The biggest threat, in terms of size, is the growing possibility of warfare conducted in space. The Chinese have tested a satellite-killer missile. But for many years, eyes have been on the U.S. as the chief danger.

Beginning with his dream of space-based weapons that to the eternal chagrin of George Lucas came to be called Star Wars, Ronald Reagan began what George W. Bush wants to intensify and expand. The Russians have picked this moment of Sputnik's 50th anniversary and the Space Treaty's 40th to warn that if any country puts weapons in space it will lead to a new arms race. And several peace organizations have chosen this week for an international week of protest to stop the militarization of space.

This is not a science fiction problem. Space-based weapons are not only a new threat to the sense of safety and security of many nations, their use--even their testing--can cause important damage. Right now, our use of space for all that satellites enable us to do is threatened by that most mundane of byproducts: garbage and debris.

It's no small problem. According to David Wright in the Bulletin of Atomic Scientists, "Some 4,500 launches have taken place since Sputnik, and there are currently 850 active satellites in space, owned by some 50 countries, as well as nearly 700,000 pieces of debris large enough to damage or destroy those satellites."

Space-based weapons could make this situation infinitely worse. Too much small debris zooming around the earth could not only disrupt, limit or even end Internet, cell phone and related communication, it could make space travel virtually impossible. If we don't destroy ourselves here (which we still can do--there are still enough hydrogen bombs atop ready missiles to do the job, and that's the quick way; for a slower way, there's the Climate Crisis), then we could imprison ourselves on this planet because spacecraft couldn't make it through the debris barrier. At least until Trek "shields" are developed, there may be nothing like Star Trek in our future.

In the meantime, our best bet is to keep space peaceful and build on the Space Treaty. Unfortunately, it is one of many international treaties that the current U.S. Bush administration ignores and wants to destroy. But as Laura Grego writes in the New Scientist: “While we look back at the achievements of half a century in space, we should look ahead, too, and make it a priority to safeguard our common heritage in space and our security on Earth.”