President Barack Obama watches as a marshmallow  is launched by a gun designed by Joey Hudy of Phoenix, Ariz., Tuesday, Feb. 7, 2012, in the State Dining Room of the White House in Washington during the White House Science Fair. For a president who promotes technology at every opportunity, Barack Obama often strikes an awed, self-effacing pose around technicians, scientists and high-tech machinery. &quot;If I&#x27;m nodding, you should just assume that everything you said is going completely over my head, he once told winners of a New York science fair. Still, he loves the stuff. On Tuesday, he revealed his inner science geek as he delightedly helped fire an eighth grader&#x27;s marshmallow air cannon at the drapes of the White House&#x27;s elegant State Dining Room.  (AP Photo/Susan Walsh)
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