In protest of the Stop Online Piracy Act, Wikipedia will go dark tomorrow. From 5 a.m. GMT tomorrow to 5 a.m. GMT Thursday, the English version of the website will be inaccessible to anyone around the globe. Instead, an explanatory letter will greet visitors and urge Wikipedia fans to contact Congress to express disapproval of the anti-piracy act. Wikipedia is the sixth-most visited site in the world, and it’s estimated 100 million English-speaking users will be affected.

Wikipedia’s participation is a definite boost to the Reddit-led anti-SOPA blackout, which, up to this point, had secured only the participation of lesser-known sites. Still, the decision by Wikipedia founder Jimmy Wales to actively join the strike didn’t inspire other Internet bigwigs to follow. In fact, it just led to jeering. Twitter chief Dick Costolo, for example, tweeted, “That’s just silly. Closing a global business in reaction to single-issue national politics is foolish.”

Nevertheless, Wales stands by his decision:

He said: “The general sentiment seemed to be that US law, as it impacts the internet, can affect everyone.

“As for me, what I am hoping is that people outside the US who have friends or family who are voters in the US, will ask them to make a call to their senator or representative, and I hope we send a broad global message that the internet as a whole will not tolerate censorship in response to mere allegations of copyright infringement.”

A major target of the protest, SOPA (the Stop Online Piracy Act), has already been effectively halted by opposition from the White House, but Wales said the blackout would go ahead anyway.

The news has led to good-natured admonitions to students to complete their homework early. Self-help articles like this one from The Washington Post offer tips to the Wikipedia-reliant to help them through a day without their crutch. As an opponent of SOPA, I hope Wikipedia’s stand against the legislation is rewarded rather than punished by users — that common visitors return in full force on Thursday. But, as a library lover, I can’t say I’d be too heartbroken if a day without Wikipedia also reminded students of the joys of non-online study.

Update: Google isn’t participating in the blackout, but neither are its executives mocking the concept. Instead, Google has settled on a nice little compromise:

Google said Tuesday that it will post a statement on its Web site voicing its opposition to the Stop Online Piracy Act, joining a drive that will see Reddit, Wikipedia, and Boing Boing take their Web sites dark for a period of time on Jan. 18. Google’s actions will not be as dramatic as others — Reddit and Boing Boing will take their sites down for 12 hours starting at 8 a.m., while Wikipedia will black out its English content for 24 hours on Wednesday — but the company’s decision to use its U.S. home page means that its arguments regarding SOPA will reach a huge audience.

In a statement, Google’s news team said, “Like many businesses, entrepreneurs and web users, we oppose these bills because there are smart, targeted ways to shut down foreign rogue websites without asking American companies to censor the Internet. So tomorrow we will be joining many other tech companies to highlight this issue on our US home page.”