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 ...

The world can be a busy place. Walking down a crowded street, there is a sea of faces in front of you. Look in a shop window, and there is an array of objects for sale. Look up in the sky, and several ...

The algorithm sifted through galaxies in mergers, revealing elongated star and gas streams; gravitational lenses bending background light into arcs and rings.

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, ...