What a beautiful word. I wonder who made it up. It crops up because I was discussing with a friend the fact that tide heights are greater at the equinoxes. Here in Broome we had particularly high (and low) tides a couple of days ago. “Ah, but,” he said “it’s not the equinox until the 20th of March”. “Ah, but” I said and changed the subject.
But he’s right of course and I went looking for the explanation and found that the biggest tide is the syzygial tide falling closest to the equinox. Progress, well given that I thought Syzygy was a Polish surname, limited progress. So I went looking for a definition I could cut and paste and found this …
“Syzygy definition: an alignment of three celestial objects, as the sun, the earth, and either the moon or a planet.” Thank you Dictionary.com.
I also found this from the Cambridge Dictionary …
“an arrangement in which two or more planets, stars, etc. are in a straight line.”
Perhaps someone should point out to the Cambridge Dictionary that two objects are always in a straight line.
The three objects with maximum impact on the tide are of course the sun, moon and earth. Their syzygy occurs twice every lunar month and gives us the spring tides (and if I’ve told you once I’ve told you a dozen times that has nothing to do with the seasons). Why should the tide be even bigger at the equinox? I am indebted to Incnis Mrsi for this explanation …
“The Moon’s orbit is inclined to the ecliptic by about 5° only (cos 5° ≈ 0.996), so two tides are aligned almost perfectly on a Moon’s syzygy during whichever season. The difference is that, during/near an equinox, this line also lies in the equatorial plane and rotational motion of Earth’s surface/hydrosphere/crust can direct the stuff to move along this tidal line to a maximal range possible. At least, on the equator.”
Streeters Jetty at low and a high spring tide, Mrs Syzygy can be seen walking her dog …
bobmcgee 