events of the year, science fair. the white house science fair today. the president got to meet geeky superstars like these teenagers who built a catapult to help you practice your basketball shooting technique. also, this florida 12-year-old who invented a type of sandless sandbag. it s made with polymers that expand when wet, which makes way more sense than a sandbag than sand does. polymers. why didn t we do that before? as you see here, this is what a polymer looks like when it s all curled up. but then when you add water, it straightens out with hydrogen bonding and ecke spands lixpand. you want to try? i do. i actually have one of these. sometimes i just stare at them in space. i know. sometimes in the oval office, i were just look at one of these. this was the fourth time the white house has hosted its own science fair, honoring about 100 students from across the country today. but there was one field of science not represented at the