But how exactly can your body tell it's nighttime? If you get these things only while sleeping at night, does that only mean you need to sleep in the dark? What happens if you travel halfway across the world, and then sleep in a blacked out room? You're still sleeping at the same time that you usually do, and it's still dark, but it's technically daytime where you are. Is there something that the sun puts into the air during the daytime that finds it's way into your house despite having the windows covered?
I don't really know what I'm talking about btw, I'm just throwing ideas around. There could be studies out there that disprove everything I'm saying, but I wouldn't know it.