There’s nothing worse than a shonky pool table with an unseen groove or bump that sends your shot off course: a new study has found that the same goes at the nano-scale, where the “billiard balls” are tiny electrons moving across a “table” made of the semiconductor gallium arsenide. Physicists have shown that in this game of “semiconductor billiards,” small bumps have an unexpectedly large effect on the paths that electrons follow.