Journey In God's Amazing Grace: Monday in London and Greenwich

Continuing on our Monday touring in Greenwich (you can see part 1 here: https://journeyinamazinggrace.blogspot.com/2026/07/monday-in-london-and-greenwich-part-1.html),

Entering the Royal Observatory Greenwich, we saw William Herschel's telescope

From Google's AI overview:

The Royal Observatory, Greenwich holds the remains of Sir William Herschel's colossal 40-foot reflecting telescope, including a 48-inch speculum metal mirror and part of the iron tube. The original telescope—funded by King George III—stood in Slough, Berkshire, and was dismantled in 1840.

The relationship between the Herschel family and the Observatory dates back over a century. William Herschel is renowned for discovering Uranus (1781) and infrared light, with his planetary findings officially verified by the 5th Astronomer Royal, Nevil Maskelyne.

Carl with one foot in the East and one foot in the West, right on the Prime Meridian line, theoretical longitude 0 degrees, 0 minutes.

However, it isn't *precisely* at longitude 0. The satellite meridian is about 100 meter east; after we finished visiting the observatory, we walked east until we got to the point where our phones said that we were at longitude 0 (nothing special happened there!).

The Royal Observatory is famous for supplying Greenwich Mean time. More on the Shepherd Gate Clock after we left the Observatory.

Mirror moon model

From https://www.rmg.co.uk/royal-observatory/attractions/mirror-moon:

A new installation by artist Luke Jerram has landed at the Royal Observatory this summer, celebrating 350 years of studying the Moon from this very location.

Since the Royal Observatory’s founding in 1675, numerous generations of astronomers have observed, mapped and photographed our closest celestial neighbour from Greenwich, seeking to understand the Solar System and our place in it.

Called Mirror Moon, this scale model is 2m in diameter and made from mirrored stainless steel. Mirror Moon uses highly accurate topographical NASA data of the lunar surface to transport the Moon from hundreds of thousands of miles away – to right beneath your fingertips.

Selfie with the Mirror Moon and London in the background

View down toward "Queen's House" and the National Maritime Museum, and on towards London.

The red ball on top of the Flamsteed House

From https://www.rmg.co.uk/stories/time/greenwich-time-ball-one-time-all:

The bright red Time Ball on top of Flamsteed House is one of the world's earliest public time signals, distributing time to ships on the Thames and many Londoners. It was first used in 1833 and still operates today.

What does the Time Ball do?

Each day, at 12.55, the time ball rises half way up its mast. At 12.58 it rises all the way to the top. At 13.00 exactly, the ball falls, and so provides a signal to anyone who happens to be looking. Of course, if you are looking the wrong way, you have to wait until the next day before it happens again.

The Time Ball drops at 13.00 GMT during the winter months and 13.00 BST during the summer. Please note: the time ball will not be run if the weather is too windy.

One of the rooms in the Flamsteed House -- designed by Sir Christopher Wren (who also supposedly designed the Wren Building on the campus of the College of William and Mary).

One of the major needs in traveling on the sea was a way to determine longitude. Latitude could be determined by stars, but longitude needed an accurate time clock to which to compare current location time. There was a contest with a £20,000 (pounds) award decreed by the government to encourage inventors to create a clock that would keep accurate time while on a ship. Clocks with pendulums did not keep accurate timework as the motion of the ship would impact the time-keeping.

Over many years, John Harrison built 4 clock models (H1, H2, H3, and H4) which are on display at the Royal Observatory.

https://www.rmg.co.uk/stories/time/harrisons-clocks-longitude-problem

His final clock had more of a watch design and was successful in keeping time on the sea.

Outside the observatory, looking toward London - we could see the London Eye (ferris wheel) and St Paul's Cathedral in the distance (you will need to click on the picture and zoom in to see them).

Outside the observatory, we could see the Shepherd clock...

Note that the Shepherd Clock is a 24-hour clock - it was a little after 12pm BST (British summer time), but the clock is displaying GMT). At 12 noon, the hour hand is pointing down.