The London Time Ball

timeball[Image: The London “time ball” at Greenwich, courtesy Royal Museums Greenwich].

Thanks to the effects of jet lag getting worse as I get older, I was basically awake for five days in London last week—but, on the bright side, it meant I got to read a ton of books.

Amongst them was an interesting new look at the history of weather science and atmospheric forecasting—sky futures!—by Peter Moore called The Weather Experiment. There were at least two things in it worth commenting on, one of which I’ll save for the next post.

This will doubtless already be common knowledge for many people, of course, but I was thrilled to learn about something called the London “time ball.” Installed at the Greenwich Royal Observatory in 1833 by John Pond, England’s Royal Astronomer, the time ball was a kind of secular church bell, an acoustic spacetime signal for ships.

It was “a large metal ball,” Moore writes, “attached to a pole at the Royal Observatory. At 1 p.m. each day it dropped to earth with an echoing thud so that ships in the Thames could calibrate their chronometers.” As such, it soon “became a familiar part of the Greenwich soundscape,” an Enlightenment variation on the Bow Bells. Born within sound of the time signal…

timeball1[Image: Historic shot of the time ball, via the South London Branch of the British Horological Institute].

There are many things I love about this, but one is the sheer fact that time was synchronized by something as unapologetically blunt as a sound reverberating over the waters. It would have passed through all manner of atmospheric conditions—through fog and smoke, through rain and wind—as well as through a labyrinth of physical obstructions, amidst overlapping ships and buildings, as if shattering the present moment into an echo chamber.

Calculating against these distortions would have presented a fascinating sort of acoustic relativity, as captains and their crew members would have needed to determine exactly how much time had been lost between the percussive thudding of the signal and their inevitably delayed hearing of it.

In fact, this suggests an interesting future design project: time-signal reflection landscapes for the Thames, or time-reflection surfaces and other acoustic follies for maritime London, helping mitigate against adverse atmospheric effects on antique devices of synchronization.

In any case, the other thing I love here is the abstract idea that, at this zero point for geography—that is, the prime meridian of the modern world—a perfect Platonic solid would knock out a moment of synchrony, and that Moore’s “echoing thud” at this precise dividing line between East and West would thus be encoded into the navigational plans of captains sailing out around the curvature of the earth, their expeditions grounded in time by this mark of sonic punctuation.

2 thoughts on “The London Time Ball”

  1. Have you seen the movie “The Conversation” with Gene Hackman?
    Two conspirators walk through a park every day, discussing their plans; that’s how they evade being spied on & listened to. Meanwhile, the investigator has set up multiple microphones nearby, with directional parabolas pointed towards the conspirators’ expected path. Later, in his office, the investigator pieces together the many separate voice recordings, which overlap somewhat, to get a complete recording of The Conversation.

    It’s the backwardization of the Time Ball’s acoustic principles.

  2. Interesting but wrong. The Time Ball is not an acoustic signal, but a visual one, being visible (in good weather) from ships along several miles of the Thames from its position on the hill above Greenwich.

    First used in 1833, it continues to perform daily and for those unable to view it directly you can see it in many videos, such as that at

    The river at its closest point is half a mile away, and ships could see the ball from several miles, and the delay of the acoustic signal would have rendered the signal useless, even if it could have been heard. As various on-line videos will show ( for example) it drops at 13.00 only partly down its pole and is virtually silent. Even standing close, if you are not looking you will miss it.

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