We can think of no possible way that a newly invented invisible drone can be used nefariously. One day, this type of design could be used for completely peaceful pursuits, the researchers say — like observing wildlife, of course. “Instead, we asked whether we could design the drone itself around the way humans perceive motion,” he added. Then they took the best configurations and used a model that simulates human perception to quantify how visible each design appeared. It’s not the first spinning drone, but it is the first that’s been optimized to be effectively invisible to the human eye.