Particle Accelerator Experiments

In particle accelerator experiments, physicists can control everything from what particles you start with to what energy they have. By the 1980s, protons were being accelerated to more than 99.99% of the speed of light. Top quarks are the most massive kind of particle that we've ever observed. A single top quark has a massive about 173 GEV, which is about 184 times as heavy as a single proton.