Vacuums provide solid ground for new definition of kilogram

Of all the standard units currently in use around the world, the kilogram - the official unit of mass in the International System of Units (SI) - is the only one that still relies on a physical object for its definition. But revising this outdated definition will require precise vacuum-based measurements that researchers are not yet able to make, said Patrick Abbott of the National Institute of Standards and Technology (NIST) in Gaithersburg, Md. Abbott will present an overview of current effort...