As more unidentified objects were shot down by the U.S. Air Force in recent days, experts warned that there were an “endless” array of potential targets. By William J. Broad The United States is going ...

Finding could have applications in acoustic-levitation-assisted 3D printing, mid-air chemical synthesis and micro-robotics ...

You often have to make quick judgments about the number of objects you encounter in the world. You might see a group of people walking toward you. It is useful to know whether there are roughly five, ...