This is a post about constancy and inconstancy, one of my favorite topics. And about how alcohol can make you smarter.
There are many quantities that we call “constants of nature”. Of course, anything we call a “constant” is merely something that, empirically, appears to be constant, to the extent we can measure it. Everything we know comes from observation and experiment, and our knowledge is always limited by how good our measurements are.
We have pretty good evidence that a number of basic physical quantities are pretty much constant. A lot of evidence comes from the constancy of the colors of light waves (i.e. the frequencies of waves of electromagnetic radiation) that are emitted by different types of atoms, which appear to be very much the same from day to day and year to year and even across billions of years (neat trick! will describe that another time), and from here to the next country and on to the moon and to the sun and across our galaxy to distant galaxies. For example, if the electron mass changed very much over time and place, or if the strength of the electromagnetic force varied, then atoms, and the precise colors they emit, would also change. Since we haven’t ever detected such an effect, it makes sense to think of the electron mass and the electromagnetic force’s strength as constants of nature.
But they’re not necessarily exactly constant. One can always imagine they vary slowly enough across time or place that we wouldn’t have noticed it yet, with our current experimental technology. So it makes sense to look at very distant places and measure whatever we can to seek signs that maybe, just maybe, some of the constants actually vary after all.
[I wrote a paper in 2001 with Paul Langacker and Gino Segre about this subject (Calmet and Fritzsch had a similar one). This followed the observational claims of this paper (now thought false) suggesting the strength of electromagnetism varies across the universe and/or with time. A lot of what follows in this post is based on what I learned writing that old paper.]
Suppose they did vary? Well, the discovery of any variation whatsoever, in any quantity, would be a bombshell, and it would open up a door to an entirely new area of scientific research. Once one quantity were known to vary, it would be much more plausible that others vary too. For instance, if the electron mass varies, why not the W particle’s mass, which affects the strength of the weak nuclear force, and thereby radioactivity rates and the properties of supernovas? If the electromagnetic force strength varies, why not that of the strong nuclear force? There would be interest in understanding whether the variation is over space, over time, or both. Is it continuous and slow, or does it occur in jumps? One can imagine dozens of new experiments that would be proposed to study these questions — and the answers might reveal relations among the laws and “constants” of nature that we are currently completely unaware of, as well as giving us new insights into the history of the universe.
So it would be a very big deal. [Though I should note it would also be puzzling: even small variations in these constants would naively lead to large variations in the “dark energy” (i.e. cosmological “constant”) of the universe, which would potentially make the universe very inhomogeneous. However, we don’t understand dark energy, so this expectation might be too naive.] Since there’s no story about it on the front page of the New York Times, you can already guess that no variation’s been found. But a nice new measurement’s been done.