Particle accelerators provide a way for scientists to test cosmic ray strength particles in labs on Earth. (Credit: GSI GmbH/Jan Michael Hosan 2018)

NASA astronaut Scott Kelly spent a year in space while scientists monitored changes in his body, as well as that of his twin, Mark Kelly, who remained on the ground. Kelly came back to Earth in good shape, the experiment showed. And, some Russian cosmonauts have also spent even longer than Kelly in space without obvious long term ill effect from