> It only appears as up and down to you on earth

Up and down aren't anything but appearances. And since we evolved on Earth, with gravity, our experience of "up" and "down" are specifically caused by indicators that tell us which way the center of our planet's mass is. Sure, it's all perception via our sensory systems, and they can get distorted, so we could sense "up" as toward the earth if something in our sensory system gets messed up (pun in that metaphor hah).