The Big Bang Theory’s Wil Wheaton and Grammy Award-winning band They Might Be Giants are among an all-star line-up of science celebrities that are performing at the free 4th USA Science & Engineering Festival Expo, sponsored by Founding and Presenting Host Lockheed Martin.  Expected to draw 350,000 attendees, the Festival takes place on April 16^th and 17^th at the  to inspire the next generation of inventors and innovators.