According to new research, a simple model is sufficient to select the right size boulder for the job. The most important factor in identifying a large enough boulder was the degree to which the boulder moved as a result of impact. “You use this (simple model) to size the boulder and to come up with a rough estimate—will this size of boulder work?” says Qiu. “We provided a tool for the Department of State to be able to size a boulder for embassy protection,” says Qiu. Source: Penn State