Are there directions in space

Ask a question, get a great answer. Learn from experts and access insider knowledge. Answer by Robert Frost , NASA Engineer with specialization in spacecraft operations, orbital mechanics, and guidance, navigation and control systems.

Navigation requires a reference frame. We need reference frames to tell us where we are with respect to other objects and we need reference frames to tell us how we are oriented with respect to other objects. There is no single universal frame that is used for all operations. Typically, the reference frame that most simplifies the mathematics and visualization is used for a particular objective. There is a reference frame that is helpful for pinpointing a location within the ISS.

It is Cartesian and gives locations with respect to forward and aft, starboard and port, overhead and deck. But since that body frame is with respect to the center of mass of the ISS, it doesn't really help us understand the orientation of the vehicle, so we need an additional frame for that, one that can take that X, Y, Z body frame and describe it as rotations about the local vertical and local horizontal.

And, although that frame LVLH is great for telling us the vehicle attitude, it isn't helpful for telling us the vehicle location. We need a frame for that, too. If you are in space and the earth is the nearest astronomical object, you fall towards earth. Down is therefore towards the earth's center and up is away from the earth's center when close to the earth. Down is not towards the earth's South Pole and up is not towards the earth's North Pole.

This mistaken notion comes from the way we traditionally hold flat maps. The Nile river would never flow north if north were really up. Unfortunately, in an effort to explain why north is not up and south is not down, many people conclude there is no up or down in space, which is clearly wrong.

If earth is the closest large body, down is always towards the center of the earth and up is always away from the center of the earth. Nothing magical happens if you are leave earth's surface and board the International Space Station: down is still in the same direction. But if you look at the astronauts on the International Space Station, they seem to be floating around with no sense of up or down. Thanks for reading Scientific American.

Create your free account or Sign in to continue. See Subscription Options. Discover World-Changing Science. Get smart. Sign up for our email newsletter. Sign Up. The orbit of the second star, still intact after its partner expanded and contracted, could set up magnetic field lines that would sculpt the burgeoning cloud into its characteristic hourglass shape. Neither of these explains why the hourglasses all point in the same direction, though. But Rees and Zijlstra have an idea.

The interstellar cloud of gas and dust out of which stars form in the first place spreads out into a disk shape and then condenses, with the newly formed star toward the center of a platter of leftover dust swirling around it.