Physics is based on the assumption that certain fundamental features of nature are constant. Some constants are considered to be more fundamental than others, including the velocity of light c and the Universal Gravitational Constant, known to physicists as Big G. Unlike the constants of mathematics, such as p, the values of the constants of nature cannot be calculated from first principles: they depend on laboratory measurements. As the name implies, the physical constants are supposed to be changeless. They are believed to reflect an underlying constancy of nature, part of the standard assumption of physics that the laws and constants of nature are fixed forever.
Are the constants really constant? The measured values continually change, as I show in my book ( in the UK). They are regularly adjusted by international committees of experts know as metrologists. Old values are replaced by new "best values", based on the recent data from laboratories around the world.
Within their laboratories, metrologists strive for ever-greater precision. In so doing, they reject unexpected data on the grounds they must be errors. Then, after deviant measurements have been weeded out, they average the values obtained at different times, and subject the final value to a series of corrections. Finally, in arriving at the latest "best values", international committees of experts then select, adjust and average the data from an international selection of laboratories.
Despite these variations, most scientists take it for granted that the constants themselves are really constant; the variations in their values are simply the result of experimental errors.
The oldest of the constants, Newton's Universal Gravitational Constant, known to physicists as Big G, shows the largest variations. As methods of measurement became more precise, the disparity in measurements of G by different laboratories increased, rather than decreased.
Between 1973 and 2010, the lowest average value of G was 6.6659, and the highest 6.734, a 1.1 percent difference. These published values are given to at least 3 places of decimals, and sometimes to 5, with estimated errors of a few parts per million. Either this appearance of precision is illusory, or G really does change. The difference between recent high and low values is more than 40 times greater than the estimated errors (expressed as standard deviations).
What if G really does change? Maybe its measured value is affected by changes in the earth's astronomical environment, as the earth moves around the sun and as the solar system moves within the galaxy. Or maybe there are inherent fluctuations in G. Such changes would never be noticed as long as measurements are averaged over time and averaged across laboratories.
In 1998, the US National Institute of Standards and Technology published values of G taken on different days, revealing a remarkable range. On one day the value was 6.73, a few months later it was 6.64, 1.3% lower. (The references for all the data cited in this blog are given in Science Set Free/The Science Delusion.)