Doug O'Dell, age 11, of Newport Nevzs, Virginia, for him question?

Which way is up in outer space?

To us grounded space agers, down is toward the center of the planet Earth and up goes off in the opposite direction, into the sky above our heads. When the astronauts blast off, our thoughts go with them up, out and away. The familiar directions we knew on the home planet are left behind and there we are, out in an endless ocean of space, with no solid ground beneath our feet.

Out in space, we leave behind our old notions that doom is toward the center of the earth ant up is toward the sky. Out there the endless sky surrounds us, extending, on and on in all directions. What's more, our old earthbound directions of north south and east west no longer apply  From the earth, we select bright stars as markers and chart directions with latitudes and longitudes. Out in space, on a much grander scale, we can use a similar system to guide a starship.

Here at home, we chart positions from fixed positions on the surface of a rotating sphere. Out in space, we must compute our position from the inside of an enormous lens shaped wheel. This is the Galaxy, a vast system of 100 billion stars, all rotating at various speeds around the center. From the earth, were have a flat view across the galaxy and see its teeming stars as the glimmering arch of the Milky Way.

The Big Wheel is about 100,000 light years wide and its central hub is perhaps less than 20 light years thick. This is the central axis around which the whole star system rotates. Naturally the galactic north and south poles are at opposite ends of its central axis. Halfway between its poles is the galactic equator. This runs along near the middle of our view of the Milky Way.

When a starship leaves the earth, it must depend on the Galaxy's poles and equator. It can use there to section outer space into galactic latitudes and longitudes. As we travel through space, our position inside the Big Wheel changes from moment to moment. A starship will need a super computer to chart its changing   positions.

Setting forth from. the earth, it is possible to make a beeline toward the Galaxy's north pole. It is out beyond a dim little constellation called Coma Iierenices. with sharp eyes and a clear slry, We can locate it somewhere between the bright stars Deneb and Arcturus. The galactic south hole is in the direction of a dimmer than dim group of stars called the Sculptor.

It would be nice if the great circles of the Galaxy matched the earth's system of co ordinates. But they do not. This is because the plane of our equator is inclined to the galactic equator. The celestial equator is a great circle directly above the earth's equator. It is inclined 62 degrees to the galactic equator. Hence, out in space, the system of celestial navigation we use on earth is useless.

However, for the first part of our space journey, some of our favorite bright stars may be useful markers to directions through the Galaxy. Antares points to galactic longitude 320 degrees, Deneb to 59 degrees and Sirius to 195 degrees. If doom means in toward the center, then we can drop about 6,000 light years in the direction of the summer constellation, Sagittarius.