The Saros Cycle and Standing Stones as Tidal Predictors?
Submitted by Andy B on Friday, 23 September 2011 Page Views: 5817
Environment
I knew that Tidal Charts did not go back to 1314, so I contacted Professor A.E. Roy of Glasgow University and asked if there was a repeatable cycle of the Sun-Moon-Earth that could be used to calculate backwards from today’s tidal charts to the time of 1314. He said that I should be able to use a cycle known as the Saros to do so.
Since 1314, there have been changes to the calendar from the Julian to the Gregorian (an 11 day modification). But after taking that into account I went back an exact number of Saros cycles (from a modern day tidal chart) to determine the times of the Tide on the Bannockburn on June 24th, 1314. It would have been easier to do if I had the Julian Day numbers of both dates-these are used by astronomers to calculate events happening hundreds of years backwards and forwards in time, and they have no need for changes from one calendar to another.
I sent my findings to the Proudman Oceanographic Laboratories in Birkenhead where John Eric Jones kindly checked my calculations and used the computer at the institute to run a check for me which used the exact positions of the Earth, Sun, and Moon on the day of the battle of Bannockburn. The computer even calculated the gravitational pull from any planets which also had an effect on the tides. I was told that my Tidal calculations gave “a reasonable approximation” to the times of the tides on the day itself.
I sent off what I had thought was my discovery – using the Saros to calculate tides for ancient events – to the Royal Astronomical Society. They told me that many people had thought they had “discovered” this use of the Saros Cycle before me. They also said that the Saros Cycle was inexact for the lengthy time period that I was using (i.e. hundreds of years). And that I had been “lucky” in getting a reasonable result
I then went to various reference libraries and investigated if I could use the Saros to calculate tides - at various coastal sites - backwards in time over a period of five Saros cycles from the initial date. The calculations all matched accurately.
I have since checked some web sites where some experts say the Saros is too inexact to be used over hundreds of years. While some other experts say it is exact enough.
All my adult life, I have been fascinated by Standing Stones and how they could be used to make astronomical predictions of, for example, the Lunar Cycle of 18.61 years: the data for which was obtained by watching the rising and setting positions of the moon on the horizon. It is my belief that a much more important Cycle to be discovered by ancient man was the Saros Cycle.
People of these ancient times (c.3,000 B.C.) had the “technology” to calculate the Saros cycle. If one measured the heights of the tide over the length of one Saros cycle, the results would be repeated almost exactly for the next Saros Cycle. Advance knowledge of the heights of tides would have saved many lifes and boats. It would have been very important, if it had been used.
The data obtained from the Saros would have to be used alongside the heights of the tide at a nearby place under sea water. Ancient peoples had no clocks of course, but could calculate sunrise, mid-day, and sunset. The weather would have had to have been fine, but, apparently, weather in those Ancient times was sunnier than it is today. I do not think the sunrise and sunset times would have been of use - because the times vary from day to day. I believe though that they would have noted the height of the tide at mid-day-which did occur at the same time each day and was easy to see.
They would have needed a measuring stick, but it would have needed to be of a standard length to make any useful measurements. Another possibility was to use a different stick for each reading of the mid-day tide and cut the stick at the highest point of the tide (at mid-day). These sticks could then be arranged in a circle around a central point (or a stone circle). This circle of 6,585 sticks (one for each day of the Saros cycle) would have been a physical recorder and predictor of tides.
I believe that the Saros can be calculated directly from the use of Standing Stones, but not being an expert I am not certain. Perhaps the Saros could also be calculated from the data found from the observations of the 18.6 year Lunar Cycle (these observations seem likely to have been made?)
The Saros can also be used as a predictor of eclipses which would have been useful to ancient peoples. But its use as a tidal predictor would have been truly life saving. It would have been enormously powerful to a community living by the sea.
A tribe or people may have valued the advantage that such knowledge of tidal changes gave them and they may have hidden its use from other tribes. The expertise may have been lost when they were taken over or conquered by other tribes.
I am no expert in standing stones or in astronomy. However, I think the question I am asking-“did the ancient peoples of Europe use Standing Stones as a Tidal Predictor?” is one that a real expert may care to look into. Perhaps there are signs at sites that could be recalculated as possible evidence for their use in tidal calculations and predictions (via use of the Saros Cycle). Perhaps rock art played a part?
The Saros cycle is 18 (tropical) years and 11 and a third days. In days it is 6585.32 days long (It is that extra 0.32 part of a day that makes the cycle not perfect for predictions over very long periods of time, as the tiny inexactitude multiplies cycle by cycle). John Edwin Wood in the excellent book, Sun, Moon and Standing Stones mentions a very accurate (accurate for 15,000 years) eclipse (and tidal) predicting cycle of 28 years and 345 days. However, I believe that the Saros is the cycle that would have been used-as it is good enough for the purpose, and the other cycle is just too long.
The most important point, perhaps, of the Saros and other lunar cycles, is that the peoples that used them must have been confident that they would be around in a hundred or so years in order to reap the benefits of their calculations and observations. We know that these ancient tribes were certainly just as intelligent as us - or they could not have used the data they obtained (or set themselves the puzzles in the first place). We know they were capable of storing the information obtained from complex and lengthy cycles-by using marks on wooden sticks and on stones. We do not know though if they had other methods of storing data, e.g. chants.
Astronomers in Ancient Babylonia definitely made use of the Saros for eclipse prediction. Ancient peoples in Britain had the intelligence to make the necessary observations and calculations. They had the motivation, and they had the “technology”. They had-almost certainly-standard measuring tools and devises that could be used for long term storage of measurements.
A people living next to the sea would have been just as interested in the mysteries of the timing of the tides as they would have been at the rising and setting of astronomical bodies. And they surely would have had a clue how to use the Saros from the observation of a very high High Tide a couple of days after a full moon and again a couple of days after a new moon.
Ashby McGowan
We would like to know more about this location. Please feel free to add a brief description and any relevant information in your own language.
Wir möchten mehr über diese Stätte erfahren. Bitte zögern Sie nicht, eine kurze Beschreibung und relevante Informationen in Deutsch hinzuzufügen.
Nous aimerions en savoir encore un peu sur les lieux. S'il vous plaît n'hesitez pas à ajouter une courte description et tous les renseignements pertinents dans votre propre langue.
Quisieramos informarnos un poco más de las lugares. No dude en añadir una breve descripción y otros datos relevantes en su propio idioma.