August 3, 2023


The most remarkable English architect, Sir Christopher Wren, died 300 years ago. He and his staff were responsible for rebuilding 52 churches after the Great Fire of London. A later project was the Royal Hospital for Seamen, serving as a retirement home for them, using “hospital” in an older sense of the word as a place of hospitality, not a medical facility. When the retired sailors were accommodated elsewhere (by the same foundation), the buildings were used for the Royal Naval College, as they still were when I had visited earlier.

The palace was the birthplace of several Tudor monarchs.

The hospital design was split so as not to block the river view from the Queen’s Palace.

The Queen’s Palace

The Painted Hall was intended to be the refectory, but was deemed too grand for an old sailors’ lunchroom.

This is another place that I should have tried the super wide angle lens on my cell phone camera instead of trying the 24mm equivalent on my travel camera. There are padded tables for people to lie on to view and to photograph the ceiling.

A lower level hallway exhibits various insignia.


After I wandered around that area, I was ready to head to the Royal Observatory, which for me was the highlight of my previous visit to Greenwich. It is set on a high hill in the Greenwich Park. The park has a pond for riding little boats and large open spaces. It was originally a royal hunting park, mostly hawking. Then Henry VIII had deer introduced.

In this picture you can see the path leading up to the observatory buildings. I didn't notice it somehow, so I took a torturous and strenuous climb on some trails, but didn’t need to ford any streams or follow every rainbow. So somewhat winded, I made it to the top and went around the buildings to find an entrance.

Once you arrive at the top, you are rewarded with great views of the Queen’s Palace, the Old Royal Naval College, Canary Wharf development, and central London. During my 2017 tour of Britain, I did not get to spend any time in Greenwich. We went there by bus from our hotel in Canterbury and put on a boat for a scenic cruise to the Tower dock. The best views of the city are from the river. Greenwich is south of the river, so the view is to the north.


Navigation before the era of GPS depended largely upon observation of the sky. You can tell where you are if you can see how high a star or the sun at noon is in the sky and you know the precise time. Quadrants, sextants, and astrolabes were used to measure altitude angles, and that left the problem of accurate time keeping at sea. That quest is chronicled in the book Longitude, which I read a little over 20 years ago. As a major naval power, England was concerned with all the issues of navigation, and over the objections of the French, who believed Paris was the center and standard of the world, the Prime Meridian of longitude was established at the line running north and south through the Royal Observatory. The exhibits still show the earlier attempts at this standard. The modern version relies upon a more accurate determination of the center of the earth, and the Coordinated Universal Time (UTC) has replaced Greenwich Mean Time as the standard for the world, and corrected periodically with leap seconds.


I took a picture of my feet standing in different hemispheres. And then outside a woman offered to take my picture standing across the line. When she took the camera, someone yelled, “Nice camera! Run!” So you can see me standing in both hemispheres as well as in four states at the same time.

In a courtyard outside the Royal Astronomer’s residence I took a couple screen shots from my iPhone. The shot on the right shows that I was facing south, but more significantly that I was only 3 seconds of longitude into the Western Hemisphere. (Each hemisphere has 180º of longitude. Each degree is divided into 60 minutes, and each minute into 60 seconds. Minutes and seconds are indicated by single and double prime marks, which are also used for feet and inches.)

Our modern time zones are spaced 15º apart from the Prime Meridian with some adjustments for political and practical reasons. (Atlanta and the western corner of the NC mountains were originally in the Central time zone, for example. Indiana has been all over the place.) Britain and most of Western Europe observe Summer Time, like our Daylight “Saving” Time. So the clock time shown in the picture on the left is 1:03 pm, but the Solar time is 11:56 am. The earth’s orbit is elliptical, it wobbles on its axis, and the poles are tilted 23.4º (declining for about 10,000 years, but also affected by ice melts and our use of ground water). Our distance from the sun varies over the course of orbit. So the position of the sun in the sky varies in a complex manner. We use the average course of the day for our time keeping. That is why the standard was called “Greenwich Mean Time” (“mean” in the sense of “average,” as in “meantone tuning” like I used to use on my harpsichord, not in the sense of “nasty and cruel”). Given all the factors going on, the calculation of the divergence of sun time from clock time is a complex one. I originally was going to put a solar clock on my home page, showing the sun time at my house—a digital 24-hour sundial, if you please. I never created it, but I did do a test page in PHP that shows my approximation of the Equation of Time (as this divergence is called) and from it the solar time at my house. As I write this in October, the sun is about 13 minutes away from its mean, so solar noon here today was about 1:10 pm EDT. Eastern time is based on 75º longitude, and we are 5º 49′ 46″ west of it.



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