A widely-used C++ program you might never have heard of: Physicists and other scientists use the GEANT4 toolkit to identify problems before they occur.

GEANT4: Forecasting the future

By Monica Friedlander

From the article:

Physicists can tell the future -- or at least foresee multiple possible versions of it. They do this through computer simulations. Simulations can help scientists predict what will happen when a particular kind of particle hits a particular kind of material in a particle detector. But physicists are not the only scientists interested in predicting how particles and other matter will interact. This information is critical in multiple fields, especially those concerned about the effects of radiation.

At CERN in 1974, scientists created the first version of GEANT (Geometry and Tracking) to help physicists create simulations. Today it is in its fourth iteration, developed by an international collaboration of about 100 scientists from 19 countries. Anyone can download the system to a personal computer, use C++ programming language to plug in details about the particle and material in question and find out what will happen when the two meet.

GEANT4 is used in some of the most advanced accelerator experiments in the world, but its user base has grown beyond the particle physics community...