On the first day of the Noughties, I sent my first email. I sent it from a different world - one in which spam was something my nan ate from a can, blackberries were a fruit you picked from a tree, and where if you told somebody you wanted to poke them, they'd punch you in the face. On the day I joined the club, there were 200 million people with email accounts. Today, there are 3.2 billion. It seemed to me that day to be a fad. Today, it seems like a second skin, spreading out over all my friends, all my colleagues, and all the world. The internet has transformed the way we think about ourselves - the groups we belong to, the information we know, the people we date, and even our sexual fantasies. The story of this decade is the story - in all its strange sinews - of the World Wide Web.
The only parallel that can help us understand the change we are living through is the invention of the printing press by Johannes Gutenberg in 1450. Until that moment, every book had to be written out by hand, by a tiny clique of monks who were known as scribes. They were the filter through which all knowledge could be transmitted or received. This gave the Church near-total power over writing. Any sophisticated communication happened on their terms, through their men.
But the invention of moveable type erased that world from history. Suddenly, the circle of people with access to information widened dramatically. The Bible could be bought and owned by any literate person - and holding it in their own hands in their own homes, they began to develop their own ideas about it. The Protestant rebellion against Catholic theocracy rose and racked Europe in a way that could never have happened if the limited scribblings of the scribes were the only way Europeans could talk to each other.
In the longer term, the printing press went even further and delivered popular nationalism into the world. The scribes wrote in Latin, and their work spoke to a tiny pan-national European elite who identified with each other not by country but by religious creed. The new presses made it possible to write in - and standardise - languages. Places like "France" or "Germany" could talk to each other in print and begin to develop a consciousness that they were one people with shared interests.
The internet might look at times like a newfangled way to go shopping or look at porn. But just as Gutenberg shifted power over information from the Church to anyone with a printing press, the internet has shifted power over information to anyone with an internet connection. Today, you can publish anything you like, to anyone on earth, for almost nothing. You can whip up a group of people with the same interest as you in a few hours. You can talk to anyone else on Earth, via Skype, for as long as you like, for nothing.
If global warming gives us that long, the long-term implications will take centuries to tease out, but for most of us the effects have been felt at first in our personal lives. It has cut straight to one of the most intimate relationships we have - how to find a partner.
In 2001, I met my then-boyfriend online, and we were too embarrassed to tell anyone that that was how we'd met. Today, every singleton seems to have a portfolio of dating profiles: five million people in Britain alone are currently seeking love online, and 15 per cent of couples met in cyberspace. It has made dating more likely to succeed and simultaneously more brutal. In the past, you had to hope that your friends would somehow introduce you to a suitable person, or that you would magically bump into them in a club. Today, you can find the four other people who like Salman Rushdie novels, or hiking in the Lake District, or reiki "healing", on www.mybestfriend.com.
But I suspect that at the same time dating has become more like shopping for men or women: we have become more ruthless in assessing people according to a checklist - too bland! Not rich enough! Too posh! - and dismissing the chance of a chalk-and-cheese attraction.
The internet has transformed the way we interact with our friends, too. When I sent that first email I was at university, and my main way of communicating with my friends if their phone was off was to leave a written note - on a piece of paper! - on their door. When I told this to my 10-year-old nephew, he gasped, as if I was describing how we had to hunt and kill our own food and then cook it on an open fire built from damp twigs.
Now, we are "in touch" with our friends more than ever: I can tell you what Jess had for lunch, what Rob is listening to at the moment, and how Chris is getting on with his holiday in France. But I haven't actually spoken to them: I have glimpsed their Facebook or Twitter feeds, while myself listening to the radio, brushing my teeth, or trying to write this article.
Social networking sites are a genuinely new way of interacting: you can feel close to somebody without actually speaking to them from one month to the next. It also keeps people in your orbit who would normally have slipped away. I know, for example, that the girl I used to sit next to at primary school has spilled coffee on her laptop three hours ago, and a woman I met at a checkpoint in Gaza is glad Lloyd was voted off The X Factor. At some point in my life, some of these people will loop back into real interaction with me, maybe, but for now they remain a constant comforting source of inane babble.
But is it more? Recently, an old friend I hadn't seen for 10 years committed suicide. I instinctively went to her Facebook page, and so, it seemed, had everyone else who knew her, leaving messages of regret and love and loss. I found myself reading over her old status updates. She was clearly trying to communicate pain and isolation - but we all missed it, leaving inane comments and thumbs up and tossed sheep below every plea for help. Could we have known, if we had read it less casually? Or am I projecting backwards?
The contrast between the transitory nature of a Facebook status update and the permanence of death made me wonder if all this social networking is actually a way of keeping people at a distance - a way of having a "friend" but not having any of the commitments and duties of friendship. When the sci-fi novelist William Gibson first put forward the notion of "cyberspace", he described it as a "consensual hallucination", where we pretend we are together, when in reality we are alone. It seemed true that night.
And yet, and yet ... the internet has a way of drawing people together who would previously have wandered around unconnected. Obsessed with 17th-century Bulgarian furniture? Or the theme tune to The Littlest Hobo? Or the diplomatic history between Germany and Angola? Before, you would have talked only to yourself. Today, there is a message board waiting for you, filled with like-minded people. And yes, it often does translate into "real" meetings. Just look at www.meetup.com or the dozens of sites where people with shared niches are meeting and becoming friends or falling in love. It's a starburst of human connections. My favourite are "flashmobs" - groups of people who gather in a public place, at a time previously agreed online, to do something gorgeously silly. I have seen a huge adult pillow fight in Belfast, a party on the Circle Line to celebrate the last night you were allowed to drink alcohol on the Tube, and a mass moonwalk at Liverpool Street station in memory of Michael Jackson.
But there's a vicious downside too. Before, pedophiles who wanted to swap porn, or anorexic girls who wanted to swap tips on how to starve themselves, or Coldplay fans, would have been isolated too. The chances of meeting another person like them were vanishingly small. Today they, too, come together at a click of a mouse. The internet gathers the good, the bad, and the ugly, all alike.
Perhaps the most overwhelming aspect of the web is the sheer tsunami of information it contains. Today, every laptop with an internet connection contains more information than the Great Library of Alexandria. At its peak, that library contained 700,000 books, until the Christian Emperor Theodosius I ordered it burned down in 39(12A)D; today, Google Books has over seven million - and that's before you count everything else online. In 1941, Jorge Luis Borges wrote a short story imagining a "total library" containing all written information. Seventy years later, it exists. It's hard to conceive of how privileged we are as the first generation of human beings who, for almost no cost, can pore through everything previous generations of humans have written down. People travelled for thousands of miles and fought and died to get access to information we have, just a mouse-click away.
The truth is more accessible then ever. At the height of the Vietnam War, only a few obscure bookshops stocked the critical writings of Noam Chomsky. Today, every voter can read his deconstruction of the Afghan and Iraq wars for free - although it still has to contend with the endless machine of bogus news that dominates our discourse.
Yet the internet can at times seem to promote the spread of lies faster than the truth: the "movements" of 9/11 Truthers or Obama-isn't-American "Birthers" have thrived in the bowels of the web. Rumours and misinformation that would previously have passed through a few hundred people now fan out to millions and become regarded as Received Truths. There's an irony in the fact that Al Gore - who played a crucial role in bringing the internet to us - became the first major victim of this internet tendency to amplify lies and let them multiply. As a Senator in the 1980s, Al Gore was fascinated by a system of connecting computers that he discovered had been pioneered by the Pentagon. He was instrumental in getting funding for them to experiment in using this more widely - and if he hadn't, the internet as we know it wouldn't exist. When he was running for president in 2000 he understandably bragged about this - but a stream of bloggers falsely quoted him as claiming he had "invented the internet". The idea spread, and it was used as one of the main ways to ridicule and discredit him as a "liar".
But the spreading of lies like slurry isn't unique to the internet: it was the print and broadcast media that told us incessantly Saddam had weapons of mass destruction. Yes, in an ocean of information it's often hard to separate the bullshit from the clear blue water. But at least online we have the opportunity to do it: in the old world, you had what the TV or print news gave you, and you had to leave your house and hunt hard for the rest.
But there's a catch. We expect this information to be free - no matter what it costs to produce. This means the beating hearts have been ripped out of the news-paper and record industries. Their products are scattered across the world for free. This is obviously good news for the consumer in the short term - but only while enough other people pick up the tab by buying the dead trees and CDs. As they fall away, there will be a hole left. We will never know all the news stories that won't get written, or the songs that will never be recorded - and there will be many. But what can be done? Attempts to erect pay walls now - as Rupert Murdoch is committed to starting - look like King Canute trying to hold back the flood of cyberspace. Once it can be digitised, it will be copied. On the web, information wants to be free - even if it means less of it will be produced.
Just as you are tempted by spin off into digital utopianism, these snags keep pulling you back. The great 18th-century German philosopher Johann Gottlieb Fichte (Google him) saw ahead to the moment all information would be available to everyone when he wrote: "When every useful discovery made at one end of the earth shall be at once made known to all the rest, then, without further interruption, without halt or regress, humanity shall move forward to a higher culture of which we can at present form no conception." But presented with all this information and all this knowledge, what is the single biggest thing we turn the internet to provide? Porn. Half of all web traffic is to sex sites.
As the musical Avenue Q puts it: "Why do you think the net was born?/Porn, porn, porn/So grab your dick and double-click/The internet is for porn." Before, porn was something you had to seek out, in highly embarrassing circumstances, and it was soft-core. (I saw porn twice in my teenage years; I remember both times.) Today, the most hard-core imagery is constantly seeping into your inbox, where the invisible hand of the market is offering to you an invisible round-the-clock hand job.
How is this changing us? There is something healthy about openly sexual images breaking into puritanical societies: half of all Saudi men, for example, watch online porn, even as women are forced to cover their faces outside. Yet porn injects teenagers at an impressionable age with wildly unrealistic expectations of sex. Go to any provincial city centre club on a Saturday night and you'll see plenty of teenage girls harming themselves by trying to live up to it. And what about the boys? Professor Jennings Bryant, a US psychologist, wanted to discover what happens to men when they are exposed to massive amounts of porn. His test subjects quickly became bored with vanilla porn, and started to seek out more and more extreme strands. Men who before had said they found violent or rape-fantasy porn unacceptable were soon "enjoying" it. It suggests a dark side to this Dionysian frenzy that we are only beginning to see.
This endless pornucopia of splayed women is only one way in which the internet addles our attention span. The journalist Maggie Jackson observed that the internet has reduced us to a kind of mass ADHD, writing: "The way we live is eroding our capacity for deep, sustained, perceptive attention - the building block of intimacy, wisdom, and cultural progress."
It's not hard to understand what she means. In the time I have been writing this article, I have received 36 emails, four texts, two phone calls, and seven instant messenger chat requests. We live in a state of "permanent partial attention", where we are trying to focus on five different windows at once. But as human beings, we're not very good at it. We evolved to focus on one big task at a time. We can adjust to a degree: if you look at brain scans of "digital natives" - kids who were born in the internet age - they look different to us "digital migrants", who came to it as adults. They can focus on more scattered distractions for longer. But we can only adjust so far. Researchers at Loughborough University recently found it takes 64 seconds for a person to recover their train of thought after it is interrupted by an email. If you check your email every five minutes, you lose 8.5 hours a week. At times, it feels like we are all desperately trying to recover our lost thread, before the next email hits.
That's why, much as I love the internet, I try to keep myself on a quite strict digital diet. I aim to only read my messages once in the morning and once at night. (I lapsed today, as I do about half the time.) I don't own a Blackberry, or even a laptop. I won't get a phone where I could neurotically check my messages. I try to keep the internet confined to the corner of my work room, and when I fail, I feel my life leaching away from me on Twitter or Google or blogs, while piles of great books go unread.
There's another strange aspect to internet communication: our systems of etiquette haven't caught up. I find it much easier to get into arguments with people online than I ever would on the phone, or in the flesh. It's partly because you can't hear their tone of voice: you can read hostility where there is none. (This is one of the reasons we have invented the abhorrent "emoticons", those smiley or frowning faces made out of punctuation marks. We need to show people that, however it sounds on a cold screen, we are friendly.) We write emails as casually as we make a phone call - but we read them with the seriousness with which we take a letter. Something written in a casual second can be reread and reread for hours. We need to develop a new system of netiquette - but how?
From this smorgasbord of small observations, does anything as vast as the changes wrought by Gutenberg become visible, even at any early stage? Just as the printing press made new identities - Protestant or national - possible, I think you can see the embryo of new identities emerging online, and then tumbling out into the world. Here comes another irony: contemporary jihadism defines itself in opposition to modernity, yet it is in part the product of the internet. If a Muslim boy living in Bradford in 1980 thought he had more in common with a boy in Gaza, he would have been very odd. Yet today, he can spend all day talking to the boy in Gaza on Skype; he can watch videos of atrocities in Gaza 24/7; he can spend most of his time networking with like-minded Islamists scattered across the globe. The idea of an Umma - a global Muslim community - no longer seems so abstract.
The web has, in turn, made possible a global web of jihad. Previous violent militants - like, say, the IRA - were shaped like national armies, with military command at the top, and footsoldiers at the bottom. Al-Qa'ida is shaped like the internet: it is a diffuse group of loosely associated people with no central organising hub. This kind of passionate post-national identity could flourish in other instances - like in a global environmental movement, for example (although this would obviously be morally the opposite of al-Qa'ida). I suspect this will be one of the trends that only grows from here, the dawn of the web. The internet collapses space and time, in ways that will change the world's politics.
Yet there is a fight looming about whether the internet will remain open enough to achieve this, or any of its greatest potential. Today, we have a doctrine called "net neutrality", which means all internet servers have to treat websites alike. Once you are online, you get treated the same, whether you are the BBC or a blogger in an attic in Mumbai. We can all plug and play. But the telecoms corporations want to change this. They are demanding the right to charge companies to have faster-streaming sites. So (say) Facebook could pay a premium to ensure it will load quickly, while any site you set up would take ages and have patchier service. John McCain is leading the charge for the telecoms companies - and, by a strange coincidence, he is the single biggest recipient of their political donations. As Al Gore put it, these proposals threaten "the very fabric of the net". If they succeed, the egalitarian ethos of the web will be badly dented.
As I was trying to think through all the ambiguities of the internet, I found myself haunted by a thought. What if you logged on tomorrow and the internet had vanished? In 2007, the Russian government punished Estonia for removing a Soviet war memorial by launching a "cyberwar" - a bombardment of hacking and viruses that brought their computers down for weeks. The country was in chaos. Their banking, government and business all existed online. Without their machines, they were paralysed. What if somebody could do the same everywhere and bring the internet down worldwide?
Would we be relieved to be suddenly freed from the endless pings of pointless emails? Would we find our concentration spans mysteriously widening again? Would we start to look at the people around us with a clear gaze, rather than at a torrent of status updates? Would we see the newspaper and record industries rise again, as people had to pay for their goods once more? Maybe. But I suspect we would we feel oddly alone if the great global conversation with 3.2 billion other people - the conversation that has defined the Noughties - went dead.