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.
The First Message Sent Over the Internet
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.
October 29, 1969 – Kleinrock sends first the message between two nodes, from UCLA to Stanford. The message was supposed to be "login" but Kleinrock was only able to type "lo" before the system crashed.
1971 – Ray Tomlinson, an engineer with BBN Technologies, sent the first network e-mail, choosing the @ symbol to separate the user's name from the host computer name. Why?
"Mostly because it seemed like a neat idea," he has said.
ARPANET Goes Global, Grows Into the Internet
1973 – ARPANET goes global with two international nodes, one in the U.K. and one in Norway.
1979 – CompuServe and The Source offer the first online services. Users paid an initial fee and then hourly fees to read news or financial information or read news or chat.
These services marked a "really big step" in bringing consumers – not just academics and government officials – online, Banks said. Although the users couldn't communicate with users of other networks or access information hosted on other networks, they still formed some of the first vibrant emerging online communities.
1980 – CB Simulator, the first online chat service, goes online. The service was hatched by CompuServe and was named after the Citizens' Band radio, an extremely popular radio service that let individuals communicate via radio over short distances.
"Lives were changed immediately. People stayed online longer and later, fascinated with the ability to interact with several people at once," Banks writes in his book, "On the Way to the Web." "The online world and its denizens took on a new aura of reality, and the online experience grew far more entertaining and unpredictable."
The Internet's First Worm
1988 – Robert T. Morris, a graduate student at Cornell, unleashed the first widely known computer "worm" (or virus that spreads over the Internet). Morris said it was a benign experiment gone awry but prosecutors said he caused hundreds – if not tens of thousands – of dollars in lost productivity for each computer affected.
He was sentenced to three years' probation, community service, and a fine of $10,000 plus legal costs. Despite his run-in with the law, he went on to great success, eventually joining a startup that was bought out by Yahoo.
Now, he's a professor in the Computer Science and Artificial Intelligence Laboratory at M.I.T.
1989 – Quantum Computer Services, which is now AOL, introduces America Online. The service included games and chat services. By 1994, it had reached 1 million users, or about a third of the consumer online population, Bank said.
Tim Berners-Lee Introduces the 'World Wide Web'
1990 – Tim Berners-Lee, a British scientist, coins the phrase the "World Wide Web." Though digital denizens now may use the "Internet" and the "Web" interchangeably, there are actually not synonymous. The Internet hosts the Web, which is Berners-Lee's breakthrough.
While working at CERN, the European Organization for Nuclear Research, he devised the Web as a way to organize, address and link information on the Internet.
1990 – The non-profit Electronic Frontier Foundation (EFF) is founded by Mitch Kapor, John Gilmore and John Perry Barlow, three technologists who were part of the WELL (Whole Earth 'Lectronic Link) community. David Weinberger, a fellow at Harvard's Berkman Center for Internet & Society, pointed out the importance of this group that, since its inception, has advocated for the public interest in digital rights issues.
1993 – Mosaic, the first Web browser to display images with text, is released by Marc Andreessen and his colleagues at the University of Illinois.
1994 – Some of the founders of Mosaic launch Netscape, the first commercial browser.
Yahoo!, Amazon and Google Come Online
1994 – Stanford Ph.D. students David Filo and Jerry Yang found Yahoo.
1995 – Jeff Bezos brings Amazon.com online, helping to revolutionize online retail.
1998 – Larry Page and Sergey Brin, computer science engineers who met at Stanford, incorporate Google (named for "googol," a mathematical term for the numeral 1 followed by 100 zeros).
1999 -- Three friends launch Blogger, a user-friendly, free blogging platform. Although Weinberger emphasizes that the blogging movement can't be traced back to one particular moment, he said that in terms of the popularization and rise of blogging, "the creation of Blogger was really important."
1999 – Craig Newmark incorporates Craiglist.org as a for-profit online classifieds site. It started in 1995 as an e-mail list for friends and co-workers about San Francisco Bay Area events. As of August 2009, it had expanded to more than 700 cities in 70 countries.
2005 – YouTube is launched and helps drive user-generated content to the mainstream.
Smart Phones Bring Mobile Internet to Millions
2006 – Facebook expands to include anyone over college age. Although Mark Zuckerberg started Facebook (initially called thefacebook.com) in 2004 while a student at Harvard, it didn't become an online force until it expanded beyond college students.
"When it launched it was a Facebook replacement for college. The day it became a genuine platform was when they opened it up," said Harvard's Weinberger.
2006 -- The one millionth article is published on Wikipedia, the online encyclopedia that anyone can edit. It launched in 2001 and quickly became the reference site of choice for Internet users. By contrast, Weinberger said that Britannica contains 65,000 articles.
2007 – Apple launches the iPhone. On June 29, Apple's hotly-anticipated smart phone went on sale, making wireless Internet access accessible to millions more. Just 74 days after its introduction, Apple sold the 1 millionth iPhone. Now, more than 40 million users access the Internet from iPhone and iPod touch models, in addition to millions of others who go online with BlackBerries and other mobile devices.
2008 – ComScore, an online analytics firm, reports that the global internet audience (aged 15 and older from home and work computers) surpassed 1 billion visitors in December 2008. The company reported that China topped the list of the most connected countries, with 179.7 million users. The United States came in at second with 163.3 million users.
The Associated Press contributed to this report.