Fear of the Dark

This is a thought that I've had before, if you came for a monster story or a tale of shadows, turn back

Fear of the dark
There's this one feeling, I can guarantee you've felt it, or even something simililar to it, but I've had it multiple times, and i can't explain it. You just can't fall asleep, and there's no particular reason, but then your air conditioner shuts off, it's as cool as the thermostat says, but you're left in the dark. That's when you get the feeling. The way that the dead silence has its own distinct sort of clamour, or even, well a noise. It just wrenches at your brain for what seems like forever... but then, it heats up a little and your AC kicks on once again. It provides a sort of comforting white noise. That's when the "Darkness Paranoia" kicks in... It's pitch black in your room, the only light is the moon shining through your window, but it's not enough light to see. Thing is, as soon as you shut your eyes, you feel as if there's something staring you down, waiting for you to peek out, and so you don't open your eyes. It's one of the most known combination of of fears, darkness and paranoia. Why are we afraid of the dark though? In addition, why silence? You would think that being able to hear EVERYTHING around you and hear any threats would be calming, but rather, it's unsettling. It seems like an Irrational fear, but it also seems instinctual for humans to fear the dark. And in case you didnt know, most instinctual things, fears included, are for a reason. So as a final thought, explain what lurks in the dark that gave us, or even maybe still gives us, this strange fear...