A measurement of positronium’s energy levels confounds scientists
The departure from theoretical calculations eludes explanation
![positronium with an electron in blue and a positron in red](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2020/08/081820_EC_positronium_feat.jpg?fit=1028%2C579&ssl=1)
A negatively charged electron (blue) and a positively charged positron (red) form positronium. A new study of this exotic variety of atom disagrees with predictions, and scientists don’t understand why.
T. Tibbitts