sciencehabit writes: It's textbook physics: An electric charge near the surface of a material gets pulled toward the surface. However, if the charge is spread out into the right shape and moves fast enough, that attraction becomes a repulsion, one physicist calculates. The odd finding could help physicists avoid unexpected effects when guiding beams of particles such as electrons.
The most difficult thing in the world is to know how to do a thing and to
watch someone else doing it wrong, without commenting.
-- T.H. White