Science fans should pack their bags, and their kids, for the U.S. Science & Engineering Festival in Washington D.C. later this month.

Half a million people are expected to visit the April 28-29 weekend expo and book sale, an event offering more than 2,000 hands-on activities and over 200 live performances by the luminaries of the science world. Speakers include Big Bang Theory's Mayim Bialik, MythBusters' Adam Savage and Jamie Hyneman and, of course, NPR's Joe Palca, author of Annoying, The Science of What Bugs Us.

"The Festival is a culmination of a month-long series of nationwide activities by the Festival to inspire the next generation of innovators," notes a festival statement touting its pre-event festivities. Sponsored by defense industry titan, Lockheed Martin, the festival opens for the second year in Washington D.C.

There's no better way to celebrate science, and take in the sights of the nation's capital. If it rains, there are always the museums (the newly-installed Space Shuttle Discovery, will have landed at the Smithsonian's Udvar-HazyCenter on April 19) and best of all, the festival is free.