TIMELINE: Internet Turns 40 Today… Or Does It?

Sept. 2, 2009— -- The Internet is officially over the hill.

Though it might try to hide its graying hairs, it was 40 years ago today that computer scientists at the University of California, Los Angeles, established a network connection between two computers, creating the very first node of what we now know as the Internet.

At the time, Leonard Kleinrock and his colleagues were charged with developing the Advanced Research Projects Agency Network (or ARPANET), a government-funded research project in global computer communications that eventually grew into the Internet.

On Sept. 2, 1969, Kleinrock and his team succeeded in getting two computers to exchange data over a network for the first time.

Although some celebrate the net's birthday today, others say it didn't really have life until October 29 of the same year. On that day, a message was typed by Kleinrock and sent to the second node at Stanford Research Institute. That, Kleinrock has said, "was the first breath of life the Internet ever took."

It's hardly surprising that a system so complex has a hard-to-pin-down date of birth and many say either date suffices.

"It's valid to consider either one because each involved transmission between computers," said Michael A. Banks, a technology writer and author of "On the Way to the Web: The Secret History of the Internet and Its Founders."

Since its academic beginnings, the Internet has come a long way, revolutionizing nearly every aspect of human interaction.

In honor of the occasion, here's a walk down memory lane and a look at some the Internet's most significant milestones.