In the early 20th century, Ernest Rutherford gave us the classic model of the atom by firing particles at gold foil. He established that atoms have a dense nucleus. For a long time, we thought we understood how charged particles bounced off each other. But in the 1950s, physicists began experimenting with electrons moving at "ultrarelativistic" speeds—speeds incredibly close to the speed of light. They discovered something strange. The electrons didn't scatter the way classical physics predicted