Physics News

Physicists at the National Institute of Standards and Technology (NIST) have used a small crystal of ions (electrically charged atoms) to detect forces at the scale of yoctonewtons. Measurements of slight forces?one yoctonewton is equivalent to the weight of a single copper atom on Earth?can be useful in force microscopy, nanoscale science, and tests of fundamental physics theories.A newton is already a small unit: roughly the force of Earth's gravity on a small apple. A yoctonewton is one septillionth of a newton (yocto means 23 zeros after the decimal place, or 0.000000000000000000000001).Measurements of vanishingly small forces typically are made with tiny mechanical oscillators, which vibrate like guitar strings. The new NIST sensor, described in Nature Nanotechnology,* is even more exotic?a flat crystal of about 60 beryllium ions trapped inside a vacuum chamber by electromagnetic fields and cooled to 500 millionths of a degree above absolute zero with an ultraviolet laser. The apparatus was developed ove