For the first time those little numbers that appear beneath some of the commonest elements in the periodic table boxes are about to change from a single value to an interval of numbers An ...

A leading American expert on Iran’s alleged nuclear weapons program asserts the U.S. Office of the Director of National Intelligence’s new report applied an obsolete definition when it assessed last ...

This week the kilogram got a new definition – one that rests on a quantity of light. The old kilogram was defined by a platinum cylinder kept in a vault in Paris, and at first glance, that system ...