A newly measured value of an electron’s magnetic moment 1 — a property of its spin and charge — is twice as precise as the one physicists have used for the past 14 years.

It is the same value measured at Brookhaven more than two decades ago, but with a much higher precision of 127 parts per billion. That is as precise as measuring the length of a football field ...

Its precise value is determined by how well the stone is cut, its colour, its size (also called its “carat”) and whether it contains flaws. The clearer, heavier, closer to colourless and more ...