I believe it's referred to as the void. I'm referring to the lighting effect that happens when you're at, or close to, bedrock level. There doesn't seem to be much of a purpose for it in town. I personally wasn't aware it until it was too late. I usually don't lay torches or anything while I dig in town because it saves time to just turn up your brightness instead. I completed half of a wool farm before I knew what was happening. I made this great looking wool farm and I can't even enjoy it without drilling a shaft down the center of my property and standing directly under it. All I'm saying is that I'd like to enjoy the entirety of my property and not be restricted by silly mechanics that aren't necessary in town.