In an invitation echoing the sentiments of the French Revolution, a Paris-based group is offering people around the world a chance to include their hopes and dreams in a time capsule to be launched into space. "Every person living on Earthsmall, weak, powerful, or rich," says project leader Jean-Marc Philippe, "is provided with four pages of liberty and equality." Free of censorship, anyone with Internet access or a postage stamp can participate. The only hitch: your message wont be read for 50,000 years.

Even the projects name, KEO, is symbolic of the teams attempt to represent the diversity of Earths cultures. The name KEO was chosen because the three sounds composing it can be pronounced in all languages. Scheduled for launch by Arianspace around the end of 2006, Philippe says "KEOs memory banks are large enough to host messages from every one of the 6 billion inhabitants of Earth."

But why not bury the messages, like other time capsules? Why subject them to the vicissitudes of space flight? "Space appeals to the human imagination," Philippe says, "and KEO is addressed to the imagination of each person." In addition, burying the message would require selecting a locationintroducing a geographical bias that contradicts the projects spirit of universality. And though there are risks to placing the message disks in Earth orbit, the environment of space is separated from catastrophes on Earthwhich could be significant over a 50,000-year span.

Protected by several layers of shielding composed of aluminum, titanium, and tungsten, KEO still remains susceptible to impacts during its journey. Orbiting about 1,800 kilometers above Earth, perhaps the greatest danger to its safe return is impact by a micrometeorite or space debris created by humans. Philippe is optimistic that humans will learn to control their pollution of space, given the risks that space junk poses to other missions.

Even if the space capsule safely returns to Earth, would its messages still be readable? As a test, the National Grand Accelerator of Heavy Ions (GANIL) in Caen, France bombarded message-bearing glass disks and DVDs with radiation to simulate the space environment. After exposure to ten times as much radiation as the craft will encounter over 50,000 years, the data remained intact.

Suppose the probe makes a safe landing on Earth as scheduled, with its messages preserved. Will the meaning of these messages ever be understood?

Decoders would need to overcome two hurdles. First, they would have to figure out how to play the DVDs. A somewhat similar challenge was anticipated by the makers of the interstellar recordings attached to two Voyager spacecraft launched in 1977. In that case, the messages were encoded in copper phonograph records, coated in gold. These Voyager missions had the luxury of each including a stylus to aid playback, with instructions about how to place the stylus on the record and turn it at 16-2/3 revolutions per minute. These instructions were etched in the records protective covering, written in a language of math and science. A similar tutorial is being developed for the KEO messages, though weight restrictions prohibit sending along a DVD player.

If our far distant descendants can reconstruct the format, will they be able to understand the contents? Will any of the languages spoken today remain in use that far into the future? If not, the first people to comprehend these messages from the twenty-first century may be scholars specializing in long forgotten civilizationssuch as ours.

"Even though KEO constitutes a formidable gift for future generations," Philippe says, "its real interest lies in the impact it will have on us today." To facilitate better human self-understanding, all messages will be freely available over the Internet, after removing identifying information to preserve anonymity. Though readers will be able to peruse individual entries, the project team is also developing computerized methods to analyze the content of the messages, with the hope of answering the questions "Who are we?" and "What could we do together to realize a more human world?"