If you happen to be near one of the world's major landmarks today, don't be alarmed if you see the lights go off. The Empire State Building, Sydney Opera House, Eiffel Tower, and Big Ben are just a few of the major tourist attractions that will go dim in recognition of global warming. The event, called "Earth Hour," started in Australia two years ago and has caught on fast. Last year, cities reported dips in power consumption by as much as 13 percent. Nearly 4,000 cities are participating this go-round. But without the glowing lights on the Vegas Strip, won't gamblers lose their bearings?