A space invader is here: an intergalactic war is going on, but not the kind we used to read about in science fiction magazines.(Andromeda galaxy on a collision course with Milky Way)

AN INTERGALACTIC WAR IS GOING ON, BUT NOT THE KIND WE USED TO READ ABOUT IN SCIENCE FICTION MAGAZINES

It's a galaxy-eat-galaxy universe out there. Big ones eat little ones, then the big ones "merge" with other big ones. Mergers start out as collisions. Two spiral galaxies sail into and through each other, pulling long trails of stars behind them, then come back and do it again. Along the way, they compress each other's gases to trigger the formation of stars, hot stars brighter than a welder's torch. Finally each is caught by the other and they merge. The two galaxies may have been the breathtaking pinwheels of astronomy picture books before the merger, but afterward all we see is a blob of light known as an elliptical galaxy. The "Local Group", namely our own and Some 25 other galaxies, someday will be one.

It could happen here. The Andromeda galaxy and we in the Milky Way galaxy are heading for each other at 300,000 miles per hour. And no one, no one, is doing anything to stop it. The excuse is that the collision, if there is one, won't happen for another three or four billion …