Just a line fit October 22, 2007Posted by dorigo in Blogroll, physics, science.
Stimulated by Louise’s hypothesis and by Kea, who on her blog mentions that the value currently accepted for the speed of light c (and now taken as a standard to define the length of one metre) is a bit lower than what was measured in 1926 by the brilliant experimenter Albert Michelson, I took an experimenter’s view of the problem: take the data and pass a line fit through the points, duh.
Here is the result. The data comes from this page, which lists all measurements in a table.
The data points correspond to measurements made by Michelson (1879), Rosa and Dorsay (1907), Michelson (1926), Essen and Gorden-Smith (1947), Froome (1958), Evanson et al. (1973). The last one is the most precise, with an accuracy of one mm/s, but since 1926 the accuracy has been to about one part in 10^5 or better.
So what does the line fit tell us ? Well, there is a slope, but it is of 0.002+-0.006 m/year. In statistical terms we have to conclude that points are well represented by a constant line with no slope. The hypothesis of a downward trend is only marginally more probable – from the statistical point of view – but the implications of a non-constancy of c of course require more proof: “extraordinary claims require extraordinary evidence”.
Just a thought before getting to a deserved sleep tonight…