It's a pivotal day for Catholicism and its 1.4 billion followers. Just minutes after today's show begins, 133 cardinals from around the world will solemnly file into the Vatican's Sistine Chapel to begin the secretive conclave, and they will not be seen again until they have elected the next pope. CNN anchor Erin Burnett begins our coverage from St. Peter's Square in Rome.  Learn more about your ad choices. Visit podcastchoices.com/adchoices