Expert: Courtney Seligman - 3/2/2010

Question
i have always wondered. is there an up down left and right when you reach outer space? let me explain. lets say you get into your little spaceship and you are able to reach intergalactic space, with complete darkness around you how would you know which way you were going? is up down left right only according to the person in that ship?

Answer
You have pretty much answered your own question, but perhaps the following will help clarify things, without going into so much detail that it just muddies the waters.

Left and right are always defined by your personal right or left. Whether on Earth or in space, if we faced each other, your left would be my right, and vice-versa.

Up and down are another matter. Obviously, on the surface of a planet, its gravity defines those; but in space, in free orbital flight, whether the terms make any sense depends upon whether you refer to a general reference direction, or what you feel or perceive. For instance, if you were in the International Space Station and looked out the window, you might consider the direction to the Earth as down, even though you wouldn't feel any gravitational tug in that direction. That is, you might think of it as down because it "is" down, even though it doesn't give you any physical feeling of up or down. However, if you don't look out the window, there would be no sensation of up or down, so up would be whatever is above your head, and down would be whatever is below your feet, no matter which way you are turned.

Far out in space, where you don't have the Earth or some other body to provide even a reference direction for up and down, the terms would be defined strictly relative to your position. Of course, if one wall was defined as the floor and another as the ceiling, what is above your head might still be called down, if it was toward the floor; but it wouldn't feel as though it was either up or down, unless you were in powered flight, which produced a sensation similar to gravity, due to your acceleration.