O.K., so what is the speed of dark?

Posted on 31 August 2018 by Douglas Chadwick

Thirty six years ago I bought an oak long-cased Grandfather clock that had been made by John Charlton of Durham. It is old, because he died in the late 1790s and one must assume that he made it before he died! Recently it needed the winding mechanism repairing and I took the opportunity of asking that the moon phasing also be fixed, as it had never worked whilst in my possession. The clock was repaired and returned to me last week. Now the moon phasing had to be set, and to my astonishment I found that it ran from zero, a new moon, for twenty nine and half days to the next new moon. My first reaction was that Mr John Charlton had made a mistake and the silly man did not know that there were thirteen lunar months of twenty-eight days in a calendar year. Just to be sure, I went to Wikipedia to check. Well as you might know already, or have guessed, he was correct and I, the long-term navigator, was wrong. In my defence, and it is not much of a defence, the sun and the stars are used for navigating and not the moon. Amazingly, it turns out there are five celestial variations of the lunar month, none of which are twenty-eight days. The twenty-eight day month is a common law period and was adopted in the Law of Property Act of 1925. I hope that this is not too boring, but I will lay out the facts as I now understand them to be.

• SIDEREAL MONTH. (27days 7hours 43minutes) This is the time it takes the Moon to return to a similar position among the stars.
• SYNODIC MONTH. (29days 12hours 44minutes) This is an average period and references a line joining the Sun and the earth. This varies because the Earth's orbit around the Sun is elliptical and not circular and the timing is dependent on the position of the Moon relative to the Earth and the Sun.
• TROPICAL MONTH. (27days 7hours 43minutes) This is a similar time to the Sidereal month and is the time taken for the Moon to cycle with respect to the vernal equinox. I am starting to get lost at this point!
• ANOMALISTIC MONTH. (27days 13hours 18minutes) This is a similar time to the Sidereal month, but is longer due to the allowance that has to be made for the fact that the Moon's orbit around the Earth is elliptical and not circular. This we can observe in the different apparent diameters of the moon at different times of the year as its distance from earth varies.
• DRACONIC MONTH. (27days 5hours 5minutes) I like this name as it refers to a mythical dragon, said to live in the lunar nodes and eat the Sun or Moon during an eclipse. The Draconic month is the average interval between two successive transits of the Moon through the same node. I said it might hurt!

SUMMARY - All Lunar months approximate to the mean length of the Synodic month, the average period the Moon takes to cycle through its phases and back again to the starting point. The Moon completes one orbit around the Earth every 27.3days (a Sidereal month), but due to the Earth's orbital motion around the Sun, the Moon does not finish a Synodic cycle until it has reached the point in its orbit where the Sun is in the same relative position. PHEW! At the moment we are all intrepid adventurers on the high seas of investment. My apologies for yet again returning to the subject of technology funds, but these are the only funds that are making progress at the moment. The recent minor correction in these funds however poses the big question. Will they return to their upward momentum of the last few years, or are we due for a real fall should the FAANG businesses falter? As a sterling investor, the strengthening of the dollar has recently made a significant contribution to the rise of these funds that have many of their investments in dollar-based businesses. This brings me to the subject of Brexit. Sorry about that! But whichever way this mop flops it will affect the value of sterling. A good deal for the U.K. (whatever that is) and one would imagine that sterling would appreciate against the dollar and other currencies. The reverse is true if there is a disorganised W.T.O. no deal result. At the moment I am in a quandary and can see no way that one can anticipate the result. Certainly not from listening to and reading the news. So for the moment, until the mists start to clear, I intend to hold on to the four technology funds that I hold. (Scottish Mortgage Trust, Smith and Williamson Artificial Intelligence, Polar Capital Technology and AXA Framlington Technology).  I have held them for some time, and they have served me well and still show favourably in our numbers. I am however on full alert. Somebody once said that there is nothing wrong with optimism, as long as you do not get your hopes up! Best wishes and good investing, Douglas. Founder & Chairman