Last week, scientists from the Max Planck Institute for Nuclear Physics published the most exact value ever observed for the weight of a single electron — a value 13 times more accurate than the previous estimate. And the Penning trap, the kooky looking device shown above, was crucial in obtaining this measurement.
To get this super-accurate weight reading, the German research team hitched a single electron to an empty carbon nucleus whose exact mass was known, and tossed the resulting combo inside the Penning trap. As diagrammed above, a magnetic field running through the Penning trap (indicated by the black arrow at left) sent the carbon-electron mashup into a circular course (shown in simplified form as the green circular arrow). The researchers were then able to measure the rotational frequency of the carbon-plus-electron duo, and using some complicated maths, came up with the most accurate measure of an electron's weight ever measured.
So why is this important? Electrons are part of what make up every physical thing we interact with, and a more accurate measure of their mass is crucial to our understanding of the physics that govern the world around us.
In fact, the new, ultra-accurate measurement of electron mass could help physicists refine the Standard Model of physics, the "theory of almost everything" that predicts nuclear interactions and electromagnetism, but that falls apart when used to try to explain gravity, dark matter or antimatter. A more precise understanding of the electron's mass could help refine the Standard Model, or a different model that explains things the Standard Model can't.
Pictures: Sven Sturm / Max Planck Institute for Nuclear Physics