It features “20,000 performers, 30,000 fireworks, 4 billion people watching. The 3 1/2-hour opening ceremony of the Beijing Olympics, which starts at 8 p.m. tomorrow at the new 3.5 billion yuan ($511 million) ‘Bird’s Nest” national stadium, will team British soprano Sarah Brightman with Chinese singer Liu Huan to head a program that the government has tried to keep secret.”