"The West Wing" (8 p.m., NBC): Poor President Bartlet. It's his last year in the White House, and he

"The West Wing" (8 p.m., NBC): Poor President Bartlet. It's his last year in the White House, and he just can't catch a break. In tonight's episode of "The West Wing," he faces the biggest challenge of his presidency when it appears that a nuclear reactor is about to explode in California.
"Nature" (8 p.m., PBS): For more than 20 years, the world-famous Monterey Bay Aquarium has enthralled and educated its nearly 2 million annual visitors. The latest installment of "Nature" takes viewers behind the scenes for a look at the complex operations required to create and maintain exhibits featuring more than 35,000 animals and plants. The program is available in high-definition.
"Nick News" (8:30 p.m., Nickelodeon): Linda Ellerbee is never afraid to touch the hot-button issues of youth, and, in her usual thoughtful style, she does it again here: "God, Science, Politics and Your School" is the next edition of "Nick News." The goal of the program, she says, "is not to debate the issues of evolution, intelligent design or creationism. We just want to give kids a better understanding of what all the shouting is about." And do it without shouting.
"It Could Happen Tomorrow" (9:30 p.m., Weather Channel): The devastation that could be caused if an F-5 tornado tore through Dallas is examined in the second installment of this new series. Next week: How the eruption of Mount Rainier would affect local Washington state residents.
"Hollywood Celebrates Al Pacino" (10 p.m., AMC): AMC will honor Academy Award-winner Al Pacino with a program hosted by Jeremy Piven. Featured actors in the taped tribute include Charlize Theron, Bruce Willis, Colin Farrell, Robert De Niro, Meryl Streep, Keanu Reeves, Andy Garcia, Marisa Tomei and James Caan.
"Bleak House" (9 p.m., PBS): Ever since "The X-Files" ended, we just haven't seen enough of Gillian Anderson. Fortunately, she makes a welcome return in this sumptuous, six-part "Masterpiece Theatre" adaptation of Charles Dickens' ninth novel. Skillfully adapted by Andrew Davies, "Bleak House" works on multiple levels as a gripping legal thriller, a juicy romance and piquant social commentary.