The measurement of time has intrigued people for many thousands of years, as is illustrated in various archeological documents. During this time many different ways have been tried of more of less telling
precisely the time of day as well as months and years. Astronomical means such as the position of the sun, moon and stars have been used, as have physical means such as the burning of
resinous chips, candles, water dripping from containers, the flow of sand in
sand-glasses as well as flow of mercury. At present the mechanical
principles of time measurement prevail, but it seems that slowly they will
be outdated by more sophisticated electronic and atomic means.
Over centuries, many other methods have been tried, many of which now seem strange
and lacking any rational bases.
One of these methods was a sunflower dial. It was the project of an unusually forward thinking and fertile investigator of the seventeenth century, the Jesuit, Atanasius Kircher (1601 - 1668). He was the author
of 44 books, and thousands of academic letters.
Kircher described his invention in a book published in Rome in 1641 (Magnes sive de Arte
Magnetica). According to his idea, one should attach a thin ledge across the
face of a sunflower, the shadow of which
projected on a circle surrounding the plant would indicate the time of day.
This method was deemed unrealistic and no practical use was found. On top of this, the known historian of clocks and watch-making, G. H. Baillie, regarded the idea as one of the most absurd and laughable inventions.
Looking at this from a current point of view with what we now know about the functioning of plants, it must be said that the idea was not absurd and not
at all laughable. Kircher was a good observer. Sunflowers 'follow' the sun,
differently in the southern hemisphere than in the northern. Kircher most probably thought that they turn themsleves around, similarly to how an owl turns its head. We now know how this mechanism works. Simply, on the sunny side of the
flower stalk, there are less growth substances, and hence the flower grows more intensely on the shaded
side. Only the growth region follows the sun thus causing the inflorescence to
'look' straight into the sun. I must say that I was quite shocked when I came across a many-hectare large sunflower plantation in
Moldova. As I turned my back to the sun, I had the mpression that I was being watched by millions of faces, that although seemed friendly, also seemed to be from another planet.
Theoretically Kircher was right. The shadow of an attached indicator on the face of a sunflower would indeed show the time of day quite precisely. Unfortunately the practicality of the invention lets it down somewhat. Sunflowers only flower for a short period of time,
although they do have a memory (for a short period of time they continue to follow the sun, even in the shade), the universality of such a time measurement system does leave a lot to be desired for.