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Dr Plot

25 June 2020

Never heard of Dr Plot? Neither had I until I stumbled on this at www.mikeoates.org/mas/leek/sunset.htm … this is an amateur astronomy web site and therefore we have research outside the box. It is quite an interesting piece of research but raises a big question – is the angle of tilt of the earth changing slowly over time. It concerns an astronomical oddity – one recognised by prehistoric people it would seem. Or does it. The double sunset seen from the churchyard of St Edward the Confessor church at Leek in Staffordshire is the starting point. It is NE of the Potteries and 12 miles or so from Macclesfield in the other direction. Mike Oates started to research this curiosity in 1998, initially from an astronomical angle. However, the research took him into archaeology and other factors came into play, the deeper into the research he travelled. This tends to happen. What starts out in good faith can end up in all kinds of alleys. It did however lead to a paper published in the Astronomy and Geoscience section of the Journal of the Royal Astronomical Society back in 1999. The present church dates to the 13th century AD. The Normans introduced stone architecture in churches replacing wooden ones of the Saxon period. It is located on a hill top that seems to have been used by locals as far back as the Neolithic period. Now, this is where Dr Plot comes in. He wrote a book, The Natural History of Staffordshire, which was published in 1686. Yes, back in 1686. It was dedicated to James II. Dr Plot was Keeper of the Ashmolean Museum in Oxford and a professor of chemistry at Oxford University. He described how on midsummer day the sun was observed from Leek churchyard to set behind a hill he called the Cloud. It would then reappear and set  again in the now distant horizon of the Cheshire Plain. He said the hill is situated with respect to the churchyard that a spectator standing there in the evening 3 or 4 days before and after midsummer day may see the disc of the sun gradually emerge from beyond the northward side of the hill, which is nearly perpendicular. The Cloud is 6 miles from Leek and still presents a distinctive profile 2 miles east of Congleton. Quarrying in the 19th century demolished most of the northern section of the hill, including a tall column known locally as Billy Thrumble. Stone extracted from the hill was used for the viaduct and canal built over the River Dane. Plot actually proposed using the phenomenon to accurately monitor changes in the cycle of the earth's tilt, which apparently varies over time. Since 3000BC, it is thought, the tilt has moved from 24 degrees to 23.5 degrees. In the Neolithic period the sun was about half a degree higher in the midsummer sky according to Mike Oates. At solstice it would have set north of where it does now, just clipping the top of the hill. Since then, as a result of changes in tilt, the sun has moved southwards, and from the churchyard the double sun set did not happen until the Iron Age, at earliest.

Dr Plot used a micrometer gadget attached to a telescope. Oates used a computer software programme to arrive at the same answer, a gradual and slow change in tilt. Is this an assumption we may wonder. Does the tilt really change slowly or can it move in fits and starts. Did one such jump occur at some point between the Neolithic and the modern day?

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