Among his many theoretical insights, Albert Einstein predicted the existence of two phenomena in our universe that have since been proved: gravitational waves and the stimulated emission of radiation. New research has found that these effects can sometimes combine into rare and exotic "gravitational lasers" — possibly leading to a new way to detect one of the most elusive substances in the universe.
You experience stimulated emission of radiation every day in the form of lasers, like the barcode scanner at your local supermarket or the fiber-optic cables beaming information around your city. Within the body of a laser, atoms give off radiation at just the right wavelength to excite nearby atoms, causing them to release radiation of the same wavelength. The radiation cascades until it becomes a coherent beam — the output of the laser. Astronomers have found natural sources of lasers as well, especially in giant cold molecular clouds (where the beams are called masers because they give off microwave radiation).
