Wikipedia has blacked out its English-language site for 24 hours. So how will its regular readers get information?
Work-averse students, corner-cutting journalists and people who simply enjoy wasting time online are in for a testing day.
Wikipedia, the user-generated internet encyclopaedia, has taken part in a temporary "blackout" in protest against the proposed US anti-piracy laws known as Sopa and Pipa. Users attempting to access the site see a black screen and a political statement: "Imagine a world without free knowledge."
Perhaps the most loyal Wikipedia addicts will find this a pleasant change. Alternatively, for those who have come to depend on it, the withdrawal symptoms might be excruciating.
Either way, the shutdown offers a rare insight into what the modern world would look like minus Wikipedia.
Go to the library
Those feeling lost without Wikipedia can turn to that most traditional of research tools - the book.
It's a habit they should get into more often, according to Andrew Orlowski, executive editor of technology news site The Register.
While he believes the internet's egalitarian ethos has been a positive force, Orlowski fears that it has also come at the expense of standards of scholarship and expertise normally required by editors of the printed word. "It encourages a kind of intellectual laziness," he adds.
The campaign to save libraries in the UK threatened by cuts might suggest they continue to occupy a unique place in the public affections, regardless of hi-tech competitors.
But for Dr Mark Graham of the Oxford Internet Institute, who has studied the Wikipedia phenomenon, they have some serious disadvantages compared with their online equivalents.
"For many people just getting to a library is hard, it's time-consuming, whereas you can consult Wikipedia anywhere, from your phone," he says. "It's open access, it's free."
Pick up the phone
It's the time-honoured technique employed by fact-checkers, researchers and journalists. If in doubt, ring an expert and ask them.
Orlowski believes it is a habit many regular Wikipedia readers could benefit from adopting. A university professor, for instance, will have attained their status though hard work and study, he says - Wikipedia editors, by contrast, only need a broadband connection.
But supporters of the site argue that it does not claim the same authority as peer-reviewed scholarship and should, instead, be seen as a starting point for research.
Moreover, Graham argues that Wikipedia's collaborative editing ensures mistakes are quickly corrected - a verdict backed up by a 2005 study by the journal Nature.
"It's hard to keep blatant falsehoods up for long because there are so many eyeballs on it," he says.
It might not be apparent from some of the more fevered coverage of the shutdown, but there is plenty of internet out there beyond Wikipedia.
As such, the site's rivals no doubt braced themselves for a surge in traffic.
Those looking a reference fix can turn to the online edition of the Encyclopaedia Britannica, which claims to be the oldest such compendium still in print.
Online-only alternatives include Scholarpedia, whose entries are peer-reviewed by experts, Encyclopedia.com, and Citizendium, which was set up by Wikipedia co-founder Larry Sanger.
If all else fails, those who cannot cope without Wikipedia for 24 hours can familiarise themselves with Google cache.
See for yourself
For the most dedicated browsers, it is perhaps the most radical solution of all - switch off your computer altogether and see the world for yourself.
Orlowski hopes this is a trend that catches on. While the internet has undoubtedly broadened the scope for sharing human knowledge, he argues, people have become accustomed to acquiring knowledge through their computer screens rather than first-hand.
"The primacy of direct experience has definitely been lost," he says. "People end up relying on other people's opinions."
Graham agrees that looking beyond Wikipedia's parameters is no bad thing. For instance, the site tells us a lot about the West but considerably less about Africa, he argues.
"Wikipedia does a great job of telling us what it knows about," he says. "But there are huge gaps."
Use your memory
Or can they?
Orlowski suspects many dedicated web users have, like him, become too accustomed to the ease and convenience of search engines and online sources to depend on their memory.
"It's too late for that," he says ruefully. "It's like second nature now."