anyone not know this already?.. it seems pretty obvious
Pretty obvious the world is flat too, but it's helpful to use the scientific method to confirm whether or not it actually is.
Actually, it's pretty obvious that the world is round if you have some basic math. Or stand up on a westward-facing beach and watch the sun set a second time. We've known the world was round since way before Columbus, it's just that we could do the math and knew it was WAY too far around the ocean to India to make it, so nobody else was stupid enough to try. Columbus was REALLY lucky there was a landmass in the middle.
However, in my experience the connection between colds and sleep is even more obvious. The more sleep you have, the weaker the cold becomes, and vice-versa. Vary your sleep a little and you'll see it's as directly observable as "When I drop a rock on my foot, OUCH!"