A wooden checkerboard with alternating black and light wood squares, shown at an angle against a light purple background. By now, you’re probably wondering why anybody would use this weird geometry.

The world is awash with the color purple — lavender flowers, amethyst gemstones, plums, eggplants and purple emperor butterflies. But if you look closely at the visible-light portion of the ...

Purple light can help detect trauma on the neck, Horn said. In addition, Aurora swabs the necks of patients who report being strangled to be tested for touch DNA at the crime lab.