Home Close Hole - Local Apparent Time.

(Home Close Hole Time)

What is this all about?

This page came into being (March 2011) because I was laid up with a bad back and couldn't manage to do anything useful, so I produced something useless, (but harmless); an explanation of the Equation of Time and Home Close Hole Time.   As ever, don't take it too seriously, but do remember:-

Warning (added Aug 2011)

The access logs show that a few misguided souls have been arriving at this page genuinely seeking information about Local Apparent Time or LAT. If this applies to you then please be aware that the opinions expressed here are not meant to be taken 100% seriously. The page was written to extol the virtues of a meridian which passes through the shaft of our cave dig at Home Close Hole, Somerset, UK; not specifically as an explanation of LAT. The facts outlined on the page are however, accurate to the best of my knowledge (although I have deliberately omitted some of the jargon words). Read on if you will, but don't say I didn't warn you.

Time is funny stuff.

It is indeed, it keeps sliding away when you try to grab hold if it, then creeps back when you are not looking. But, whatever, early people got hold of the idea that things happened in a sort of cyclical way and they used the passage of the sun across the sky, or the rotation of the earth, to measure the passage of time.

People have been using the sun to measure the passage of time for at least 3500 years and it is only within the last hundred or so years that they have stopped using the sun to set their clocks. Time from the sun comes with free warmth as well and it is not plagued with the pernickerty accuracy of digital systems. However, it does have some peculiar but quite interesting properties.

These require a bit of explanation.

The Meridian

Meridian is an important word in this context, but it is plagued with a variety of meanings. The word comes originally from the Roman adjective meaning 'of mid-day'. Since then, other layers of meaning have been plastered onto the word. People talk now of the Greenwich Meridian. Strictly speaking, they are referring to the Greenwich Terrestrial Meridian, a line passing through the poles of the globe and Greenwich. The sun crosses this line at Greenwich's noon. Greenwich, by the way is a place far to the east of Frome, so don't worry about it too much.

More important is, of course, the HOME CLOSE HOLE TERRESTRIAL MERIDIAN. This lies some 2.63161 degrees to the west of Greenwich and so, as the sun rises in the east, beetles across the sky and then sets in the west, it has to cross the Greenwich Meridian before Home Close Hole Meridian. In other words, it is noon at Greenwich before it is noon at Home Close Hole. In fact, Home Close Hole noon occurs 10 minutes and 31.6 seconds after Greenwich noon.

An Aside

Incidentally, I realised (July 2011) that the Home Close Meridian is ideally placed to serve the country, far better than that Greenwich monstrosity.

A person who takes it into their head to walk north from the south coast along the line of the Greenwich Meridian will cover a little over 300Km on dry land. After that they will be up to their necks in the North Sea. On the other hand, a person walking north along the line of the Home Close Meridian can walk dryshod for over 750Km (assuming a ferry is available to cross the Forth of Fifth). Dry land ends for a while at the Moray Firth but then returns as the Meridian crosses Stronsay and Sanday in Orkney.

You just have to admit that the Home Close Meridian is altogether more democratic and more in touch with the needs of the country. It's the PEOPLE'S MERIDIAN ! Down with Greenwich !

Getting back to the point - There is another complication

The sun's apparent motion is not regular, so the sun is not always quite where you might think it ought to be. There are two reasons for this; one is that the earth's velocity changes as it orbits the sun, being greater when it is nearer to the sun (the orbit is not circular, so the distance varies). The second is that there are two components to the sun's apparent motion, up/down and sideways. The resultant of the two motions remains constant, but minor variations in the relative importance of the two components in different parts of the earth's orbit means that the sideways motion (the important bit as far as we are concerned) varies periodically. The combination of this and the velocity changes means that apparent noon varies in a wave-like pattern throughout the year.

This variation is known as the Equation of Time. It shows that a sundial indicates the correct time only four times a year; round about the 15th April (day 105), 16th June (day 167), 30th August (day 242) and 24th December (day 358). At other times of the year a sundial is either ahead of or behind GMT. (These dates are deliberately a little vague, because they do vary a bit from year to year, also the model I used to produce the graph is a little bit off).

Graphs, or tables like the above can often be seen today still pasted to the inside of the doors of long case clocks ("grandfather clocks") because people used to set their clocks from sundials and correct the reading using the Equation of Time. In those days all people used local time. In the U.K., it was only the arrival of the railways and, in particular, the Great Western Railway that required us to adopt "Railway Time". However, there are still some reminders of our old local time, the clock on the Corn Exchange in Bristol has two minute hands, set just over ten minutes apart. One indicates Bristol Time and the other Greenwich Time.

'Bristol Time' on the Corn Exchange clock
The clock on the Corn Exchange, Bristol.
The red minute hand shows London time, the black minute hand shows proper Bristol time.

What does Mean mean?

The final attempt to tame and subdue good old sun time was the introduction of the concept of the MEAN sun. An old Astronomer Royal took the motion of the real sun and averaged it, smoothed it and generally beat it into submission and so produced a pretend sun that moved in a regular and predictably boring manner. From this we get Greenwich Mean (or Pretend) Time. Do we need it? Remember, there is nothing Mean or artificial about Home Close Hole Time (HCHT), it is entirely natural and good for you.

Another Aside

On 25thNovember 1858 at the Dorchester Assizes, a case (Curtis v. March) was due to be tried at 10 o'clock.   The court clock was set to GMT, but the town clock was set to local time.   The defendant and his lawyer (using local time) were not in court at 10.00 GMT, so the judge found in favour of the plaintiff.   On appeal, the judge's decision was overturned, on the grounds that ten o'clock is ten o'clock according to the time of the place.   This ruling was the definition of time in Great Britain until 1880, when an Act of Parliament was passed defining GMT as the official time.

G. J. Whitrow, Time in History (Oxford University Press, 1989), p165

The end result!

At this moment, Home Close Hole Time is UK time plus/minus whatever the Equation of Time is for today minus 10 minutes 31.6 seconds. That's it, forget the rest.