The twenty-first century is an exciting time for mass spectrometrists. But things were quite exhilarating even at the technique's birth, more than a hundred years ago. The discovery of the electron ...

It’s confirmed: Protons and antiprotons are well-matched. The two types of subatomic particles mirror each other in the ratios of their electric charge to mass, a new extremely precise experiment ...

The constant — the ratio of the mass of a proton to the mass of an electron — has changed by only one hundred thousandth of a percent or less over the past 7 billion years, the observations show. The ...