How Constant Are The Fundamental Constants?.

Are the constants really constant? The values given in handbooks of physics do in fact change from time to time. They are continually adjusted by international committees of experts know as metrologists. Old values are replaced by new “best values” based on the latest 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 the final value is then subjected to a series of corrections. Finally, in arriving at the latest “best values”, international committees of experts then select, adjust and average data from laboratories around the world.

Although the actual values change, most scientists take it for granted that the constants themselves are really constant; the variations in their values are simply a result of experimental errors. The latest values are the best, and previous values are forgotten. However, some physicists, notably Paul Dirac (1902-1984), speculated that at least some of the fundamental constants might change with time. In particular, Dirac proposed that the Universal Gravitational Constant might decrease slightly as the universe expands. But Dirac was not challenging the idea of eternal mathematical laws; he was merely proposing that a mathematical law might govern the gradual variation of a constant.

What about the data? All the published values of constants vary with time, as I discuss in my new book Science Set Free, but here I look at only two of them: the Universal Gravitational Constant, and the speed of light.

The oldest of the constants, Newton’s Universal Gravitational Constant, G, is also the one that shows the largest variations. Towards the end of the twentieth century as methods of measurement became more precise, the disparity in measurements of G by different laboratories increased, rather than decreased. The difference between recent high and low values was more than 40 times greater than the estimated errors (expressed as standard deviations).

What if G really does change? Maybe it does so because measurements are 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, rather than averaging them to iron out variations, revealing that there was a remarkable range; for example on one day the value was 6.73, a few months later it was 6.64, 1.3% lower.

In 2002, a team lead by Mikhail Gershteyn, of the Massachusetts Institute of Technology, published the first systematic attempt to study changes in G at different times of day and night. G was measured around the clock for seven months, using two independent methods. They found a clear daily rhythm, with maximum values of G 23.93 hours apart, correlating with the length of the sidereal day, the period of the earth’s rotation in relation to the stars.

Gershteyn’s team looked only for daily fluctuations, but G may well vary over longer time periods as well; there is already some evidence of an annual variation. By comparing measurements from different locations, it should be possible to find more evidence of underlying patterns. Such measurements already exist, buried in the files of metrological laboratories. The simplest and cheapest starting point for this enquiry would be to collect the measurements of G at different times from laboratories all over the world. Then these measurements could be compared to see if the fluctuations are correlated. If they are, we will discover something new.

What about the speed of light, c? According to Einstein’s theory of relativity, the speed of light in a vacuum is an absolute constant, and modern physics is based on this assumption.

Not surprisingly, early measurements of the speed of light varied considerably, but by 1927, the measured values had converged to 299,796 kilometres per second. At the time, the leading authority on the subject concluded, “the present value of c is entirely satisfactory and can be considered more or less permanently established”. However, all around the world from about 1928 to 1945, the speed of light dropped by about 20 kilometres per second. The “best” values found by leading investigators were in impressively close agreement with each other. Some scientists suggested that the data pointed to cyclic variations in the velocity of light.

In the late 1940s the speed of light went up again by about 20 kilometres per second and a new consensus developed around the higher value. In 1972, the embarrassing possibility of variations in c was eliminated when the speed of light was fixed by definition. In addition, in 1983 the unit of distance, the metre, was redefined in terms of light. Therefore if any further changes in the speed of light happen, we will be blind to them because the length of the metre will change with the speed of light.

Existing theories of varying constants, like Paul Dirac’s, assume that the changes are small, slow and systematic. Another possibility is that the constants oscillate within fairly narrow limits, or even vary chaotically. We are used to fluctuations in the weather and in human activities; newspapers and web sites routinely report changes in the weather, stock market indices, currency exchange rates and the price of gold. Maybe the constants fluctuate too, and perhaps one day scientific periodicals will carry regular news reports on their latest values.

The implications of varying constants would be enormous. The course of nature would no longer seem blandly uniform; there would be fluctuations at the heart of physical reality. If different constants varied at different rates, these changes would create differing qualities of time.

Rupert Sheldrake, Ph.D. is a biologist and author of more than 80 scientific papers and 10 books, including Science Set Free (September 2012). He was a Fellow of Clare College, Cambridge University, a Research Fellow of the Royal Society, Principal Plant Physiologist at ICRISAT (the International Crops Research Institute for the Semi-Arid Tropics) in Hyderabad, India, and from 2005-2010 the Director of the Perrott-Warrick Project, funded from Trinity College, Cambridge University. His web site is www.sheldrake.org.