A laser beam is cut every second by the pendulum's course. My computer
is set to capture the total time for 10 swings and
record the average time for a swing in a data file. In the image above the middle of the picture is set at one second and the grey
scale intervals are set to 0.000050 seconds.
Horologists are always looking for the flatest line. An higher line
tells us that the clock is too fast, and a lower one shows
that the pendulum's beat is too slow. The graph above looks reasonably good but the software does not plot all of the points.
A more detailed look at the data using Microsoft Excel is considerably more interesting. An heavy (5 Mo) Excel file with much
more details of the datas recorded can be downloaded on my website: click here
This view of Chronolith's data clearly shows that the pendulum is sometime
seconds too fast and just after
approximately 0.000020 too slow. Why? The histogram below shows the distribution of time intervals measured.
Histogram calculated by Bob Holmstrom
This cannot be the chance. (details can be found here)
The only thing I'm shure is that this fact happens more and more often
when the air pressure inside
the pipe increases. If I let slowly some air penetrate inside the pipe until the radiometric effect vanishes, we can see that the
perturbations appears more and more often in a wider range until the pendulum stops.
The question why we can see this kind of phenomen has never been answered