"The brain is soft, like Jell-O, and floats in fluid. It is only loosely anchored. A direct hit or whiplash-type motion can cause the brain to shake, spin, or do both.” The result is a concussion, which, if repeated, can be fatal. In clear, lively language, this volume explains the science behind concussions, and the ways sports have changed in response to growing public awareness of that science.