Yes, that's the unrecognizably dark Las Vegas Strip during Earth Hour 2009. Credit: Ethan Miller, Getty Images

On March 27th, millions (perhaps even billions) of people will switch off their lights and electric appliances from 8:30-9:30 local time as part of Earth Hour. And then they will spend that hour wondering, "Is this really making a difference?" Well, that's a good question, because a holiday on which you do something as boring as sit in the dark damned well better be worth it.

I know what you're thinking: "Earth Hour is not a holiday!" That's true. Technically speaking, it's a holi-hour, but all those hours add up, especially if you consider that Earth Hour is observed in all of Earth's standard time zones. In fact, 92 countries will officially take part in this year's Earth Hour, with who knows how much ad-hoc participation elsewhere.

According to EarthHour.org, 4,159 cities took part in 2009's Earth Hour, including 73 national capitals and 9 out of 10 of the world's most populous metropolises. In addition, 1,095 major landmarks went dark, including the pyramids of Giza, the Eiffel Tower and, most impressively, the Las Vegas Strip.

Of course, that doesn't mean that everyone in those cities took part, it just means that either a landmark went dark, a government official supported EH, or the city had the support of an official EH ambassador. As it stands, there's really no way to tabulate just how many people observed Earth Hour in 2009. We do know that the World Wildlife Federation's goal was 1 billion participants, and their Web site says that "hundreds of millions" participated in Earth Hour 2009. Perhaps that's accurate.

When it comes to how much electricity was saved, there are some reasonably trustworthy numbers out there. For example, Chicago's utility provider claims that the city saved 818 megawatt hours, or 1.3M pounds of CO2 in 2008 (the equivalent of taking two 400MW coal plants offline for an hour). Last year, the city of Toronto reportedly saw a 15.1% drop in its normal power consumption during Earth Hour. Suffice to say, it all adds up.

So how can you turn Earth Hour into a holiday? well, the TV may be off for an hour, but there are still lots of things you can do in the dark. Don't make us elaborate. Please.