Ask & Experiment
Ask & Experiment has experiments for you to try at home, activity books to download, PhysicsQuest resources for your school or after school group, and a way you can get your physics questions answered by real physicists.
PhysicsQuestPhysicsQuest, a free competition for 69th grade students and after school groups, consisting of four science experiments that give students clues to solve a mystery. Classes can submit their answers online and be entered in a random drawing for prizes. PhysicsQuest kits are free to registered classrooms and groups. 

In general relativity, gravity is described as a distortion of space time. Most vulgarized books use the simplified image of a 2D plane being bent downwards by a mass, so that any matter traveling in the area would have to follow the bending of the plane, which would then explain why things are attracted to one another. Keeping the same simplified metaphor, could we imagine something that would bend the plane upwards, thus causing objects to be repelled? Would such a thing be considered to have negative mass? Is the concept theoretically possible? Find out the answer » 