass that was completely lit up at night without any light source having been there.
I've tried a range of things: putting up and taking down torches, adding more blocks, breaking parts of the ceiling and closing it up again. Nothing does anything. Does anyone know what glitch is causing this or what can be done to fix it? or am I going to have to tear it down and build a new one?
A couple of notes: I am playing version 1.7.9, vanilla edition, single player, on a mac OSX.