(This was my original title for my article, but my editors evidently didn’t like it. I guess I’m too old school. Ahem. Moving right along.)

As you may know, quantum physics shows that matter has both a wavelike and particle-like character. When you combine quantum physics and special relativity, you find that a particle at rest vibrates with a frequency that depends only on its mass: the Compton frequency. For most purposes, the Compton frequency is useless: it’s huge, even for low-mass particles like electrons, and scales up proportionally for more massive particles like protons. However, researchers have figured out a way to access the Compton frequency of cesium atoms by stimulating them with lasers in a particular way. This could lead to more precise atomic clocks, enabling even more detailed measurement of the second of time—and provide a new way to measure the masses of subatomic particles.

Shau-Yu Lan and colleagues exploited advanced techniques to construct an atomic clock based on a single cesium atom, a device capable of dividing the huge natural frequencies of the atom into more manageable quantities. This provided a strong demonstration of the ability to construct clocks based on a single microscopic mass. And, because we already have excellent clocks to compare them with, this can potentially work in the opposite direction, leading to accurate mass measurements in the future. [Read more…]

Straight outta Compton…

Certain physical quantities—the fundamental electric charge, the masses of certain particles, the strengths of the basic forces of the Universe—are generally assumed to be constant in time and space. Some of our theories depend on that constancy, but it’s not an absolute certainty: it’s possible that in distant galaxies, the rules might be a little different. They can’t be drastically different, though: observations show that (for example) the hydrogen spectrum appears to be the same 12 billion years ago. A new observation has clarified the constancy of another relation: the ratio of the proton mass to the electron mass, one of the quantities that dictates the structure of all atoms. They found this by measuring the spectrum of methanol, the simplest type of alcohol.

New observations of methanol (also known as methyl alcohol) that absorbed light in a galaxy 7 billion years ago show that it behaves the same as molecules on Earth, to one part in 10 million. The spectrum of methanol depends sensitively on the ratio of the proton mass to the electron mass, considered in most theories to be one of the fundamental constants of nature. In other words, because the spectrum of methanol at a cosmologically significant distance is indistinguishable from that in the lab, at least one fundamental constant hasn’t changed measurably in at least 7 billion years. [Read more…]

A drink from the cosmic cellar shows that some things never change