Up and down are arbitrary in space. Actually, they're really arbitrary down here. On earth, however, there's a very good reason to have everyone agree on "down"...it's where the earth is, and where gravity pulls us.<br /><br />In physics, I can call up, down, or right, or somewhere just off to the left. As long as I'm consistent, I'll get the same answer (and if I'm not, I'll get the wrong answer).<br /><br />In space, it isn't easy to tell where gravity pulls you, as you're in "free fall" everything else moves along with you. So you may fall towards the earth, but the ship you're in falls at the same rate, with you (mimicking true weightlessness). In such a situation there is no reason to pick one direction over the other as "up" or down. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>