Tweets and status updates have been buzzing for weeks about DARPA's Network Challenge, even though the event does not officially kick off until 10 A.M. Eastern time Saturday when hundreds of technophiles will compete in an effort to be the first to track down the locations of 10 large red weather balloons positioned across the U.S. throughout the day (pdf).

Commemorating the 40th anniversary of ARPANET (the Internet's predecessor), the event has already met one of its main goals in demonstrating the effectiveness of social networking. Groups have sprung up on Facebook and Twitter to share news of the challenge and recruit team members for more efficient geographic coverage, and there is a wiki where game-day strategies are being discussed.

Saturday marks exactly four decades since DARPA's predecessor, the Advanced Research Projects Agency (ARPA), connected four computer network nodes for the first time. This doubled the size of the fledgling ARPANET, which would later grow into today's Internet.

DARPA's Transformational Convergence Technology Office (TCTO) created the Network Challenge to acknowledge this important moment in Internet history as well as to provide a test bed for better understanding the dynamics of social networking. The agency will award a $40,000 cash prize to the first entrant (an individual or a team) that submits the latitude and longitude of all 10 balloons. The balloons will be lofted 30.5 meters into the air at locations that DARPA says will be visible from nearby roadways; agency representatives will be present at each locale.

As of Tuesday, 300 teams had registered to compete and submit balloon coordinates to the TCTO.

The nature of the challenge provides some sense of how far the Internet has come, considering the resources that would have been required to compete in the same event in 1969. Back then, participants would have needed an affinity for navigation to be able to compute a balloon's coordinates, and they would have had to rely on long-distance phone calls, most likely from public phones if they were reporting in from the field, to register their findings with DARPA, says Peter Lee, TCTO director. Today's portable GPS units, phones and computers as well as Web-based mapping software remove a lot of barriers, he says, adding: "That contrast is really remarkable."

The way people are networked socially via the Web today, they can be part of a team without necessarily leaving their homes or even living in the U.S. Some people might even do the legwork and then offer to give (or sell) information to participants, Lee says. "We want to understand the effect of trust in social networks," and the prize money offered is one element of the competition meant to test that trust, he adds.

"This is not just a commemoration of 40 years since ARPANET, it's also a science project," Lee says, adding that his office plans to interview winners to find out how they approached the challenge and what was (and was not) successful.

Just one of the many fascinating aspects of the Internet's birth was the remarkable farsightedness of the people developing the systems, protocols and networking technology to make it all work. "There were technical decisions in terms of routing and packet switching that really looked ahead at scaling up," Lee says. "Who knows why they did this, but it turned out to be genius."

The same year that Neil Armstrong and Buzz Aldrin walked on the moon, the new ARPANET was used for the first time in a demonstration to show how people working from different locations could collaborate on the same document, notes Lee, who joined DARPA in August for a two-year stint, taking a leave of absence as head of Carnegie Mellon University's Computer Science Department. "Zoom ahead 40 years," he adds, "and you can hardly find anyone who hasn't been touched by, and whose life hasn't been improved by the Internet."