When people think of particle accelerators, they tend to think of giant structures: tunnels many miles long that electrons and protons race through at tremendous speeds, packing enormous energy.
But scientists in California think small is beautiful. They want to build an accelerator on semiconductor chips. An accelerator built that way won't achieve the energy of its much larger cousins, but it could accelerate material research and revolutionize medical therapy.
First of all, what is an accelerator?